Fix: update writeback instrumentation for kernel 4.14
[lttng-modules.git] / lttng-events.c
index 97d82a297b911d9ad945cc6b88e484d87d2d8fb3..21c41133b859623e6a5ea63c65927021cb646171 100644 (file)
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+/*
+ * This page_alloc.h wrapper needs to be included before gfpflags.h because it
+ * overrides a function with a define.
+ */
+#include "wrapper/page_alloc.h"
+
 #include <linux/module.h>
-#include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/jiffies.h>
 #include <linux/utsname.h>
 #include <linux/err.h>
-#include "wrapper/uuid.h"
-#include "wrapper/vmalloc.h"   /* for wrapper_vmalloc_sync_all() */
-#include "wrapper/random.h"
-#include "wrapper/tracepoint.h"
-#include "lttng-kernel-version.h"
-#include "lttng-events.h"
-#include "lttng-tracer.h"
-#include "lttng-abi-old.h"
+#include <linux/seq_file.h>
+#include <linux/file.h>
+#include <linux/anon_inodes.h>
+#include <wrapper/file.h>
+#include <linux/jhash.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+
+#include <wrapper/uuid.h>
+#include <wrapper/vmalloc.h>   /* for wrapper_vmalloc_sync_all() */
+#include <wrapper/random.h>
+#include <wrapper/tracepoint.h>
+#include <wrapper/list.h>
+#include <wrapper/types.h>
+#include <lttng-kernel-version.h>
+#include <lttng-events.h>
+#include <lttng-tracer.h>
+#include <lttng-abi-old.h>
+#include <lttng-endian.h>
+#include <lttng-string-utils.h>
+#include <wrapper/vzalloc.h>
+#include <wrapper/ringbuffer/backend.h>
+#include <wrapper/ringbuffer/frontend.h>
 
 #define METADATA_CACHE_DEFAULT_SIZE 4096
 
@@ -47,6 +67,10 @@ static LIST_HEAD(lttng_transport_list);
 static DEFINE_MUTEX(sessions_mutex);
 static struct kmem_cache *event_cache;
 
+static void lttng_session_lazy_sync_enablers(struct lttng_session *session);
+static void lttng_session_sync_enablers(struct lttng_session *session);
+static void lttng_enabler_destroy(struct lttng_enabler *enabler);
+
 static void _lttng_event_destroy(struct lttng_event *event);
 static void _lttng_channel_destroy(struct lttng_channel *chan);
 static int _lttng_event_unregister(struct lttng_event *event);
@@ -58,6 +82,10 @@ static
 int _lttng_session_metadata_statedump(struct lttng_session *session);
 static
 void _lttng_metadata_channel_hangup(struct lttng_metadata_stream *stream);
+static
+int _lttng_field_statedump(struct lttng_session *session,
+               const struct lttng_event_field *field,
+               size_t nesting);
 
 void synchronize_trace(void)
 {
@@ -73,13 +101,38 @@ void synchronize_trace(void)
 #endif /* (LINUX_VERSION_CODE >= KERNEL_VERSION(3,4,0)) */
 }
 
+void lttng_lock_sessions(void)
+{
+       mutex_lock(&sessions_mutex);
+}
+
+void lttng_unlock_sessions(void)
+{
+       mutex_unlock(&sessions_mutex);
+}
+
+/*
+ * Called with sessions lock held.
+ */
+int lttng_session_active(void)
+{
+       struct lttng_session *iter;
+
+       list_for_each_entry(iter, &sessions, list) {
+               if (iter->active)
+                       return 1;
+       }
+       return 0;
+}
+
 struct lttng_session *lttng_session_create(void)
 {
        struct lttng_session *session;
        struct lttng_metadata_cache *metadata_cache;
+       int i;
 
        mutex_lock(&sessions_mutex);
-       session = kzalloc(sizeof(struct lttng_session), GFP_KERNEL);
+       session = lttng_kvzalloc(sizeof(struct lttng_session), GFP_KERNEL);
        if (!session)
                goto err;
        INIT_LIST_HEAD(&session->chan);
@@ -90,14 +143,19 @@ struct lttng_session *lttng_session_create(void)
                        GFP_KERNEL);
        if (!metadata_cache)
                goto err_free_session;
-       metadata_cache->data = kzalloc(METADATA_CACHE_DEFAULT_SIZE,
-                       GFP_KERNEL);
+       metadata_cache->data = lttng_vzalloc(METADATA_CACHE_DEFAULT_SIZE);
        if (!metadata_cache->data)
                goto err_free_cache;
        metadata_cache->cache_alloc = METADATA_CACHE_DEFAULT_SIZE;
        kref_init(&metadata_cache->refcount);
+       mutex_init(&metadata_cache->lock);
        session->metadata_cache = metadata_cache;
        INIT_LIST_HEAD(&metadata_cache->metadata_stream);
+       memcpy(&metadata_cache->uuid, &session->uuid,
+               sizeof(metadata_cache->uuid));
+       INIT_LIST_HEAD(&session->enablers_head);
+       for (i = 0; i < LTTNG_EVENT_HT_SIZE; i++)
+               INIT_HLIST_HEAD(&session->events_ht.table[i]);
        list_add(&session->list, &sessions);
        mutex_unlock(&sessions_mutex);
        return session;
@@ -105,7 +163,7 @@ struct lttng_session *lttng_session_create(void)
 err_free_cache:
        kfree(metadata_cache);
 err_free_session:
-       kfree(session);
+       lttng_kvfree(session);
 err:
        mutex_unlock(&sessions_mutex);
        return NULL;
@@ -115,7 +173,7 @@ void metadata_cache_destroy(struct kref *kref)
 {
        struct lttng_metadata_cache *cache =
                container_of(kref, struct lttng_metadata_cache, refcount);
-       kfree(cache->data);
+       vfree(cache->data);
        kfree(cache);
 }
 
@@ -124,6 +182,7 @@ void lttng_session_destroy(struct lttng_session *session)
        struct lttng_channel *chan, *tmpchan;
        struct lttng_event *event, *tmpevent;
        struct lttng_metadata_stream *metadata_stream;
+       struct lttng_enabler *enabler, *tmpenabler;
        int ret;
 
        mutex_lock(&sessions_mutex);
@@ -137,6 +196,9 @@ void lttng_session_destroy(struct lttng_session *session)
                WARN_ON(ret);
        }
        synchronize_trace();    /* Wait for in-flight events to complete */
+       list_for_each_entry_safe(enabler, tmpenabler,
+                       &session->enablers_head, node)
+               lttng_enabler_destroy(enabler);
        list_for_each_entry_safe(event, tmpevent, &session->events, list)
                _lttng_event_destroy(event);
        list_for_each_entry_safe(chan, tmpchan, &session->chan, list) {
@@ -145,10 +207,22 @@ void lttng_session_destroy(struct lttng_session *session)
        }
        list_for_each_entry(metadata_stream, &session->metadata_cache->metadata_stream, list)
                _lttng_metadata_channel_hangup(metadata_stream);
+       if (session->pid_tracker)
+               lttng_pid_tracker_destroy(session->pid_tracker);
        kref_put(&session->metadata_cache->refcount, metadata_cache_destroy);
        list_del(&session->list);
        mutex_unlock(&sessions_mutex);
-       kfree(session);
+       lttng_kvfree(session);
+}
+
+int lttng_session_statedump(struct lttng_session *session)
+{
+       int ret;
+
+       mutex_lock(&sessions_mutex);
+       ret = lttng_statedump_start(session);
+       mutex_unlock(&sessions_mutex);
+       return ret;
 }
 
 int lttng_session_enable(struct lttng_session *session)
@@ -162,6 +236,9 @@ int lttng_session_enable(struct lttng_session *session)
                goto end;
        }
 
+       /* Set transient enabler state to "enabled" */
+       session->tstate = 1;
+
        /*
         * Snapshot the number of events per channel to know the type of header
         * we need to use.
@@ -175,6 +252,15 @@ int lttng_session_enable(struct lttng_session *session)
                        chan->header_type = 2;  /* large */
        }
 
+       /* We need to sync enablers with session before activation. */
+       lttng_session_sync_enablers(session);
+
+       /* Clear each stream's quiescent state. */
+       list_for_each_entry(chan, &session->chan, list) {
+               if (chan->channel_type != METADATA_CHANNEL)
+                       lib_ring_buffer_clear_quiescent_channel(chan->chan);
+       }
+
        ACCESS_ONCE(session->active) = 1;
        ACCESS_ONCE(session->been_active) = 1;
        ret = _lttng_session_metadata_statedump(session);
@@ -193,6 +279,7 @@ end:
 int lttng_session_disable(struct lttng_session *session)
 {
        int ret = 0;
+       struct lttng_channel *chan;
 
        mutex_lock(&sessions_mutex);
        if (!session->active) {
@@ -200,57 +287,177 @@ int lttng_session_disable(struct lttng_session *session)
                goto end;
        }
        ACCESS_ONCE(session->active) = 0;
+
+       /* Set transient enabler state to "disabled" */
+       session->tstate = 0;
+       lttng_session_sync_enablers(session);
+
+       /* Set each stream's quiescent state. */
+       list_for_each_entry(chan, &session->chan, list) {
+               if (chan->channel_type != METADATA_CHANNEL)
+                       lib_ring_buffer_set_quiescent_channel(chan->chan);
+       }
+end:
+       mutex_unlock(&sessions_mutex);
+       return ret;
+}
+
+int lttng_session_metadata_regenerate(struct lttng_session *session)
+{
+       int ret = 0;
+       struct lttng_channel *chan;
+       struct lttng_event *event;
+       struct lttng_metadata_cache *cache = session->metadata_cache;
+       struct lttng_metadata_stream *stream;
+
+       mutex_lock(&sessions_mutex);
+       if (!session->active) {
+               ret = -EBUSY;
+               goto end;
+       }
+
+       mutex_lock(&cache->lock);
+       memset(cache->data, 0, cache->cache_alloc);
+       cache->metadata_written = 0;
+       cache->version++;
+       list_for_each_entry(stream, &session->metadata_cache->metadata_stream, list) {
+               stream->metadata_out = 0;
+               stream->metadata_in = 0;
+       }
+       mutex_unlock(&cache->lock);
+
+       session->metadata_dumped = 0;
+       list_for_each_entry(chan, &session->chan, list) {
+               chan->metadata_dumped = 0;
+       }
+
+       list_for_each_entry(event, &session->events, list) {
+               event->metadata_dumped = 0;
+       }
+
+       ret = _lttng_session_metadata_statedump(session);
+
 end:
        mutex_unlock(&sessions_mutex);
        return ret;
 }
 
