[Beignet] [PATCH] runtime: Fix a dangling pointer issue

[Ruiling Song]

ctx->events points to the head of 'event list' under the ctx.
When deleting an event from the list, we should also update
the head pointer besides updating its neighbour's next & prev,

Signed-off-by: Ruiling Song <ruiling.song at intel.com>
---
 src/cl_event.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/cl_event.c b/src/cl_event.c
index 212f1ee..1dc02ae 100644
--- a/src/cl_event.c
+++ b/src/cl_event.c
@@ -124,12 +124,15 @@ void cl_event_delete(cl_event event)
   /* Remove it from the list */
   assert(event->ctx);
   pthread_mutex_lock(&event->ctx->event_lock);
-    if (event->prev)
-      event->prev->next = event->next;
-    if (event->next)
-      event->next->prev = event->prev;
-    if (event->prev == NULL && event->next == NULL)
-      event->ctx->events = NULL;
+
+  if (event->prev)
+    event->prev->next = event->next;
+  if (event->next)
+    event->next->prev = event->prev;
+  /* if this is the head, update head pointer ctx->events */
+  if (event->ctx->events == event)
+    event->ctx->events = event->next;
+
   pthread_mutex_unlock(&event->ctx->event_lock);
   cl_context_delete(event->ctx);
 
-- 
1.7.9.5