Linaro-mm-sig August 2016

linaro-mm-sig@lists.linaro.org

14 participants
17 discussions

[PATCH] allow buffers allocation with DMABUF memory type

by Benjamin Gaignard

Until now the only way to make the driver allocate buffers and share them using dma_buf was to use V4L2_MEMORY_MMAP memory type. Use of MMAP memory type is a problem because vb2 never call dma_buf_map_attachment() to attach itself while queuing the buffer so dma_buf importer will not know that another device use this buffer. This patch allow to allocate buffer even for DMABUF memory type and correctly manage dma_buf buffer attachment. vb2_mem_ops attach_dmabuf() prototype has been changed to be able to distinguish if the attachment is done on a already existing buffer or on imported one. Signed-off-by: Benjamin Gaignard <benjamin.gaignard(a)linaro.org> --- drivers/media/v4l2-core/videobuf2-core.c | 76 ++++++++++++++++++++++++-- drivers/media/v4l2-core/videobuf2-dma-contig.c | 10 ++-- drivers/media/v4l2-core/videobuf2-dma-sg.c | 8 ++- drivers/media/v4l2-core/videobuf2-vmalloc.c | 8 ++- include/media/videobuf2-core.h | 5 +- 5 files changed, 91 insertions(+), 16 deletions(-) diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c index 1329dcc..c5968aa 100644 --- a/drivers/media/v4l2-core/videobuf2-core.c +++ b/drivers/media/v4l2-core/videobuf2-core.c @@ -337,6 +337,67 @@ static void __setup_offsets(struct vb2_queue *q, unsigned int n) } /** + * __setup_dmabufs() - setup dmabuf fd for every plane in + * every buffer on the queue + */ +static void __setup_dmabufs(struct vb2_queue *q, unsigned int n) +{ + unsigned int buffer, plane; + struct vb2_buffer *vb; + struct vb2_plane *vb_plane; + struct dma_buf *dbuf; + void *mem_priv; + int fd; + int write = !V4L2_TYPE_IS_OUTPUT(q->type); + int flags = write ? O_WRONLY : O_RDONLY; + + for (buffer = q->num_buffers; buffer < q->num_buffers + n; ++buffer) { + vb = q->bufs[buffer]; + if (!vb) + continue; + + for (plane = 0; plane < vb->num_planes; ++plane) { + vb_plane = &vb->planes[plane]; + + dbuf = call_ptr_memop(vb, get_dmabuf, + vb_plane->mem_priv, + flags & O_ACCMODE); + if (IS_ERR_OR_NULL(dbuf)) { + dprintk(1, "Failed to export buffer %d, " \ + "plane %d\n", buffer, plane); + continue; + } + + fd = dma_buf_fd(dbuf, flags & ~O_ACCMODE); + if (fd < 0) { + dprintk(3, "buffer %d, plane %d failed " \ + "to export (%d)\n", buffer, plane, fd); + dma_buf_put(dbuf); + continue; + } + + /* Acquire each plane's memory */ + mem_priv = call_ptr_memop(vb, attach_dmabuf, + q->alloc_ctx[plane], dbuf, + vb->v4l2_planes[plane].length, + write, vb_plane->mem_priv); + if (IS_ERR(mem_priv)) { + dprintk(1, "Buffer %d plane %d failed "\ + "to attach dmabuf\n", buffer, plane); + dma_buf_put(dbuf); + continue; + } + + vb_plane->dbuf = dbuf; + vb->v4l2_planes[plane].m.fd = fd; + + dprintk(3, "Buffer %d, plane %d fd %x\n", + buffer, plane, fd); + } + } +} + +/** * __vb2_queue_alloc() - allocate videobuf buffer structures and (for MMAP type) * video buffer memory for all buffers/planes on the queue and initializes the * queue @@ -369,8 +430,9 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum v4l2_memory memory, vb->v4l2_buf.type = q->type; vb->v4l2_buf.memory = memory; - /* Allocate video buffer memory for the MMAP type */ - if (memory == V4L2_MEMORY_MMAP) { + /* Allocate video buffer memory for the MMAP and DMABUF types */ + if (memory == V4L2_MEMORY_MMAP || + memory == V4L2_MEMORY_DMABUF) { ret = __vb2_buf_mem_alloc(vb); if (ret) { dprintk(1, "failed allocating memory for " @@ -400,6 +462,9 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum v4l2_memory memory, if (memory == V4L2_MEMORY_MMAP) __setup_offsets(q, buffer); + if (memory == V4L2_MEMORY_DMABUF) + __setup_dmabufs(q, buffer); + dprintk(1, "allocated %d buffers, %d plane(s) each\n", buffer, num_planes); @@ -859,7 +924,7 @@ static int __verify_memory_type(struct vb2_queue *q, * to be used during streaming, * 4) allocates internal buffer structures (struct vb2_buffer), according to * the agreed parameters, - * 5) for MMAP memory type, allocates actual video memory, using the + * 5) for MMAP and DMABUF memory types, allocates actual video memory, using the * memory handling/allocation routines provided during queue initialization * * If req->count is 0, all the memory will be freed instead. @@ -885,7 +950,8 @@ static int __reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req) * are not in use and can be freed. */ mutex_lock(&q->mmap_lock); - if (q->memory == V4L2_MEMORY_MMAP && __buffers_in_use(q)) { + if ((q->memory == V4L2_MEMORY_MMAP || + q->memory == V4L2_MEMORY_DMABUF) && __buffers_in_use(q)) { mutex_unlock(&q->mmap_lock); dprintk(1, "memory in use, cannot free\n"); return -EBUSY; @@ -1540,7 +1606,7 @@ static int __qbuf_dmabuf(struct vb2_buffer *vb, const struct v4l2_buffer *b) /* Acquire each plane's memory */ mem_priv = call_ptr_memop(vb, attach_dmabuf, q->alloc_ctx[plane], - dbuf, planes[plane].length, dma_dir); + dbuf, planes[plane].length, dma_dir, NULL); if (IS_ERR(mem_priv)) { dprintk(1, "failed to attach dmabuf\n"); ret = PTR_ERR(mem_priv); diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c index b481d20..8dc945e 100644 --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c @@ -793,7 +793,7 @@ static void vb2_dc_detach_dmabuf(void *mem_priv) struct vb2_dc_buf *buf = mem_priv; /* if vb2 works correctly you should never detach mapped buffer */ - if (WARN_ON(buf->dma_addr)) + if (WARN_ON(buf->dma_sgt)) vb2_dc_unmap_dmabuf(buf); /* detach this attachment */ @@ -802,16 +802,18 @@ static void vb2_dc_detach_dmabuf(void *mem_priv) } static void *vb2_dc_attach_dmabuf(void *alloc_ctx, struct dma_buf *dbuf, - unsigned long size, enum dma_data_direction dma_dir) + unsigned long size, enum dma_data_direction dma_dir, void *buf_priv) { struct vb2_dc_conf *conf = alloc_ctx; - struct vb2_dc_buf *buf; + struct vb2_dc_buf *buf = buf_priv; struct dma_buf_attachment *dba; if (dbuf->size < size) return ERR_PTR(-EFAULT); - buf = kzalloc(sizeof(*buf), GFP_KERNEL); + if (!buf) + buf = kzalloc(sizeof(*buf), GFP_KERNEL); + if (!buf) return ERR_PTR(-ENOMEM); diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c index b1838ab..b9855fd 100644 --- a/drivers/media/v4l2-core/videobuf2-dma-sg.c +++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c @@ -667,16 +667,18 @@ static void vb2_dma_sg_detach_dmabuf(void *mem_priv) } static void *vb2_dma_sg_attach_dmabuf(void *alloc_ctx, struct dma_buf *dbuf, - unsigned long size, enum dma_data_direction dma_dir) + unsigned long size, enum dma_data_direction dma_dir, void *buf_priv) { struct vb2_dma_sg_conf *conf = alloc_ctx; - struct vb2_dma_sg_buf *buf; + struct vb2_dma_sg_buf *buf = buf_priv; struct dma_buf_attachment *dba; if (dbuf->size < size) return ERR_PTR(-EFAULT); - buf = kzalloc(sizeof(*buf), GFP_KERNEL); + if (!buf) + buf = kzalloc(sizeof(*buf), GFP_KERNEL); + if (!buf) return ERR_PTR(-ENOMEM); diff --git a/drivers/media/v4l2-core/videobuf2-vmalloc.c b/drivers/media/v4l2-core/videobuf2-vmalloc.c index bcde885..373294c 100644 --- a/drivers/media/v4l2-core/videobuf2-vmalloc.c +++ b/drivers/media/v4l2-core/videobuf2-vmalloc.c @@ -416,14 +416,16 @@ static void vb2_vmalloc_detach_dmabuf(void *mem_priv) } static void *vb2_vmalloc_attach_dmabuf(void *alloc_ctx, struct dma_buf *dbuf, - unsigned long size, enum dma_data_direction dma_dir) + unsigned long size, enum dma_data_direction dma_dir, void *buf_priv) { - struct vb2_vmalloc_buf *buf; + struct vb2_vmalloc_buf *buf = buf_priv; if (dbuf->size < size) return ERR_PTR(-EFAULT); - buf = kzalloc(sizeof(*buf), GFP_KERNEL); + if (!buf) + buf = kzalloc(sizeof(*buf), GFP_KERNEL); + if (!buf) return ERR_PTR(-ENOMEM); diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h index a5790fd..374b26b 100644 --- a/include/media/videobuf2-core.h +++ b/include/media/videobuf2-core.h @@ -49,6 +49,8 @@ struct vb2_threadio_data; * used for DMABUF memory types; alloc_ctx is the alloc context * dbuf is the shared dma_buf; returns NULL on failure; * allocator private per-buffer structure on success; + * if private per-buffer structure is provided reuse it + * instead of allocating a new one. * this needs to be used for further accesses to the buffer. * @detach_dmabuf: inform the exporter of the buffer that the current DMABUF * buffer is no longer used; the buf_priv argument is the @@ -98,7 +100,8 @@ struct vb2_mem_ops { void *(*attach_dmabuf)(void *alloc_ctx, struct dma_buf *dbuf, unsigned long size, - enum dma_data_direction dma_dir); + enum dma_data_direction dma_dir, + void *buf_priv); void (*detach_dmabuf)(void *buf_priv); int (*map_dmabuf)(void *buf_priv); void (*unmap_dmabuf)(void *buf_priv); -- 1.9.1