+
+
 int lttng_channel_enable(struct lttng_channel *channel)
 {
-       int old;
+       int ret = 0;
 
-       if (channel->channel_type == METADATA_CHANNEL)
-               return -EPERM;
-       old = xchg(&channel->enabled, 1);
-       if (old)
-               return -EEXIST;
-       return 0;
+       mutex_lock(&sessions_mutex);
+       if (channel->channel_type == METADATA_CHANNEL) {
+               ret = -EPERM;
+               goto end;
+       }
+       if (channel->enabled) {
+               ret = -EEXIST;
+               goto end;
+       }
+       /* Set transient enabler state to "enabled" */
+       channel->tstate = 1;
+       lttng_session_sync_enablers(channel->session);
+       /* Set atomically the state to "enabled" */
+       ACCESS_ONCE(channel->enabled) = 1;
+end:
+       mutex_unlock(&sessions_mutex);
+       return ret;
 }
 
 int lttng_channel_disable(struct lttng_channel *channel)
 {
-       int old;
+       int ret = 0;
 
-       if (channel->channel_type == METADATA_CHANNEL)
-               return -EPERM;
-       old = xchg(&channel->enabled, 0);
-       if (!old)
-               return -EEXIST;
-       return 0;
+       mutex_lock(&sessions_mutex);
+       if (channel->channel_type == METADATA_CHANNEL) {
+               ret = -EPERM;
+               goto end;
+       }
+       if (!channel->enabled) {
+               ret = -EEXIST;
+               goto end;
+       }
+       /* Set atomically the state to "disabled" */
+       ACCESS_ONCE(channel->enabled) = 0;
+       /* Set transient enabler state to "enabled" */
+       channel->tstate = 0;
+       lttng_session_sync_enablers(channel->session);
+end:
+       mutex_unlock(&sessions_mutex);
+       return ret;
 }
 
 int lttng_event_enable(struct lttng_event *event)
 {
-       int old;
+       int ret = 0;
 
-       if (event->chan->channel_type == METADATA_CHANNEL)
-               return -EPERM;
-       old = xchg(&event->enabled, 1);
-       if (old)
-               return -EEXIST;
-       return 0;
+       mutex_lock(&sessions_mutex);
+       if (event->chan->channel_type == METADATA_CHANNEL) {
+               ret = -EPERM;
+               goto end;
+       }
+       if (event->enabled) {
+               ret = -EEXIST;
+               goto end;
+       }
+       switch (event->instrumentation) {
+       case LTTNG_KERNEL_TRACEPOINT:
+       case LTTNG_KERNEL_SYSCALL:
+               ret = -EINVAL;
+               break;
+       case LTTNG_KERNEL_KPROBE:
+       case LTTNG_KERNEL_FUNCTION:
+       case LTTNG_KERNEL_NOOP:
+               ACCESS_ONCE(event->enabled) = 1;
+               break;
+       case LTTNG_KERNEL_KRETPROBE:
+               ret = lttng_kretprobes_event_enable_state(event, 1);
+               break;
+       default:
+               WARN_ON_ONCE(1);
+               ret = -EINVAL;
+       }
+end:
+       mutex_unlock(&sessions_mutex);
+       return ret;
 }
 
 int lttng_event_disable(struct lttng_event *event)
 {
-       int old;
+       int ret = 0;
 
-       if (event->chan->channel_type == METADATA_CHANNEL)
-               return -EPERM;
-       old = xchg(&event->enabled, 0);
-       if (!old)
-               return -EEXIST;
-       return 0;
+       mutex_lock(&sessions_mutex);
+       if (event->chan->channel_type == METADATA_CHANNEL) {
+               ret = -EPERM;
+               goto end;
+       }
+       if (!event->enabled) {
+               ret = -EEXIST;
+               goto end;
+       }
+       switch (event->instrumentation) {
+       case LTTNG_KERNEL_TRACEPOINT:
+       case LTTNG_KERNEL_SYSCALL:
+               ret = -EINVAL;
+               break;
+       case LTTNG_KERNEL_KPROBE:
+       case LTTNG_KERNEL_FUNCTION:
+       case LTTNG_KERNEL_NOOP:
+               ACCESS_ONCE(event->enabled) = 0;
+               break;
+       case LTTNG_KERNEL_KRETPROBE:
+               ret = lttng_kretprobes_event_enable_state(event, 0);
+               break;
+       default:
+               WARN_ON_ONCE(1);
+               ret = -EINVAL;
+       }
+end:
+       mutex_unlock(&sessions_mutex);
+       return ret;
 }
 
 static struct lttng_transport *lttng_transport_find(const char *name)
@@ -304,6 +511,7 @@ struct lttng_channel *lttng_channel_create(struct lttng_session *session,
                        switch_timer_interval, read_timer_interval);
        if (!chan->chan)
                goto create_error;
+       chan->tstate = 1;
        chan->enabled = 1;
        chan->transport = transport;
        chan->channel_type = channel_type;
@@ -357,65 +565,101 @@ void _lttng_metadata_channel_hangup(struct lttng_metadata_stream *stream)
 
 /*
  * Supports event creation while tracing session is active.
+ * Needs to be called with sessions mutex held.
  */
-struct lttng_event *lttng_event_create(struct lttng_channel *chan,
-                                  struct lttng_kernel_event *event_param,
-                                  void *filter,
-                                  const struct lttng_event_desc *internal_desc)
+struct lttng_event *_lttng_event_create(struct lttng_channel *chan,
+                               struct lttng_kernel_event *event_param,
+                               void *filter,
+                               const struct lttng_event_desc *event_desc,
+                               enum lttng_kernel_instrumentation itype)
 {
+       struct lttng_session *session = chan->session;
        struct lttng_event *event;
+       const char *event_name;
+       struct hlist_head *head;
+       size_t name_len;
+       uint32_t hash;
        int ret;
 
-       mutex_lock(&sessions_mutex);
        if (chan->free_event_id == -1U) {
-               event = ERR_PTR(-EMFILE);
+               ret = -EMFILE;
                goto full;
        }
-       /*
-        * This is O(n^2) (for each event, the loop is called at event
-        * creation). Might require a hash if we have lots of events.
-        */
-       list_for_each_entry(event, &chan->session->events, list) {
-               if (!strcmp(event->desc->name, event_param->name)) {
-                       event = ERR_PTR(-EEXIST);
+
+       switch (itype) {
+       case LTTNG_KERNEL_TRACEPOINT:
+               event_name = event_desc->name;
+               break;
+       case LTTNG_KERNEL_KPROBE:
+       case LTTNG_KERNEL_KRETPROBE:
+       case LTTNG_KERNEL_FUNCTION:
+       case LTTNG_KERNEL_NOOP:
+       case LTTNG_KERNEL_SYSCALL:
+               event_name = event_param->name;
+               break;
+       default:
+               WARN_ON_ONCE(1);
+               ret = -EINVAL;
+               goto type_error;
+       }
+       name_len = strlen(event_name);
+       hash = jhash(event_name, name_len, 0);
+       head = &session->events_ht.table[hash & (LTTNG_EVENT_HT_SIZE - 1)];
+       lttng_hlist_for_each_entry(event, head, hlist) {
+               WARN_ON_ONCE(!event->desc);
+               if (!strncmp(event->desc->name, event_name,
+                                       LTTNG_KERNEL_SYM_NAME_LEN - 1)
+                               && chan == event->chan) {
+                       ret = -EEXIST;
                        goto exist;
                }
        }
+
        event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
        if (!event) {
-               event = ERR_PTR(-ENOMEM);
+               ret = -ENOMEM;
                goto cache_error;
        }
        event->chan = chan;
        event->filter = filter;
        event->id = chan->free_event_id++;
-       event->enabled = 1;
-       event->instrumentation = event_param->instrumentation;
-       /* Populate lttng_event structure before tracepoint registration. */
-       smp_wmb();
-       switch (event_param->instrumentation) {
+       event->instrumentation = itype;
+       event->evtype = LTTNG_TYPE_EVENT;
+       INIT_LIST_HEAD(&event->bytecode_runtime_head);
+       INIT_LIST_HEAD(&event->enablers_ref_head);
+
+       switch (itype) {
        case LTTNG_KERNEL_TRACEPOINT:
-               event->desc = lttng_event_get(event_param->name);
+               /* Event will be enabled by enabler sync. */
+               event->enabled = 0;
+               event->registered = 0;
+               event->desc = lttng_event_get(event_name);
                if (!event->desc) {
-                       event = ERR_PTR(-ENOENT);
-                       goto register_error;
-               }
-               ret = kabi_2635_tracepoint_probe_register(event_param->name,
-                               event->desc->probe_callback,
-                               event);
-               if (ret) {
-                       event = ERR_PTR(-EINVAL);
+                       ret = -ENOENT;
                        goto register_error;
                }
+               /* Populate lttng_event structure before event registration. */
+               smp_wmb();
                break;
        case LTTNG_KERNEL_KPROBE:
-               ret = lttng_kprobes_register(event_param->name,
+               /*
+                * Needs to be explicitly enabled after creation, since
+                * we may want to apply filters.
+                */
+               event->enabled = 0;
+               event->registered = 1;
+               /*
+                * Populate lttng_event structure before event
+                * registration.
+                */
+               smp_wmb();
+               ret = lttng_kprobes_register(event_name,
                                event_param->u.kprobe.symbol_name,
                                event_param->u.kprobe.offset,
                                event_param->u.kprobe.addr,
                                event);
                if (ret) {
-                       event = ERR_PTR(-EINVAL);
+                       ret = -EINVAL;
                        goto register_error;
                }
                ret = try_module_get(event->desc->owner);
@@ -426,29 +670,36 @@ struct lttng_event *lttng_event_create(struct lttng_channel *chan,
                struct lttng_event *event_return;
 
