[Beignet] [PATCH] Fix: Event callback that were not executed when command was already CL_COMPLETE + thread safety for callbacks
Yang, Rong R
rong.r.yang at intel.com
Tue Mar 24 00:28:24 PDT 2015
Find one issue, see comment.
And beignet use two space as indent, can you convert tab to space? Thanks.
> -----Original Message-----
> From: Beignet [mailto:beignet-bounces at lists.freedesktop.org] On Behalf Of
> David Couturier
> Sent: Tuesday, March 24, 2015 13:38
> To: beignet at lists.freedesktop.org
> Cc: David Couturier
> Subject: [Beignet] [PATCH] Fix: Event callback that were not executed when
> command was already CL_COMPLETE + thread safety for callbacks
>
> When trying to register a callback on the clEnqueueReadBuffer command,
> since it is processed synchroniously all the time, the command was marked
> CL_COMPLETE every time. If the event returned by clEnqueueReadBuffer
> was then used to register a callback function, the callback function did no
> check to execute it if nessary.
>
> Modified the handling of the callback registration in cl_set_event_callback to
> only call the callback being created if it's status is already reached.
>
> Added thread safety measures for pfn_notify calls since the status value can
> be changed while executing the callback.
>
> Grouped the pfn_notify calls to a unified function cl_event_call_callback that
> handles thread safety: it queues callbacks in a node list while under the
> protection of pthread_mutex and then calls the callbacks outside of the
> pthread_mutex (this is required because the callback can deadlock if it calls a
> cl_api function that uses the mutex)
>
> Signed-off-by: David Couturier <david.couturier at polymtl.ca>
> ---
> src/cl_event.c | 77 ++++++++++++++++++++++++++++++++++++++++++---
> -------------
> src/cl_event.h | 4 ++-
> 2 files changed, 59 insertions(+), 22 deletions(-)
>
> diff --git a/src/cl_event.c b/src/cl_event.c index f70e531..eb5d54b 100644
> --- a/src/cl_event.c
> +++ b/src/cl_event.c
> @@ -119,16 +119,7 @@ void cl_event_delete(cl_event event)
> event->queue->last_event = NULL;
>
> /* Call all user's callback if haven't execute */
> - user_callback *cb = event->user_cb;
> - while(event->user_cb) {
> - cb = event->user_cb;
> - if(cb->executed == CL_FALSE) {
> - cb->executed = CL_TRUE;
> - cb->pfn_notify(event, event->status, cb->user_data);
> - }
> - event->user_cb = cb->next;
> - cl_free(cb);
> - }
> + cl_event_call_callback(event, CL_COMPLETE, CL_TRUE); // CL_COMPLETE
> + status will force all callbacks that are not executed to run
>
> /* delete gpgpu event object */
> if(event->gpgpu_event)
> @@ -180,8 +171,22 @@ cl_int cl_event_set_callback(cl_event event ,
> cb->status = command_exec_callback_type;
> cb->executed = CL_FALSE;
>
> - cb->next = event->user_cb;
> - event->user_cb = cb;
> +
> + // It is possible that the event enqueued is already completed.
> + // clEnqueueReadBuffer can be synchronous and when the callback
> + // is registered after, it still needs to get executed.
> + pthread_mutex_lock(&event->ctx->event_lock); // Thread safety
> +required: operations on the event->status can be made from many
> +different threads
> + if(event->status <= command_exec_callback_type) {
> + /* Call user callback */
> + pthread_mutex_unlock(&event->ctx->event_lock); // pfn_notify
> can call clFunctions that use the event_lock and from here it's not required
> + cb->pfn_notify(event, event->status, cb->user_data);
> + cl_free(cb);
> + } else {
> + // Enqueue to callback list
> + cb->next = event->user_cb;
> + event->user_cb = cb;
> + pthread_mutex_unlock(&event->ctx->event_lock);
> + }
>
> exit:
> return err;
> @@ -388,9 +393,46 @@ error:
> goto exit;
> }
>
> +void cl_event_call_callback(cl_event event, cl_int status, cl_bool free_cb) {
> + user_callback *user_cb = NULL;
> + user_callback *queue_cb = NULL; // For thread safety, we create a
> queue that holds user_callback's pfn_notify contents
> + user_callback *temp_cb = NULL;
> + user_cb = event->user_cb;
> + pthread_mutex_lock(&event->ctx->event_lock);
> + while(user_cb) {
> + if(user_cb->status >= status
> + && user_cb->executed == CL_FALSE) { //
> Added check to not execute a callback when it was already handled
> + user_cb->executed = CL_TRUE;
> + temp_cb = cl_malloc(sizeof(user_callback));
> + if(!temp_cb) {
> + break; // Out of memory
> + }
> + temp_cb->pfn_notify = user_cb->pfn_notify; //
> Minor struct copy to call ppfn_notify out of the pthread_mutex
> + temp_cb->user_data = user_cb->user_data;
> + if(free_cb) {
> + cl_free(user_cb);
> + }
> + if(!queue_cb) {
> + queue_cb = temp_cb;
> + queue_cb->next = NULL;
> + } else { // Enqueue
> + temp_cb->next = queue_cb;
Should be temp_cb->next = queue_cb->next here.
> + queue_cb->next = temp_cb;
> + }
> + }
> + user_cb = user_cb->next;
> + }
> + pthread_mutex_unlock(&event->ctx->event_lock);
> + // Calling the callbacks outside of the event_lock is required because
> the callback can call cl_api functions and get deadlocked
> + while(queue_cb) { // For each callback queued, actually execute the
> callback
> + queue_cb->pfn_notify(event, event->status, queue_cb-
> >user_data);
> + temp_cb = queue_cb;
> + queue_cb = queue_cb->next;
> + cl_free(temp_cb);
> + }
> +}
> void cl_event_set_status(cl_event event, cl_int status) {
> - user_callback *user_cb;
> cl_int ret, i;
> cl_event evt;
>
> @@ -437,14 +479,7 @@ void cl_event_set_status(cl_event event, cl_int
> status)
> pthread_mutex_unlock(&event->ctx->event_lock);
>
> /* Call user callback */
> - user_cb = event->user_cb;
> - while(user_cb) {
> - if(user_cb->status >= status) {
> - user_cb->executed = CL_TRUE;
> - user_cb->pfn_notify(event, event->status, user_cb->user_data);
> - }
> - user_cb = user_cb->next;
> - }
> + cl_event_call_callback(event, status, CL_FALSE);
>
> if(event->type == CL_COMMAND_USER) {
> /* Check all defer enqueue */
> diff --git a/src/cl_event.h b/src/cl_event.h index 0730530..9bb2ac8 100644
> --- a/src/cl_event.h
> +++ b/src/cl_event.h
> @@ -78,8 +78,10 @@ cl_event cl_event_new(cl_context,
> cl_command_queue, cl_command_type, cl_bool); void
> cl_event_delete(cl_event);
> /* Add one more reference to this object */ void
> cl_event_add_ref(cl_event);
> -/* Rigister a user callback function for specific commond execution status */
> +/* Register a user callback function for specific commond execution
> +status */
> cl_int cl_event_set_callback(cl_event, cl_int, EVENT_NOTIFY, void *);
> +/* Execute the event's callback if the event's status supersedes the
> +callback's status. Free the callback if specified */ void
> +cl_event_call_callback(cl_event event, cl_int status, cl_bool free_cb);
> /* Check events wait list for enqueue commonds */ cl_int
> cl_event_check_waitlist(cl_uint, const cl_event *, cl_event *, cl_context);
> /* Wait the all events in wait list complete */
> --
> 1.9.1
>
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