Fix: stream fd leaks on error
[lttng-ust.git] / liblttng-ust / lttng-ust-comm.c
index 0cf5ecd9687536be5fc7794c4bfeb28ed135a11f..708b9192f22b62b14985f8d7ffa3c7d423813d2d 100644 (file)
  */
 
 #define _LGPL_SOURCE
-#define _GNU_SOURCE
+#include <stddef.h>
+#include <stdint.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <dlfcn.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <errno.h>
 #include <signal.h>
 #include <limits.h>
 #include <urcu/uatomic.h>
-#include <urcu/futex.h>
+#include "futex.h"
 #include <urcu/compiler.h>
+#include <lttng/urcu/urcu-ust.h>
 
+#include <lttng/align.h>
 #include <lttng/ust-events.h>
 #include <lttng/ust-abi.h>
 #include <lttng/ust.h>
 #include "clock.h"
 #include "../libringbuffer/getcpu.h"
 #include "getenv.h"
+#include "ust-events-internal.h"
+
+/* Concatenate lttng ust shared library name with its major version number. */
+#define LTTNG_UST_LIB_SO_NAME "liblttng-ust.so." __ust_stringify(CONFIG_LTTNG_UST_LIBRARY_VERSION_MAJOR)
 
 /*
  * Has lttng ust comm constructor been called ?
@@ -82,6 +90,8 @@ static int initialized;
  *
  * ust_lock nests within the dynamic loader lock (within glibc) because
  * it is taken within the library constructor.
+ *
+ * The ust fd tracker lock nests within the ust_mutex.
  */
 static pthread_mutex_t ust_mutex = PTHREAD_MUTEX_INITIALIZER;
 
@@ -224,7 +234,11 @@ static sem_t constructor_wait;
 /*
  * Doing this for both the global and local sessiond.
  */
-static int sem_count = { 2 };
+enum {
+       sem_count_initial_value = 4,
+};
+
+static int sem_count = sem_count_initial_value;
 
 /*
  * Counting nesting within lttng-ust. Used to ensure that calling fork()
@@ -239,7 +253,7 @@ struct sock_info {
        const char *name;
        pthread_t ust_listener; /* listener thread */
        int root_handle;
-       int constructor_sem_posted;
+       int registration_done;
        int allowed;
        int global;
        int thread_active;
@@ -252,6 +266,9 @@ struct sock_info {
        char *wait_shm_mmap;
        /* Keep track of lazy state dump not performed yet. */
        int statedump_pending;
+       int initial_statedump_done;
+       /* Keep procname for statedump */
+       char procname[LTTNG_UST_ABI_PROCNAME_LEN];
 };
 
 /* Socket from app (connect) to session daemon (listen) for communication */
@@ -260,7 +277,8 @@ struct sock_info global_apps = {
        .global = 1,
 
        .root_handle = -1,
-       .allowed = 1,
+       .registration_done = 0,
+       .allowed = 0,
        .thread_active = 0,
 
        .sock_path = LTTNG_DEFAULT_RUNDIR "/" LTTNG_UST_SOCK_FILENAME,
@@ -270,6 +288,8 @@ struct sock_info global_apps = {
        .wait_shm_path = "/" LTTNG_UST_WAIT_FILENAME,
 
        .statedump_pending = 0,
+       .initial_statedump_done = 0,
+       .procname[0] = '\0'
 };
 
 /* TODO: allow global_apps_sock_path override */
@@ -278,6 +298,7 @@ struct sock_info local_apps = {
        .name = "local",
        .global = 0,
        .root_handle = -1,
+       .registration_done = 0,
        .allowed = 0,   /* Check setuid bit first */
        .thread_active = 0,
 
@@ -285,6 +306,8 @@ struct sock_info local_apps = {
        .notify_socket = -1,
 
        .statedump_pending = 0,
+       .initial_statedump_done = 0,
+       .procname[0] = '\0'
 };
 
 static int wait_poll_fallback;
@@ -299,6 +322,8 @@ static const char *cmd_name_mapping[] = {
        [ LTTNG_UST_REGISTER_DONE ] = "Registration Done",
        [ LTTNG_UST_TRACEPOINT_FIELD_LIST ] = "Create Tracepoint Field List",
 
+       [ LTTNG_UST_EVENT_NOTIFIER_GROUP_CREATE ] = "Create event notifier group",
+
        /* Session FD commands */
        [ LTTNG_UST_CHANNEL ] = "Create Channel",
        [ LTTNG_UST_SESSION_START ] = "Start Session",
@@ -323,6 +348,16 @@ static const char *cmd_name_mapping[] = {
        /* Event FD commands */
        [ LTTNG_UST_FILTER ] = "Create Filter",
        [ LTTNG_UST_EXCLUSION ] = "Add exclusions to event",
+
+       /* Event notifier group commands */
+       [ LTTNG_UST_EVENT_NOTIFIER_CREATE ] = "Create event notifier",
+
+       /* Session and event notifier group commands */
+       [ LTTNG_UST_COUNTER ] = "Create Counter",
+
+       /* Counter commands */
+       [ LTTNG_UST_COUNTER_GLOBAL ] = "Create Counter Global",
+       [ LTTNG_UST_COUNTER_CPU ] = "Create Counter CPU",
 };
 
