[PATCH 4.19 051/115] media: cec: check transmit_in_progress, not transmitting

Greg Kroah-Hartman
2020-01-07T21:16:38Z

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

commit ac479b51f3f4aaa852b5d3f00ecfb9290230cf64 upstream.

Currently wait_event_interruptible_timeout is called in cec_thread_func()
when adap->transmitting is set. But if the adapter is unconfigured
while transmitting, then adap->transmitting is set to NULL. But the
hardware is still actually transmitting the message, and that's
indicated by adap->transmit_in_progress and we should wait until that
is finished or times out before transmitting new messages.

As the original commit says: adap->transmitting is the userspace view,
adap->transmit_in_progress reflects the hardware state.

However, if adap->transmitting is NULL and adap->transmit_in_progress
is true, then wait_event_interruptible is called (no timeout), which
can get stuck indefinitely if the CEC driver is flaky and never marks
the transmit-in-progress as 'done'.

So test against transmit_in_progress when deciding whether to use
the timeout variant or not, instead of testing against adap->transmitting.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Fixes: 32804fcb612b ("media: cec: keep track of outstanding transmits")
Cc: <stable@vger.kernel.org> # for v4.19 and up
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/media/cec/cec-adap.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)

--- a/drivers/media/cec/cec-adap.c
+++ b/drivers/media/cec/cec-adap.c
@@ -450,7 +450,7 @@ int cec_thread_func(void *_adap)
bool timeout = false;
u8 attempts;

- if (adap->transmitting) {
+ if (adap->transmit_in_progress) {
int err;

/*
@@ -485,7 +485,7 @@ int cec_thread_func(void *_adap)
goto unlock;
}

- if (adap->transmitting && timeout) {
+ if (adap->transmit_in_progress && timeout) {
/*
* If we timeout, then log that. Normally this does
* not happen and it is an indication of a faulty CEC
@@ -494,14 +494,18 @@ int cec_thread_func(void *_adap)
* so much traffic on the bus that the adapter was
* unable to transmit for CEC_XFER_TIMEOUT_MS (2.1s).
*/
- pr_warn("cec-%s: message %*ph timed out\n", adap->name,
- adap->transmitting->msg.len,
- adap->transmitting->msg.msg);
+ if (adap->transmitting) {
+ pr_warn("cec-%s: message %*ph timed out\n", adap->name,
+ adap->transmitting->msg.len,
+ adap->transmitting->msg.msg);
+ /* Just give up on this. */
+ cec_data_cancel(adap->transmitting,
+ CEC_TX_STATUS_TIMEOUT);
+ } else {
+ pr_warn("cec-%s: transmit timed out\n", adap->name);
+ }
adap->transmit_in_progress = false;
adap->tx_timeouts++;
- /* Just give up on this. */
- cec_data_cancel(adap->transmitting,
- CEC_TX_STATUS_TIMEOUT);
goto unlock;
}