The locking order for taking two fence locks is implicitly defined in
at least two ways in the code:
1) 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-...@lists.linaro.org
Cc: dri-devel@lists.freedesktop.org
Cc: Christian König <christian.koe...@amd.com>
Signed-off-by: Thomas Hellström <thomas.hellst...@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);
return array;
}
diff --git a/drivers/dma-buf/dma-fence-chain.c
b/drivers/dma-buf/dma-fence-chain.c
index 1b4cb3e5cec9..0518e53880f6 100644
--- a/drivers/dma-buf/dma-fence-chain.c
+++ b/drivers/dma-buf/dma-fence-chain.c
@@ -152,7 +152,8 @@ static bool dma_fence_chain_enable_signaling(struct
dma_fence *fence)
struct dma_fence *f = chain ? chain->fence : fence;
dma_fence_get(f);
- if (!dma_fence_add_callback(f, &head->cb, dma_fence_chain_cb)) {
+ if (!dma_fence_add_callback_nested(f, &head->cb,
+ dma_fence_chain_cb)) {
dma_fence_put(fence);
return true;
}
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 066400ed8841..90a3d5121746 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -610,6 +610,37 @@ void dma_fence_enable_sw_signaling(struct dma_fence *fence)
}
EXPORT_SYMBOL(dma_fence_enable_sw_signaling);
+static int __dma_fence_add_callback(struct dma_fence *fence,
+ struct dma_fence_cb *cb,
+ dma_fence_func_t func,
+ int nest_level)
+{
+ unsigned long flags;
+ int ret = 0;
+
+ if (WARN_ON(!fence || !func))
+ return -EINVAL;
+
+ if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
+ INIT_LIST_HEAD(&cb->node);
+ return -ENOENT;
+ }
+
+ spin_lock_irqsave_nested(fence->lock, flags, 0);
