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Message-ID: <cb377661e760d7728d11bd155b016f852b2681eb.camel@sipsolutions.net>
Subject: Re: 6.7.0-rc1 + hacks deadlock bug, wifi netdev delete + cat of
 debugfs file.
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Ben Greear <greearb@candelatech.com>,
        linux-wireless <linux-wireless@vger.kernel.org>
Date:   Wed, 08 Nov 2023 11:31:57 +0100
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On Tue, 2023-11-07 at 14:08 -0800, Ben Greear wrote:
> Hello,
>=20
> I think this lockup is because iw is holding rtnl and wiphy mutex,
> and is blocked waiting for debugfs to be closed.  Another 'cat'
> program has debugfs file open, and is blocking on trying to acquire
> wiphy mutex.
>=20
> I think we must not acquire wiphy mutex in debugfs methods, somehow,
> to resolve this deadlock.  I do not know a safe way to do that.

Hmm. I almost want to say "don't do that then", but I guess you're just
randomly accessing debugfs files.

I guess we can at least make the mutex acquisition in debugfs killable
(or interruptible), so you can recover from this.

But fundamentally this is probably not really even a new issue.

I don't know how to interrupt a specific task that's stuck in a specific
debugfs file though, e.g. when removing them.

johannes