Received-SPF: pass (google.com: domain of linux-bluetooth-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <CAD+dNTsbuU4w+Y_P7o+VEN7BYCAbZuwZx2+tH+OTzCdcZF82YA@mail.gmail.com>
 <24e95c8b-dc05-0d00-50bb-58b71c5baf94@molgen.mpg.de>
In-Reply-To: <24e95c8b-dc05-0d00-50bb-58b71c5baf94@molgen.mpg.de>
From:   Peter Sutton <peter@foxdogstudios.com>
Date:   Mon, 30 May 2022 12:44:09 +0100
Message-ID: <CAD+dNTuRThoa2OSzQ27tENB29GJ4oD0j3D+P4k42HzopEeTJMw@mail.gmail.com>
Subject: Re: [Bug] [Deadlock] Kernel thread deadlock in rfcomm socket release
 when connect interrupted
To:     Paul Menzel <pmenzel@molgen.mpg.de>
Cc:     Marcel Holtmann <marcel@holtmann.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        Matthew Leach <matthew@mattleach.net>,
        Lloyd Henning <lloyd@foxdogstudios.com>,
        linux-bluetooth@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Commit b7ce436a5d798bc59e71797952566608a4b4626b is the probable cause.
I compiled a custom Arch Linux kernel package [1] and the bug was
present. Reverting the commit fixed the bug. Below is the reply I was
writing before Matt found the suspect commit and I tested with the
custom kernel.

> What hardware is that?

$ dmesg | grep iwlwifi
Me: Intel(R) Dual Band Wireless AC 8260, REV=0x204
Matt: Intel(R) Dual Band Wireless AC 8265, REV=0x230

We both get:

$ lsusb | grep Bluetooth
Me & Matt: Bus 001 Device 006: ID 8087:0a2b Intel Corp. Bluetooth
wireless interface

> As a lot of patches are also applied to the stable series, do you know,
> if this is a regression? Does it work with Linux 5.15(.0) or 5.10?

Bug is present on current Arch Linux LTS kernel:

$ uname -a
Linux taffer 5.15.43-1-lts #1 SMP Wed, 25 May 2022 14:08:34 +0000
x86_64 GNU/Linux

Matt tested on 5.10.115 and the bug is not present. So I guess it's a
regression. Anecdotally, we encountered this behaviour 1 yr ago
(difficult to say exactly), then it went away but came back about 1 or
2 months ago. All of this is on Arch Linux, I update about once a
week.

[1] https://wiki.archlinux.org/title/Kernel/Arch_Build_System