a fixed amount of time and therefore can't be used as dependency in memory
management.
Because of this user fences are marked with DMA_FENCE_FLAG_USER. Lockdep
is checked that we can at least fault user pages when we check them for
signaling.
This patch also adds a flag to dma_fence_get_stub() so that we can
retrieve a signaled user fence. This can be used together with lockdep to
test the handling in code path supporting user fences.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
drivers/dma-buf/dma-fence-unwrap.c | 4 +--
drivers/dma-buf/dma-fence.c | 31 ++++++++++++-------
drivers/dma-buf/st-dma-fence.c | 2 +-
.../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 2 +-
drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 2 +-
drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c | 2 +-
drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 4 +--
drivers/gpu/drm/drm_syncobj.c | 10 +++---
include/linux/dma-fence.h | 17 +++++++++-
9 files changed, 49 insertions(+), 25 deletions(-)
diff --git a/drivers/dma-buf/dma-fence-unwrap.c b/drivers/dma-buf/dma-fence-unwrap.c
index c9becc74896d..87ee2efced10 100644
--- a/drivers/dma-buf/dma-fence-unwrap.c
+++ b/drivers/dma-buf/dma-fence-unwrap.c
@@ -76,7 +76,7 @@ struct dma_fence *__dma_fence_merge(unsigned int num_fences,
}
if (count == 0)
- return dma_fence_get_stub();
+ return dma_fence_get_stub(false);
if (count > INT_MAX)
return NULL;
@@ -129,7 +129,7 @@ struct dma_fence *__dma_fence_merge(unsigned int num_fences,
} while (tmp);
if (count == 0) {
- tmp = dma_fence_get_stub();
+ tmp = dma_fence_get_stub(false);
goto return_tmp;
}
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 066400ed8841..52873f5eaeba 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -26,6 +26,7 @@ EXPORT_TRACEPOINT_SYMBOL(dma_fence_signaled);
static DEFINE_SPINLOCK(dma_fence_stub_lock);
static struct dma_fence dma_fence_stub;
+static struct dma_fence dma_fence_user_stub;
/*
* fence context counter: each execution context should have its own
@@ -123,24 +124,28 @@ static const struct dma_fence_ops dma_fence_stub_ops = {
/**
* dma_fence_get_stub - return a signaled fence
+ * @user: if true the returned fence is an user fence
*
- * Return a stub fence which is already signaled. The fence's
- * timestamp corresponds to the first time after boot this
- * function is called.
+ * Return a stub fence which is already signaled. The fence's timestamp
+ * corresponds to the first time after boot this function is called. If @user is
+ * true an user fence is returned which can be used with lockdep to test user
+ * fence saveness in a code path.
*/
-struct dma_fence *dma_fence_get_stub(void)
+struct dma_fence *dma_fence_get_stub(bool user)
{
+ struct dma_fence *fence = user ? &dma_fence_stub : &dma_fence_user_stub;
+
spin_lock(&dma_fence_stub_lock);
- if (!dma_fence_stub.ops) {
- dma_fence_init(&dma_fence_stub,
- &dma_fence_stub_ops,
- &dma_fence_stub_lock,
+ if (!fence->ops) {
+ dma_fence_init(fence, &dma_fence_stub_ops, &dma_fence_stub_lock,
0, 0);
- dma_fence_signal_locked(&dma_fence_stub);
+ if (user)
+ set_bit(DMA_FENCE_FLAG_USER, &fence->flags);
+ dma_fence_signal_locked(fence);
}
spin_unlock(&dma_fence_stub_lock);
- return dma_fence_get(&dma_fence_stub);
+ return dma_fence_get(fence);
}
EXPORT_SYMBOL(dma_fence_get_stub);
@@ -497,8 +502,9 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
return -EINVAL;
might_sleep();
-
__dma_fence_might_wait();
+ if (test_bit(DMA_FENCE_FLAG_USER, &fence->flags))
+ might_fault();
trace_dma_fence_wait_start(fence);
if (fence->ops->wait)
@@ -870,6 +876,9 @@ dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count,
for (i = 0; i < count; ++i) {
struct dma_fence *fence = fences[i];
+ if (test_bit(DMA_FENCE_FLAG_USER, &fence->flags))
+ might_fault();
+
cb[i].task = current;
if (dma_fence_add_callback(fence, &cb[i].base,
dma_fence_default_wait_cb)) {
diff --git a/drivers/dma-buf/st-dma-fence.c b/drivers/dma-buf/st-dma-fence.c
index c8a12d7ad71a..50f757f75645 100644
--- a/drivers/dma-buf/st-dma-fence.c
+++ b/drivers/dma-buf/st-dma-fence.c
@@ -412,7 +412,7 @@ static int test_stub(void *arg)
int i;
for (i = 0; i < ARRAY_SIZE(f); i++) {
- f[i] = dma_fence_get_stub();
+ f[i] = dma_fence_get_stub((i % 2) == 1);
if (!dma_fence_is_signaled(f[i])) {
pr_err("Obtained unsignaled stub fence!\n");
goto err;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index 64ac4f8f49be..541c59635c34 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -263,7 +263,7 @@ static int amdgpu_amdkfd_remove_eviction_fence(struct amdgpu_bo *bo,
/* TODO: Instead of block before we should use the fence of the page
* table update and TLB flush here directly.
