linux-kernel - Re: [PATCH] rfkill: fix deadlock in rfkill_send

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Message-ID: <20231014072943.GV29570@kernel.org>
Date:   Sat, 14 Oct 2023 09:29:43 +0200
From:   Simon Horman <horms@...nel.org>
To:     Edward AD <twuufnxlz@...il.com>
Cc:     davem@...emloft.net, edumazet@...gle.com, johannes.berg@...el.com,
        johannes@...solutions.net, kuba@...nel.org,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, pabeni@...hat.com,
        syzbot+509238e523e032442b80@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] rfkill: fix deadlock in rfkill_send_events

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.

> > 
> > Perhaps it doesn't work for some reason (compile tested only!).
> > But this does seem somehow cleaner for me.
> BR,
> edward
>