Re: [Linaro-acpi] [PATCH] Mailbox: Complete wait event only if Tx was successful
From: Ashwin Chaugule
Date: Fri Dec 12 2014 - 12:47:34 EST
On 12 December 2014 at 03:43, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
> Hi Ashwin,
> On Thursday 11 December 2014 01:46 AM, Ashwin Chaugule 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@xxxxxxxxxx>
>> 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)
> Just curious to check if there's another possible race which is
> a different issue.
> Suppose the timer fired and indicated that the Tx is complete, then
> it tries to execute complete while the wait_for_completion_timeout timed
> out. Does that make sense ?
> So if yes, how about adding !completion_done(..) to the check while you
> are at this ?
Yea. Seems like another race condition. I'll add it along with this..
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