diff options
author | Chris Wilson <chris@chris-wilson.co.uk> | 2017-11-14 19:27:19 +0300 |
---|---|---|
committer | Sumit Semwal <sumit.semwal@linaro.org> | 2017-11-21 20:07:05 +0300 |
commit | 03e4e0a9e02cf703da331ff6cfd57d0be9bf5692 (patch) | |
tree | dc27892dd1af53bf9d6f5f1925762e7b8286f992 /drivers/dma-buf/dma-fence-array.c | |
parent | 70c5f93669249886b151812076509f30569aff80 (diff) |
dma-buf/fence: Fix lock inversion within dma-fence-array
Ages ago Rob Clark noted,
"Currently with fence-array, we have a potential deadlock situation. If
we fence_add_callback() on an array-fence, the array-fence's lock is
acquired first, and in it's ->enable_signaling() callback, it will install
cbs on it's array-member fences, so the array-member's lock is acquired
second.
But in the signal path, the array-member's lock is acquired first, and
the array-fence's lock acquired second."
Rob proposed either extensive changes to dma-fence to unnest the
fence-array signaling, or to defer the signaling onto a workqueue. This
is a more refined version of the later, that should keep the latency
of the fence signaling to a minimum by using an irq-work, which is
executed asap.
Reported-by: Rob Clark <robdclark@gmail.com>
Suggested-by: Rob Clark <robdclark@gmail.com>
References: 1476635975-21981-1-git-send-email-robdclark@gmail.com
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Christian König <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20171114162719.30958-1-chris@chris-wilson.co.uk
Diffstat (limited to 'drivers/dma-buf/dma-fence-array.c')
-rw-r--r-- | drivers/dma-buf/dma-fence-array.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c index 0350829ba62e..dd1edfb27b61 100644 --- a/drivers/dma-buf/dma-fence-array.c +++ b/drivers/dma-buf/dma-fence-array.c @@ -31,6 +31,14 @@ static const char *dma_fence_array_get_timeline_name(struct dma_fence *fence) return "unbound"; } +static void irq_dma_fence_array_work(struct irq_work *wrk) +{ + struct dma_fence_array *array = container_of(wrk, typeof(*array), work); + + dma_fence_signal(&array->base); + dma_fence_put(&array->base); +} + static void dma_fence_array_cb_func(struct dma_fence *f, struct dma_fence_cb *cb) { @@ -39,8 +47,9 @@ static void dma_fence_array_cb_func(struct dma_fence *f, struct dma_fence_array *array = array_cb->array; if (atomic_dec_and_test(&array->num_pending)) - dma_fence_signal(&array->base); - dma_fence_put(&array->base); + irq_work_queue(&array->work); + else + dma_fence_put(&array->base); } static bool dma_fence_array_enable_signaling(struct dma_fence *fence) @@ -136,6 +145,7 @@ struct dma_fence_array *dma_fence_array_create(int num_fences, spin_lock_init(&array->lock); dma_fence_init(&array->base, &dma_fence_array_ops, &array->lock, context, seqno); + init_irq_work(&array->work, irq_dma_fence_array_work); array->num_fences = num_fences; atomic_set(&array->num_pending, signal_on_any ? 1 : num_fences); |