 static const char *str_timeout;
@@ -338,6 +373,12 @@ extern void lttng_ring_buffer_client_overwrite_rt_exit(void);
 extern void lttng_ring_buffer_client_discard_exit(void);
 extern void lttng_ring_buffer_client_discard_rt_exit(void);
 extern void lttng_ring_buffer_metadata_client_exit(void);
+extern void lttng_counter_client_percpu_32_modular_init(void);
+extern void lttng_counter_client_percpu_32_modular_exit(void);
+extern void lttng_counter_client_percpu_64_modular_init(void);
+extern void lttng_counter_client_percpu_64_modular_exit(void);
+
+static char *get_map_shm(struct sock_info *sock_info);
 
 ssize_t lttng_ust_read(int fd, void *buf, size_t len)
 {
@@ -394,8 +435,7 @@ void lttng_fixup_ust_mutex_nest_tls(void)
 static
 void lttng_fixup_urcu_bp_tls(void)
 {
-       rcu_read_lock();
-       rcu_read_unlock();
+       (void) lttng_ust_urcu_read_ongoing();
 }
 
 void lttng_ust_fixup_tls(void)
@@ -406,7 +446,13 @@ void lttng_ust_fixup_tls(void)
        lttng_fixup_nest_count_tls();
        lttng_fixup_procname_tls();
        lttng_fixup_ust_mutex_nest_tls();
+       lttng_ust_fixup_perf_counter_tls();
        lttng_ust_fixup_fd_tracker_tls();
+       lttng_fixup_cgroup_ns_tls();
+       lttng_fixup_ipc_ns_tls();
+       lttng_fixup_net_ns_tls();
+       lttng_fixup_time_ns_tls();
+       lttng_fixup_uts_ns_tls();
 }
 
 int lttng_get_notify_socket(void *owner)
@@ -416,6 +462,15 @@ int lttng_get_notify_socket(void *owner)
        return info->notify_socket;
 }
 
+
+LTTNG_HIDDEN
+char* lttng_ust_sockinfo_get_procname(void *owner)
+{
+       struct sock_info *info = owner;
+
+       return info->procname;
+}
+
 static
 void print_cmd(int cmd, int handle)
 {
@@ -430,25 +485,49 @@ void print_cmd(int cmd, int handle)
                lttng_ust_obj_get_name(handle), handle);
 }
 
+static
+int setup_global_apps(void)
+{
+       int ret = 0;
+       assert(!global_apps.wait_shm_mmap);
+
+       global_apps.wait_shm_mmap = get_map_shm(&global_apps);
+       if (!global_apps.wait_shm_mmap) {
+               WARN("Unable to get map shm for global apps. Disabling LTTng-UST global tracing.");
+               global_apps.allowed = 0;
+               ret = -EIO;
+               goto error;
+       }
+
+       global_apps.allowed = 1;
+       lttng_pthread_getname_np(global_apps.procname, LTTNG_UST_ABI_PROCNAME_LEN);
+error:
+       return ret;
+}
 static
 int setup_local_apps(void)
 {
+       int ret = 0;
        const char *home_dir;
        uid_t uid;
 
+       assert(!local_apps.wait_shm_mmap);
+
        uid = getuid();
        /*
         * Disallow per-user tracing for setuid binaries.
         */
        if (uid != geteuid()) {
                assert(local_apps.allowed == 0);
-               return 0;
+               ret = 0;
+               goto end;
        }
        home_dir = get_lttng_home_dir();
        if (!home_dir) {
                WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing.");
                assert(local_apps.allowed == 0);
-               return -ENOENT;
+               ret = -ENOENT;
+               goto end;
        }
        local_apps.allowed = 1;
        snprintf(local_apps.sock_path, PATH_MAX, "%s/%s/%s",
@@ -458,7 +537,18 @@ int setup_local_apps(void)
        snprintf(local_apps.wait_shm_path, PATH_MAX, "/%s-%u",
                LTTNG_UST_WAIT_FILENAME,
                uid);
-       return 0;
+
+       local_apps.wait_shm_mmap = get_map_shm(&local_apps);
+       if (!local_apps.wait_shm_mmap) {
+               WARN("Unable to get map shm for local apps. Disabling LTTng-UST per-user tracing.");
+               local_apps.allowed = 0;
+               ret = -EIO;
+               goto end;
+       }
+
+       lttng_pthread_getname_np(local_apps.procname, LTTNG_UST_ABI_PROCNAME_LEN);
+end:
+       return ret;
 }
 
 /*
@@ -583,48 +673,213 @@ int send_reply(int sock, struct ustcomm_ust_reply *lur)
 }
 
 static
-int handle_register_done(struct sock_info *sock_info)
+void decrement_sem_count(unsigned int count)
 {
        int ret;
 
