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

[Nam Cao]

On 2024-04-19 Patrik Jakobsson wrote:
> Neither cancel_delayed_work_sync() or flush_delayed_work() prevent new
> work from being scheduled after they return.

flush_delayed_work() is called during device closing. And because no
writes are performed after the device has been closed, no new work
should be queued after flush_delayed_work().

> But
> cancel_delayed_work_sync() at least makes sure the queue is empty so
> the problem becomes less apparent.
> 
> Could this explain what we're seeing?

I suspect that cancel_delayed_work_sync() is only treating the symptoms
by preventing the deferred work from running. The real bug is "someone"
giving fb_deferred_io_work() invalid pages to work with. But that's
just a blind guess.

Best regards,
Nam