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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Valentin Schneider <vschneid@redhat.com>
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 11:31:51 +0200	[thread overview]
Message-ID: <YrQzB7sPD8BNxSFq@linutronix.de> (raw)
In-Reply-To: <20220620111520.1039685-1-vschneid@redhat.com>

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.
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: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Valentin Schneider <vschneid@redhat.com>
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 11:31:51 +0200	[thread overview]
Message-ID: <YrQzB7sPD8BNxSFq@linutronix.de> (raw)
In-Reply-To: <20220620111520.1039685-1-vschneid@redhat.com>

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.
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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kexec@lists.infradead.org
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  reply	other threads:[~2022-06-23  9:31 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 [this message]
2022-06-23  9:31   ` Sebastian Andrzej Siewior
2022-06-23 11:39   ` Valentin Schneider
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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