-       if (sock_info->constructor_sem_posted)
-               return 0;
-       sock_info->constructor_sem_posted = 1;
+       assert(uatomic_read(&sem_count) >= count);
+
        if (uatomic_read(&sem_count) <= 0) {
-               return 0;
+               return;
        }
-       ret = uatomic_add_return(&sem_count, -1);
+
+       ret = uatomic_add_return(&sem_count, -count);
        if (ret == 0) {
                ret = sem_post(&constructor_wait);
                assert(!ret);
        }
+}
+
+static
+int handle_register_done(struct sock_info *sock_info)
+{
+       if (sock_info->registration_done)
+               return 0;
+       sock_info->registration_done = 1;
+
+       decrement_sem_count(1);
+       if (!sock_info->statedump_pending) {
+               sock_info->initial_statedump_done = 1;
+               decrement_sem_count(1);
+       }
+
+       return 0;
+}
+
+static
+int handle_register_failed(struct sock_info *sock_info)
+{
+       if (sock_info->registration_done)
+               return 0;
+       sock_info->registration_done = 1;
+       sock_info->initial_statedump_done = 1;
+
+       decrement_sem_count(2);
+
        return 0;
 }
 
 /*
  * Only execute pending statedump after the constructor semaphore has
- * been posted by each listener thread. This means statedump will only
- * be performed after the "registration done" command is received from
- * each session daemon the application is connected to.
+ * been posted by the current listener thread. This means statedump will
+ * only be performed after the "registration done" command is received
+ * from this thread's session daemon.
  *
  * This ensures we don't run into deadlock issues with the dynamic
  * loader mutex, which is held while the constructor is called and
  * waiting on the constructor semaphore. All operations requiring this
  * dynamic loader lock need to be postponed using this mechanism.
+ *
+ * In a scenario with two session daemons connected to the application,
+ * it is possible that the first listener thread which receives the
+ * registration done command issues its statedump while the dynamic
+ * loader lock is still held by the application constructor waiting on
+ * the semaphore. It will however be allowed to proceed when the
+ * second session daemon sends the registration done command to the
+ * second listener thread. This situation therefore does not produce
+ * a deadlock.
  */
 static
 void handle_pending_statedump(struct sock_info *sock_info)
 {
-       int ctor_passed = sock_info->constructor_sem_posted;
-
-       if (ctor_passed && sock_info->statedump_pending) {
+       if (sock_info->registration_done && sock_info->statedump_pending) {
                sock_info->statedump_pending = 0;
                pthread_mutex_lock(&ust_fork_mutex);
                lttng_handle_pending_statedump(sock_info);
                pthread_mutex_unlock(&ust_fork_mutex);
+
+               if (!sock_info->initial_statedump_done) {
+                       sock_info->initial_statedump_done = 1;
+                       decrement_sem_count(1);
+               }
+       }
+}
+
+static inline
+const char *bytecode_type_str(uint32_t cmd)
+{
+       switch (cmd) {
+       case LTTNG_UST_CAPTURE:
+               return "capture";
+       case LTTNG_UST_FILTER:
+               return "filter";
+       default:
+               abort();
        }
 }
 
