On 12 December 2014 at 05:21, Jassi Brar jaswinder.singh@linaro.org wrote:
On 11 December 2014 at 01:46, Ashwin Chaugule ashwin.chaugule@linaro.org wrote:
If a wait_for_completion_timeout() call returns due to a timeout, the mbox code can still call complete() after returning from the wait. This can cause subsequent transmissions on a channel to fail, since the wait_for_completion_timeout() sees the completion variable is !=0, caused by the erroneous complete() call, and immediately returns without waiting for the time as expected by the client.
Fix this by calling complete() only if the TX was successful.
Signed-off-by: Ashwin Chaugule ashwin.chaugule@linaro.org
drivers/mailbox/mailbox.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c index 17e9e4a..4acaddb 100644 --- a/drivers/mailbox/mailbox.c +++ b/drivers/mailbox/mailbox.c @@ -101,7 +101,7 @@ static void tx_tick(struct mbox_chan *chan, int r) if (mssg && chan->cl->tx_done) chan->cl->tx_done(chan->cl, mssg, r);
if (chan->cl->tx_block)
if ((!r) && chan->cl->tx_block) complete(&chan->tx_complete);Thanks for finding the bug. However the fix is flawed. complete() could also be done from mbox_chan_txdone() calling tx_tick(). And if the controller returned error, we could never pass on that error code to the user (timeout fires and then we will move on with -EIO).
If the controller returned error, wouldnt it be passed to the user via chan->cl->tx_done()? However, I agree that with this fix, it won't call complete(), when the controller finished the Tx with an Err.
Since we could never prevent the controller from returning -EIO as the error, I think we have to explicitly tell tx_tick() if it needs to complete() or not.
Hm. How about checking if the wait_for_completion_timeout() returned the timeout value? If so, then return with -EIO and don't complete().
-Jassi