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From: Miroslav Benes <>
To: Vasily Gorbik <>
Cc: Josh Poimboeuf <>,
	Jiri Kosina <>, Petr Mladek <>,
	Joe Lawrence <>,
	Ingo Molnar <>,
	Peter Zijlstra <>,
	Frederic Weisbecker <>,
	Thomas Gleixner <>,
	Heiko Carstens <>,
	Sven Schnelle <>,
	Sumanth Korikkar <>,,
Subject: Re: [PATCH] livepatch: Fix idle cpu's tasks transition
Date: Fri, 10 Sep 2021 11:32:19 +0200 (CEST)	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, 9 Sep 2021, Vasily Gorbik wrote:

> On an idle system with large amount of cpus it might happen that
> klp_update_patch_state() is not reached in do_idle() for a long periods
> of time. With debug messages enabled log is filled with:
> [  499.442643] livepatch: klp_try_switch_task: swapper/63:0 is running
> without any signs of progress. Ending up with "failed to complete
> transition".
> On s390 LPAR with 128 cpus not a single transition is able to complete
> and livepatch kselftests fail. Tests on idling x86 kvm instance with 128
> cpus demonstrate similar symptoms with and without CONFIG_NO_HZ.
> To deal with that, since runqueue is already locked in
> klp_try_switch_task() identify idling cpus and trigger rescheduling
> potentially waking them up and making sure idle tasks break out of
> do_idle() inner loop and reach klp_update_patch_state(). This helps to
> speed up transition time while avoiding unnecessary extra system load.
> Signed-off-by: Vasily Gorbik <>

Seems reasonable to me.

Acked-by: Miroslav Benes <>


  parent reply	other threads:[~2021-09-10  9:32 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-09  9:16 [PATCH] livepatch: Fix idle cpu's tasks transition Vasily Gorbik
2021-09-10  9:17 ` Petr Mladek
2021-09-10  9:32 ` Miroslav Benes [this message]
2021-09-10 16:03 ` Josh Poimboeuf

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