+static
+int handle_bytecode_recv(struct sock_info *sock_info,
+               int sock, struct ustcomm_ust_msg *lum)
+{
+       struct lttng_ust_bytecode_node *bytecode;
+       enum lttng_ust_bytecode_node_type type;
+       const struct lttng_ust_objd_ops *ops;
+       uint32_t data_size, data_size_max, reloc_offset;
+       uint64_t seqnum;
+       ssize_t len;
+       int ret = 0;
+
+       switch (lum->cmd) {
+       case LTTNG_UST_FILTER:
+               type = LTTNG_UST_BYTECODE_NODE_TYPE_FILTER;
+               data_size = lum->u.filter.data_size;
+               data_size_max = FILTER_BYTECODE_MAX_LEN;
+               reloc_offset = lum->u.filter.reloc_offset;
+               seqnum = lum->u.filter.seqnum;
+               break;
+       case LTTNG_UST_CAPTURE:
+               type = LTTNG_UST_BYTECODE_NODE_TYPE_CAPTURE;
+               data_size = lum->u.capture.data_size;
+               data_size_max = CAPTURE_BYTECODE_MAX_LEN;
+               reloc_offset = lum->u.capture.reloc_offset;
+               seqnum = lum->u.capture.seqnum;
+               break;
+       default:
+               abort();
+       }
+
+       if (data_size > data_size_max) {
+               ERR("Bytecode %s data size is too large: %u bytes",
+                               bytecode_type_str(lum->cmd), data_size);
+               ret = -EINVAL;
+               goto end;
+       }
+
+       if (reloc_offset > data_size) {
+               ERR("Bytecode %s reloc offset %u is not within data",
+                               bytecode_type_str(lum->cmd), reloc_offset);
+               ret = -EINVAL;
+               goto end;
+       }
+
+       /* Allocate the structure AND the `data[]` field. */
+       bytecode = zmalloc(sizeof(*bytecode) + data_size);
+       if (!bytecode) {
+               ret = -ENOMEM;
+               goto end;
+       }
+
+       bytecode->bc.len = data_size;
+       bytecode->bc.reloc_offset = reloc_offset;
+       bytecode->bc.seqnum = seqnum;
+       bytecode->type = type;
+
+       len = ustcomm_recv_unix_sock(sock, bytecode->bc.data, bytecode->bc.len);
+       switch (len) {
+       case 0: /* orderly shutdown */
+               ret = 0;
+               goto error_free_bytecode;
+       default:
+               if (len == bytecode->bc.len) {
+                       DBG("Bytecode %s data received",
+                                       bytecode_type_str(lum->cmd));
+                       break;
+               } else if (len < 0) {
+                       DBG("Receive failed from lttng-sessiond with errno %d",
+                                       (int) -len);
+                       if (len == -ECONNRESET) {
+                               ERR("%s remote end closed connection",
+                                               sock_info->name);
+                               ret = len;
+                               goto error_free_bytecode;
+                       }
+                       ret = len;
+                       goto error_free_bytecode;
+               } else {
+                       DBG("Incorrect %s bytecode data message size: %zd",
+                                       bytecode_type_str(lum->cmd), len);
+                       ret = -EINVAL;
+                       goto error_free_bytecode;
+               }
+       }
+
+       ops = objd_ops(lum->handle);
+       if (!ops) {
+               ret = -ENOENT;
+               goto error_free_bytecode;
+       }
+
+       if (ops->cmd) {
+               ret = ops->cmd(lum->handle, lum->cmd,
+                       (unsigned long) bytecode,
+                       NULL, sock_info);
+               if (ret)
+                       goto error_free_bytecode;
+               /* don't free bytecode if everything went fine. */
+       } else {
+               ret = -ENOSYS;
+               goto error_free_bytecode;
+       }
+
+       goto end;
+
+error_free_bytecode:
+       free(bytecode);
+end:
+       return ret;
+}
+
 static
 int handle_message(struct sock_info *sock_info,
                int sock, struct ustcomm_ust_msg *lum)
@@ -662,76 +917,12 @@ int handle_message(struct sock_info *sock_info,
                else
                        ret = lttng_ust_objd_unref(lum->handle, 1);
                break;
+       case LTTNG_UST_CAPTURE:
        case LTTNG_UST_FILTER:
-       {
-               /* Receive filter data */
-               struct lttng_ust_filter_bytecode_node *bytecode;
-
-               if (lum->u.filter.data_size > FILTER_BYTECODE_MAX_LEN) {
-                       ERR("Filter data size is too large: %u bytes",
-                               lum->u.filter.data_size);
-                       ret = -EINVAL;
-                       goto error;
-               }
-
-               if (lum->u.filter.reloc_offset > lum->u.filter.data_size) {
-                       ERR("Filter reloc offset %u is not within data",
-                               lum->u.filter.reloc_offset);
-                       ret = -EINVAL;
-                       goto error;
-               }
-
-               bytecode = zmalloc(sizeof(*bytecode) + lum->u.filter.data_size);
-               if (!bytecode) {
-                       ret = -ENOMEM;
+               ret = handle_bytecode_recv(sock_info, sock, lum);
+               if (ret)
                        goto error;
-               }
-               len = ustcomm_recv_unix_sock(sock, bytecode->bc.data,
-                               lum->u.filter.data_size);
-               switch (len) {
-               case 0: /* orderly shutdown */
-                       ret = 0;
-                       free(bytecode);
-                       goto error;
-               default:
-                       if (len == lum->u.filter.data_size) {
-                               DBG("filter data received");
-                               break;
-                       } else if (len < 0) {
-                               DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
-                               if (len == -ECONNRESET) {
-                                       ERR("%s remote end closed connection", sock_info->name);
-                                       ret = len;
-                                       free(bytecode);
-                                       goto error;
-                               }
-                               ret = len;
-                               free(bytecode);
-                               goto error;
-                       } else {
-                               DBG("incorrect filter data message size: %zd", len);
-                               ret = -EINVAL;
-                               free(bytecode);
-                               goto error;
-                       }
-               }
-               bytecode->bc.len = lum->u.filter.data_size;
-               bytecode->bc.reloc_offset = lum->u.filter.reloc_offset;
-               bytecode->bc.seqnum = lum->u.filter.seqnum;
-               if (ops->cmd) {
-                       ret = ops->cmd(lum->handle, lum->cmd,
-                                       (unsigned long) bytecode,
-                                       &args, sock_info);
-                       if (ret) {
-                               free(bytecode);
-                       }
-                       /* don't free bytecode if everything went fine. */
-               } else {
-                       ret = -ENOSYS;
-                       free(bytecode);
-               }
                break;
-       }
        case LTTNG_UST_EXCLUSION:
        {
                /* Receive exclusion names */
@@ -794,6 +985,47 @@ int handle_message(struct sock_info *sock_info,
                }
                break;
        }
+       case LTTNG_UST_EVENT_NOTIFIER_GROUP_CREATE:
+       {
+               int event_notifier_notif_fd;
+
+               len = ustcomm_recv_event_notifier_notif_fd_from_sessiond(sock,
+                       &event_notifier_notif_fd);
+               switch (len) {
+               case 0: /* orderly shutdown */
+                       ret = 0;
+                       goto error;
+               case 1:
+                       break;
+               default:
+                       if (len < 0) {
+                               DBG("Receive failed from lttng-sessiond with errno %d",
+                                               (int) -len);
+                               if (len == -ECONNRESET) {
+                                       ERR("%s remote end closed connection",
+                                                       sock_info->name);
+                                       ret = len;
