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From: Valentin Schneider <vschneid@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
	linux-rt-users@vger.kernel.org,
	Eric Biederman <ebiederm@xmission.com>,
	Arnd Bergmann <arnd@arndb.de>, Petr Mladek <pmladek@suse.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Juri Lelli <jlelli@redhat.com>,
	"Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Subject: Re: [PATCH v2] panic, kexec: Make __crash_kexec() NMI safe
Date: Thu, 23 Jun 2022 12:39:57 +0100	[thread overview]
Message-ID: <xhsmhy1xn622a.mognet@vschneid.remote.csb> (raw)
In-Reply-To: <YrQzB7sPD8BNxSFq@linutronix.de>

On 23/06/22 11:31, Sebastian Andrzej Siewior wrote:
> On 2022-06-20 12:15:20 [+0100], Valentin Schneider wrote:
>> Attempting to get a crash dump out of a debug PREEMPT_RT kernel via an NMI
>> panic() doesn't work. The cause of that lies in the PREEMPT_RT definition
>> of mutex_trylock():
>> 
> …
>
>> Fixes: 6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softirq context")
>> Signed-off-by: Valentin Schneider <vschneid@redhat.com>
>
> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>
>> ---
>> v1 -> v2
>> ++++++++
>> 
>> o Changed from Peterson-like synchronization to simpler atomic_cmpxchg
>>   (Petr)
>> o Slightly reworded changelog
>> o Added Fixes: tag. Technically should be up to since kexec can happen
>>   in an NMI, but that isn't such a clear target
>
> RT-wise it would be needed for each release.

So git tells me the Fixes: commit dates from v4.2; from [1] and [2] I get
that both current longterm stable and stable-rt trees go as far back as
v4.9, so I'm guessing if that gets picked up for the stable trees then it
should make its way into the stable -rt trees?

[1]: https://wiki.linuxfoundation.org/realtime/preempt_rt_versions
[2]: https://www.kernel.org/category/releases.html

> There is also a mutex_unlock() in case an image is missing. This can go
> via the scheduler if there is a waiter which does not look good with the
> NMI in the picture.
>
> Sebastian


WARNING: multiple messages have this Message-ID (diff)
From: Valentin Schneider <vschneid@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
	linux-rt-users@vger.kernel.org,
	Eric Biederman <ebiederm@xmission.com>,
	Arnd Bergmann <arnd@arndb.de>, Petr Mladek <pmladek@suse.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Juri Lelli <jlelli@redhat.com>,
	"Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Subject: Re: [PATCH v2] panic, kexec: Make __crash_kexec() NMI safe
Date: Thu, 23 Jun 2022 12:39:57 +0100	[thread overview]
Message-ID: <xhsmhy1xn622a.mognet@vschneid.remote.csb> (raw)
In-Reply-To: <YrQzB7sPD8BNxSFq@linutronix.de>

On 23/06/22 11:31, Sebastian Andrzej Siewior wrote:
> On 2022-06-20 12:15:20 [+0100], Valentin Schneider wrote:
>> Attempting to get a crash dump out of a debug PREEMPT_RT kernel via an NMI
>> panic() doesn't work. The cause of that lies in the PREEMPT_RT definition
>> of mutex_trylock():
>> 
> …
>
>> Fixes: 6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softirq context")
>> Signed-off-by: Valentin Schneider <vschneid@redhat.com>
>
> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>
>> ---
>> v1 -> v2
>> ++++++++
>> 
>> o Changed from Peterson-like synchronization to simpler atomic_cmpxchg
>>   (Petr)
>> o Slightly reworded changelog
>> o Added Fixes: tag. Technically should be up to since kexec can happen
>>   in an NMI, but that isn't such a clear target
>
> RT-wise it would be needed for each release.

So git tells me the Fixes: commit dates from v4.2; from [1] and [2] I get
that both current longterm stable and stable-rt trees go as far back as
v4.9, so I'm guessing if that gets picked up for the stable trees then it
should make its way into the stable -rt trees?

[1]: https://wiki.linuxfoundation.org/realtime/preempt_rt_versions
[2]: https://www.kernel.org/category/releases.html

> There is also a mutex_unlock() in case an image is missing. This can go
> via the scheduler if there is a waiter which does not look good with the
> NMI in the picture.
>
> Sebastian


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  reply	other threads:[~2022-06-23 11:40 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-20 11:15 [PATCH v2] panic, kexec: Make __crash_kexec() NMI safe Valentin Schneider
2022-06-20 11:15 ` Valentin Schneider
2022-06-23  9:31 ` Sebastian Andrzej Siewior
2022-06-23  9:31   ` Sebastian Andrzej Siewior
2022-06-23 11:39   ` Valentin Schneider [this message]
2022-06-23 11:39     ` Valentin Schneider
2022-06-23 13:35     ` Sebastian Andrzej Siewior
2022-06-23 13:35       ` Sebastian Andrzej Siewior
2022-06-24  1:30 ` Baoquan He
2022-06-24  1:30   ` Baoquan He
2022-06-24 13:37   ` Valentin Schneider
2022-06-24 13:37     ` Valentin Schneider
2022-06-26 10:37     ` Baoquan He
2022-06-26 10:37       ` Baoquan He
2022-06-26 10:45       ` Baoquan He
2022-06-26 10:45         ` Baoquan He
2022-06-25 17:04 ` Eric W. Biederman
2022-06-25 17:04   ` Eric W. Biederman
2022-06-27 12:42   ` Valentin Schneider
2022-06-27 12:42     ` Valentin Schneider
2022-06-28 17:33     ` Valentin Schneider
2022-06-28 17:33       ` Valentin Schneider
2022-06-29 11:55       ` Petr Mladek
2022-06-29 11:55         ` Petr Mladek
2022-06-29 12:23         ` Valentin Schneider
2022-06-29 12:23           ` Valentin Schneider

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