7 years, 10 months

[PATCH] dma-buf: Wait on the reservation object when sync'ing before CPU access

by Chris Wilson

Rendering operations to the dma-buf are tracked implicitly via the reservation_object (dmabuf->resv). This is used to allow poll() to wait upon outstanding rendering (or just query the current status of rendering). The dma-buf sync ioctl allows userspace to prepare the dma-buf for CPU access, which should include waiting upon rendering. (Some drivers may need to do more work to ensure that the dma-buf mmap is coherent as well as complete.) Signed-off-by: Chris Wilson <chris(a)chris-wilson.co.uk> Cc: Sumit Semwal <sumit.semwal(a)linaro.org> Cc: Daniel Vetter <daniel.vetter(a)ffwll.ch> Cc: linux-media(a)vger.kernel.org Cc: dri-devel(a)lists.freedesktop.org Cc: linaro-mm-sig(a)lists.linaro.org Cc: linux-kernel(a)vger.kernel.org --- I'm wondering whether it makes sense just to always do the wait first. It is one of the first operations every driver has to make. A driver that wants to implement it differently (e.g. they can special case native waits) will still require a wait on the reservation object to finish external rendering. -Chris --- drivers/dma-buf/dma-buf.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index ddaee60ae52a..123f14b8e882 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -586,6 +586,22 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, } EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment); +static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf, + enum dma_data_direction direction) +{ + bool write = (direction == DMA_BIDIRECTIONAL || + direction == DMA_TO_DEVICE); + struct reservation_object *resv = dma_buf->resv; + long ret; + + /* Wait on any implicit rendering fences */ + ret = reservation_object_wait_timeout_rcu(resv, write, true, + MAX_SCHEDULE_TIMEOUT); + if (ret < 0) + return ret; + + return 0; +} /** * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the @@ -607,6 +623,8 @@ int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, if (dmabuf->ops->begin_cpu_access) ret = dmabuf->ops->begin_cpu_access(dmabuf, direction); + else + ret = __dma_buf_begin_cpu_access(dmabuf, direction); return ret; } -- 2.8.1

