From: Sebastian Andrzej Siewior Date: Wed, 14 Aug 2019 16:38:43 +0200 Subject: [PATCH 289/351] dma-buf: Use seqlock_t instread disabling preemption Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=74f78801989fbf28092a53ce1c657e83766bb5cd [ Upstream commit 240610aa31094f51f299f06eb8dae8d4cd8d4500 ] "dma reservation" disables preemption while acquiring the write access for "seqcount" and then may acquire a spinlock_t. Replace the seqcount with a seqlock_t which provides seqcount like semantic and lock for writer. Link: https://lkml.kernel.org/r/f410b429-db86-f81c-7c67-f563fa808b62@free.fr Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (VMware) --- drivers/dma-buf/dma-buf.c | 8 ++-- drivers/dma-buf/reservation.c | 43 +++++++------------ .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 6 +-- drivers/gpu/drm/i915/i915_gem.c | 10 ++--- include/linux/reservation.h | 4 +- 5 files changed, 29 insertions(+), 42 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 69842145c223..4c3ef46e7149 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -179,7 +179,7 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) return 0; retry: - seq = read_seqcount_begin(&resv->seq); + seq = read_seqbegin(&resv->seq); rcu_read_lock(); fobj = rcu_dereference(resv->fence); @@ -188,7 +188,7 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) else shared_count = 0; fence_excl = rcu_dereference(resv->fence_excl); - if (read_seqcount_retry(&resv->seq, seq)) { + if (read_seqretry(&resv->seq, seq)) { rcu_read_unlock(); goto retry; } @@ -1046,12 +1046,12 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused) robj = buf_obj->resv; while (true) { - seq = read_seqcount_begin(&robj->seq); + seq = read_seqbegin(&robj->seq); rcu_read_lock(); fobj = rcu_dereference(robj->fence); shared_count = fobj ? fobj->shared_count : 0; fence = rcu_dereference(robj->fence_excl); - if (!read_seqcount_retry(&robj->seq, seq)) + if (!read_seqretry(&robj->seq, seq)) break; rcu_read_unlock(); } diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c index 49ab09468ba1..f11d58492216 100644 --- a/drivers/dma-buf/reservation.c +++ b/drivers/dma-buf/reservation.c @@ -109,8 +109,7 @@ reservation_object_add_shared_inplace(struct reservation_object *obj, dma_fence_get(fence); - preempt_disable(); - write_seqcount_begin(&obj->seq); + write_seqlock(&obj->seq); for (i = 0; i < fobj->shared_count; ++i) { struct dma_fence *old_fence; @@ -121,8 +120,7 @@ reservation_object_add_shared_inplace(struct reservation_object *obj, if (old_fence->context == fence->context) { /* memory barrier is added by write_seqcount_begin */ RCU_INIT_POINTER(fobj->shared[i], fence); - write_seqcount_end(&obj->seq); - preempt_enable(); + write_sequnlock(&obj->seq); dma_fence_put(old_fence); return; @@ -146,8 +144,7 @@ reservation_object_add_shared_inplace(struct reservation_object *obj, fobj->shared_count++; } - write_seqcount_end(&obj->seq); - preempt_enable(); + write_sequnlock(&obj->seq); dma_fence_put(signaled); } @@ -191,15 +188,13 @@ reservation_object_add_shared_replace(struct reservation_object *obj, fobj->shared_count++; done: - preempt_disable(); - write_seqcount_begin(&obj->seq); + write_seqlock(&obj->seq); /* * RCU_INIT_POINTER can be used here, * seqcount provides the necessary barriers */ RCU_INIT_POINTER(obj->fence, fobj); - write_seqcount_end(&obj->seq); - preempt_enable(); + write_sequnlock(&obj->seq); if (!old) return; @@ -259,14 +254,11 @@ void reservation_object_add_excl_fence(struct reservation_object *obj, if (fence) dma_fence_get(fence); - preempt_disable(); - write_seqcount_begin(&obj->seq); - /* write_seqcount_begin provides the necessary memory barrier */ + write_seqlock(&obj->seq); RCU_INIT_POINTER(obj->fence_excl, fence); if (old) old->shared_count = 0; - write_seqcount_end(&obj->seq); - preempt_enable(); + write_sequnlock(&obj->seq); /* inplace update, no shared fences */ while (i--) @@ -349,13 +341,10 @@ int reservation_object_copy_fences(struct reservation_object *dst, src_list = reservation_object_get_list(dst); old = reservation_object_get_excl(dst); - preempt_disable(); - write_seqcount_begin(&dst->seq); - /* write_seqcount_begin provides the necessary memory barrier */ + write_seqlock(&dst->seq); RCU_INIT_POINTER(dst->fence_excl, new); RCU_INIT_POINTER(dst->fence, dst_list); - write_seqcount_end(&dst->seq); - preempt_enable(); + write_sequnlock(&dst->seq); if (src_list) kfree_rcu(src_list, rcu); @@ -396,7 +385,7 