+                                       goto error;
+                               }
+                               ret = len;
+                               goto error;
+                       } else {
+                               DBG("Incorrect event notifier fd message size: %zd",
+                                               len);
+                               ret = -EINVAL;
+                               goto error;
+                       }
+               }
+               args.event_notifier_handle.event_notifier_notif_fd =
+                               event_notifier_notif_fd;
+               if (ops->cmd)
+                       ret = ops->cmd(lum->handle, lum->cmd,
+                                       (unsigned long) &lum->u,
+                                       &args, sock_info);
+               else
+                       ret = -ENOSYS;
+               break;
+       }
        case LTTNG_UST_CHANNEL:
        {
                void *chan_data;
@@ -833,24 +1065,54 @@ int handle_message(struct sock_info *sock_info,
                                        &args, sock_info);
                else
                        ret = -ENOSYS;
+               if (args.channel.wakeup_fd >= 0) {
+                       int close_ret;
+
+                       lttng_ust_lock_fd_tracker();
+                       close_ret = close(args.channel.wakeup_fd);
+                       lttng_ust_unlock_fd_tracker();
+                       args.channel.wakeup_fd = -1;
+                       if (close_ret)
+                               PERROR("close");
+               }
+               free(args.channel.chan_data);
                break;
        }
        case LTTNG_UST_STREAM:
        {
+               int close_ret;
+
                /* Receive shm_fd, wakeup_fd */
                ret = ustcomm_recv_stream_from_sessiond(sock,
-                       &lum->u.stream.len,
+                       NULL,
                        &args.stream.shm_fd,
                        &args.stream.wakeup_fd);
                if (ret) {
                        goto error;
                }
+
                if (ops->cmd)
                        ret = ops->cmd(lum->handle, lum->cmd,
                                        (unsigned long) &lum->u,
                                        &args, sock_info);
                else
                        ret = -ENOSYS;
+               if (args.stream.shm_fd >= 0) {
+                       lttng_ust_lock_fd_tracker();
+                       close_ret = close(args.stream.shm_fd);
+                       lttng_ust_unlock_fd_tracker();
+                       args.stream.shm_fd = -1;
+                       if (close_ret)
+                               PERROR("close");
+               }
+               if (args.stream.wakeup_fd >= 0) {
+                       lttng_ust_lock_fd_tracker();
+                       close_ret = close(args.stream.wakeup_fd);
+                       lttng_ust_unlock_fd_tracker();
+                       args.stream.wakeup_fd = -1;
+                       if (close_ret)
+                               PERROR("close");
+               }
                break;
        }
        case LTTNG_UST_CONTEXT:
@@ -911,6 +1173,121 @@ int handle_message(struct sock_info *sock_info,
                        ret = -ENOSYS;
                }
                break;
+       case LTTNG_UST_COUNTER:
+       {
+               void *counter_data;
+
+               len = ustcomm_recv_counter_from_sessiond(sock,
+                               &counter_data, lum->u.counter.len);
+               switch (len) {
+               case 0: /* orderly shutdown */
+                       ret = 0;
+                       goto error;
+               default:
+                       if (len == lum->u.counter.len) {
+                               DBG("counter data received");
+                               break;
+                       } else if (len < 0) {
+                               DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
+                               if (len == -ECONNRESET) {
+                                       ERR("%s remote end closed connection", sock_info->name);
+                                       ret = len;
+                                       goto error;
+                               }
+                               ret = len;
+                               goto error;
+                       } else {
+                               DBG("incorrect counter data message size: %zd", len);
+                               ret = -EINVAL;
+                               goto error;
+                       }
+               }
+               args.counter.counter_data = counter_data;
+               if (ops->cmd)
+                       ret = ops->cmd(lum->handle, lum->cmd,
+                                       (unsigned long) &lum->u,
+                                       &args, sock_info);
+               else
+                       ret = -ENOSYS;
+               break;
+       }
+       case LTTNG_UST_COUNTER_GLOBAL:
+       {
+               /* Receive shm_fd */
+               ret = ustcomm_recv_counter_shm_from_sessiond(sock,
+                       &args.counter_shm.shm_fd);
+               if (ret) {
+                       goto error;
+               }
+
+               if (ops->cmd)
+                       ret = ops->cmd(lum->handle, lum->cmd,
+                                       (unsigned long) &lum->u,
+                                       &args, sock_info);
+               else
+                       ret = -ENOSYS;
+               break;
+       }
+       case LTTNG_UST_COUNTER_CPU:
+       {
+               /* Receive shm_fd */
+               ret = ustcomm_recv_counter_shm_from_sessiond(sock,
+                       &args.counter_shm.shm_fd);
+               if (ret) {
+                       goto error;
+               }
+
+               if (ops->cmd)
+                       ret = ops->cmd(lum->handle, lum->cmd,
+                                       (unsigned long) &lum->u,
+                                       &args, sock_info);
+               else
+                       ret = -ENOSYS;
+               break;
+       }
+       case LTTNG_UST_EVENT_NOTIFIER_CREATE:
+       {
+               /* Receive struct lttng_ust_event_notifier */
+               struct lttng_ust_event_notifier event_notifier;
+
+               if (sizeof(event_notifier) != lum->u.event_notifier.len) {
+                       DBG("incorrect event notifier data message size: %u", lum->u.event_notifier.len);
+                       ret = -EINVAL;
+                       goto error;
+               }
+               len = ustcomm_recv_unix_sock(sock, &event_notifier, sizeof(event_notifier));
+               switch (len) {
+               case 0: /* orderly shutdown */
+                       ret = 0;
+                       goto error;
+               default:
+                       if (len == sizeof(event_notifier)) {
+                               DBG("event notifier data received");
+                               break;
+                       } else if (len < 0) {
+                               DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
+                               if (len == -ECONNRESET) {
+                                       ERR("%s remote end closed connection", sock_info->name);
+                                       ret = len;
+                                       goto error;
+                               }
+                               ret = len;
+                               goto error;
+                       } else {
+                               DBG("incorrect event notifier data message size: %zd", len);
+                               ret = -EINVAL;
+                               goto error;
+                       }
+               }
+               if (ops->cmd)
+                       ret = ops->cmd(lum->handle, lum->cmd,
+                                       (unsigned long) &event_notifier,
+                                       &args, sock_info);
+               else
+                       ret = -ENOSYS;
+               break;
+       }
+
        default:
                if (ops->cmd)
                        ret = ops->cmd(lum->handle, lum->cmd,
@@ -1030,7 +1407,8 @@ void cleanup_sock_info(struct sock_info *sock_info, int exiting)
                }
                sock_info->root_handle = -1;
        }
-       sock_info->constructor_sem_posted = 0;
+       sock_info->registration_done = 0;
+       sock_info->initial_statedump_done = 0;
 
