From: Johannes Berg <johannes@sipsolutions.net>
To: Simon Horman <horms@kernel.org>, Edward AD <twuufnxlz@gmail.com>
Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org,
netdev@vger.kernel.org, pabeni@redhat.com,
syzbot+509238e523e032442b80@syzkaller.appspotmail.com,
syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH] rfkill: fix deadlock in rfkill_send_events
Date: Sat, 14 Oct 2023 22:01:45 +0200 [thread overview]
Message-ID: <fec9cfe4436786f6f9b61ee6e9bb7766efb29d34.camel@sipsolutions.net> (raw)
In-Reply-To: <20231014072943.GV29570@kernel.org>
On Sat, 2023-10-14 at 09:29 +0200, Simon Horman wrote:
> On Sat, Oct 14, 2023 at 10:43:22AM +0800, Edward AD wrote:
> > Hi Simon Horman,
> > On Fri, 13 Oct 2023 13:06:38 +0200, Simon Horman wrote:
> > > I am wondering if you considered moving the rfkill_sync() calls
> > > to before &data->mtx is taken, to avoid the need to drop and
> > > retake it?
> > If you move rfkill_sync() before calling &data->mtx, more code will be added
> > because rfkill_sync() is in the loop body.
>
> Maybe that is true. And maybe that is a good argument for
> not taking the approach that I suggested. But I do think it
> is simpler from a locking perspective, and that has some merit.
>
FWIW, I missed this patch and discussion until now, but I already fixed
the issue differently:
https://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless.git/commit/?id=f2ac54ebf85615a6d78f5eb213a8bbeeb17ebe5d
There was never any need to hold the data->mtx for anything but the list
manipulation, and even that isn't _really_ needed since the 'data' is
completely fresh and not seen anywhere else yet.
(I'll also note that the subject of this thread is wrong since this was
never an *actual* deadlock, just a *possible* one reported by lockdep.)
johannes
prev parent reply other threads:[~2023-10-14 20:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-09 20:09 [syzbot] [net?] [wireless?] possible deadlock in rfkill_send_events syzbot
2023-10-10 1:08 ` [PATCH] rfkill: fix " Edward AD
2023-10-13 11:06 ` Simon Horman
2023-10-14 2:43 ` Edward AD
2023-10-14 7:29 ` Simon Horman
2023-10-14 20:01 ` Johannes Berg [this message]
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