Drop the event mutex around backtrace.

1 files changed, 14 insertions, 7 deletions

diff --git a/src/lwp.c b/src/lwp.c
index 054df59..86f81d1 100644
--- a/src/lwp.c
+++ b/src/lwp.c
@@ -664,16 +664,12 @@ _lwp_record_event (LWP_EventType type, const LWP_Event *ev)
 {
     static LWP_EventRecord events[N_EVENTS];
     static guint n_events;
-    static guint depth;
     static gboolean _write_failed;
+    static __thread guint depth;
 
     gboolean lookup_allocator = TRUE;
     gboolean force_send = FALSE;
 
-    pthread_mutex_lock (&event_mutex);
-    if (depth++ || _write_failed)
-	goto unlock;
-
     switch (type) {
     case LWP_INIT:
 	force_send = TRUE;
@@ -702,6 +698,10 @@ _lwp_record_event (LWP_EventType type, const LWP_Event *ev)
 	break;
     }
 
+    pthread_mutex_lock (&event_mutex);
+    if (depth++ || _write_failed)
+	goto unlock;
+
     if (! lookup_allocator) {
 	events[n_events].allocator = 0;
     } else if (! _lwp_disable_stacktraces) {
@@ -712,6 +712,9 @@ _lwp_record_event (LWP_EventType type, const LWP_Event *ev)
 	if (max_ips > _lwp_num_callers)
 	    max_ips = _lwp_num_callers;
 
+	/* drop the mutex to avoid a deadlock with dl */
+	pthread_mutex_unlock (&event_mutex);
+
 	ips = stack_ips;
 	n_ips = backtrace (ips, max_ips);
 	while (n_ips == max_ips && max_ips < _lwp_num_callers) {
@@ -725,12 +728,16 @@ _lwp_record_event (LWP_EventType type, const LWP_Event *ev)
 	    n_ips = backtrace (ips, max_ips);
 	}
 
+	pthread_mutex_lock (&event_mutex);
+	if (_write_failed) /* need to recheck after acquiring mutex */
+	    goto unlock;
+
 	if (G_UNLIKELY (n_ips + n_pending_symbols > G_MAXUSHORT)) {
 	    _write_failed = ! _lwp_write_events (events, n_events);
+	    n_events = 0;
+
 	    if (_write_failed)
 		goto unlock;
-
-	    n_events = 0;
 	}
 
 	events[n_events].allocator = _lwp_add_allocator (ips+1, n_ips-1);