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When vb2_buffer_done is called the buffer is unbound from the request and put. The media_request_object_put also 'put's the request reference. If the application has already closed the request fd, then that means that the request reference at that point goes to 0 and the whole request is released. This means that the control handler associated with the request is also freed and that causes this kernel oops: [174705.995401] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:908 [174705.995411] in_atomic(): 1, irqs_disabled(): 1, pid: 28071, name: vivid-000-vid-o [174705.995416] 2 locks held by vivid-000-vid-o/28071: [174705.995420] #0: 000000001ea3a232 (&dev->mutex#3){....}, at: vivid_thread_vid_out+0x3f5/0x550 [vivid] [174705.995447] #1: 00000000e30a0d1e (&(&q->done_lock)->rlock){....}, at: vb2_buffer_done+0x92/0x1d0 [videobuf2_common] [174705.995460] Preemption disabled at: [174705.995461] [<0000000000000000>] (null) [174705.995472] CPU: 11 PID: 28071 Comm: vivid-000-vid-o Tainted: G W 4.20.0-rc1-test-no #88 [174705.995476] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/19/2017 [174705.995481] Call Trace: [174705.995500] dump_stack+0x46/0x60 [174705.995512] ___might_sleep.cold.79+0xe1/0xf1 [174705.995523] __mutex_lock+0x50/0x8f0 [174705.995531] ? find_held_lock+0x2d/0x90 [174705.995536] ? find_held_lock+0x2d/0x90 [174705.995542] ? find_held_lock+0x2d/0x90 [174705.995564] ? v4l2_ctrl_handler_free.part.13+0x44/0x1d0 [videodev] [174705.995576] v4l2_ctrl_handler_free.part.13+0x44/0x1d0 [videodev] [174705.995590] v4l2_ctrl_request_release+0x1c/0x30 [videodev] [174705.995600] media_request_clean+0x64/0xe0 [media] [174705.995609] media_request_release+0x19/0x40 [media] [174705.995617] vb2_buffer_done+0xef/0x1d0 [videobuf2_common] [174705.995630] vivid_thread_vid_out+0x2c1/0x550 [vivid] [174705.995645] ? vivid_stop_generating_vid_cap+0x1c0/0x1c0 [vivid] [174705.995653] kthread+0x113/0x130 [174705.995659] ? kthread_park+0x80/0x80 [174705.995667] ret_from_fork+0x35/0x40 The vb2_buffer_done function can be called from interrupt context, so anything that sleeps is not allowed. The solution is to increment the request refcount when the buffer is queued and decrement it when the buffer is dequeued. Releasing the request is fine if that happens from VIDIOC_DQBUF. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> |
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