Re: [RFC 0/5] fix races in CDC-WDM

[Oliver Neukum <oneukum@suse.com>]

Am Dienstag, den 15.09.2020, 19:30 +0900 schrieb Tetsuo Handa:
> On 2020/09/15 18:14, Oliver Neukum wrote

> > Is there something we can do in flush()?
> 
> I consider that wdm_flush() is a wrong place to return an error. It is possible that

I am afraid that is a basic problem we need to resolve. As I understand
 it, flush() as a method exists precisely to report errors. Otherwise
you could implement it in release(). But this is not called for every
close().

Hence a driver is supposed to start IO upon write() and report the
result to the next call, which can be either write() or close(), the
latter corresponding to flush().

> a userspace process reaches wdm_flush() due to being killed by SIGKILL (rather than
> via calling close() syscall). Then, that userspace process will never receive the error

If you are killed by a signal you are in a race condition
anyway. It cannot be handled.

> fetched from wdm_flush(). Also, if that userspace process is killed by the OOM killer,
> being able to terminate and release resources as soon as possible is more preferable
> than try to wait for response.

Right, so should we just proceed in case of a dieing task? How do we
do that?

	Regards
		Oliver