*/
- replacement = dma_fence_get_stub();
+ replacement = dma_fence_get_stub(false);
dma_resv_replace_fences(bo->tbo.base.resv, ef->base.context,
replacement, DMA_RESV_USAGE_READ);
dma_fence_put(replacement);
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index a28b7947a034..95eeab527ca9 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -1399,7 +1399,7 @@ int amdgpu_cs_fence_to_handle_ioctl(struct drm_device *dev, void *data,
return PTR_ERR(fence);
if (!fence)
- fence = dma_fence_get_stub();
+ fence = dma_fence_get_stub(false);
switch (info->in.what) {
case AMDGPU_FENCE_TO_HANDLE_GET_SYNCOBJ:
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
index 7f33ae87cb41..73165f387f3b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
@@ -193,7 +193,7 @@ int amdgpu_ring_init(struct amdgpu_device *adev, struct amdgpu_ring *ring,
adev->rings[ring->idx] = ring;
ring->num_hw_submission = sched_hw_submission;
ring->sched_score = sched_score;
- ring->vmid_wait = dma_fence_get_stub();
+ ring->vmid_wait = dma_fence_get_stub(false);
r = amdgpu_fence_driver_init_ring(ring);
if (r)
return r;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index 7e5cc8323329..e5c8e72a9485 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -1689,7 +1689,7 @@ int amdgpu_vm_bo_update_mapping(struct amdgpu_device *adev,
}
if (!unlocked && !dma_fence_is_signaled(vm->last_unlocked)) {
- struct dma_fence *tmp = dma_fence_get_stub();
+ struct dma_fence *tmp = dma_fence_get_stub(false);
amdgpu_bo_fence(vm->root.bo, vm->last_unlocked, true);
swap(vm->last_unlocked, tmp);
@@ -2905,7 +2905,7 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm)
else
vm->update_funcs = &amdgpu_vm_sdma_funcs;
vm->last_update = NULL;
- vm->last_unlocked = dma_fence_get_stub();
+ vm->last_unlocked = dma_fence_get_stub(false);
mutex_init(&vm->eviction_lock);
vm->evicting = false;
diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index 7e48dcd1bee4..5a961ea90a35 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -255,7 +255,7 @@ static void drm_syncobj_fence_add_wait(struct drm_syncobj *syncobj,
dma_fence_put(fence);
list_add_tail(&wait->node, &syncobj->cb_list);
} else if (!fence) {
- wait->fence = dma_fence_get_stub();
+ wait->fence = dma_fence_get_stub(false);
} else {
wait->fence = fence;
}
@@ -411,7 +411,7 @@ int drm_syncobj_find_fence(struct drm_file *file_private,
* signalled, use a new fence instead.
*/
if (!*fence)
- *fence = dma_fence_get_stub();
+ *fence = dma_fence_get_stub(false);
goto out;
}
@@ -1000,7 +1000,7 @@ static void syncobj_wait_syncobj_func(struct drm_syncobj *syncobj,
dma_fence_put(fence);
return;
} else if (!fence) {
- wait->fence = dma_fence_get_stub();
+ wait->fence = dma_fence_get_stub(false);
} else {
wait->fence = fence;
}
@@ -1067,7 +1067,7 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
if (fence)
entries[i].fence = fence;
else
- entries[i].fence = dma_fence_get_stub();
+ entries[i].fence = dma_fence_get_stub(false);
if ((flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE) ||
dma_fence_is_signaled(entries[i].fence)) {
@@ -1472,7 +1472,7 @@ drm_syncobj_timeline_signal_ioctl(struct drm_device *dev, void *data,
}
for (i = 0; i < args->count_handles; i++) {
- struct dma_fence *fence = dma_fence_get_stub();
+ struct dma_fence *fence = dma_fence_get_stub(false);
drm_syncobj_add_point(syncobjs[i], chains[i],
fence, points[i]);
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index afea82ec5946..be96687d31d8 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -99,6 +99,16 @@ enum dma_fence_flag_bits {
DMA_FENCE_FLAG_SIGNALED_BIT,
DMA_FENCE_FLAG_TIMESTAMP_BIT,
DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
+
+ /**
+ * @DMA_FENCE_FLAG_USER:
+ *
+ * Indicates an user fence. User fences are not guaranteed to signal in
+ * a finite amount of time. Because of this it is not allowed to wait for user
+ * fences with any lock held nor depend the signaling of none user
+ * fences on them.
+ */
+ DMA_FENCE_FLAG_USER,
DMA_FENCE_FLAG_DRIVER, /* must always be last member */
};
@@ -398,6 +408,8 @@ void dma_fence_enable_sw_signaling(struct dma_fence *fence);
static inline bool
dma_fence_is_signaled_locked(struct dma_fence *fence)
{
+ WARN_ON(test_bit(DMA_FENCE_FLAG_USER, &fence->flags));
+
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
return true;
@@ -428,6 +440,9 @@ dma_fence_is_signaled_locked(struct dma_fence *fence)
static inline bool
dma_fence_is_signaled(struct dma_fence *fence)
{
+ if (test_bit(DMA_FENCE_FLAG_USER, &fence->flags))
+ might_fault();
