the first patch can work on freescale's 4.1.2 kernel ! My case maybe can't cover other changes. in file drivers/media/v4l2-core/videobuf-core.c, the function 'videobuf_poll_stream' may return POLLERR without calling 'poll_wait', it looks like different with 'vb2_poll''s process, maybe need further check. Thanks! Yi Qingliang On Mon, Jan 7, 2019 at 2:29 PM Yi Qingliang <niqingliang2003@xxxxxxxxx> wrote: > > Thanks! It should work now. > BTW, I don't know if we should think about the error case before > calling poll_wait, just like not streamon. > if poll return error, does epoll framework need and how to remove > waiter for client? > for epoll framework, does it have some requirements or some tutorial > for the implementation of client's poll? > > and I think it's better to split the two operation: adding waiter and > polling, not only for epoll framework, and also for all clients. > > Yi Qingliang > > On Mon, Jan 7, 2019 at 1:45 PM Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > > > > On 12/29/2018 03:10 AM, Yi Qingliang wrote: > > > Hello, I encountered a "can't wake_up" problem when use camera on imx6. > > > > > > if delay some time after 'streamon' the /dev/video0, then add fd > > > through epoll_ctl, then the process can't be waken_up after some time. > > > > > > I checked both the epoll / vb2_poll(videobuf2_core.c) code. > > > > > > epoll will pass 'poll_table' structure to vb2_poll, but it only > > > contain valid function pointer when inserting fd. > > > > > > in vb2_poll, if found new data in done list, it will not call 'poll_wait'. > > > after that, every call to vb2_poll will not contain valid poll_table, > > > which will result in all calling to poll_wait will not work. > > > > > > so if app can process frames quickly, and found frame data when > > > inserting fd (i.e. poll_wait will not be called or not contain valid > > > function pointer), it will not found valid frame in 'vb2_poll' finally > > > at some time, then call 'poll_wait' to expect be waken up at following > > > vb2_buffer_done, but no good luck. > > > > > > I also checked the 'videobuf-core.c', there is no this problem. > > > > > > of course, both epoll and vb2_poll are right by itself side, but the > > > result is we can't get new frames. > > > > > > I think by epoll's implementation, the user should always call poll_wait. > > > > > > and it's better to split the two actions: 'wait' and 'poll' both for > > > epoll framework and all epoll users, for example, v4l2. > > > > > > am I right? > > > > > > Yi Qingliang > > > > > > > Can you test this patch? > > > > Looking at what other drivers/frameworks do it seems that calling > > poll_wait() at the start of the poll function is the right approach. > > > > Regards, > > > > Hans > > > > Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx> > > --- > > diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c > > index 70e8c3366f9c..b1809628475d 100644 > > --- a/drivers/media/common/videobuf2/videobuf2-core.c > > +++ b/drivers/media/common/videobuf2/videobuf2-core.c > > @@ -2273,6 +2273,8 @@ __poll_t vb2_core_poll(struct vb2_queue *q, struct file *file, > > struct vb2_buffer *vb = NULL; > > unsigned long flags; > > > > + poll_wait(file, &q->done_wq, wait); > > + > > if (!q->is_output && !(req_events & (EPOLLIN | EPOLLRDNORM))) > > return 0; > > if (q->is_output && !(req_events & (EPOLLOUT | EPOLLWRNORM))) > > @@ -2329,8 +2331,6 @@ __poll_t vb2_core_poll(struct vb2_queue *q, struct file *file, > > */ > > if (q->last_buffer_dequeued) > > return EPOLLIN | EPOLLRDNORM; > > - > > - poll_wait(file, &q->done_wq, wait); > > } > > > > /*
