[RFC PATCH 8/8] dvb-core: fix epoll() by calling poll_wait first

[hverkuil-cisco]

From: Hans Verkuil <hverkuil-ci...@xs4all.nl>

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 dvb_demux_poll(), dvb_dvr_poll() and
dvb_ca_en50221_io_poll(). Fix this, otherwise epoll()
can timeout when it shouldn't.

Signed-off-by: Hans Verkuil <hverkuil-ci...@xs4all.nl>
---
 drivers/media/dvb-core/dmxdev.c         | 8 ++++----
 drivers/media/dvb-core/dvb_ca_en50221.c | 5 ++---
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/media/dvb-core/dmxdev.c b/drivers/media/dvb-core/dmxdev.c
index 1544e8cef564..f14a872d1268 100644
--- a/drivers/media/dvb-core/dmxdev.c
+++ b/drivers/media/dvb-core/dmxdev.c
@@ -1195,13 +1195,13 @@ static __poll_t dvb_demux_poll(struct file *file, 
poll_table *wait)
        struct dmxdev_filter *dmxdevfilter = file->private_data;
        __poll_t mask = 0;
 
+       poll_wait(file, &dmxdevfilter->buffer.queue, wait);
+
        if ((!dmxdevfilter) || dmxdevfilter->dev->exit)
                return EPOLLERR;
        if (dvb_vb2_is_streaming(&dmxdevfilter->vb2_ctx))
                return dvb_vb2_poll(&dmxdevfilter->vb2_ctx, file, wait);
 
-       poll_wait(file, &dmxdevfilter->buffer.queue, wait);
-
        if (dmxdevfilter->state != DMXDEV_STATE_GO &&
            dmxdevfilter->state != DMXDEV_STATE_DONE &&
            dmxdevfilter->state != DMXDEV_STATE_TIMEDOUT)
@@ -1346,13 +1346,13 @@ static __poll_t dvb_dvr_poll(struct file *file, 
poll_table *wait)
 
        dprintk("%s\n", __func__);
 
+       poll_wait(file, &dmxdev->dvr_buffer.queue, wait);
+
        if (dmxdev->exit)
                return EPOLLERR;
        if (dvb_vb2_is_streaming(&dmxdev->dvr_vb2_ctx))
                return dvb_vb2_poll(&dmxdev->dvr_vb2_ctx, file, wait);
 
-       poll_wait(file, &dmxdev->dvr_buffer.queue, wait);
-
        if (((file->f_flags & O_ACCMODE) == O_RDONLY) ||
            dmxdev->may_do_mmap) {
                if (dmxdev->dvr_buffer.error)
diff --git a/drivers/media/dvb-core/dvb_ca_en50221.c 
b/drivers/media/dvb-core/dvb_ca_en50221.c
index 4d371cea0d5d..ebf1e3b03819 100644
--- a/drivers/media/dvb-core/dvb_ca_en50221.c
+++ b/drivers/media/dvb-core/dvb_ca_en50221.c
@@ -1797,6 +1797,8 @@ static __poll_t dvb_ca_en50221_io_poll(struct file *file, 
poll_table *wait)
 
        dprintk("%s\n", __func__);
 
+       poll_wait(file, &ca->wait_queue, wait);
+
        if (dvb_ca_en50221_io_read_condition(ca, &result, &slot) == 1)
                mask |= EPOLLIN;
 
@@ -1804,9 +1806,6 @@ static __poll_t dvb_ca_en50221_io_poll(struct file *file, 
poll_table *wait)
        if (mask)
                return mask;
 
-       /* wait for something to happen */
-       poll_wait(file, &ca->wait_queue, wait);
-
        if (dvb_ca_en50221_io_read_condition(ca, &result, &slot) == 1)
                mask |= EPOLLIN;
 
-- 
2.20.1