                /* kretprobe defines 2 events */
+               /*
+                * Needs to be explicitly enabled after creation, since
+                * we may want to apply filters.
+                */
+               event->enabled = 0;
+               event->registered = 1;
                event_return =
                        kmem_cache_zalloc(event_cache, GFP_KERNEL);
                if (!event_return) {
-                       event = ERR_PTR(-ENOMEM);
+                       ret = -ENOMEM;
                        goto register_error;
                }
                event_return->chan = chan;
                event_return->filter = filter;
                event_return->id = chan->free_event_id++;
-               event_return->enabled = 1;
-               event_return->instrumentation = event_param->instrumentation;
+               event_return->enabled = 0;
+               event_return->registered = 1;
+               event_return->instrumentation = itype;
                /*
                 * Populate lttng_event structure before kretprobe registration.
                 */
                smp_wmb();
-               ret = lttng_kretprobes_register(event_param->name,
+               ret = lttng_kretprobes_register(event_name,
                                event_param->u.kretprobe.symbol_name,
                                event_param->u.kretprobe.offset,
                                event_param->u.kretprobe.addr,
                                event, event_return);
                if (ret) {
                        kmem_cache_free(event_cache, event_return);
-                       event = ERR_PTR(-EINVAL);
+                       ret = -EINVAL;
                        goto register_error;
                }
                /* Take 2 refs on the module: one per event. */
@@ -463,43 +714,58 @@ struct lttng_event *lttng_event_create(struct lttng_channel *chan,
                        kmem_cache_free(event_cache, event_return);
                        module_put(event->desc->owner);
                        module_put(event->desc->owner);
-                       event = ERR_PTR(ret);
                        goto statedump_error;
                }
                list_add(&event_return->list, &chan->session->events);
                break;
        }
        case LTTNG_KERNEL_FUNCTION:
-               ret = lttng_ftrace_register(event_param->name,
+               /*
+                * Needs to be explicitly enabled after creation, since
+                * we may want to apply filters.
+                */
+               event->enabled = 0;
+               event->registered = 1;
+               /*
+                * Populate lttng_event structure before event
+                * registration.
+                */
+               smp_wmb();
+               ret = lttng_ftrace_register(event_name,
                                event_param->u.ftrace.symbol_name,
                                event);
                if (ret) {
-                       event = ERR_PTR(ret);
                        goto register_error;
                }
                ret = try_module_get(event->desc->owner);
                WARN_ON_ONCE(!ret);
                break;
        case LTTNG_KERNEL_NOOP:
-               event->desc = internal_desc;
+       case LTTNG_KERNEL_SYSCALL:
+               /*
+                * Needs to be explicitly enabled after creation, since
+                * we may want to apply filters.
+                */
+               event->enabled = 0;
+               event->registered = 0;
+               event->desc = event_desc;
                if (!event->desc) {
-                       event = ERR_PTR(-EINVAL);
+                       ret = -EINVAL;
                        goto register_error;
                }
                break;
        default:
                WARN_ON_ONCE(1);
-               event = ERR_PTR(-EINVAL);
+               ret = -EINVAL;
                goto register_error;
        }
        ret = _lttng_event_metadata_statedump(chan->session, chan, event);
        WARN_ON_ONCE(ret > 0);
        if (ret) {
-               event = ERR_PTR(ret);
                goto statedump_error;
        }
+       hlist_add_head(&event->hlist, head);
        list_add(&event->list, &chan->session->events);
-       mutex_unlock(&sessions_mutex);
        return event;
 
 statedump_error:
@@ -508,25 +774,77 @@ register_error:
        kmem_cache_free(event_cache, event);
 cache_error:
 exist:
+type_error:
 full:
+       return ERR_PTR(ret);
+}
+
+struct lttng_event *lttng_event_create(struct lttng_channel *chan,
+                               struct lttng_kernel_event *event_param,
+                               void *filter,
+                               const struct lttng_event_desc *event_desc,
+                               enum lttng_kernel_instrumentation itype)
+{
+       struct lttng_event *event;
+
+       mutex_lock(&sessions_mutex);
+       event = _lttng_event_create(chan, event_param, filter, event_desc,
+                               itype);
        mutex_unlock(&sessions_mutex);
        return event;
 }
 
+/* Only used for tracepoints for now. */
+static
+void register_event(struct lttng_event *event)
+{
+       const struct lttng_event_desc *desc;
+       int ret = -EINVAL;
+
+       if (event->registered)
+               return;
+
+       desc = event->desc;
+       switch (event->instrumentation) {
+       case LTTNG_KERNEL_TRACEPOINT:
+               ret = lttng_wrapper_tracepoint_probe_register(desc->kname,
+                                                 desc->probe_callback,
+                                                 event);
+               break;
+       case LTTNG_KERNEL_SYSCALL:
+               ret = lttng_syscall_filter_enable(event->chan,
+                       desc->name);
+               break;
+       case LTTNG_KERNEL_KPROBE:
+       case LTTNG_KERNEL_KRETPROBE:
+       case LTTNG_KERNEL_FUNCTION:
+       case LTTNG_KERNEL_NOOP:
+               ret = 0;
+               break;
+       default:
+               WARN_ON_ONCE(1);
+       }
+       if (!ret)
+               event->registered = 1;
+}
+
 /*
  * Only used internally at session destruction.
  */
 int _lttng_event_unregister(struct lttng_event *event)
 {
+       const struct lttng_event_desc *desc;
        int ret = -EINVAL;
 
+       if (!event->registered)
+               return 0;
+
+       desc = event->desc;
        switch (event->instrumentation) {
        case LTTNG_KERNEL_TRACEPOINT:
-               ret = kabi_2635_tracepoint_probe_unregister(event->desc->name,
+               ret = lttng_wrapper_tracepoint_probe_unregister(event->desc->kname,
                                                  event->desc->probe_callback,
                                                  event);
-               if (ret)
-                       return ret;
                break;
        case LTTNG_KERNEL_KPROBE:
                lttng_kprobes_unregister(event);
@@ -540,12 +858,18 @@ int _lttng_event_unregister(struct lttng_event *event)
                lttng_ftrace_unregister(event);
                ret = 0;
                break;
+       case LTTNG_KERNEL_SYSCALL:
+               ret = lttng_syscall_filter_disable(event->chan,
+                       desc->name);
+               break;
        case LTTNG_KERNEL_NOOP:
                ret = 0;
                break;
        default:
                WARN_ON_ONCE(1);
        }
+       if (!ret)
+               event->registered = 0;
        return ret;
 }
 
