From cf6f8129b6af78116e00b1d781e0bcc8c4b73890 Mon Sep 17 00:00:00 2001 From: John Sheu Date: Thu, 15 Oct 2015 18:05:25 +0900 Subject: [PATCH 282/806] media: vb2: Allow reqbufs(0) with "in use" MMAP buffers Videobuf2 presently does not allow VIDIOC_REQBUFS to destroy outstanding buffers if the queue is of type V4L2_MEMORY_MMAP, and if the buffers are considered "in use". This is different behavior than for other memory types and prevents us from deallocating buffers in following two cases: 1) There are outstanding mmap()ed views on the buffer. However even if we put the buffer in reqbufs(0), there will be remaining references, due to vma .open/close() adjusting vb2 buffer refcount appropriately. This means that the buffer will be in fact freed only when the last mmap()ed view is unmapped. 2) Buffer has been exported as a DMABUF. Refcount of the vb2 buffer is managed properly by VB2 DMABUF ops, i.e. incremented on DMABUF get and decremented on DMABUF release. This means that the buffer will be alive until all importers release it. Considering both cases above, there does not seem to be any need to prevent reqbufs(0) operation, because buffer lifetime is already properly managed by both mmap() and DMABUF code paths. Let's remove it and allow userspace freeing the queue (and potentially allocating a new one) even though old buffers might be still in processing. Signed-off-by: John Sheu Reviewed-by: Pawel Osciak Reviewed-by: Tomasz Figa Signed-off-by: Tomasz Figa --- .../media/common/videobuf2/videobuf2-core.c | 23 ------------------- 1 file changed, 23 deletions(-) --- a/drivers/media/common/videobuf2/videobuf2-core.c +++ b/drivers/media/common/videobuf2/videobuf2-core.c @@ -554,20 +554,6 @@ bool vb2_buffer_in_use(struct vb2_queue } EXPORT_SYMBOL(vb2_buffer_in_use); -/* - * __buffers_in_use() - return true if any buffers on the queue are in use and - * the queue cannot be freed (by the means of REQBUFS(0)) call - */ -static bool __buffers_in_use(struct vb2_queue *q) -{ - unsigned int buffer; - for (buffer = 0; buffer < q->num_buffers; ++buffer) { - if (vb2_buffer_in_use(q, q->bufs[buffer])) - return true; - } - return false; -} - void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb) { call_void_bufop(q, fill_user_buffer, q->bufs[index], pb); @@ -679,16 +665,7 @@ int vb2_core_reqbufs(struct vb2_queue *q if (*count == 0 || q->num_buffers != 0 || (q->memory != VB2_MEMORY_UNKNOWN && q->memory != memory)) { - /* - * We already have buffers allocated, so first check if they - * are not in use and can be freed. - */ mutex_lock(&q->mmap_lock); - if (q->memory == VB2_MEMORY_MMAP && __buffers_in_use(q)) { - mutex_unlock(&q->mmap_lock); - dprintk(1, "memory in use, cannot free\n"); - return -EBUSY; - } /* * Call queue_cancel to clean up any buffers in the PREPARED or