From: Michael Ellerman <mpe@ellerman.id.au>
To: Laurent Dufour <ldufour@linux.ibm.com>,
benh@kernel.crashing.org, paulus@samba.org,
nathanl@linux.ibm.com, haren@linux.vnet.ibm.com,
npiggin@gmail.com
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/4] watchdog: export watchdog_mutex and lockup_detector_reconfigure
Date: Fri, 24 Jun 2022 16:31:55 +1000 [thread overview]
Message-ID: <871qve6084.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <20220614135414.37746-3-ldufour@linux.ibm.com>
Laurent Dufour <ldufour@linux.ibm.com> writes:
> In some cricunstances it may be interesting to reconfigure the watchdog
> from inside the kernel.
>
> On PowerPC, this may helpful before and after a LPAR migration (LPM) is
> initiated, because it implies some latencies, watchdog, and especially NMI
> watchdog is expected to be triggered during this operation. Reconfiguring
> the watchdog, would prevent it to happen too frequently during LPM.
>
> The watchdog_mutex is exported to allow some variable to be changed under
> its protection and prevent any conflict.
> The lockup_detector_reconfigure() function is exported and is expected to
> be called under the protection of watchdog_mutex.
>
> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
> ---
> include/linux/nmi.h | 3 +++
> kernel/watchdog.c | 6 +++---
> 2 files changed, 6 insertions(+), 3 deletions(-)
Is there a maintainer for kernel/watchdog.c ?
There's Wim & Guenter at linux-watchdog@vger but I think that's only for
drivers/watchdog?
Maybe we should Cc that list anyway?
> diff --git a/include/linux/nmi.h b/include/linux/nmi.h
> index 750c7f395ca9..84300fb0f90a 100644
> --- a/include/linux/nmi.h
> +++ b/include/linux/nmi.h
> @@ -122,6 +122,9 @@ int watchdog_nmi_probe(void);
> int watchdog_nmi_enable(unsigned int cpu);
> void watchdog_nmi_disable(unsigned int cpu);
>
> +extern struct mutex watchdog_mutex;
> +void lockup_detector_reconfigure(void);
It would be preferable if we didn't export the mutex.
I think you could arrange that by ...
Renaming lockup_detector_configure() to __lockup_detector_configure()
and then adding a new lockup_detector_configure() that is non-static and
takes the lock around __lockup_detector_configure().
cheers
next prev parent reply other threads:[~2022-06-24 6:32 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-14 13:54 [PATCH v2 0/4] Extending NMI watchdog during LPM Laurent Dufour
2022-06-14 13:54 ` [PATCH v2 1/4] powerpc/mobility: Wait for memory transfer to complete Laurent Dufour
2022-06-21 16:52 ` Nathan Lynch
2022-06-14 13:54 ` [PATCH v2 2/4] watchdog: export watchdog_mutex and lockup_detector_reconfigure Laurent Dufour
2022-06-24 6:31 ` Michael Ellerman [this message]
2022-06-24 8:27 ` Laurent Dufour
2022-06-24 9:37 ` Christoph Hellwig
2022-06-24 12:45 ` Laurent Dufour
2022-06-14 13:54 ` [PATCH v2 3/4] powerpc/watchdog: introduce a LPM factor Laurent Dufour
2022-06-22 9:26 ` kernel test robot
2022-06-14 13:54 ` [PATCH v2 4/4] pseries/mobility: Set NMI watchdog factor during LPM Laurent Dufour
2022-06-23 17:28 ` Nathan Lynch
2022-06-24 14:09 ` Laurent Dufour
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