@@ -572,22 +896,682 @@ void _lttng_event_destroy(struct lttng_event *event)
                lttng_ftrace_destroy_private(event);
                break;
        case LTTNG_KERNEL_NOOP:
+       case LTTNG_KERNEL_SYSCALL:
+               break;
+       default:
+               WARN_ON_ONCE(1);
+       }
+       list_del(&event->list);
+       lttng_destroy_context(event->ctx);
+       kmem_cache_free(event_cache, event);
+}
+
+int lttng_session_track_pid(struct lttng_session *session, int pid)
+{
+       int ret;
+
+       if (pid < -1)
+               return -EINVAL;
+       mutex_lock(&sessions_mutex);
+       if (pid == -1) {
+               /* track all pids: destroy tracker. */
+               if (session->pid_tracker) {
+                       struct lttng_pid_tracker *lpf;
+
+                       lpf = session->pid_tracker;
+                       rcu_assign_pointer(session->pid_tracker, NULL);
+                       synchronize_trace();
+                       lttng_pid_tracker_destroy(lpf);
+               }
+               ret = 0;
+       } else {
+               if (!session->pid_tracker) {
+                       struct lttng_pid_tracker *lpf;
+
+                       lpf = lttng_pid_tracker_create();
+                       if (!lpf) {
+                               ret = -ENOMEM;
+                               goto unlock;
+                       }
+                       ret = lttng_pid_tracker_add(lpf, pid);
+                       rcu_assign_pointer(session->pid_tracker, lpf);
+               } else {
+                       ret = lttng_pid_tracker_add(session->pid_tracker, pid);
+               }
+       }
+unlock:
+       mutex_unlock(&sessions_mutex);
+       return ret;
+}
+
+int lttng_session_untrack_pid(struct lttng_session *session, int pid)
+{
+       int ret;
+
+       if (pid < -1)
+               return -EINVAL;
+       mutex_lock(&sessions_mutex);
+       if (pid == -1) {
+               /* untrack all pids: replace by empty tracker. */
+               struct lttng_pid_tracker *old_lpf = session->pid_tracker;
+               struct lttng_pid_tracker *lpf;
+
+               lpf = lttng_pid_tracker_create();
+               if (!lpf) {
+                       ret = -ENOMEM;
+                       goto unlock;
+               }
+               rcu_assign_pointer(session->pid_tracker, lpf);
+               synchronize_trace();
+               if (old_lpf)
+                       lttng_pid_tracker_destroy(old_lpf);
+               ret = 0;
+       } else {
+               if (!session->pid_tracker) {
+                       ret = -ENOENT;
+                       goto unlock;
+               }
+               ret = lttng_pid_tracker_del(session->pid_tracker, pid);
+       }
+unlock:
+       mutex_unlock(&sessions_mutex);
+       return ret;
+}
+
+static
+void *pid_list_start(struct seq_file *m, loff_t *pos)
+{
+       struct lttng_session *session = m->private;
+       struct lttng_pid_tracker *lpf;
+       struct lttng_pid_hash_node *e;
+       int iter = 0, i;
+
+       mutex_lock(&sessions_mutex);
+       lpf = session->pid_tracker;
+       if (lpf) {
+               for (i = 0; i < LTTNG_PID_TABLE_SIZE; i++) {
+                       struct hlist_head *head = &lpf->pid_hash[i];
+
+                       lttng_hlist_for_each_entry(e, head, hlist) {
+                               if (iter++ >= *pos)
+                                       return e;
+                       }
+               }
+       } else {
+               /* PID tracker disabled. */
+               if (iter >= *pos && iter == 0) {
+                       return session; /* empty tracker */
+               }
+               iter++;
+       }
+       /* End of list */
+       return NULL;
+}
+
+/* Called with sessions_mutex held. */
+static
+void *pid_list_next(struct seq_file *m, void *p, loff_t *ppos)
+{
+       struct lttng_session *session = m->private;
+       struct lttng_pid_tracker *lpf;
+       struct lttng_pid_hash_node *e;
+       int iter = 0, i;
+
+       (*ppos)++;
+       lpf = session->pid_tracker;
+       if (lpf) {
+               for (i = 0; i < LTTNG_PID_TABLE_SIZE; i++) {
+                       struct hlist_head *head = &lpf->pid_hash[i];
+
+                       lttng_hlist_for_each_entry(e, head, hlist) {
+                               if (iter++ >= *ppos)
+                                       return e;
+                       }
+               }
+       } else {
+               /* PID tracker disabled. */
+               if (iter >= *ppos && iter == 0)
+                       return session; /* empty tracker */
+               iter++;
+       }
+
+       /* End of list */
+       return NULL;
+}
+
+static
+void pid_list_stop(struct seq_file *m, void *p)
+{
+       mutex_unlock(&sessions_mutex);
+}
+
+static
+int pid_list_show(struct seq_file *m, void *p)
+{
+       int pid;
+
+       if (p == m->private) {
+               /* Tracker disabled. */
+               pid = -1;
+       } else {
+               const struct lttng_pid_hash_node *e = p;
+
+               pid = lttng_pid_tracker_get_node_pid(e);
+       }
+       seq_printf(m,   "process { pid = %d; };\n", pid);
+       return 0;
+}
+
+static
+const struct seq_operations lttng_tracker_pids_list_seq_ops = {
+       .start = pid_list_start,
+       .next = pid_list_next,
+       .stop = pid_list_stop,
+       .show = pid_list_show,
+};
+
+static
+int lttng_tracker_pids_list_open(struct inode *inode, struct file *file)
+{
+       return seq_open(file, &lttng_tracker_pids_list_seq_ops);
+}
+
+static
+int lttng_tracker_pids_list_release(struct inode *inode, struct file *file)
+{
+       struct seq_file *m = file->private_data;
+       struct lttng_session *session = m->private;
+       int ret;
+
+       WARN_ON_ONCE(!session);
+       ret = seq_release(inode, file);
+       if (!ret && session)
+               fput(session->file);
+       return ret;
+}
+
+const struct file_operations lttng_tracker_pids_list_fops = {
+       .owner = THIS_MODULE,
+       .open = lttng_tracker_pids_list_open,
+       .read = seq_read,
+       .llseek = seq_lseek,
+       .release = lttng_tracker_pids_list_release,
+};
+
+int lttng_session_list_tracker_pids(struct lttng_session *session)
+{
+       struct file *tracker_pids_list_file;
+       struct seq_file *m;
+       int file_fd, ret;
+
+       file_fd = lttng_get_unused_fd();
+       if (file_fd < 0) {
+               ret = file_fd;
+               goto fd_error;
+       }
+
+       tracker_pids_list_file = anon_inode_getfile("[lttng_tracker_pids_list]",
+                                         &lttng_tracker_pids_list_fops,
+                                         NULL, O_RDWR);
+       if (IS_ERR(tracker_pids_list_file)) {
+               ret = PTR_ERR(tracker_pids_list_file);
+               goto file_error;
+       }
+       if (atomic_long_add_unless(&session->file->f_count,
+               1, INT_MAX) == INT_MAX) {
+               goto refcount_error;
+       }
+       ret = lttng_tracker_pids_list_fops.open(NULL, tracker_pids_list_file);
+       if (ret < 0)
+               goto open_error;
+       m = tracker_pids_list_file->private_data;
+       m->private = session;
+       fd_install(file_fd, tracker_pids_list_file);
+
+       return file_fd;
+
+open_error:
+       atomic_long_dec(&session->file->f_count);
+refcount_error:
+       fput(tracker_pids_list_file);
+file_error:
+       put_unused_fd(file_fd);
+fd_error:
+       return ret;
+}
+
+/*
+ * Enabler management.
+ */
+static
+int lttng_match_enabler_star_glob(const char *desc_name,
+               const char *pattern)
+{
+       if (!strutils_star_glob_match(pattern, LTTNG_SIZE_MAX,
+                       desc_name, LTTNG_SIZE_MAX))
+               return 0;
+       return 1;
+}
+
+static
+int lttng_match_enabler_name(const char *desc_name,
+               const char *name)
+{
+       if (strcmp(desc_name, name))
+               return 0;
+       return 1;
+}
+
+static
+int lttng_desc_match_enabler(const struct lttng_event_desc *desc,
+               struct lttng_enabler *enabler)
+{
+       const char *desc_name, *enabler_name;
+
+       enabler_name = enabler->event_param.name;
+       switch (enabler->event_param.instrumentation) {
+       case LTTNG_KERNEL_TRACEPOINT:
+               desc_name = desc->name;
+               break;
+       case LTTNG_KERNEL_SYSCALL:
+               desc_name = desc->name;
+               if (!strncmp(desc_name, "compat_", strlen("compat_")))
+                       desc_name += strlen("compat_");
+               if (!strncmp(desc_name, "syscall_exit_",
+                               strlen("syscall_exit_"))) {
+                       desc_name += strlen("syscall_exit_");
+               } else if (!strncmp(desc_name, "syscall_entry_",
+                               strlen("syscall_entry_"))) {
+                       desc_name += strlen("syscall_entry_");
+               } else {
+                       WARN_ON_ONCE(1);
+                       return -EINVAL;
+               }
                break;
        default:
                WARN_ON_ONCE(1);
+               return -EINVAL;
+       }
+       switch (enabler->type) {
+       case LTTNG_ENABLER_STAR_GLOB:
+               return lttng_match_enabler_star_glob(desc_name, enabler_name);
+       case LTTNG_ENABLER_NAME:
+               return lttng_match_enabler_name(desc_name, enabler_name);
+       default:
+               return -EINVAL;
+       }
+}
+
+static
+int lttng_event_match_enabler(struct lttng_event *event,
+               struct lttng_enabler *enabler)
+{
+       if (enabler->event_param.instrumentation != event->instrumentation)
+               return 0;
+       if (lttng_desc_match_enabler(event->desc, enabler)
+                       && event->chan == enabler->chan)
+               return 1;
+       else
+               return 0;
+}
+
+static
+struct lttng_enabler_ref *lttng_event_enabler_ref(struct lttng_event *event,
+               struct lttng_enabler *enabler)
+{
+       struct lttng_enabler_ref *enabler_ref;
+
+       list_for_each_entry(enabler_ref,
+                       &event->enablers_ref_head, node) {
+               if (enabler_ref->ref == enabler)
+                       return enabler_ref;
+       }
+       return NULL;
+}
+
+static
+void lttng_create_tracepoint_if_missing(struct lttng_enabler *enabler)
+{
+       struct lttng_session *session = enabler->chan->session;
+       struct lttng_probe_desc *probe_desc;
+       const struct lttng_event_desc *desc;
+       int i;
+       struct list_head *probe_list;
+
+       probe_list = lttng_get_probe_list_head();
+       /*
+        * For each probe event, if we find that a probe event matches
+        * our enabler, create an associated lttng_event if not
+        * already present.
+        */
+       list_for_each_entry(probe_desc, probe_list, head) {
+               for (i = 0; i < probe_desc->nr_events; i++) {
+                       int found = 0;
+                       struct hlist_head *head;
+                       const char *event_name;
+                       size_t name_len;
+                       uint32_t hash;
+                       struct lttng_event *event;
+
+                       desc = probe_desc->event_desc[i];
+                       if (!lttng_desc_match_enabler(desc, enabler))
+                               continue;
+                       event_name = desc->name;
+                       name_len = strlen(event_name);
+
+                       /*
+                        * Check if already created.
+                        */
+                       hash = jhash(event_name, name_len, 0);
+                       head = &session->events_ht.table[hash & (LTTNG_EVENT_HT_SIZE - 1)];
+                       lttng_hlist_for_each_entry(event, head, hlist) {
+                               if (event->desc == desc
+                                               && event->chan == enabler->chan)
+                                       found = 1;
+                       }
+                       if (found)
+                               continue;
+
+                       /*
+                        * We need to create an event for this
+                        * event probe.
+                        */
+                       event = _lttng_event_create(enabler->chan,
+                                       NULL, NULL, desc,
+                                       LTTNG_KERNEL_TRACEPOINT);
+                       if (!event) {
+                               printk(KERN_INFO "Unable to create event %s\n",
+                                       probe_desc->event_desc[i]->name);
+                       }
+               }
+       }
+}
+
+static
+void lttng_create_syscall_if_missing(struct lttng_enabler *enabler)
+{
+       int ret;
+
+       ret = lttng_syscalls_register(enabler->chan, NULL);
+       WARN_ON_ONCE(ret);
+}
+
+/*
+ * Create struct lttng_event if it is missing and present in the list of
+ * tracepoint probes.
+ * Should be called with sessions mutex held.
+ */
+static
+void lttng_create_event_if_missing(struct lttng_enabler *enabler)
+{
+       switch (enabler->event_param.instrumentation) {
+       case LTTNG_KERNEL_TRACEPOINT:
+               lttng_create_tracepoint_if_missing(enabler);
+               break;
+       case LTTNG_KERNEL_SYSCALL:
+               lttng_create_syscall_if_missing(enabler);
+               break;
+       default:
+               WARN_ON_ONCE(1);
+               break;
+       }
+}
+
+/*
+ * Create events associated with an enabler (if not already present),
+ * and add backward reference from the event to the enabler.
+ * Should be called with sessions mutex held.
+ */
+static
+int lttng_enabler_ref_events(struct lttng_enabler *enabler)
+{
+       struct lttng_session *session = enabler->chan->session;
+       struct lttng_event *event;
+
+       /* First ensure that probe events are created for this enabler. */
+       lttng_create_event_if_missing(enabler);
+
+       /* For each event matching enabler in session event list. */
+       list_for_each_entry(event, &session->events, list) {
+               struct lttng_enabler_ref *enabler_ref;
+
+               if (!lttng_event_match_enabler(event, enabler))
+                       continue;
+               enabler_ref = lttng_event_enabler_ref(event, enabler);
+               if (!enabler_ref) {
+                       /*
+                        * If no backward ref, create it.
+                        * Add backward ref from event to enabler.
+                        */
+                       enabler_ref = kzalloc(sizeof(*enabler_ref), GFP_KERNEL);
+                       if (!enabler_ref)
+                               return -ENOMEM;
+                       enabler_ref->ref = enabler;
+                       list_add(&enabler_ref->node,
+                               &event->enablers_ref_head);
+               }
+
+               /*
+                * Link filter bytecodes if not linked yet.
+                */
+               lttng_enabler_event_link_bytecode(event, enabler);
+
+               /* TODO: merge event context. */
+       }
+       return 0;
+}
+
+/*
+ * Called at module load: connect the probe on all enablers matching
+ * this event.
+ * Called with sessions lock held.
+ */
+int lttng_fix_pending_events(void)
+{
+       struct lttng_session *session;
+
+       list_for_each_entry(session, &sessions, list)
+               lttng_session_lazy_sync_enablers(session);
+       return 0;
+}
+
+struct lttng_enabler *lttng_enabler_create(enum lttng_enabler_type type,
+               struct lttng_kernel_event *event_param,
+               struct lttng_channel *chan)
+{
+       struct lttng_enabler *enabler;
+
+       enabler = kzalloc(sizeof(*enabler), GFP_KERNEL);
+       if (!enabler)
+               return NULL;
+       enabler->type = type;
+       INIT_LIST_HEAD(&enabler->filter_bytecode_head);
+       memcpy(&enabler->event_param, event_param,
+               sizeof(enabler->event_param));
+       enabler->chan = chan;
+       /* ctx left NULL */
+       enabler->enabled = 0;
+       enabler->evtype = LTTNG_TYPE_ENABLER;
+       mutex_lock(&sessions_mutex);
+       list_add(&enabler->node, &enabler->chan->session->enablers_head);
+       lttng_session_lazy_sync_enablers(enabler->chan->session);
+       mutex_unlock(&sessions_mutex);
+       return enabler;
+}
+
+int lttng_enabler_enable(struct lttng_enabler *enabler)
+{
+       mutex_lock(&sessions_mutex);
+       enabler->enabled = 1;
+       lttng_session_lazy_sync_enablers(enabler->chan->session);
+       mutex_unlock(&sessions_mutex);
+       return 0;
+}
+
+int lttng_enabler_disable(struct lttng_enabler *enabler)
+{
+       mutex_lock(&sessions_mutex);
+       enabler->enabled = 0;
+       lttng_session_lazy_sync_enablers(enabler->chan->session);
+       mutex_unlock(&sessions_mutex);
+       return 0;
+}
+
+int lttng_enabler_attach_bytecode(struct lttng_enabler *enabler,
+               struct lttng_kernel_filter_bytecode __user *bytecode)
+{
+       struct lttng_filter_bytecode_node *bytecode_node;
+       uint32_t bytecode_len;
+       int ret;
+
+       ret = get_user(bytecode_len, &bytecode->len);
+       if (ret)
+               return ret;
+       bytecode_node = kzalloc(sizeof(*bytecode_node) + bytecode_len,
+                       GFP_KERNEL);
+       if (!bytecode_node)
+               return -ENOMEM;
+       ret = copy_from_user(&bytecode_node->bc, bytecode,
+               sizeof(*bytecode) + bytecode_len);
+       if (ret)
+               goto error_free;
+       bytecode_node->enabler = enabler;
+       /* Enforce length based on allocated size */
+       bytecode_node->bc.len = bytecode_len;
+       list_add_tail(&bytecode_node->node, &enabler->filter_bytecode_head);
+       lttng_session_lazy_sync_enablers(enabler->chan->session);
+       return 0;
+
+error_free:
+       kfree(bytecode_node);
+       return ret;
+}
+
+int lttng_enabler_attach_context(struct lttng_enabler *enabler,
+               struct lttng_kernel_context *context_param)
+{
+       return -ENOSYS;
+}
+
+static
+void lttng_enabler_destroy(struct lttng_enabler *enabler)
+{
+       struct lttng_filter_bytecode_node *filter_node, *tmp_filter_node;
+
+       /* Destroy filter bytecode */
+       list_for_each_entry_safe(filter_node, tmp_filter_node,
+                       &enabler->filter_bytecode_head, node) {
+               kfree(filter_node);
+       }
+
+       /* Destroy contexts */
+       lttng_destroy_context(enabler->ctx);
+
+       list_del(&enabler->node);
+       kfree(enabler);
+}
+
+/*
+ * lttng_session_sync_enablers should be called just before starting a
+ * session.
+ * Should be called with sessions mutex held.
+ */
+static
+void lttng_session_sync_enablers(struct lttng_session *session)
+{
+       struct lttng_enabler *enabler;
+       struct lttng_event *event;
+
+       list_for_each_entry(enabler, &session->enablers_head, node)
+               lttng_enabler_ref_events(enabler);
+       /*
+        * For each event, if at least one of its enablers is enabled,
+        * and its channel and session transient states are enabled, we
+        * enable the event, else we disable it.
+        */
+       list_for_each_entry(event, &session->events, list) {
+               struct lttng_enabler_ref *enabler_ref;
+               struct lttng_bytecode_runtime *runtime;
+               int enabled = 0, has_enablers_without_bytecode = 0;
+
+               switch (event->instrumentation) {
+               case LTTNG_KERNEL_TRACEPOINT:
+               case LTTNG_KERNEL_SYSCALL:
+                       /* Enable events */
+                       list_for_each_entry(enabler_ref,
+                                       &event->enablers_ref_head, node) {
+                               if (enabler_ref->ref->enabled) {
+                                       enabled = 1;
+                                       break;
+                               }
+                       }
+                       break;
+               default:
+                       /* Not handled with lazy sync. */
+                       continue;
+               }
+               /*
+                * Enabled state is based on union of enablers, with
+                * intesection of session and channel transient enable
+                * states.
+                */
+               enabled = enabled && session->tstate && event->chan->tstate;
+
+               ACCESS_ONCE(event->enabled) = enabled;
+               /*
+                * Sync tracepoint registration with event enabled
+                * state.
+                */
+               if (enabled) {
+                       register_event(event);
+               } else {
+                       _lttng_event_unregister(event);
+               }
+
+               /* Check if has enablers without bytecode enabled */
+               list_for_each_entry(enabler_ref,
+                               &event->enablers_ref_head, node) {
+                       if (enabler_ref->ref->enabled
+                                       && list_empty(&enabler_ref->ref->filter_bytecode_head)) {
+                               has_enablers_without_bytecode = 1;
+                               break;
+                       }
+               }
+               event->has_enablers_without_bytecode =
+                       has_enablers_without_bytecode;
+
+               /* Enable filters */
+               list_for_each_entry(runtime,
+                               &event->bytecode_runtime_head, node)
+                       lttng_filter_sync_state(runtime);
        }
-       list_del(&event->list);
-       lttng_destroy_context(event->ctx);
-       kmem_cache_free(event_cache, event);
+}
+
+/*
+ * Apply enablers to session events, adding events to session if need
+ * be. It is required after each modification applied to an active
+ * session, and right before session "start".
+ * "lazy" sync means we only sync if required.
+ * Should be called with sessions mutex held.
+ */
+static
+void lttng_session_lazy_sync_enablers(struct lttng_session *session)
+{
+       /* We can skip if session is not active */
+       if (!session->active)
+               return;
+       lttng_session_sync_enablers(session);
 }
 