        /*
         * wait_shm_mmap, socket and notify socket are used by listener
@@ -1059,7 +1437,7 @@ void cleanup_sock_info(struct sock_info *sock_info, int exiting)
        if (sock_info->wait_shm_mmap) {
                long page_size;
 
-               page_size = sysconf(_SC_PAGE_SIZE);
+               page_size = LTTNG_UST_PAGE_SIZE;
                if (page_size <= 0) {
                        if (!page_size) {
                                errno = EINVAL;
@@ -1301,25 +1679,23 @@ error:
 static
 void wait_for_sessiond(struct sock_info *sock_info)
 {
+       /* Use ust_lock to check if we should quit. */
        if (ust_lock()) {
                goto quit;
        }
        if (wait_poll_fallback) {
                goto error;
        }
-       if (!sock_info->wait_shm_mmap) {
-               sock_info->wait_shm_mmap = get_map_shm(sock_info);
-               if (!sock_info->wait_shm_mmap)
-                       goto error;
-       }
        ust_unlock();
 
+       assert(sock_info->wait_shm_mmap);
+
        DBG("Waiting for %s apps sessiond", sock_info->name);
        /* Wait for futex wakeup */
        if (uatomic_read((int32_t *) sock_info->wait_shm_mmap))
                goto end_wait;
 
-       while (futex_async((int32_t *) sock_info->wait_shm_mmap,
+       while (lttng_ust_futex_async((int32_t *) sock_info->wait_shm_mmap,
                        FUTEX_WAIT, 0, NULL, NULL, 0)) {
                switch (errno) {
                case EWOULDBLOCK:
@@ -1440,7 +1816,7 @@ restart:
                 * If we cannot find the sessiond daemon, don't delay
                 * constructor execution.
                 */
-               ret = handle_register_done(sock_info);
+               ret = handle_register_failed(sock_info);
                assert(!ret);
                ust_unlock();
                goto restart;
@@ -1494,7 +1870,7 @@ restart:
                 * If we cannot register to the sessiond daemon, don't
                 * delay constructor execution.
                 */
-               ret = handle_register_done(sock_info);
+               ret = handle_register_failed(sock_info);
                assert(!ret);
                ust_unlock();
                goto restart;
@@ -1523,7 +1899,7 @@ restart:
                 * If we cannot find the sessiond daemon, don't delay
                 * constructor execution.
                 */
-               ret = handle_register_done(sock_info);
+               ret = handle_register_failed(sock_info);
                assert(!ret);
                ust_unlock();
                goto restart;
@@ -1587,7 +1963,7 @@ restart:
                 * If we cannot register to the sessiond daemon, don't
                 * delay constructor execution.
                 */
-               ret = handle_register_done(sock_info);
+               ret = handle_register_failed(sock_info);
                assert(!ret);
                ust_unlock();
                goto restart;
@@ -1617,7 +1993,7 @@ restart:
                         * If we cannot register to the sessiond daemon, don't
                         * delay constructor execution.
                         */
-                       ret = handle_register_done(sock_info);
+                       ret = handle_register_failed(sock_info);
                        assert(!ret);
                        ust_unlock();
                        goto end;
@@ -1685,6 +2061,7 @@ void __attribute__((constructor)) lttng_ust_init(void)
        pthread_attr_t thread_attr;
        int timeout_mode;
        int ret;
+       void *handle;
 
