On 11/30/21 13:19, Thomas Hellström wrote:
The locking order for taking two fence locks is implicitly defined in at least two ways in the code:
- Fence containers first and other fences next, which is defined by
the enable_signaling() callbacks of dma_fence_chain and dma_fence_array. 2) Reverse signal order, which is used by __i915_active_fence_set().
Now 1) implies 2), except for the signal_on_any mode of dma_fence_array and 2) does not imply 1), and also 1) makes locking order between different containers confusing.
Establish 2) and fix up the signal_on_any mode by calling enable_signaling() on such fences unlocked at creation.
Cc: linaro-mm-sig@lists.linaro.org Cc: dri-devel@lists.freedesktop.org Cc: Christian König christian.koenig@amd.com Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com
drivers/dma-buf/dma-fence-array.c | 13 +++-- drivers/dma-buf/dma-fence-chain.c | 3 +- drivers/dma-buf/dma-fence.c | 79 +++++++++++++++++++++---------- include/linux/dma-fence.h | 3 ++ 4 files changed, 69 insertions(+), 29 deletions(-)
diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c index 3e07f961e2f3..0322b92909fe 100644 --- a/drivers/dma-buf/dma-fence-array.c +++ b/drivers/dma-buf/dma-fence-array.c @@ -84,8 +84,8 @@ static bool dma_fence_array_enable_signaling(struct dma_fence *fence) * insufficient). */ dma_fence_get(&array->base);
if (dma_fence_add_callback(array->fences[i], &cb[i].cb,dma_fence_array_cb_func)) {
if (dma_fence_add_callback_nested(array->fences[i], &cb[i].cb,dma_fence_array_cb_func)) { int error = array->fences[i]->error; dma_fence_array_set_pending_error(array, error);@@ -158,6 +158,7 @@ struct dma_fence_array *dma_fence_array_create(int num_fences, { struct dma_fence_array *array; size_t size = sizeof(*array);
struct dma_fence *fence;
/* Allocate the callback structures behind the array. */ size += num_fences * sizeof(struct dma_fence_array_cb);
@@ -165,8 +166,9 @@ struct dma_fence_array *dma_fence_array_create(int num_fences, if (!array) return NULL;
- fence = &array->base; spin_lock_init(&array->lock);
- dma_fence_init(&array->base, &dma_fence_array_ops, &array->lock,
- dma_fence_init(fence, &dma_fence_array_ops, &array->lock, context, seqno); init_irq_work(&array->work, irq_dma_fence_array_work);
@@ -174,7 +176,10 @@ struct dma_fence_array *dma_fence_array_create(int num_fences, atomic_set(&array->num_pending, signal_on_any ? 1 : num_fences); array->fences = fences;
- array->base.error = PENDING_ERROR;
- fence->error = PENDING_ERROR;
- if (signal_on_any)
dma_fence_enable_sw_signaling(fence);
Oh, this looks strange. Was meant to call the dma_fence_array_enable_signaling() without the lock held here.
/Thomas