 /*
  * Serialize at most one packet worth of metadata into a metadata
  * channel.
- * We have exclusive access to our metadata buffer (protected by the
- * sessions_mutex), so we can do racy operations such as looking for
- * remaining space left in packet and write, since mutual exclusion
- * protects us from concurrent writes.
+ * We grab the metadata cache mutex to get exclusive access to our metadata
+ * buffer and to the metadata cache. Exclusive access to the metadata buffer
+ * allows us to do racy operations such as looking for remaining space left in
+ * packet and write, since mutual exclusion protects us from concurrent writes.
+ * Mutual exclusion on the metadata cache allow us to read the cache content
+ * without racing against reallocation of the cache by updates.
  * Returns the number of bytes written in the channel, 0 if no data
  * was written and a negative value on error.
  */
@@ -599,17 +1583,27 @@ int lttng_metadata_output_channel(struct lttng_metadata_stream *stream,
        size_t len, reserve_len;
 
        /*
-        * Ensure we support mutiple get_next / put sequences followed
-        * by put_next.
+        * Ensure we support mutiple get_next / put sequences followed by
+        * put_next. The metadata cache lock protects reading the metadata
+        * cache. It can indeed be read concurrently by "get_next_subbuf" and
+        * "flush" operations on the buffer invoked by different processes.
+        * Moreover, since the metadata cache memory can be reallocated, we
+        * need to have exclusive access against updates even though we only
+        * read it.
         */
+       mutex_lock(&stream->metadata_cache->lock);
        WARN_ON(stream->metadata_in < stream->metadata_out);
        if (stream->metadata_in != stream->metadata_out)
-               return 0;
+               goto end;
+
+       /* Metadata regenerated, change the version. */
+       if (stream->metadata_cache->version != stream->version)
+               stream->version = stream->metadata_cache->version;
 
        len = stream->metadata_cache->metadata_written -
                stream->metadata_in;
        if (!len)
-               return 0;
+               goto end;
        reserve_len = min_t(size_t,
                        stream->transport->ops.packet_avail_size(chan),
                        len);
@@ -631,12 +1625,15 @@ int lttng_metadata_output_channel(struct lttng_metadata_stream *stream,
        ret = reserve_len;
 
 end:
+       mutex_unlock(&stream->metadata_cache->lock);
        return ret;
 }
 
 /*
  * Write the metadata to the metadata cache.
  * Must be called with sessions_mutex held.
+ * The metadata cache lock protects us from concurrent read access from
+ * thread outputting metadata content to ring buffer.
  */
 int lttng_metadata_printf(struct lttng_session *session,
                          const char *fmt, ...)
@@ -655,6 +1652,7 @@ int lttng_metadata_printf(struct lttng_session *session,
                return -ENOMEM;
 
