staging: vchiq: Fix local event signalling
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Message ID 1547206493-105303-1-git-send-email-phil@raspberrypi.org
State New
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Series
  • staging: vchiq: Fix local event signalling
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Commit Message

Phil Elwell Jan. 11, 2019, 11:34 a.m. UTC
Prior to the recent event reworking (see Fixes), thread synchronisation
was implemented using completions, the worker thread being woken with
a call to complete(). The replacement uses waitqueues, which are more
like condition variables in that the waiting thread is only woken if
the condition is true.

When the VPU signals the ARM, it first sets the event's fired flag to
indicate which event is being signalled, but the places in the
ARM-side code where the worker thread is being woken -
remote_event_signal_local via request_poll - did not do so as it
wasn't previously necessary, and since the armed flag was being
cleared this lead to a deadlock.

Fixes: 852b2876a8a8 ("staging: vchiq: rework remove_event handling")
Signed-off-by: Phil Elwell <phil@raspberrypi.org>
---
 drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Stefan Wahren Jan. 12, 2019, 12:14 a.m. UTC | #1
> Phil Elwell <phil@raspberrypi.org> hat am 11. Januar 2019 um 12:34 geschrieben:
> 
> 
> Prior to the recent event reworking (see Fixes), thread synchronisation
> was implemented using completions, the worker thread being woken with
> a call to complete(). The replacement uses waitqueues, which are more
> like condition variables in that the waiting thread is only woken if
> the condition is true.
> 
> When the VPU signals the ARM, it first sets the event's fired flag to
> indicate which event is being signalled, but the places in the
> ARM-side code where the worker thread is being woken -
> remote_event_signal_local via request_poll - did not do so as it
> wasn't previously necessary, and since the armed flag was being
> cleared this lead to a deadlock.
> 
> Fixes: 852b2876a8a8 ("staging: vchiq: rework remove_event handling")
> Signed-off-by: Phil Elwell <phil@raspberrypi.org>

Tested-by: Stefan Wahren <stefan.wahren@i2se.com>

Thanks

Patch
diff mbox series

diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c
index 9e17ec6..53f5a1c 100644
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c
@@ -446,6 +446,7 @@  remote_event_wait(wait_queue_head_t *wq, struct remote_event *event)
 static inline void
 remote_event_signal_local(wait_queue_head_t *wq, struct remote_event *event)
 {
+	event->fired = 1;
 	event->armed = 0;
 	wake_up_all(wq);
 }