From 96726fe50feae74812a2ccf5d5da23cb01c0a413 Mon Sep 17 00:00:00 2001 From: Thomas Hellstrom Date: Wed, 17 Nov 2010 12:28:28 +0000 Subject: drm/ttm: Don't deadlock on recursive multi-bo reservations Add an aid for the driver to detect deadlocks on multi-bo reservations Update documentation. Signed-off-by: Thomas Hellstrom Reviewed-by: Jerome Glisse Signed-off-by: Dave Airlie --- drivers/gpu/drm/ttm/ttm_bo.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) (limited to 'drivers/gpu/drm') diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index 9ef893d5da88..5d8750830dc3 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -223,9 +223,18 @@ int ttm_bo_reserve_locked(struct ttm_buffer_object *bo, /** * Deadlock avoidance for multi-bo reserving. */ - if (use_sequence && bo->seq_valid && - (sequence - bo->val_seq < (1 << 31))) { - return -EAGAIN; + if (use_sequence && bo->seq_valid) { + /** + * We've already reserved this one. + */ + if (unlikely(sequence == bo->val_seq)) + return -EDEADLK; + /** + * Already reserved by a thread that will not back + * off for us. We need to back off. + */ + if (unlikely(sequence - bo->val_seq < (1 << 31))) + return -EAGAIN; } if (no_wait) -- cgit v1.2.1