        len = strlen(str);
+       mutex_lock(&session->metadata_cache->lock);
        if (session->metadata_cache->metadata_written + len >
                        session->metadata_cache->cache_alloc) {
                char *tmp_cache_realloc;
@@ -663,10 +1661,16 @@ int lttng_metadata_printf(struct lttng_session *session,
                tmp_cache_alloc_size = max_t(unsigned int,
                                session->metadata_cache->cache_alloc + len,
                                session->metadata_cache->cache_alloc << 1);
-               tmp_cache_realloc = krealloc(session->metadata_cache->data,
-                               tmp_cache_alloc_size, GFP_KERNEL);
+               tmp_cache_realloc = lttng_vzalloc(tmp_cache_alloc_size);
                if (!tmp_cache_realloc)
                        goto err;
+               if (session->metadata_cache->data) {
+                       memcpy(tmp_cache_realloc,
+                               session->metadata_cache->data,
+                               session->metadata_cache->cache_alloc);
+                       vfree(session->metadata_cache->data);
+               }
+
                session->metadata_cache->cache_alloc = tmp_cache_alloc_size;
                session->metadata_cache->data = tmp_cache_realloc;
        }
@@ -674,6 +1678,7 @@ int lttng_metadata_printf(struct lttng_session *session,
                        session->metadata_cache->metadata_written,
                        str, len);
        session->metadata_cache->metadata_written += len;
+       mutex_unlock(&session->metadata_cache->lock);
        kfree(str);
 
        list_for_each_entry(stream, &session->metadata_cache->metadata_stream, list)
@@ -682,23 +1687,349 @@ int lttng_metadata_printf(struct lttng_session *session,
        return 0;
 
 err:
+       mutex_unlock(&session->metadata_cache->lock);
        kfree(str);
        return -ENOMEM;
 }
 
+static
+int print_tabs(struct lttng_session *session, size_t nesting)
+{
+       size_t i;
+
+       for (i = 0; i < nesting; i++) {
+               int ret;
+
+               ret = lttng_metadata_printf(session, "  ");
+               if (ret) {
+                       return ret;
+               }
+       }
+       return 0;
+}
+
+/*
+ * Must be called with sessions_mutex held.
+ */
+static
+int _lttng_struct_type_statedump(struct lttng_session *session,
+               const struct lttng_type *type,
+               size_t nesting)
+{
+       int ret;
+       uint32_t i, nr_fields;
+
+       ret = print_tabs(session, nesting);
+       if (ret)
+               return ret;
+       ret = lttng_metadata_printf(session,
+               "struct {\n");
+       if (ret)
+               return ret;
+       nr_fields = type->u._struct.nr_fields;
+       for (i = 0; i < nr_fields; i++) {
+               const struct lttng_event_field *iter_field;
+
+               iter_field = &type->u._struct.fields[i];
+               ret = _lttng_field_statedump(session, iter_field, nesting + 1);
+               if (ret)
+                       return ret;
+       }
+       ret = print_tabs(session, nesting);
+       if (ret)
+               return ret;
+       ret = lttng_metadata_printf(session,
+               "}");
+       return ret;
+}
+
+/*
+ * Must be called with sessions_mutex held.
+ */
+static
+int _lttng_struct_statedump(struct lttng_session *session,
+               const struct lttng_event_field *field,
+               size_t nesting)
+{
+       int ret;
+
+       ret = _lttng_struct_type_statedump(session,
+                       &field->type, nesting);
+       if (ret)
+               return ret;
+       ret = lttng_metadata_printf(session,
+               "_%s;\n",
+               field->name);
+       return ret;
+}
+
+/*
+ * Must be called with sessions_mutex held.
+ */
+static
+int _lttng_variant_type_statedump(struct lttng_session *session,
+               const struct lttng_type *type,
+               size_t nesting)
+{
+       int ret;
+       uint32_t i, nr_choices;
+
+       ret = print_tabs(session, nesting);
+       if (ret)
+               return ret;
+       ret = lttng_metadata_printf(session,
+               "variant <_%s> {\n",
+               type->u.variant.tag_name);
+       if (ret)
+               return ret;
+       nr_choices = type->u.variant.nr_choices;
+       for (i = 0; i < nr_choices; i++) {
+               const struct lttng_event_field *iter_field;
+
+               iter_field = &type->u.variant.choices[i];
+               ret = _lttng_field_statedump(session, iter_field, nesting + 1);
+               if (ret)
+                       return ret;
+       }
+       ret = print_tabs(session, nesting);
+       if (ret)
+               return ret;
+       ret = lttng_metadata_printf(session,
+               "}");
+       return ret;
+}
+
+/*
+ * Must be called with sessions_mutex held.
+ */
+static
+int _lttng_variant_statedump(struct lttng_session *session,
+               const struct lttng_event_field *field,
+               size_t nesting)
+{
+       int ret;
+
+       ret = _lttng_variant_type_statedump(session,
+                       &field->type, nesting);
+       if (ret)
+               return ret;
+       ret = lttng_metadata_printf(session,
+               "_%s;\n",
+               field->name);
+       return ret;
+}
+
+/*
+ * Must be called with sessions_mutex held.
+ */
+static
+int _lttng_array_compound_statedump(struct lttng_session *session,
+               const struct lttng_event_field *field,
+               size_t nesting)
+{
+       int ret;
+       const struct lttng_type *elem_type;
+
+       /* Only array of structures and variants are currently supported. */
+       elem_type = field->type.u.array_compound.elem_type;
+       switch (elem_type->atype) {
+       case atype_struct:
+               ret = _lttng_struct_type_statedump(session, elem_type, nesting);
+               if (ret)
+                       return ret;
+               break;
+       case atype_variant:
+               ret = _lttng_variant_type_statedump(session, elem_type, nesting);
+               if (ret)
+                       return ret;
+               break;
+       default:
+               return -EINVAL;
+       }
+       ret = lttng_metadata_printf(session,
+               " _%s[%u];\n",
+               field->name,
+               field->type.u.array_compound.length);
+       return ret;
+}
+
+/*
+ * Must be called with sessions_mutex held.
+ */
+static
+int _lttng_sequence_compound_statedump(struct lttng_session *session,
+               const struct lttng_event_field *field,
+               size_t nesting)
+{
+       int ret;
+       const char *length_name;
+       const struct lttng_type *elem_type;
+
+       length_name = field->type.u.sequence_compound.length_name;
+
+       /* Only array of structures and variants are currently supported. */
+       elem_type = field->type.u.sequence_compound.elem_type;
+       switch (elem_type->atype) {
+       case atype_struct:
+               ret = _lttng_struct_type_statedump(session, elem_type, nesting);
+               if (ret)
+                       return ret;
+               break;
+       case atype_variant:
+               ret = _lttng_variant_type_statedump(session, elem_type, nesting);
+               if (ret)
+                       return ret;
+               break;
+       default:
+               return -EINVAL;
+       }
+       ret = lttng_metadata_printf(session,
+               " _%s[ _%s ];\n",
+               field->name,
+               length_name);
+       return ret;
+}
+
+/*
+ * Must be called with sessions_mutex held.
+ */
+static
+int _lttng_enum_statedump(struct lttng_session *session,
+               const struct lttng_event_field *field,
+               size_t nesting)
+{
+       const struct lttng_enum_desc *enum_desc;
+       const struct lttng_integer_type *container_type;
+       int ret;
+       unsigned int i, nr_entries;
+
+       enum_desc = field->type.u.basic.enumeration.desc;
+       container_type = &field->type.u.basic.enumeration.container_type;
+       nr_entries = enum_desc->nr_entries;
+
+       ret = print_tabs(session, nesting);
+       if (ret)
+               goto end;
+       ret = lttng_metadata_printf(session,
+               "enum : integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } {\n",
+               container_type->size,
+               container_type->alignment,
+               container_type->signedness,
+               (container_type->encoding == lttng_encode_none)
+                       ? "none"
+                       : (container_type->encoding == lttng_encode_UTF8)
+                               ? "UTF8"
+                               : "ASCII",
+               container_type->base,
+#if __BYTE_ORDER == __BIG_ENDIAN
+               container_type->reverse_byte_order ? " byte_order = le;" : ""
+#else
+               container_type->reverse_byte_order ? " byte_order = be;" : ""
+#endif
+               );
+       if (ret)
+               goto end;
+       /* Dump all entries */
+       for (i = 0; i < nr_entries; i++) {
+               const struct lttng_enum_entry *entry = &enum_desc->entries[i];
+               int j, len;
+
+               ret = print_tabs(session, nesting + 1);
+               if (ret)
+                       goto end;
+               ret = lttng_metadata_printf(session,
+                               "\"");
+               if (ret)
+                       goto end;
+               len = strlen(entry->string);
+               /* Escape the character '"' */
+               for (j = 0; j < len; j++) {
+                       char c = entry->string[j];
+
+                       switch (c) {
+                       case '"':
+                               ret = lttng_metadata_printf(session,
+                                               "\\\"");
+                               break;
+                       case '\\':
+                               ret = lttng_metadata_printf(session,
+                                               "\\\\");
+                               break;
+                       default:
+                               ret = lttng_metadata_printf(session,
+                                               "%c", c);
+                               break;
+                       }
+                       if (ret)
+                               goto end;
+               }
+               ret = lttng_metadata_printf(session, "\"");
+               if (ret)
+                       goto end;
+
+               if (entry->options.is_auto) {
+                       ret = lttng_metadata_printf(session, ",\n");
+                       if (ret)
+                               goto end;
+               } else {
+                       ret = lttng_metadata_printf(session,
+                                       " = ");
+                       if (ret)
+                               goto end;
+                       if (entry->start.signedness)
+                               ret = lttng_metadata_printf(session,
+                                       "%lld", (long long) entry->start.value);
+                       else
+                               ret = lttng_metadata_printf(session,
+                                       "%llu", entry->start.value);
+                       if (ret)
+                               goto end;
+                       if (entry->start.signedness == entry->end.signedness &&
+                                       entry->start.value
+                                               == entry->end.value) {
+                               ret = lttng_metadata_printf(session,
+                                       ",\n");
+                       } else {
+                               if (entry->end.signedness) {
+                                       ret = lttng_metadata_printf(session,
+                                               " ... %lld,\n",
+                                               (long long) entry->end.value);
+                               } else {
+                                       ret = lttng_metadata_printf(session,
+                                               " ... %llu,\n",
+                                               entry->end.value);
+                               }
+                       }
+                       if (ret)
+                               goto end;
+               }
+       }
+       ret = print_tabs(session, nesting);
+       if (ret)
+               goto end;
+       ret = lttng_metadata_printf(session, "} _%s;\n",
+                       field->name);
+end:
+       return ret;
+}
+
 /*
  * Must be called with sessions_mutex held.
  */
 static
 int _lttng_field_statedump(struct lttng_session *session,
-                        const struct lttng_event_field *field)
+               const struct lttng_event_field *field,
+               size_t nesting)
 {
        int ret = 0;
 
