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| author | Thomas Hellstrom <thellstrom@vmware.com> | 2010-11-11 10:04:53 +0100 |
|---|---|---|
| committer | Dave Airlie <airlied@redhat.com> | 2010-11-18 15:00:42 +1000 |
| commit | 95ccb0f3bdc4438bf470c25450e6a8a6090ca253 (patch) | |
| tree | a4a55496a9483ddf43d8bd72c149341536628874 /drivers | |
| parent | 9a03d3487abe89e3650bb2533c5d909143955499 (diff) | |
| download | linux-95ccb0f3bdc4438bf470c25450e6a8a6090ca253.tar.gz linux-95ccb0f3bdc4438bf470c25450e6a8a6090ca253.tar.bz2 linux-95ccb0f3bdc4438bf470c25450e6a8a6090ca253.zip | |
drm/ttm: Fix up a theoretical deadlock
A process suspended waiting for a higher sequence or no sequence to unreserve,
a bo may be beaten to the reservation by a process with a lower sequence.
In that case the first process should give up trying to reserve and
return -EAGAIN. In order for that to happen, we must wake waiting processes
when we change sequence, so that they have a chance to detect the new
sequence.
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/gpu/drm/ttm/ttm_bo.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index 3ca77dc03915..148a322d8f5d 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -224,6 +224,9 @@ int ttm_bo_reserve_locked(struct ttm_buffer_object *bo, int ret; while (unlikely(atomic_cmpxchg(&bo->reserved, 0, 1) != 0)) { + /** + * Deadlock avoidance for multi-bo reserving. + */ if (use_sequence && bo->seq_valid && (sequence - bo->val_seq < (1 << 31))) { return -EAGAIN; @@ -241,6 +244,14 @@ int ttm_bo_reserve_locked(struct ttm_buffer_object *bo, } if (use_sequence) { + /** + * Wake up waiters that may need to recheck for deadlock, + * if we decreased the sequence number. + */ + if (unlikely((bo->val_seq - sequence < (1 << 31)) + || !bo->seq_valid)) + wake_up_all(&bo->event_queue); + bo->val_seq = sequence; bo->seq_valid = true; } else { |