Fix: filter attach vs event enable race

[lttng-ust.git] / liblttng-ust / lttng-events.c

diff --git a/liblttng-ust/lttng-events.c b/liblttng-ust/lttng-events.c
index 915cffb744613c2973e599bf8a617673ad732b97..68c024c4647e9206f6b9bec37d17f63e40425be8 100644 (file)
--- a/liblttng-ust/lttng-events.c
+++ b/liblttng-ust/lttng-events.c
@@ -54,29 +54,23 @@
 #include "tracepoint-internal.h"
 #include "lttng-tracer.h"
 #include "lttng-tracer-core.h"
+#include "lttng-ust-baddr.h"
 #include "wait.h"
 #include "../libringbuffer/shm.h"
 #include "jhash.h"
 
 /*
- * The sessions mutex is the centralized mutex across UST tracing
- * control and probe registration. All operations within this file are
- * called by the communication thread, under ust_lock protection.
+ * All operations within this file are called by the communication
+ * thread, under ust_lock protection.
  */
-static pthread_mutex_t sessions_mutex = PTHREAD_MUTEX_INITIALIZER;
 
-void ust_lock(void)
-{
-       pthread_mutex_lock(&sessions_mutex);
-}
+static CDS_LIST_HEAD(sessions);
 
-void ust_unlock(void)
+struct cds_list_head *_lttng_get_sessions(void)
 {
-       pthread_mutex_unlock(&sessions_mutex);
+       return &sessions;
 }
 
-static CDS_LIST_HEAD(sessions);
-
 static void _lttng_event_destroy(struct lttng_event *event);
 
 static
@@ -106,8 +100,6 @@ int lttng_loglevel_match(int loglevel,
                enum lttng_ust_loglevel_type req_type,
                int req_loglevel)
 {
-       if (req_type == LTTNG_UST_LOGLEVEL_ALL)
-               return 1;
        if (!has_loglevel)
                loglevel = TRACE_DEFAULT;
        switch (req_type) {
@@ -251,8 +243,6 @@ int lttng_session_enable(struct lttng_session *session)
 
        /* Set transient enabler state to "enabled" */
        session->tstate = 1;
-       /* We need to sync enablers with session before activation. */
-       lttng_session_sync_enablers(session);
 
        /*
         * Snapshot the number of events per channel to know the type of header
@@ -290,9 +280,15 @@ int lttng_session_enable(struct lttng_session *session)
                }
        }
 
+       /* We need to sync enablers with session before activation. */
+       lttng_session_sync_enablers(session);
+
        /* Set atomically the state to "active" */
        CMM_ACCESS_ONCE(session->active) = 1;
        CMM_ACCESS_ONCE(session->been_active) = 1;
+
+       session->statedump_pending = 1;
+       lttng_ust_sockinfo_session_enabled(session->owner);
 end:
        return ret;
 }
@@ -491,6 +487,31 @@ static
 int lttng_desc_match_enabler(const struct lttng_event_desc *desc,
                struct lttng_enabler *enabler)
 {
+       struct lttng_ust_excluder_node *excluder;
+
+       /* If event matches with an excluder, return 'does not match' */
+       cds_list_for_each_entry(excluder, &enabler->excluder_head, node) {
+               int count;
+
+               for (count = 0; count < excluder->excluder.count; count++) {
+                       int found, len;
+                       char *excluder_name;
+
+                       excluder_name = (char *) (excluder->excluder.names)
+                                       + count * LTTNG_UST_SYM_NAME_LEN;
+                       len = strnlen(excluder_name, LTTNG_UST_SYM_NAME_LEN);
+                       if (len > 0 && excluder_name[len - 1] == '*') {
+                               found = !strncmp(desc->name, excluder_name,
+                                               len - 1);
+                       } else {
+                               found = !strncmp(desc->name, excluder_name,
+                                               LTTNG_UST_SYM_NAME_LEN - 1);
+                       }
+                       if (found) {
+                               return 0;
+                       }
+               }
+       }
        switch (enabler->type) {
        case LTTNG_ENABLER_WILDCARD:
                return lttng_desc_match_wildcard_enabler(desc, enabler);
@@ -647,6 +668,34 @@ int lttng_fix_pending_events(void)
        return 0;
 }
 
+/*
+ * For each session of the owner thread, execute pending statedump.
+ * Only dump state for the sessions owned by the caller thread, because
+ * we don't keep ust_lock across the entire iteration.
+ */
+void lttng_handle_pending_statedump(void *owner)
+{
+       struct lttng_session *session;
+
+       /* Execute state dump */
+       lttng_ust_baddr_statedump(owner);
+
+       /* Clear pending state dump */
+       if (ust_lock()) {
+               goto end;
+       }
+       cds_list_for_each_entry(session, &sessions, node) {
+               if (session->owner != owner)
+                       continue;
+               if (!session->statedump_pending)
+                       continue;
+               session->statedump_pending = 0;
+       }
+end:
+       ust_unlock();
+       return;
+}
+
 /*
  * Only used internally at session destruction.
  */
@@ -692,7 +741,16 @@ struct lttng_enabler *lttng_enabler_create(enum lttng_enabler_type type,
                sizeof(enabler->event_param));
        enabler->chan = chan;
        /* ctx left NULL */
-       enabler->enabled = 1;
+       /*
+        * The "disable" event create comm field has been added to fix a
+        * race between event creation (of a started trace) and enabling
+        * filtering. New session daemon always set the "disable" field
+        * to 1, and are aware that they need to explicitly enable the
+        * event. Older session daemon (within same ABI) leave it at 0,
+        * and therefore we need to enable it here, keeping the original
+        * racy behavior.
+        */
+       enabler->enabled = !event_param->disabled;
        cds_list_add(&enabler->node, &enabler->chan->session->enablers_head);
        lttng_session_lazy_sync_enablers(enabler->chan->session);
        return enabler;