        switch (field->type.atype) {
        case atype_integer:
+               ret = print_tabs(session, nesting);
+               if (ret)
+                       return ret;
                ret = lttng_metadata_printf(session,
-                       "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s;\n",
+                       "integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s;\n",
                        field->type.u.basic.integer.size,
                        field->type.u.basic.integer.alignment,
                        field->type.u.basic.integer.signedness,
@@ -708,7 +2039,7 @@ int _lttng_field_statedump(struct lttng_session *session,
                                        ? "UTF8"
                                        : "ASCII",
                        field->type.u.basic.integer.base,
-#ifdef __BIG_ENDIAN
+#if __BYTE_ORDER == __BIG_ENDIAN
                        field->type.u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 #else
                        field->type.u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
@@ -716,18 +2047,29 @@ int _lttng_field_statedump(struct lttng_session *session,
                        field->name);
                break;
        case atype_enum:
-               ret = lttng_metadata_printf(session,
-                       "               %s _%s;\n",
-                       field->type.u.basic.enumeration.name,
-                       field->name);
+               ret = _lttng_enum_statedump(session, field, nesting);
                break;
        case atype_array:
        {
                const struct lttng_basic_type *elem_type;
 
                elem_type = &field->type.u.array.elem_type;
+               if (field->type.u.array.elem_alignment) {
+                       ret = print_tabs(session, nesting);
+                       if (ret)
+                               return ret;
+                       ret = lttng_metadata_printf(session,
+                       "struct { } align(%u) _%s_padding;\n",
+                                       field->type.u.array.elem_alignment * CHAR_BIT,
+                                       field->name);
+                       if (ret)
+                               return ret;
+               }
+               ret = print_tabs(session, nesting);
+               if (ret)
+                       return ret;
                ret = lttng_metadata_printf(session,
-                       "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[%u];\n",
+                       "integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[%u];\n",
                        elem_type->u.basic.integer.size,
                        elem_type->u.basic.integer.alignment,
                        elem_type->u.basic.integer.signedness,
@@ -737,7 +2079,7 @@ int _lttng_field_statedump(struct lttng_session *session,
                                        ? "UTF8"
                                        : "ASCII",
                        elem_type->u.basic.integer.base,
-#ifdef __BIG_ENDIAN
+#if __BYTE_ORDER == __BIG_ENDIAN
                        elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 #else
                        elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
@@ -752,8 +2094,11 @@ int _lttng_field_statedump(struct lttng_session *session,
 
                elem_type = &field->type.u.sequence.elem_type;
                length_type = &field->type.u.sequence.length_type;
+               ret = print_tabs(session, nesting);
+               if (ret)
+                       return ret;
                ret = lttng_metadata_printf(session,
-                       "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } __%s_length;\n",
+                       "integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } __%s_length;\n",
                        length_type->u.basic.integer.size,
                        (unsigned int) length_type->u.basic.integer.alignment,
                        length_type->u.basic.integer.signedness,
@@ -763,7 +2108,7 @@ int _lttng_field_statedump(struct lttng_session *session,
                                        ? "UTF8"
                                        : "ASCII"),
                        length_type->u.basic.integer.base,
-#ifdef __BIG_ENDIAN
+#if __BYTE_ORDER == __BIG_ENDIAN
                        length_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 #else
                        length_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
@@ -772,8 +2117,22 @@ int _lttng_field_statedump(struct lttng_session *session,
                if (ret)
                        return ret;
 
+               if (field->type.u.sequence.elem_alignment) {
+                       ret = print_tabs(session, nesting);
+                       if (ret)
+                               return ret;
+                       ret = lttng_metadata_printf(session,
+                       "struct { } align(%u) _%s_padding;\n",
+                                       field->type.u.sequence.elem_alignment * CHAR_BIT,
+                                       field->name);
+                       if (ret)
+                               return ret;
+               }
+               ret = print_tabs(session, nesting);
+               if (ret)
+                       return ret;
                ret = lttng_metadata_printf(session,
-                       "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[ __%s_length ];\n",
+                       "integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[ __%s_length ];\n",
                        elem_type->u.basic.integer.size,
                        (unsigned int) elem_type->u.basic.integer.alignment,
                        elem_type->u.basic.integer.signedness,
@@ -783,7 +2142,7 @@ int _lttng_field_statedump(struct lttng_session *session,
                                        ? "UTF8"
                                        : "ASCII"),
                        elem_type->u.basic.integer.base,
-#ifdef __BIG_ENDIAN
+#if __BYTE_ORDER == __BIG_ENDIAN
                        elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 #else
                        elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
@@ -795,12 +2154,28 @@ int _lttng_field_statedump(struct lttng_session *session,
 
        case atype_string:
                /* Default encoding is UTF8 */
+               ret = print_tabs(session, nesting);
+               if (ret)
+                       return ret;
                ret = lttng_metadata_printf(session,
-                       "               string%s _%s;\n",
+                       "string%s _%s;\n",
                        field->type.u.basic.string.encoding == lttng_encode_ASCII ?
                                " { encoding = ASCII; }" : "",
                        field->name);
                break;
+       case atype_struct:
+               ret = _lttng_struct_statedump(session, field, nesting);
+               break;
+       case atype_array_compound:
+               ret = _lttng_array_compound_statedump(session, field, nesting);
+               break;
+       case atype_sequence_compound:
+               ret = _lttng_sequence_compound_statedump(session, field, nesting);
+               break;
+       case atype_variant:
+               ret = _lttng_variant_statedump(session, field, nesting);
+               break;
+
        default:
                WARN_ON_ONCE(1);
                return -EINVAL;
@@ -820,7 +2195,7 @@ int _lttng_context_metadata_statedump(struct lttng_session *session,
        for (i = 0; i < ctx->nr_fields; i++) {
                const struct lttng_ctx_field *field = &ctx->fields[i];
 
-               ret = _lttng_field_statedump(session, &field->event_field);
+               ret = _lttng_field_statedump(session, &field->event_field, 2);
                if (ret)
                        return ret;
        }
@@ -838,7 +2213,7 @@ int _lttng_fields_metadata_statedump(struct lttng_session *session,
        for (i = 0; i < desc->nr_fields; i++) {
                const struct lttng_event_field *field = &desc->fields[i];
 
-               ret = _lttng_field_statedump(session, field);
+               ret = _lttng_field_statedump(session, field, 2);
                if (ret)
                        return ret;
        }
@@ -976,6 +2351,7 @@ int _lttng_stream_packet_context_declare(struct lttng_session *session)
                "       uint64_clock_monotonic_t timestamp_end;\n"
                "       uint64_t content_size;\n"
                "       uint64_t packet_size;\n"
+               "       uint64_t packet_seq_num;\n"
                "       unsigned long events_discarded;\n"
                "       uint32_t cpu_id;\n"
                "};\n\n"
@@ -1032,25 +2408,36 @@ int _lttng_event_header_declare(struct lttng_session *session)
  * taken at start of trace.
  * Yes, this is only an approximation. Yes, we can (and will) do better
  * in future versions.
+ * This function may return a negative offset. It may happen if the
+ * system sets the REALTIME clock to 0 after boot.
  */
 static
-uint64_t measure_clock_offset(void)
+int64_t measure_clock_offset(void)
 {
-       uint64_t offset, monotonic[2], realtime;
+       uint64_t monotonic_avg, monotonic[2], realtime;
+       uint64_t tcf = trace_clock_freq();
+       int64_t offset;
        struct timespec rts = { 0, 0 };
        unsigned long flags;
 
        /* Disable interrupts to increase correlation precision. */
        local_irq_save(flags);
        monotonic[0] = trace_clock_read64();
-       getnstimeofday(&rts);      
+       getnstimeofday(&rts);
        monotonic[1] = trace_clock_read64();
        local_irq_restore(flags);
 
-       offset = (monotonic[0] + monotonic[1]) >> 1;
-       realtime = (uint64_t) rts.tv_sec * NSEC_PER_SEC;
-       realtime += rts.tv_nsec;
-       offset = realtime - offset;
+       monotonic_avg = (monotonic[0] + monotonic[1]) >> 1;
+       realtime = (uint64_t) rts.tv_sec * tcf;
+       if (tcf == NSEC_PER_SEC) {
+               realtime += rts.tv_nsec;
+       } else {
+               uint64_t n = rts.tv_nsec * tcf;
+
+               do_div(n, NSEC_PER_SEC);
+               realtime += n;
+       }
+       offset = (int64_t) realtime - monotonic_avg;
        return offset;
 }
 
