media: cedrus: Fix watchdog race condition

The watchdog needs to be scheduled before we trigger the decode
operation, otherwise there is a risk that the decoder IRQ will be
called before we have schedule the watchdog. As a side effect, the
watchdog would never be cancelled and its function would be called
at an inappropriate time.

This was observed while running Fluster with GStreamer as a backend.
Some programming error would cause the decoder IRQ to be call very
quickly after the trigger. Later calls into the driver would deadlock
due to the unbalanced state.

Cc: stable@vger.kernel.org
Fixes: 7c38a551bda1 ("media: cedrus: Add watchdog for job completion")
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
index 3b6aa78..e7f7602 100644 (file)
--- a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
+++ b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
@@ -106,11 +106,11 @@ void cedrus_device_run(void *priv)
 
        /* Trigger decoding if setup went well, bail out otherwise. */
        if (!error) {
-               dev->dec_ops[ctx->current_codec]->trigger(ctx);
-
                /* Start the watchdog timer. */
                schedule_delayed_work(&dev->watchdog_work,
                                      msecs_to_jiffies(2000));
+
+               dev->dec_ops[ctx->current_codec]->trigger(ctx);
        } else {
                v4l2_m2m_buf_done_and_job_finish(ctx->dev->m2m_dev,
                                                 ctx->fh.m2m_ctx,