Re: [BUG] fs: dlm: possible ABBA deadlock
From: David Teigland
Date: Thu Aug 19 2021 - 11:55:27 EST
On Thu, Aug 19, 2021 at 04:54:57PM +0800, Jia-Ju Bai wrote:
> Hello,
>
> My static analysis tool reports a possible ABBA deadlock in the dlm
> filesystem in Linux 5.10:
>
> dlm_recover_waiters_pre()
> mutex_lock(&ls->ls_waiters_mutex); --> line 5130
> recover_convert_waiter()
> _receive_convert_reply()
> lock_rsb()
> mutex_lock(&r->res_mutex); --> line 69
>
> dlm_recover_waiters_post()
> lock_rsb()
> mutex_lock(&r->res_mutex); --> line 69
> mutex_lock(&ls->ls_waiters_mutex); --> line 5307
>
> When dlm_recover_waiters_pre() and dlm_recover_waiters_post() are
> concurrently executed, the deadlock can occur.
>
> I am not quite sure whether this possible deadlock is real and how to fix it
> if it is real.
> Any feedback would be appreciated, thanks :)
They won't be concurrent, "pre" runs before recovery, and "post" is after.
Dave