linux-kernel - Re: [PATCH v3 2/3] livepatch,sched: Add livepatch task switching to cond

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Date:   Mon, 27 Feb 2023 16:55:47 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Seth Forshee <sforshee@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Song Liu <song@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Jiri Kosina <jikos@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH v3 2/3] livepatch,sched: Add livepatch task switching to
 cond_resched()

On Fri 2023-02-24 08:50:00, Josh Poimboeuf wrote:
> There have been reports [1][2] of live patches failing to complete
> within a reasonable amount of time due to CPU-bound kthreads.
> 
> Fix it by patching tasks in cond_resched().
> 
> There are four different flavors of cond_resched(), depending on the
> kernel configuration.  Hook into all of them.
> 
> A more elegant solution might be to use a preempt notifier.  However,
> non-ORC unwinders can't unwind a preempted task reliably.
> 
> [1] https://lore.kernel.org/lkml/20220507174628.2086373-1-song@kernel.org/
> [2] https://lkml.kernel.org/lkml/20230120-vhost-klp-switching-v1-0-7c2b65519c43@kernel.org
> 
> Tested-by: Seth Forshee (DigitalOcean) <sforshee@...nel.org>
> Reviewed-by: Petr Mladek <pmladek@...e.com>
> Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>

Just for record, I have double checked the changes against v2
and everything looks good to me.

Best Regards,
Petr