8 years

[PATCH 10/11] dma-buf: Use seqlock to close RCU race in test_signaled_single

by Chris Wilson

With the seqlock now extended to cover the lookup of the fence and its testing, we can perform that testing solely under the seqlock guard and avoid the effective locking and serialisation of acquiring a reference to the request. As the fence is RCU protected we know it cannot disappear as we test it, the same guarantee that made it safe to acquire the reference previously. The seqlock tests whether the fence was replaced as we are testing it telling us whether or not we can trust the result (if not, we just repeat the test until stable). Signed-off-by: Chris Wilson <chris(a)chris-wilson.co.uk> Cc: Sumit Semwal <sumit.semwal(a)linaro.org> Cc: linux-media(a)vger.kernel.org Cc: dri-devel(a)lists.freedesktop.org Cc: linaro-mm-sig(a)lists.linaro.org --- drivers/dma-buf/reservation.c | 32 ++++---------------------------- 1 file changed, 4 insertions(+), 28 deletions(-) diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c index e74493e7332b..1ddffa5adb5a 100644 --- a/drivers/dma-buf/reservation.c +++ b/drivers/dma-buf/reservation.c @@ -442,24 +442,6 @@ unlock_retry: } EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu); - -static inline int -reservation_object_test_signaled_single(struct fence *passed_fence) -{ - struct fence *fence, *lfence = passed_fence; - int ret = 1; - - if (!test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) { - fence = fence_get_rcu(lfence); - if (!fence) - return -1; - - ret = !!fence_is_signaled(fence); - fence_put(fence); - } - return ret; -} - /** * reservation_object_test_signaled_rcu - Test if a reservation object's * fences have been signaled. @@ -474,7 +456,7 @@ bool reservation_object_test_signaled_rcu(struct reservation_object *obj, bool test_all) { unsigned seq, shared_count; - int ret; + bool ret; rcu_read_lock(); retry: @@ -494,10 +476,8 @@ retry: for (i = 0; i < shared_count; ++i) { struct fence *fence = rcu_dereference(fobj->shared[i]); - ret = reservation_object_test_signaled_single(fence); - if (ret < 0) - goto retry; - else if (!ret) + ret = fence_is_signaled(fence); + if (!ret) break; } @@ -509,11 +489,7 @@ retry: struct fence *fence_excl = rcu_dereference(obj->fence_excl); if (fence_excl) { - ret = reservation_object_test_signaled_single( - fence_excl); - if (ret < 0) - goto retry; - + ret = fence_is_signaled(fence_excl); if (read_seqcount_retry(&obj->seq, seq)) goto retry; } -- 2.9.3

8 years, 3 months

[PATCH 11/11] dma-buf: Do a fast lockless check for poll with timeout=0

by Chris Wilson

Currently we install a callback for performing poll on a dma-buf, irrespective of the timeout. This involves taking a spinlock, as well as unnecessary work, and greatly reduces scaling of poll(.timeout=0) across multiple threads. We can query whether the poll will block prior to installing the callback to make the busy-query fast. Single thread: 60% faster 8 threads on 4 (+4 HT) cores: 600% faster Still not quite the perfect scaling we get with a native busy ioctl, but poll(dmabuf) is faster due to the quicker lookup of the object and avoiding drm_ioctl(). Signed-off-by: Chris Wilson <chris(a)chris-wilson.co.uk> Cc: Sumit Semwal <sumit.semwal(a)linaro.org> Cc: linux-media(a)vger.kernel.org Cc: dri-devel(a)lists.freedesktop.org Cc: linaro-mm-sig(a)lists.linaro.org Reviewed-by: Daniel Vetter <daniel.vetter(a)ffwll.ch> --- drivers/dma-buf/dma-buf.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index cf04d249a6a4..c7a7bc579941 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -156,6 +156,18 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll) if (!events) return 0; + if (poll_does_not_wait(poll)) { + if (events & POLLOUT && + !reservation_object_test_signaled_rcu(resv, true)) + events &= ~(POLLOUT | POLLIN); + + if (events & POLLIN && + !reservation_object_test_signaled_rcu(resv, false)) + events &= ~POLLIN; + + return events; + } + retry: seq = read_seqcount_begin(&resv->seq); rcu_read_lock(); -- 2.9.3

8 years, 3 months

[PATCH 09/11] dma-buf: Restart reservation_object_test_signaled_rcu() after writes

by Chris Wilson

In order to be completely generic, we have to double check the read seqlock after acquiring a reference to the fence. If the driver is allocating fences from a SLAB_DESTROY_BY_RCU, or similar freelist, then within an RCU grace period a fence may be freed and reallocated. The RCU read side critical section does not prevent this reallocation, instead we have to inspect the reservation's seqlock to double check if the fences have been reassigned as we were acquiring our reference. Signed-off-by: Chris Wilson <chris(a)chris-wilson.co.uk> Cc: Daniel Vetter <daniel.vetter(a)ffwll.ch> Cc: Maarten Lankhorst <maarten.lankhorst(a)linux.intel.com> Cc: Christian König <christian.koenig(a)amd.com> Cc: Alex Deucher <alexander.deucher(a)amd.com> Cc: Sumit Semwal <sumit.semwal(a)linaro.org> Cc: linux-media(a)vger.kernel.org Cc: dri-devel(a)lists.freedesktop.org Cc: linaro-mm-sig(a)lists.linaro.org --- drivers/dma-buf/reservation.c | 30 ++++++++++-------------------- 1 file changed, 10 insertions(+), 20 deletions(-) diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c index 3369e4668e96..e74493e7332b 100644 --- a/drivers/dma-buf/reservation.c +++ b/drivers/dma-buf/reservation.c @@ -474,12 +474,13 @@ bool reservation_object_test_signaled_rcu(struct reservation_object *obj, bool test_all) { unsigned seq, shared_count; - int ret = true; + int ret; + rcu_read_lock(); retry: + ret = true; shared_count = 0; seq = read_seqcount_begin(&obj->seq); - rcu_read_lock(); if (test_all) { unsigned i; @@ -490,46 +491,35 @@ retry: if (fobj) shared_count = fobj->shared_count; - if (read_seqcount_retry(&obj->seq, seq)) - goto unlock_retry; - for (i = 0; i < shared_count; ++i) { struct fence *fence = rcu_dereference(fobj->shared[i]); ret = reservation_object_test_signaled_single(fence); if (ret < 0) - goto unlock_retry; + goto retry; else if (!ret) break; } - /* - * There could be a read_seqcount_retry here, but nothing cares - * about whether it's the old or newer fence pointers that are - * signaled. That race could still have happened after checking - * read_seqcount_retry. If you care, use ww_mutex_lock. - */ + if (read_seqcount_retry(&obj->seq, seq)) + goto retry; } if (!shared_count) { struct fence *fence_excl = rcu_dereference(obj->fence_excl); - if (read_seqcount_retry(&obj->seq, seq)) - goto unlock_retry; - if (fence_excl) { ret = reservation_object_test_signaled_single( fence_excl); if (ret < 0) - goto unlock_retry; + goto retry; + + if (read_seqcount_retry(&obj->seq, seq)) + goto retry; } } rcu_read_unlock(); return ret; - -unlock_retry: - rcu_read_unlock(); - goto retry; } EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu); -- 2.9.3

