media: v4l2-mem2mem: fix epoll() by calling poll_wait first

The epoll function expects that whenever the poll file op is
called, the poll_wait function is also called. That didn't
always happen in v4l2_m2m_poll(). Fix this, otherwise
epoll() would timeout when it shouldn't.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
index add228c98a9ac1e13e757141e436cce1219e2b2d..36ae6123dceff6d0af83eec2823b76b1e0e28e43 100644 (file)
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -617,20 +617,22 @@ __poll_t v4l2_m2m_poll(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
        __poll_t rc = 0;
        unsigned long flags;
 
+       src_q = v4l2_m2m_get_src_vq(m2m_ctx);
+       dst_q = v4l2_m2m_get_dst_vq(m2m_ctx);
+
+       poll_wait(file, &src_q->done_wq, wait);
+       poll_wait(file, &dst_q->done_wq, wait);
+
        if (test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags)) {
                struct v4l2_fh *fh = file->private_data;
 
+               poll_wait(file, &fh->wait, wait);
                if (v4l2_event_pending(fh))
                        rc = EPOLLPRI;
-               else if (req_events & EPOLLPRI)
-                       poll_wait(file, &fh->wait, wait);
                if (!(req_events & (EPOLLOUT | EPOLLWRNORM | EPOLLIN | EPOLLRDNORM)))
                        return rc;
        }
 
-       src_q = v4l2_m2m_get_src_vq(m2m_ctx);
-       dst_q = v4l2_m2m_get_dst_vq(m2m_ctx);
-
        /*
         * There has to be at least one buffer queued on each queued_list, which
         * means either in driver already or waiting for driver to claim it
@@ -642,11 +644,6 @@ __poll_t v4l2_m2m_poll(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                goto end;
        }
 
-       spin_lock_irqsave(&src_q->done_lock, flags);
-       if (list_empty(&src_q->done_list))
-               poll_wait(file, &src_q->done_wq, wait);
-       spin_unlock_irqrestore(&src_q->done_lock, flags);
-
        spin_lock_irqsave(&dst_q->done_lock, flags);
        if (list_empty(&dst_q->done_list)) {
                /*
@@ -657,8 +654,6 @@ __poll_t v4l2_m2m_poll(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                        spin_unlock_irqrestore(&dst_q->done_lock, flags);
                        return rc | EPOLLIN | EPOLLRDNORM;
                }
-
-               poll_wait(file, &dst_q->done_wq, wait);
        }
        spin_unlock_irqrestore(&dst_q->done_lock, flags);