@@ -1097,6 +2484,7 @@ int _lttng_session_metadata_statedump(struct lttng_session *session)
                "               uint32_t magic;\n"
                "               uint8_t  uuid[16];\n"
                "               uint32_t stream_id;\n"
+               "               uint64_t stream_instance_id;\n"
                "       };\n"
                "};\n\n",
                lttng_alignof(uint8_t) * CHAR_BIT,
@@ -1108,7 +2496,7 @@ int _lttng_session_metadata_statedump(struct lttng_session *session)
                CTF_SPEC_MAJOR,
                CTF_SPEC_MINOR,
                uuid_s,
-#ifdef __BIG_ENDIAN
+#if __BYTE_ORDER == __BIG_ENDIAN
                "be"
 #else
                "le"
@@ -1142,8 +2530,8 @@ int _lttng_session_metadata_statedump(struct lttng_session *session)
 
        ret = lttng_metadata_printf(session,
                "clock {\n"
-               "       name = %s;\n",
-               "monotonic"
+               "       name = \"%s\";\n",
+               trace_clock_name()
                );
        if (ret)
                goto end;
@@ -1158,13 +2546,14 @@ int _lttng_session_metadata_statedump(struct lttng_session *session)
        }
 
        ret = lttng_metadata_printf(session,
-               "       description = \"Monotonic Clock\";\n"
+               "       description = \"%s\";\n"
                "       freq = %llu; /* Frequency, in Hz */\n"
                "       /* clock value offset from Epoch is: offset * (1/freq) */\n"
-               "       offset = %llu;\n"
+               "       offset = %lld;\n"
                "};\n\n",
+               trace_clock_description(),
                (unsigned long long) trace_clock_freq(),
-               (unsigned long long) measure_clock_offset()
+               (long long) measure_clock_offset()
                );
        if (ret)
                goto end;
@@ -1172,20 +2561,23 @@ int _lttng_session_metadata_statedump(struct lttng_session *session)
        ret = lttng_metadata_printf(session,
                "typealias integer {\n"
                "       size = 27; align = 1; signed = false;\n"
-               "       map = clock.monotonic.value;\n"
+               "       map = clock.%s.value;\n"
                "} := uint27_clock_monotonic_t;\n"
                "\n"
                "typealias integer {\n"
                "       size = 32; align = %u; signed = false;\n"
-               "       map = clock.monotonic.value;\n"
+               "       map = clock.%s.value;\n"
                "} := uint32_clock_monotonic_t;\n"
                "\n"
                "typealias integer {\n"
                "       size = 64; align = %u; signed = false;\n"
-               "       map = clock.monotonic.value;\n"
+               "       map = clock.%s.value;\n"
                "} := uint64_clock_monotonic_t;\n\n",
+               trace_clock_name(),
                lttng_alignof(uint32_t) * CHAR_BIT,
-               lttng_alignof(uint64_t) * CHAR_BIT
+               trace_clock_name(),
+               lttng_alignof(uint64_t) * CHAR_BIT,
+               trace_clock_name()
                );
        if (ret)
                goto end;
@@ -1254,19 +2646,193 @@ void lttng_transport_unregister(struct lttng_transport *transport)
 }
 EXPORT_SYMBOL_GPL(lttng_transport_unregister);
 
+#if (defined(CONFIG_HOTPLUG_CPU) && (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)))
+
+enum cpuhp_state lttng_hp_prepare;
+enum cpuhp_state lttng_hp_online;
+
+static int lttng_hotplug_prepare(unsigned int cpu, struct hlist_node *node)
+{
+       struct lttng_cpuhp_node *lttng_node;
+
+       lttng_node = container_of(node, struct lttng_cpuhp_node, node);
+       switch (lttng_node->component) {
+       case LTTNG_RING_BUFFER_FRONTEND:
+               return 0;
+       case LTTNG_RING_BUFFER_BACKEND:
+               return lttng_cpuhp_rb_backend_prepare(cpu, lttng_node);
+       case LTTNG_RING_BUFFER_ITER:
+               return 0;
+       case LTTNG_CONTEXT_PERF_COUNTERS:
+               return 0;
+       default:
+               return -EINVAL;
+       }
+}
+
+static int lttng_hotplug_dead(unsigned int cpu, struct hlist_node *node)
+{
+       struct lttng_cpuhp_node *lttng_node;
+
+       lttng_node = container_of(node, struct lttng_cpuhp_node, node);
+       switch (lttng_node->component) {
+       case LTTNG_RING_BUFFER_FRONTEND:
+               return lttng_cpuhp_rb_frontend_dead(cpu, lttng_node);
+       case LTTNG_RING_BUFFER_BACKEND:
+               return 0;
+       case LTTNG_RING_BUFFER_ITER:
+               return 0;
+       case LTTNG_CONTEXT_PERF_COUNTERS:
+               return lttng_cpuhp_perf_counter_dead(cpu, lttng_node);
+       default:
+               return -EINVAL;
+       }
+}
+
+static int lttng_hotplug_online(unsigned int cpu, struct hlist_node *node)
+{
+       struct lttng_cpuhp_node *lttng_node;
+
+       lttng_node = container_of(node, struct lttng_cpuhp_node, node);
+       switch (lttng_node->component) {
+       case LTTNG_RING_BUFFER_FRONTEND:
+               return lttng_cpuhp_rb_frontend_online(cpu, lttng_node);
+       case LTTNG_RING_BUFFER_BACKEND:
+               return 0;
+       case LTTNG_RING_BUFFER_ITER:
+               return lttng_cpuhp_rb_iter_online(cpu, lttng_node);
+       case LTTNG_CONTEXT_PERF_COUNTERS:
+               return lttng_cpuhp_perf_counter_online(cpu, lttng_node);
+       default:
+               return -EINVAL;
+       }
+}
+
+static int lttng_hotplug_offline(unsigned int cpu, struct hlist_node *node)
+{
+       struct lttng_cpuhp_node *lttng_node;
+
+       lttng_node = container_of(node, struct lttng_cpuhp_node, node);
+       switch (lttng_node->component) {
+       case LTTNG_RING_BUFFER_FRONTEND:
+               return lttng_cpuhp_rb_frontend_offline(cpu, lttng_node);
+       case LTTNG_RING_BUFFER_BACKEND:
+               return 0;
+       case LTTNG_RING_BUFFER_ITER:
+               return 0;
+       case LTTNG_CONTEXT_PERF_COUNTERS:
+               return 0;
+       default:
+               return -EINVAL;
+       }
+}
+
+static int __init lttng_init_cpu_hotplug(void)
+{
+       int ret;
+
+       ret = cpuhp_setup_state_multi(CPUHP_BP_PREPARE_DYN, "lttng:prepare",
+                       lttng_hotplug_prepare,
+                       lttng_hotplug_dead);
+       if (ret < 0) {
+               return ret;
+       }
+       lttng_hp_prepare = ret;
+       lttng_rb_set_hp_prepare(ret);
+
+       ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "lttng:online",
+                       lttng_hotplug_online,
+                       lttng_hotplug_offline);
+       if (ret < 0) {
+               cpuhp_remove_multi_state(lttng_hp_prepare);
+               lttng_hp_prepare = 0;
+               return ret;
+       }
+       lttng_hp_online = ret;
+       lttng_rb_set_hp_online(ret);
+
+       return 0;
+}
+
+static void __exit lttng_exit_cpu_hotplug(void)
+{
+       lttng_rb_set_hp_online(0);
+       cpuhp_remove_multi_state(lttng_hp_online);
+       lttng_rb_set_hp_prepare(0);
+       cpuhp_remove_multi_state(lttng_hp_prepare);
+}
+
+#else /* #if (CONFIG_HOTPLUG_CPU && (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))) */
+static int lttng_init_cpu_hotplug(void)
+{
+       return 0;
+}
+static void lttng_exit_cpu_hotplug(void)
+{
+}
+#endif /* #else #if (CONFIG_HOTPLUG_CPU && (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))) */
+
+
 static int __init lttng_events_init(void)
 {
        int ret;
 
+       ret = wrapper_lttng_fixup_sig(THIS_MODULE);
+       if (ret)
+               return ret;
+       ret = wrapper_get_pfnblock_flags_mask_init();
+       if (ret)
+               return ret;
+       ret = wrapper_get_pageblock_flags_mask_init();
+       if (ret)
+               return ret;
+       ret = lttng_probes_init();
+       if (ret)
+               return ret;
+       ret = lttng_context_init();
+       if (ret)
+               return ret;
+       ret = lttng_tracepoint_init();
+       if (ret)
+               goto error_tp;
        event_cache = KMEM_CACHE(lttng_event, 0);
-       if (!event_cache)
-               return -ENOMEM;
+       if (!event_cache) {
+               ret = -ENOMEM;
+               goto error_kmem;
+       }
        ret = lttng_abi_init();
        if (ret)
                goto error_abi;
+       ret = lttng_logger_init();
+       if (ret)
+               goto error_logger;
+       ret = lttng_init_cpu_hotplug();
+       if (ret)
+               goto error_hotplug;
+       printk(KERN_NOTICE "LTTng: Loaded modules v%s.%s.%s%s (%s)\n",
+               __stringify(LTTNG_MODULES_MAJOR_VERSION),
+               __stringify(LTTNG_MODULES_MINOR_VERSION),
+               __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION),
+               LTTNG_MODULES_EXTRAVERSION,
+               LTTNG_VERSION_NAME);
        return 0;
+
+error_hotplug:
+       lttng_logger_exit();
+error_logger:
+       lttng_abi_exit();
 error_abi:
        kmem_cache_destroy(event_cache);
+error_kmem:
+       lttng_tracepoint_exit();
+error_tp:
+       lttng_context_exit();
+       printk(KERN_NOTICE "LTTng: Failed to load modules v%s.%s.%s%s (%s)\n",
+               __stringify(LTTNG_MODULES_MAJOR_VERSION),
+               __stringify(LTTNG_MODULES_MINOR_VERSION),
+               __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION),
+               LTTNG_MODULES_EXTRAVERSION,
+               LTTNG_VERSION_NAME);
        return ret;
 }
 
@@ -1276,10 +2842,20 @@ static void __exit lttng_events_exit(void)
 {
        struct lttng_session *session, *tmpsession;
 
+       lttng_exit_cpu_hotplug();
+       lttng_logger_exit();
        lttng_abi_exit();
        list_for_each_entry_safe(session, tmpsession, &sessions, list)
                lttng_session_destroy(session);
        kmem_cache_destroy(event_cache);
+       lttng_tracepoint_exit();
+       lttng_context_exit();
+       printk(KERN_NOTICE "LTTng: Unloaded modules v%s.%s.%s%s (%s)\n",
+               __stringify(LTTNG_MODULES_MAJOR_VERSION),
+               __stringify(LTTNG_MODULES_MINOR_VERSION),
+               __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION),
+               LTTNG_MODULES_EXTRAVERSION,
+               LTTNG_VERSION_NAME);
 }
 
 module_exit(lttng_events_exit);
@@ -1289,4 +2865,5 @@ MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 MODULE_DESCRIPTION("LTTng Events");
 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
        __stringify(LTTNG_MODULES_MINOR_VERSION) "."
-       __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION));
+       __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
+       LTTNG_MODULES_EXTRAVERSION);
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