8 years, 3 months

[PATCH 06/11] dma-buf: Introduce fence_get_rcu_safe()

by Chris Wilson

This variant of fence_get_rcu() takes an RCU protected pointer to a fence and carefully returns a reference to the fence ensuring that it is not reallocated as it does. This is required when mixing fences and SLAB_DESTROY_BY_RCU - although it serves a more pedagogical function atm Signed-off-by: Chris Wilson <chris(a)chris-wilson.co.uk> Cc: Daniel Vetter <daniel.vetter(a)ffwll.ch> Cc: Sumit Semwal <sumit.semwal(a)linaro.org> Cc: linux-media(a)vger.kernel.org Cc: dri-devel(a)lists.freedesktop.org Cc: linaro-mm-sig(a)lists.linaro.org --- include/linux/fence.h | 56 ++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 51 insertions(+), 5 deletions(-) diff --git a/include/linux/fence.h b/include/linux/fence.h index 0d763053f97a..c9c5ba98c302 100644 --- a/include/linux/fence.h +++ b/include/linux/fence.h @@ -183,6 +183,16 @@ void fence_release(struct kref *kref); void fence_free(struct fence *fence); /** + * fence_put - decreases refcount of the fence + * @fence: [in] fence to reduce refcount of + */ +static inline void fence_put(struct fence *fence) +{ + if (fence) + kref_put(&fence->refcount, fence_release); +} + +/** * fence_get - increases refcount of the fence * @fence: [in] fence to increase refcount of * @@ -210,13 +220,49 @@ static inline struct fence *fence_get_rcu(struct fence *fence) } /** - * fence_put - decreases refcount of the fence - * @fence: [in] fence to reduce refcount of + * fence_get_rcu_safe - acquire a reference to an RCU tracked fence + * @fence: [in] pointer to fence to increase refcount of + * + * Function returns NULL if no refcount could be obtained, or the fence. + * This function handles acquiring a reference to a fence that may be + * reallocated within the RCU grace period (such as with SLAB_DESTROY_BY_RCU), + * so long as the caller is using RCU on the pointer to the fence. + * + * An alternative mechanism is to employ a seqlock to protect a bunch of + * fences, such as used by struct reservation_object. When using a seqlock, + * the seqlock must be taken before and checked after a reference to the + * fence is acquired (as shown here). + * + * The caller is required to hold the RCU read lock. */ -static inline void fence_put(struct fence *fence) +static inline struct fence *fence_get_rcu_safe(struct fence * __rcu *fencep) { - if (fence) - kref_put(&fence->refcount, fence_release); + do { + struct fence *fence; + + fence = rcu_dereference(*fencep); + if (!fence || !fence_get_rcu(fence)) + return NULL; + + /* The atomic_inc_not_zero() inside fence_get_rcu() + * provides a full memory barrier upon success (such as now). + * This is paired with the write barrier from assigning + * to the __rcu protected fence pointer so that if that + * pointer still matches the current fence, we know we + * have successfully acquire a reference to it. If it no + * longer matches, we are holding a reference to some other + * reallocated pointer. This is possible if the allocator + * is using a freelist like SLAB_DESTROY_BY_RCU where the + * fence remains valid for the RCU grace period, but it + * may be reallocated. When using such allocators, we are + * responsible for ensuring the reference we get is to + * the right fence, as below. + */ + if (fence == rcu_access_pointer(*fencep)) + return rcu_pointer_handoff(fence); + + fence_put(fence); + } while (1); } int fence_signal(struct fence *fence); -- 2.9.3

8 years, 3 months

[PATCH 08/11] dma-buf: Restart reservation_object_wait_timeout_rcu() after writes

