Re: [bug-report] task info hung problem in fb_deferred_io_work()

[Nam Cao]

On 2024-04-18 Patrik Jakobsson wrote:
> This sounds similar to the SUSE bug [1]. We fixed it by reverting [2]
> in the SUSE kernel. The problem seems to be that flush_delayed_work()
> kills the timer and re-queues the work but doesn't guarantee that it
> is finished when returning. So when the device is closed, the
> fb_deferred_io_work() function can still be queued and tries to access
> memory that's been freed.

flush_delayed_work() *does* guarantee the work is finished before
returning.

> Patch [2] tries to solve the problem of not throwing away pending data
> when closing the device. Perhaps calling cancel_delayed_work_sync()
> and then follow up with a manual call to fb_deferred_io_work() would
> be enough to flush the remaining data?
> 
> -Patrik
> 
> [1] https://bugzilla.suse.com/show_bug.cgi?id=1221814
> [2] 33cd6ea9c067 fbdev: flush deferred IO before closing
> 
> >
> >
> > Thanks,
> > Harshit