Re: [PATCH] bdi: Fix another oops in wb_workfn()

From: Linus Torvalds
Date: Wed Jun 13 2018 - 10:07:02 EST

On Wed, Jun 13, 2018 at 3:44 AM Tetsuo Handa
<penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:
> Can't we utilize RCU grace period (like shown below) ?

_Please_ don't do conditional locking. Particularly not the kind where
then a function drops the lock that was taken in another function -
and only does it based on some parameter.

Yes, we have cases where we do it, but it's seldom a great idea, and
it _really_ makes for subtle code (and subtle bugs).