by Chris Wilson

8 years, 3 months

[PATCH 07/11] dma-buf: Restart reservation_object_get_fences_rcu() after writes

by Chris Wilson

In order to be completely generic, we have to double check the read seqlock after acquiring a reference to the fence. If the driver is allocating fences from a SLAB_DESTROY_BY_RCU, or similar freelist, then within an RCU grace period a fence may be freed and reallocated. The RCU read side critical section does not prevent this reallocation, instead we have to inspect the reservation's seqlock to double check if the fences have been reassigned as we were acquiring our reference. Signed-off-by: Chris Wilson <chris(a)chris-wilson.co.uk> Cc: Daniel Vetter <daniel.vetter(a)ffwll.ch> Cc: Maarten Lankhorst <maarten.lankhorst(a)linux.intel.com> Cc: Christian König <christian.koenig(a)amd.com> Cc: Alex Deucher <alexander.deucher(a)amd.com> Cc: Sumit Semwal <sumit.semwal(a)linaro.org> Cc: linux-media(a)vger.kernel.org Cc: dri-devel(a)lists.freedesktop.org Cc: linaro-mm-sig(a)lists.linaro.org --- drivers/dma-buf/reservation.c | 71 +++++++++++++++++++------------------------ 1 file changed, 31 insertions(+), 40 deletions(-) diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c index 723d8af988e5..10fd441dd4ed 100644 --- a/drivers/dma-buf/reservation.c +++ b/drivers/dma-buf/reservation.c @@ -280,18 +280,24 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj, unsigned *pshared_count, struct fence ***pshared) { - unsigned shared_count = 0; - unsigned retry = 1; - struct fence **shared = NULL, *fence_excl = NULL; - int ret = 0; + struct fence **shared = NULL; + struct fence *fence_excl; + unsigned shared_count; + int ret = 1; - while (retry) { + do { struct reservation_object_list *fobj; unsigned seq; + unsigned i; - seq = read_seqcount_begin(&obj->seq); + shared_count = i = 0; rcu_read_lock(); + seq = read_seqcount_begin(&obj->seq); + + fence_excl = rcu_dereference(obj->fence_excl); + if (fence_excl && !fence_get_rcu(fence_excl)) + goto unlock; fobj = rcu_dereference(obj->fence); if (fobj) { @@ -309,52 +315,37 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj, } ret = -ENOMEM; - shared_count = 0; break; } shared = nshared; - memcpy(shared, fobj->shared, sz); shared_count = fobj->shared_count; - } else - shared_count = 0; - fence_excl = rcu_dereference(obj->fence_excl); - - retry = read_seqcount_retry(&obj->seq, seq); - if (retry) - goto unlock; - - if (!fence_excl || fence_get_rcu(fence_excl)) { - unsigned i; for (i = 0; i < shared_count; ++i) { - if (fence_get_rcu(shared[i])) - continue; - - /* uh oh, refcount failed, abort and retry */ - while (i--) - fence_put(shared[i]); - - if (fence_excl) { - fence_put(fence_excl); - fence_excl = NULL; - } - - retry = 1; - break; + shared[i] = rcu_dereference(fobj->shared[i]); + if (!fence_get_rcu(shared[i])) + break; } - } else - retry = 1; + } + + if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) { + while (i--) + fence_put(shared[i]); + fence_put(fence_excl); + goto unlock; + } + ret = 0; unlock: rcu_read_unlock(); - } - *pshared_count = shared_count; - if (shared_count) - *pshared = shared; - else { - *pshared = NULL; + } while (ret); + + if (!shared_count) { kfree(shared); + shared = NULL; } + + *pshared_count = shared_count; + *pshared = shared; *pfence_excl = fence_excl; return ret; -- 2.9.3

8 years, 3 months

Re: [Linaro-mm-sig] [Mesa-dev] [RFC] New dma_buf -> EGLImage EGL extension - Final spec published!

