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From:   Thomas Gleixner <tglx@linutronix.de>
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To:     Hillf Danton <hdanton@sina.com>
Cc:     syzbot <syzbot+6fb78d577e89e69602f9@syzkaller.appspotmail.com>,
        linux-kernel@vger.kernel.org, pbonzini@redhat.com,
        syzkaller-bugs@googlegroups.com,
        Steven Rostedt <rosted@goodmis.org>,
        Marcel Holtmann <marcel@holtmann.org>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Subject: Re: [syzbot] WARNING in call_timer_fn
In-Reply-To: <20221117125523.3783-1-hdanton@sina.com>
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 <20221117024511.3606-1-hdanton@sina.com>
 <20221117125523.3783-1-hdanton@sina.com>
Date:   Thu, 17 Nov 2022 17:06:48 +0100
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On Thu, Nov 17 2022 at 20:55, Hillf Danton wrote:
> On 17 Nov 2022 12:54:28 +0100 Thomas Gleixner <tglx@linutronix.de>
>> 
>> The work has been canceled already before in the same function and there
>> are some more delayed works which can trigger this.
>> 
>> So no, this whole close_sync() function is prone to teardown races and
>> just slapping a single cancel here without deeper analysis does not cut
>> it.
>
> Agree.
>
> A set of sync cancelations can do the job, given what is defined in struct
> hci_dev wrt workqueue.

It's only part of the solution because you also have to prevent that
work is queued from other parts of the code....