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj, shared_count = i = 0; rcu_read_lock(); - seq = read_seqcount_begin(&obj->seq); + seq = read_seqbegin(&obj->seq); fence_excl = rcu_dereference(obj->fence_excl); if (fence_excl && !dma_fence_get_rcu(fence_excl)) @@ -445,7 +434,7 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj, } } - if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) { + if (i != shared_count || read_seqretry(&obj->seq, seq)) { while (i--) dma_fence_put(shared[i]); dma_fence_put(fence_excl); @@ -494,7 +483,7 @@ long reservation_object_wait_timeout_rcu(struct reservation_object *obj, retry: shared_count = 0; - seq = read_seqcount_begin(&obj->seq); + seq = read_seqbegin(&obj->seq); rcu_read_lock(); i = -1; @@ -541,7 +530,7 @@ long reservation_object_wait_timeout_rcu(struct reservation_object *obj, rcu_read_unlock(); if (fence) { - if (read_seqcount_retry(&obj->seq, seq)) { + if (read_seqretry(&obj->seq, seq)) { dma_fence_put(fence); goto retry; } @@ -597,7 +586,7 @@ bool reservation_object_test_signaled_rcu(struct reservation_object *obj, retry: ret = true; shared_count = 0; - seq = read_seqcount_begin(&obj->seq); + seq = read_seqbegin(&obj->seq); if (test_all) { unsigned i; @@ -618,7 +607,7 @@ bool reservation_object_test_signaled_rcu(struct reservation_object *obj, break; } - if (read_seqcount_retry(&obj->seq, seq)) + if (read_seqretry(&obj->seq, seq)) goto retry; } @@ -631,7 +620,7 @@ bool reservation_object_test_signaled_rcu(struct reservation_object *obj, if (ret < 0) goto retry; - if (read_seqcount_retry(&obj->seq, seq)) + if (read_seqretry(&obj->seq, seq)) goto retry; } } diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c index 4488aad64643..f22feb25eba9 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c @@ -261,11 +261,9 @@ static int amdgpu_amdkfd_remove_eviction_fence(struct amdgpu_bo *bo, } /* Install the new fence list, seqcount provides the barriers */ - preempt_disable(); - write_seqcount_begin(&resv->seq); + write_seqlock(&resv->seq); RCU_INIT_POINTER(resv->fence, new); - write_seqcount_end(&resv->seq); - preempt_enable(); + write_sequnlock(&resv->seq); /* Drop the references to the removed fences or move them to ef_list */ for (i = j, k = 0; i < old->shared_count; ++i) { diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 5b0d6d8b3ab8..3fe4a1e93a1a 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -516,7 +516,7 @@ i915_gem_object_wait_reservation(struct reservation_object *resv, long timeout, struct intel_rps_client *rps_client) { - unsigned int seq = __read_seqcount_begin(&resv->seq); + unsigned int seq = read_seqbegin(&resv->seq); struct dma_fence *excl; bool prune_fences = false; @@ -569,9 +569,9 @@ i915_gem_object_wait_reservation(struct reservation_object *resv, * signaled and that the reservation object has not been changed (i.e. * no new fences have been added). */ - if (prune_fences && !__read_seqcount_retry(&resv->seq, seq)) { + if (prune_fences && !read_seqretry(&resv->seq, seq)) { if (reservation_object_trylock(resv)) { - if (!__read_seqcount_retry(&resv->seq, seq)) + if (!read_seqretry(&resv->seq, seq)) reservation_object_add_excl_fence(resv, NULL); reservation_object_unlock(resv); } @@ -4696,7 +4696,7 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data, * */ retry: - seq = raw_read_seqcount(&obj->resv->seq); + seq = read_seqbegin(&obj->resv->seq); /* Translate the exclusive fence to the READ *and* WRITE engine */ args->busy = busy_check_writer(rcu_dereference(obj->resv->fence_excl)); @@ -4714,7 +4714,7 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data, } } - if (args->busy && read_seqcount_retry(&obj->resv->seq, seq)) + if (args->busy && read_seqretry(&obj->resv->seq, seq)) goto retry; err = 0; diff --git a/include/linux/reservation.h b/include/linux/reservation.h index 02166e815afb..0b31df1af698 100644 --- a/include/linux/reservation.h +++ b/include/linux/reservation.h @@ -72,7 +72,7 @@ struct reservation_object_list { */ struct reservation_object { struct ww_mutex lock; - seqcount_t seq; + seqlock_t seq; struct dma_fence __rcu *fence_excl; struct reservation_object_list __rcu *fence; @@ -92,7 +92,7 @@ reservation_object_init(struct reservation_object *obj) { ww_mutex_init(&obj->lock, &reservation_ww_class); - __seqcount_init(&obj->seq, reservation_seqcount_string, &reservation_seqcount_class); + seqlock_init(&obj->seq); RCU_INIT_POINTER(obj->fence, NULL); RCU_INIT_POINTER(obj->fence_excl, NULL); obj->staged = NULL;