by Rob Clark

Tom, hmm, I wonder if it was a bug/oversight for the YUV capabilities of this extension to not depend on OES_EGL_image_external (which unfortunately, doesn't seem to have a GL counterpart)? I think this currently implies that you could sample from an imported YUV eglimg using (for example) sampler2D in GL or GLES, which I think was not the intention. BR, -R On Mon, Feb 25, 2013 at 6:54 AM, Tom Cooksey <tom.cooksey(a)arm.com> wrote: > Hi All, > > The final spec has had enum values assigned and been published on Khronos: > > http://www.khronos.org/registry/egl/extensions/EXT/EGL_EXT_image_dma_buf_im… > > Thanks to all who've provided input. > > > Cheers, > > Tom > > > >> -----Original Message----- >> From: mesa-dev-bounces+tom.cooksey=arm.com(a)lists.freedesktop.org [mailto:mesa-dev- >> bounces+tom.cooksey=arm.com(a)lists.freedesktop.org] On Behalf Of Tom Cooksey >> Sent: 04 October 2012 13:10 >> To: mesa-dev(a)lists.freedesktop.org; linaro-mm-sig(a)lists.linaro.org; dri- >> devel(a)lists.freedesktop.org; linux-media(a)vger.kernel.org >> Subject: [Mesa-dev] [RFC] New dma_buf -> EGLImage EGL extension - New draft! >> >> Hi All, >> >> After receiving a fair bit of feedback (thanks!), I've updated the >> EGL_EXT_image_dma_buf_import spec >> and expanded it to resolve a number of the issues. Please find the latest draft below and let >> me >> know any additional feedback you might have, either on the lists or by private e-mail - I >> don't mind >> which. >> >> I think the only remaining issue now is if we need a mechanism whereby an application can >> query >> which drm_fourcc.h formats EGL supports or if just failing with EGL_BAD_MATCH when the >> application >> has use one EGL doesn't support is sufficient. Any thoughts? >> >> >> Cheers, >> >> Tom >> >> >> --------------------8<-------------------- >> >> >> Name >> >> EXT_image_dma_buf_import >> >> Name Strings >> >> EGL_EXT_image_dma_buf_import >> >> Contributors >> >> Jesse Barker >> Rob Clark >> Tom Cooksey >> >> Contacts >> >> Jesse Barker (jesse 'dot' barker 'at' linaro 'dot' org) >> Tom Cooksey (tom 'dot' cooksey 'at' arm 'dot' com) >> >> Status >> >> DRAFT >> >> Version >> >> Version 4, October 04, 2012 >> >> Number >> >> EGL Extension ??? >> >> Dependencies >> >> EGL 1.2 is required. >> >> EGL_KHR_image_base is required. >> >> The EGL implementation must be running on a Linux kernel supporting the >> dma_buf buffer sharing mechanism. >> >> This extension is written against the wording of the EGL 1.2 Specification. >> >> Overview >> >> This extension allows creating an EGLImage from a Linux dma_buf file >> descriptor or multiple file descriptors in the case of multi-plane YUV >> images. >> >> New Types >> >> None >> >> New Procedures and Functions >> >> None >> >> New Tokens >> >> Accepted by the <target> parameter of eglCreateImageKHR: >> >> EGL_LINUX_DMA_BUF_EXT >> >> Accepted as an attribute in the <attrib_list> parameter of >> eglCreateImageKHR: >> >> EGL_LINUX_DRM_FOURCC_EXT >> EGL_DMA_BUF_PLANE0_FD_EXT >> EGL_DMA_BUF_PLANE0_OFFSET_EXT >> EGL_DMA_BUF_PLANE0_PITCH_EXT >> EGL_DMA_BUF_PLANE1_FD_EXT >> EGL_DMA_BUF_PLANE1_OFFSET_EXT >> EGL_DMA_BUF_PLANE1_PITCH_EXT >> EGL_DMA_BUF_PLANE2_FD_EXT >> EGL_DMA_BUF_PLANE2_OFFSET_EXT >> EGL_DMA_BUF_PLANE2_PITCH_EXT >> EGL_YUV_COLOR_SPACE_HINT_EXT >> EGL_SAMPLE_RANGE_HINT_EXT >> EGL_YUV_CHROMA_HORIZONTAL_SITING_HINT_EXT >> EGL_YUV_CHROMA_VERTICAL_SITING_HINT_EXT >> >> Accepted as the value for the EGL_YUV_COLOR_SPACE_HINT_EXT attribute: >> >> EGL_ITU_REC601_EXT >> EGL_ITU_REC709_EXT >> EGL_ITU_REC2020_EXT >> >> Accepted as the value for the EGL_SAMPLE_RANGE_HINT_EXT attribute: >> >> EGL_YUV_FULL_RANGE_EXT >> EGL_YUV_NARROW_RANGE_EXT >> >> Accepted as the value for the EGL_YUV_CHROMA_HORIZONTAL_SITING_HINT_EXT & >> EGL_YUV_CHROMA_VERTICAL_SITING_HINT_EXT attributes: >> >> EGL_YUV_CHROMA_SITING_0_EXT >> EGL_YUV_CHROMA_SITING_0_5_EXT >> >> >> Additions to Chapter 2 of the EGL 1.2 Specification (EGL Operation) >> >> Add to section 2.5.1 "EGLImage Specification" (as defined by the >> EGL_KHR_image_base specification), in the description of >> eglCreateImageKHR: >> >> "Values accepted for <target> are listed in Table aaa, below. >> >> +-------------------------+--------------------------------------------+ >> | <target> | Notes | >> +-------------------------+--------------------------------------------+ >> | EGL_LINUX_DMA_BUF_EXT | Used for EGLImages imported from Linux | >> | | dma_buf file descriptors | >> +-------------------------+--------------------------------------------+ >> Table aaa. Legal values for eglCreateImageKHR <target> parameter >> >> ... >> >> If <target> is EGL_LINUX_DMA_BUF_EXT, <dpy> must be a valid display, <ctx> >> must be EGL_NO_CONTEXT, and <buffer> must be NULL, cast into the type >> EGLClientBuffer. The details of the image is specified by the attributes >> passed into eglCreateImageKHR. Required attributes and their values are as >> follows: >> >> * EGL_WIDTH & EGL_HEIGHT: The logical dimensions of the buffer in pixels >> >> * EGL_LINUX_DRM_FOURCC_EXT: The pixel format of the buffer, as specified >> by drm_fourcc.h and used as the pixel_format parameter of the >> drm_mode_fb_cmd2 ioctl. >> >> * EGL_DMA_BUF_PLANE0_FD_EXT: The dma_buf file descriptor of plane 0 of >> the image. >> >> * EGL_DMA_BUF_PLANE0_OFFSET_EXT: The offset from the start of the >> dma_buf of the first sample in plane 0, in bytes. >> >> * EGL_DMA_BUF_PLANE0_PITCH_EXT: The number of bytes between the start of >> subsequent rows of samples in plane 0. May have special meaning for >> non-linear formats. >> >> For images in an RGB color-space or those using a single-plane YUV format, >> only the first plane's file descriptor, offset & pitch should be specified. >> For semi-planar YUV formats, the chroma samples are stored in plane 1 and >> for fully planar formats, U-samples are stored in plane 1 and V-samples are >> stored in plane 2. Planes 1 & 2 are specified by the following attributes, >> which have the same meanings as defined above for plane 0: >> >> * EGL_DMA_BUF_PLANE1_FD_EXT >> * EGL_DMA_BUF_PLANE1_OFFSET_EXT >> * EGL_DMA_BUF_PLANE1_PITCH_EXT >> * EGL_DMA_BUF_PLANE2_FD_EXT >> * EGL_DMA_BUF_PLANE2_OFFSET_EXT >> * EGL_DMA_BUF_PLANE2_PITCH_EXT >> >> In addition to the above required attributes, the application may also >> provide hints as to how the data should be interpreted by the GL. If any of >> these hints are not specified, the GL will guess based on the pixel format >> passed as the EGL_LINUX_DRM_FOURCC_EXT attribute or may fall-back to some >> default value. Not all GLs will be able to support all combinations of >> these hints and are free to use whatever settings they choose to achieve >> the closest possible match. >> >> * EGL_YUV_COLOR_SPACE_HINT_EXT: The color-space the data is in. Only >> relevant for images in a YUV format, ignored when specified for an >> image in an RGB format. Accepted values are: >> EGL_ITU_REC601_EXT, EGL_ITU_REC709_EXT & EGL_ITU_REC2020_EXT. >> >> * EGL_YUV_CHROMA_HORIZONTAL_SITING_HINT_EXT & >> EGL_YUV_CHROMA_VERTICAL_SITING_HINT_EXT: Where chroma samples are >> sited relative to luma samples when the image is in a sub-sampled >> format. When the image is not using chroma sub-sampling, the luma and >> chroma samples are assumed to be co-sited. Siting is split into the >> vertical and horizontal and is in a fixed range. A siting of zero >> means the first luma sample is taken from the same position in that >> dimension as the chroma sample. This is best illustrated in the >> diagram below: >> >> (0.5, 0.5) (0.0, 0.5) (0.0, 0.0) >> + + + + + + + + * + * + >> x x x x >> + + + + + + + + + + + + >> >> + + + + + + + + * + * + >> x x x x >> + + + + + + + + + + + + >> >> Luma samples (+), Chroma samples (x) Chrome & Luma samples (*) >> >> Note this attribute is ignored for RGB images and non sub-sampled >> YUV images. Accepted values are: EGL_YUV_CHROMA_SITING_0_EXT (0.0) >> & EGL_YUV_CHROMA_SITING_0_5_EXT (0.5) >> >> * EGL_SAMPLE_RANGE_HINT_EXT: The numerical range of samples. Only >> relevant for images in a YUV format, ignored when specified for >> images in an RGB format. Accepted values are: EGL_YUV_FULL_RANGE_EXT >> (0-256) & EGL_YUV_NARROW_RANGE_EXT (16-235). >> >> >> If eglCreateImageKHR is successful for a EGL_LINUX_DMA_BUF_EXT target, the >> EGL takes ownership of the file descriptor and is responsible for closing >> it, which it may do at any time while the EGLDisplay is initialized." >> >> >> Add to the list of error conditions for eglCreateImageKHR: >> >> "* If <target> is EGL_LINUX_DMA_BUF_EXT and <buffer> is not NULL, the >> error EGL_BAD_PARAMETER is generated. >> >> * If <target> is EGL_LINUX_DMA_BUF_EXT, and the list of attributes is >> incomplete, EGL_BAD_PARAMETER is generated. >> >> * If <target> is EGL_LINUX_DMA_BUF_EXT, and the EGL_LINUX_DRM_FOURCC_EXT >> attribute is set to a format not supported by the EGL, EGL_BAD_MATCH >> is generated. >> >> * If <target> is EGL_LINUX_DMA_BUF_EXT, and the EGL_LINUX_DRM_FOURCC_EXT >> attribute indicates a single-plane format, EGL_BAD_ATTRIBUTE is >> generated if any of the EGL_DMA_BUF_PLANE1_* or EGL_DMA_BUF_PLANE2_* >> attributes are specified. >> >> * If <target> is EGL_LINUX_DMA_BUF_EXT and the value specified for >> EGL_YUV_COLOR_SPACE_HINT_EXT is not EGL_ITU_REC601_EXT, >> EGL_ITU_REC709_EXT or EGL_ITU_REC2020_EXT, EGL_BAD_ATTRIBUTE is >> generated. >> >> * If <target> is EGL_LINUX_DMA_BUF_EXT and the value specified for >> EGL_SAMPLE_RANGE_HINT_EXT is not EGL_YUV_FULL_RANGE_EXT or >> EGL_YUV_NARROW_RANGE_EXT, EGL_BAD_ATTRIBUTE is generated. >> >> * If <target> is EGL_LINUX_DMA_BUF_EXT and the value specified for >> EGL_YUV_CHROMA_HORIZONTAL_SITING_HINT_EXT or >> EGL_YUV_CHROMA_VERTICAL_SITING_HINT_EXT is not >> EGL_YUV_CHROMA_SITING_0_EXT or EGL_YUV_CHROMA_SITING_0_5_EXT, >> EGL_BAD_ATTRIBUTE is generated. >> >> * If <target> is EGL_LINUX_DMA_BUF_EXT and one or more of the values >> specified for a plane's pitch or offset isn't supported by EGL, >> EGL_BAD_ACCESS is generated. >> >> * If <target> is EGL_LINUX_DMA_BUF_EXT and eglCreateImageKHR fails, >> EGL does not retain ownership of the file descriptor and it is the >> responsibility of the application to close it." >> >> >> Issues >> >> 1. Should this be a KHR or EXT extension? >> >> ANSWER: EXT. Khronos EGL working group not keen on this extension as it is >> seen as contradicting the EGLStream direction the specification is going in. >> The working group recommends creating additional specs to allow an EGLStream >> producer/consumer connected to v4l2/DRM or any other Linux interface. >> >> 2. Should this be a generic any platform extension, or a Linux-only >> extension which explicitly states the handles are dma_buf fds? >> >> ANSWER: There's currently no intention to port this extension to any OS not >> based on the Linux kernel. Consequently, this spec can be explicitly written >> against Linux and the dma_buf API. >> >> 3. Does ownership of the file descriptor pass to the EGL library? >> >> ANSWER: If eglCreateImageKHR is successful, EGL assumes ownership of the >> file descriptors and is responsible for closing them. >> >> 4. How are the different YUV color spaces handled (BT.709/BT.601)? >> >> ANSWER: The pixel formats defined in drm_fourcc.h only specify how the data >> is laid out in memory. It does not define how that data should be >> interpreted. Added a new EGL_YUV_COLOR_SPACE_HINT_EXT attribute to allow the >> application to specify which color space the data is in to allow the GL to >> choose an appropriate set of co-efficients if it needs to convert that data >> to RGB for example. >> >> 5. What chroma-siting is used for sub-sampled YUV formats? >> >> ANSWER: The chroma siting is not specified by either the v4l2 or DRM APIs. >> This is similar to the color-space issue (4) in that the chroma siting >> doesn't affect how the data is stored in memory. However, the GL will need >> to know the siting in order to filter the image correctly. While the visual >> impact of getting the siting wrong is minor, provision should be made to >> allow an application to specify the siting if desired. Added additional >> EGL_YUV_CHROMA_HORIZONTAL_SITING_HINT_EXT & >> EGL_YUV_CHROMA_VERTICAL_SITING_HINT_EXT attributes to allow the siting to >> be specified using a set of pre-defined values (0 or 0.5). >> >> 6. How can an application query which formats the EGL implementation >> supports? >> >> PROPOSAL: Don't provide a query mechanism but instead add an error condition >> that EGL_BAD_MATCH is raised if the EGL implementation doesn't support that >> particular format. >> >> 7. Which image formats should be supported and how is format specified? >> >> Seem to be two options 1) specify a new enum in this specification and >> enumerate all possible formats. 2) Use an existing enum already in Linux, >> either v4l2_mbus_pixelcode and/or those formats listed in drm_fourcc.h? >> >> ANSWER: Go for option 2) and just use values defined in drm_fourcc.h. >> >> 8. How can AYUV images be handled? >> >> ANSWER: At least on fourcc.org and in drm_fourcc.h, there only seems to be >> a single AYUV format and that is a packed format, so everything, including >> the alpha component would be in the first plane. >> >> 9. How can you import interlaced images? >> >> ANSWER: Interlaced frames are usually stored with the top & bottom fields >> interleaved in a single buffer. As the fields would need to be displayed as >> at different times, the application would create two EGLImages from the same >> buffer, one for the top field and another for the bottom. Both EGLImages >> would set the pitch to 2x the buffer width and the second EGLImage would use >> a suitable offset to indicate it started on the second line of the buffer. >> This should work regardless of whether the data is packed in a single plane, >> semi-planar or multi-planar. >> >> If each interlaced field is stored in a separate buffer then it should be >> trivial to create two EGLImages, one for each field's buffer. >> >> 10. How are semi-planar/planar formats handled that have a different >> width/height for Y' and CbCr such as YUV420? >> >> ANSWER: The spec says EGL_WIDTH & EGL_HEIGHT specify the *logical* width and >> height of the buffer in pixels. For pixel formats with sub-sampled Chroma >> values, it should be trivial for the EGL implementation to calculate the >> width/height of the Chroma sample buffers using the logical width & height >> and by inspecting the pixel format passed as the EGL_LINUX_DRM_FOURCC_EXT >> attribute. I.e. If the pixel format says it's YUV420, the Chroma buffer's >> width = EGL_WIDTH/2 & height =EGL_HEIGHT/2. >> >> 11. How are Bayer formats handled? >> >> ANSWER: As of Linux 2.6.34, drm_fourcc.h does not include any Bayer formats. >> However, future kernel versions may add such formats in which case they >> would be handled in the same way as any other format. >> >> 12. Should the spec support buffers which have samples in a "narrow range"? >> >> Content sampled from older analogue sources typically don't use the full >> (0-256) range of the data type storing the sample and instead use a narrow >> (16-235) range to allow some headroom & toeroom in the signals to avoid >> clipping signals which overshoot slightly during processing. This is >> sometimes known as signals using "studio swing". >> >> ANSWER: Add a new attribute to define if the samples use a narrow 16-235 >> range or the full 0-256 range. >> >> 13. Specifying the color space and range seems cumbersome, why not just >> allow the application to specify the full YUV->RGB color conversion matrix? >> >> ANSWER: Some hardware may not be able to use an arbitrary conversion matrix >> and needs to select an appropriate pre-defined matrix based on the color >> space and the sample range. >> >> 14. How do you handle EGL implementations which have restrictions on pitch >> and/or offset? >> >> ANSWER: Buffers being imported using dma_buf pretty much have to be >> allocated by a kernel-space driver. As such, it is expected that a system >> integrator would make sure all devices which allocate buffers suitable for >> exporting make sure they use a pitch supported by all possible importers. >> However, it is still possible eglCreateImageKHR can fail due to an >> unsupported pitch. Added a new error to the list indicating this. >> >> 15. Should this specification also describe how to export an existing >> EGLImage as a dma_buf file descriptor? >> >> ANSWER: No. Importing and exporting buffers are two separate operations and >> importing an existing dma_buf fd into an EGLImage is useful functionality in >> itself. Agree that exporting an EGLImage as a dma_buf fd is useful, E.g. it >> could be used by an OpenMAX IL implementation's OMX_UseEGLImage function to >> give access to the buffer backing an EGLImage to video hardware. However, >> exporting can be split into a separate extension specification. >> >> >> Revision History >> >> #4 (Tom Cooksey, October 04, 2012) >> - Fixed issue numbering! >> - Added issues 8 - 15. >> - Promoted proposal for Issue 3 to be the answer. >> - Added an additional attribute to allow an application to specify the color >> space as a hint which should address issue 4. >> - Added an additional attribute to allow an application to specify the chroma >> siting as a hint which should address issue 5. >> - Added an additional attribute to allow an application to specify the sample >> range as a hint which should address the new issue 12. >> - Added language to end of error section clarifying who owns the fd passed >> to eglCreateImageKHR if an error is generated. >> >> #3 (Tom Cooksey, August 16, 2012) >> - Changed name from EGL_EXT_image_external and re-written language to >> explicitly state this for use with Linux & dma_buf. >> - Added a list of issues, including some still open ones. >> >> #2 (Jesse Barker, May 30, 2012) >> - Revision to split eglCreateImageKHR functionality from export >> Functionality. >> - Update definition of EGLNativeBufferType to be a struct containing a list >> of handles to support multi-buffer/multi-planar formats. >> >> #1 (Jesse Barker, March 20, 2012) >> - Initial draft. >> >> >> >> >> _______________________________________________ >> mesa-dev mailing list >> mesa-dev(a)lists.freedesktop.org >> http://lists.freedesktop.org/mailman/listinfo/mesa-dev > > > > > _______________________________________________ > mesa-dev mailing list > mesa-dev(a)lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/mesa-dev

