linux-kernel - 答复: 答复: 答复: 答复: [PATCH] kdb: Fix the deadlock issue in KDB debugging.

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Message-ID: <410a443612e8441cb729c640a0d606c6@h3c.com>
Date: Wed, 13 Mar 2024 01:22:17 +0000
From: Liuye <liu.yeC@....com>
To: Daniel Thompson <daniel.thompson@...aro.org>
CC: "jason.wessel@...driver.com" <jason.wessel@...driver.com>,
        "dianders@...omium.org" <dianders@...omium.org>,
        "gregkh@...uxfoundation.org"
	<gregkh@...uxfoundation.org>,
        "jirislaby@...nel.org" <jirislaby@...nel.org>,
        "kgdb-bugreport@...ts.sourceforge.net"
	<kgdb-bugreport@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "linux-serial@...r.kernel.org"
	<linux-serial@...r.kernel.org>
Subject: 答复: 答复: 答复: 答复: [PATCH] kdb: Fix the deadlock issue in KDB debugging.

>On Tue, Mar 12, 2024 at 10:04:54AM +0000, Liuye wrote:
>> >On Tue, Mar 12, 2024 at 08:37:11AM +0000, Liuye wrote:
>> >> I know that you said schedule_work is not NMI save, which is the 
>> >> first issue. Perhaps it can be fixed using irq_work_queue. But even 
>> >> if irq_work_queue is used to implement it, there will still be a 
>> >> deadlock problem because slave cpu1 still has not released the 
>> >> running queue lock of master CPU0.
>> >
>> >This doesn't sound right to me. Why do you think CPU1 won't release 
>> >the run queue lock?
>>
>> In this example, CPU1 is waiting for CPU0 to release dbg_slave_lock.
>
>That shouldn't be a problem. CPU0 will have released that lock by the time the irq work is dispatched.

Release dbg_slave_lock in CPU0. Before that, shcedule_work needs to be handled, and we are back to the previous issue.