        if (uatomic_xchg(&initialized, 1) == 1)
                return;
@@ -1698,6 +2075,26 @@ void __attribute__((constructor)) lttng_ust_init(void)
 
        lttng_ust_loaded = 1;
 
+       /*
+        * We need to ensure that the liblttng-ust library is not unloaded to avoid
+        * the unloading of code used by the ust_listener_threads as we can not
+        * reliably know when they exited. To do that, manually load
+        * liblttng-ust.so to increment the dynamic loader's internal refcount for
+        * this library so it never becomes zero, thus never gets unloaded from the
+        * address space of the process. Since we are already running in the
+        * constructor of the LTTNG_UST_LIB_SO_NAME library, calling dlopen will
+        * simply increment the refcount and no additionnal work is needed by the
+        * dynamic loader as the shared library is already loaded in the address
+        * space. As a safe guard, we use the RTLD_NODELETE flag to prevent
+        * unloading of the UST library if its refcount becomes zero (which should
+        * never happen). Do the return value check but discard the handle at the
+        * end of the function as it's not needed.
+        */
+       handle = dlopen(LTTNG_UST_LIB_SO_NAME, RTLD_LAZY | RTLD_NODELETE);
+       if (!handle) {
+               ERR("dlopen of liblttng-ust shared library (%s).", LTTNG_UST_LIB_SO_NAME);
+       }
+
        /*
         * We want precise control over the order in which we construct
         * our sub-libraries vs starting to receive commands from
@@ -1716,6 +2113,8 @@ void __attribute__((constructor)) lttng_ust_init(void)
        lttng_ring_buffer_client_overwrite_rt_init();
        lttng_ring_buffer_client_discard_init();
        lttng_ring_buffer_client_discard_rt_init();
+       lttng_counter_client_percpu_32_modular_init();
+       lttng_counter_client_percpu_64_modular_init();
        lttng_perf_counter_init();
        /*
         * Invoke ust malloc wrapper init before starting other threads.
@@ -1731,8 +2130,15 @@ void __attribute__((constructor)) lttng_ust_init(void)
                PERROR("sem_init");
        }
 
+       ret = setup_global_apps();
+       if (ret) {
+               assert(global_apps.allowed == 0);
+               DBG("global apps setup returned %d", ret);
+       }
+
        ret = setup_local_apps();
        if (ret) {
+               assert(local_apps.allowed == 0);
                DBG("local apps setup returned %d", ret);
        }
 
@@ -1756,14 +2162,18 @@ void __attribute__((constructor)) lttng_ust_init(void)
                ERR("pthread_attr_setdetachstate: %s", strerror(ret));
        }
 
-       pthread_mutex_lock(&ust_exit_mutex);
-       ret = pthread_create(&global_apps.ust_listener, &thread_attr,
-                       ust_listener_thread, &global_apps);
-       if (ret) {
-               ERR("pthread_create global: %s", strerror(ret));
+       if (global_apps.allowed) {
+               pthread_mutex_lock(&ust_exit_mutex);
+               ret = pthread_create(&global_apps.ust_listener, &thread_attr,
+                               ust_listener_thread, &global_apps);
+               if (ret) {
+                       ERR("pthread_create global: %s", strerror(ret));
+               }
+               global_apps.thread_active = 1;
+               pthread_mutex_unlock(&ust_exit_mutex);
+       } else {
+               handle_register_done(&global_apps);
        }
-       global_apps.thread_active = 1;
-       pthread_mutex_unlock(&ust_exit_mutex);
 
        if (local_apps.allowed) {
                pthread_mutex_lock(&ust_exit_mutex);
@@ -1834,6 +2244,7 @@ void lttng_ust_cleanup(int exiting)
        cleanup_sock_info(&global_apps, exiting);
        cleanup_sock_info(&local_apps, exiting);
        local_apps.allowed = 0;
+       global_apps.allowed = 0;
        /*
         * The teardown in this function all affect data structures
         * accessed under the UST lock by the listener thread. This
@@ -1849,11 +2260,13 @@ void lttng_ust_cleanup(int exiting)
        lttng_ring_buffer_client_overwrite_rt_exit();
        lttng_ring_buffer_client_overwrite_exit();
        lttng_ring_buffer_metadata_client_exit();
+       lttng_counter_client_percpu_32_modular_exit();
+       lttng_counter_client_percpu_64_modular_exit();
        lttng_ust_statedump_destroy();
        exit_tracepoint();
        if (!exiting) {
                /* Reinitialize values for fork */
-               sem_count = 2;
+               sem_count = sem_count_initial_value;
                lttng_ust_comm_should_quit = 0;
                initialized = 0;
        }
@@ -1911,6 +2324,35 @@ void __attribute__((destructor)) lttng_ust_exit(void)
        lttng_ust_cleanup(1);
 }
 