8 years, 3 months

[PATCH] dma-buf: Do a fast lockless check for poll with timeout=0

by Chris Wilson

Currently we install a callback for performing poll on a dma-buf, irrespective of the timeout. This involves taking a spinlock, as well as unnecessary work, and greatly reduces scaling of poll(.timeout=0) across multiple threads. We can query whether the poll will block prior to installing the callback to make the busy-query fast. Single thread: 60% faster 8 threads on 4 (+4 HT) cores: 600% faster Still not quite the perfect scaling we get with a native busy ioctl, but poll(dmabuf) is faster due to the quicker lookup of the object and avoiding drm_ioctl(). Signed-off-by: Chris Wilson <chris(a)chris-wilson.co.uk> Cc: Sumit Semwal <sumit.semwal(a)linaro.org> Cc: linux-media(a)vger.kernel.org Cc: dri-devel(a)lists.freedesktop.org Cc: linaro-mm-sig(a)lists.linaro.org --- drivers/dma-buf/dma-buf.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index cf04d249a6a4..c7a7bc579941 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -156,6 +156,18 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll) if (!events) return 0; + if (poll_does_not_wait(poll)) { + if (events & POLLOUT && + !reservation_object_test_signaled_rcu(resv, true)) + events &= ~(POLLOUT | POLLIN); + + if (events & POLLIN && + !reservation_object_test_signaled_rcu(resv, false)) + events &= ~POLLIN; + + return events; + } + retry: seq = read_seqcount_begin(&resv->seq); rcu_read_lock(); -- 2.9.3

8 years, 3 months

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