Re: [PATCH] tty/n_hdlc: fix sleep in !TASK_RUNNING state warning
From: Paul Fulghum
Date: Wed Jan 02 2019 - 15:55:48 EST
> On Jan 2, 2019, at 7:04 AM, Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:
> On 2019/01/01 12:11, Paul Fulghum wrote:
>> NAK to this patch. It causes lost wakeups in both read and write paths.
>> The write path does not need changing.
>> The read path can be fixed by setting current to TASK_RUNNING at the top of the if (rbuf) block
>> so the warning is not triggered by copy_to_user(). If this block runs the condition is satisfied
>> and it breaks out of the polling loop where it is already being set to TASK_RUNNING and removed
>> from the wait queue. This particular path just needs to account for the copy_to_user which occurs
>> before breaking out.
>> Iâll make a patch to do this when I have the ability to test it in a day or two.
> OK. Then, any chance it is rewritten using wait_event_interruptible() in order to reduce lines?
> ( wait_event_interruptible() automatically calls might_sleep(), but is it acceptable for you? )
This looks good to me. I applied it and tested blocking (sleep/no sleep) and non-blocking (success/EAGAIN) paths for both read and write.