+static
+void ust_context_ns_reset(void)
+{
+       lttng_context_pid_ns_reset();
+       lttng_context_cgroup_ns_reset();
+       lttng_context_ipc_ns_reset();
+       lttng_context_mnt_ns_reset();
+       lttng_context_net_ns_reset();
+       lttng_context_user_ns_reset();
+       lttng_context_time_ns_reset();
+       lttng_context_uts_ns_reset();
+}
+
+static
+void ust_context_vuids_reset(void)
+{
+       lttng_context_vuid_reset();
+       lttng_context_veuid_reset();
+       lttng_context_vsuid_reset();
+}
+
+static
+void ust_context_vgids_reset(void)
+{
+       lttng_context_vgid_reset();
+       lttng_context_vegid_reset();
+       lttng_context_vsgid_reset();
+}
+
 /*
  * We exclude the worker threads across fork and clone (except
  * CLONE_VM), because these system calls only keep the forking thread
@@ -1944,7 +2386,11 @@ void ust_before_fork(sigset_t *save_sigset)
        pthread_mutex_lock(&ust_fork_mutex);
 
        ust_lock_nocheck();
-       rcu_bp_before_fork();
+       lttng_ust_urcu_before_fork();
+       if (lttng_ust_liburcu_bp_before_fork)
+               lttng_ust_liburcu_bp_before_fork();
+       lttng_ust_lock_fd_tracker();
+       lttng_perf_lock();
 }
 
 static void ust_after_fork_common(sigset_t *restore_sigset)
@@ -1952,6 +2398,8 @@ static void ust_after_fork_common(sigset_t *restore_sigset)
        int ret;
 
        DBG("process %d", getpid());
+       lttng_perf_unlock();
+       lttng_ust_unlock_fd_tracker();
        ust_unlock();
 
        pthread_mutex_unlock(&ust_fork_mutex);
@@ -1968,7 +2416,9 @@ void ust_after_fork_parent(sigset_t *restore_sigset)
        if (URCU_TLS(lttng_ust_nest_count))
                return;
        DBG("process %d", getpid());
-       rcu_bp_after_fork_parent();
+       lttng_ust_urcu_after_fork_parent();
+       if (lttng_ust_liburcu_bp_after_fork_parent)
+               lttng_ust_liburcu_bp_after_fork_parent();
        /* Release mutexes and reenable signals */
        ust_after_fork_common(restore_sigset);
 }
@@ -1986,16 +2436,77 @@ void ust_after_fork_child(sigset_t *restore_sigset)
 {
        if (URCU_TLS(lttng_ust_nest_count))
                return;
+       lttng_context_vpid_reset();
        lttng_context_vtid_reset();
+       lttng_context_procname_reset();
+       ust_context_ns_reset();
+       ust_context_vuids_reset();
+       ust_context_vgids_reset();
        DBG("process %d", getpid());
        /* Release urcu mutexes */
-       rcu_bp_after_fork_child();
+       lttng_ust_urcu_after_fork_child();
+       if (lttng_ust_liburcu_bp_after_fork_child)
+               lttng_ust_liburcu_bp_after_fork_child();
        lttng_ust_cleanup(0);
        /* Release mutexes and reenable signals */
        ust_after_fork_common(restore_sigset);
        lttng_ust_init();
 }
 
+void ust_after_setns(void)
+{
+       ust_context_ns_reset();
+       ust_context_vuids_reset();
+       ust_context_vgids_reset();
+}
+
+void ust_after_unshare(void)
+{
+       ust_context_ns_reset();
+       ust_context_vuids_reset();
+       ust_context_vgids_reset();
+}
+
+void ust_after_setuid(void)
+{
+       ust_context_vuids_reset();
+}
+
+void ust_after_seteuid(void)
+{
+       ust_context_vuids_reset();
+}
+
+void ust_after_setreuid(void)
+{
+       ust_context_vuids_reset();
+}
+
+void ust_after_setresuid(void)
+{
+       ust_context_vuids_reset();
+}
+
+void ust_after_setgid(void)
+{
+       ust_context_vgids_reset();
+}
+
+void ust_after_setegid(void)
+{
+       ust_context_vgids_reset();
+}
+
+void ust_after_setregid(void)
+{
+       ust_context_vgids_reset();
+}
+
+void ust_after_setresgid(void)
+{
+       ust_context_vgids_reset();
+}
+
 void lttng_ust_sockinfo_session_enabled(void *owner)
 {
        struct sock_info *sock_info = owner;
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