diff options
author | Prakash Kamliya <pkamliya@codeaurora.org> | 2013-10-04 17:50:50 +0530 |
---|---|---|
committer | Colin Cross <ccross@android.com> | 2013-10-13 00:36:03 +0000 |
commit | 763b334bd467a1f9453fe19ab19354e3b8c351e2 (patch) | |
tree | c4280c0b1e9546818a368b4ecbef7be9959f6f44 | |
parent | 4fe1f96d0bc0cce09c41a6818153fea81d645a39 (diff) |
sync: signal pt before sync_timeline object gets destroyed
There is a race condition
Assume we have *one* sync_fence object, with *one* sync_pt
which belongs to *one* sync_timeline, given this condition,
sync_timeline->kref will have two counts, one for sync_timeline
(implicit) and another for sync_pt.
Assume following is the situation on CPU
Theead-1 : (Thread which calls sync_timeline_destroy())
-> (some function calls)
-> sync_timeline_destory()
-> sync_timeline_signal() (CPU is inside this
function after putting reference to sync_timeline)
At this time Thread-2 comes and does following
Thread-2 : (fclose on fence fd)
> sync_fence_release() -> because of fclose() on fence object
-> sync_fence_free()
-> sync_pt_free()
-> kref_put(&pt->parent->kref, sync_timeline_free);
-> sync_timeline_free() (CPU is inside this because
this time kref will be zero after _put)
Thread-2 will free sync_timeline object before Thread-1
has finished its work inside sync_timeline_signal.
With this change we signals all sync_pt before putting
reference to sync_timeline object.
Change-Id: Ic680e4d0bbef1c46bcb7cfba693395645241d203
Signed-off-by: Prakash Kamliya <pkamliya@codeaurora.org>
-rw-r--r-- | drivers/staging/android/sync.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c index 3893a357476..c5a43934e85 100644 --- a/drivers/staging/android/sync.c +++ b/drivers/staging/android/sync.c @@ -92,14 +92,14 @@ static void sync_timeline_free(struct kref *kref) void sync_timeline_destroy(struct sync_timeline *obj) { obj->destroyed = true; + smp_wmb(); /* - * If this is not the last reference, signal any children - * that their parent is going away. + * signal any children that their parent is going away. */ + sync_timeline_signal(obj); - if (!kref_put(&obj->kref, sync_timeline_free)) - sync_timeline_signal(obj); + kref_put(&obj->kref, sync_timeline_free); } EXPORT_SYMBOL(sync_timeline_destroy); |