From: Josh Poimboeuf <jpoimboe@kernel.org>
To: Rik van Riel <riel@surriel.com>
Cc: Song Liu <song@kernel.org>,
linux-kernel@vger.kernel.org, live-patching@vger.kernel.org,
mingo@redhat.com, peterz@infradead.org,
vincent.guittot@linaro.org, jpoimboe@redhat.com,
joe.lawrence@redhat.com, kernel-team@fb.com
Subject: Re: [RFC] sched,livepatch: call stop_one_cpu in klp_check_and_switch_task
Date: Mon, 9 May 2022 13:09:49 -0700 [thread overview]
Message-ID: <20220509200949.vzx4g5xpebomkok4@treble> (raw)
In-Reply-To: <1f94c48b4e0e7d73a689a076f78f0892095b4d89.camel@surriel.com>
On Mon, May 09, 2022 at 03:49:52PM -0400, Rik van Riel wrote:
> On Mon, 2022-05-09 at 12:17 -0700, Josh Poimboeuf wrote:
> > On Mon, May 09, 2022 at 03:10:16PM -0400, Rik van Riel wrote:
> >
> >
> > > Should kernel threads that can use a lot of CPU have
> > > something in their outer loop to transition KLPs,
> > > just like the idle task does?
> >
> > Maybe - I suppose this is the first time we've had an issue with
> > CPU-bound kthreads. I didn't know that was a thing ;-)
> >
> Kworkers have as much work as you want them to do, and with
> things like btrfs compression that can be quite a bit.
To prevent patching, it would need to be some kind of sustained CPU
activity, rather than a burst. I guess we haven't seen that show up as
a real-world problem until now.
If you're able to identify which kthreads would be problematic, then
yeah, defining a "transition point" in their outer loops could be an
option.
We could look also at a more general approach, like stack checking from
an irq handler. But as Petr alluded to, that would be problematic for
CONFIG_FRAME_POINTER.
We could maybe deprecate frame pointers on x86 for live patching, but I
think other arches would have a similar problem unless they were to do
something like the ORC unwinder.
--
Josh
next prev parent reply other threads:[~2022-05-09 20:23 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-07 17:46 [RFC] sched,livepatch: call klp_try_switch_task in __cond_resched Song Liu
2022-05-07 18:26 ` Rik van Riel
2022-05-07 19:04 ` Song Liu
2022-05-07 19:18 ` Rik van Riel
2022-05-08 20:41 ` Peter Zijlstra
2022-05-09 1:07 ` Rik van Riel
2022-05-09 7:04 ` Peter Zijlstra
2022-05-09 8:06 ` Song Liu
2022-05-09 9:38 ` Peter Zijlstra
2022-05-09 14:13 ` Rik van Riel
2022-05-09 15:22 ` Petr Mladek
2022-05-09 15:07 ` Petr Mladek
2022-05-09 16:22 ` Song Liu
2022-05-10 7:56 ` Petr Mladek
2022-05-10 13:33 ` Rik van Riel
2022-05-10 15:44 ` Petr Mladek
2022-05-10 16:07 ` Rik van Riel
2022-05-10 16:52 ` Josh Poimboeuf
2022-05-10 18:07 ` Rik van Riel
2022-05-10 18:42 ` Josh Poimboeuf
2022-05-10 19:45 ` Song Liu
2022-05-10 23:04 ` Josh Poimboeuf
2022-05-10 23:57 ` Song Liu
2022-05-11 0:33 ` Josh Poimboeuf
2022-05-11 9:24 ` Petr Mladek
2022-05-11 16:33 ` Song Liu
2022-05-12 4:07 ` Josh Poimboeuf
2022-05-13 12:33 ` Petr Mladek
2022-05-13 13:34 ` Peter Zijlstra
2022-05-11 0:35 ` Rik van Riel
2022-05-11 0:37 ` Josh Poimboeuf
2022-05-11 0:46 ` Rik van Riel
2022-05-11 1:12 ` Josh Poimboeuf
2022-05-11 18:09 ` Rik van Riel
2022-05-12 3:59 ` Josh Poimboeuf
2022-05-09 15:52 ` [RFC] sched,livepatch: call stop_one_cpu in klp_check_and_switch_task Rik van Riel
2022-05-09 16:28 ` Song Liu
2022-05-09 18:00 ` Josh Poimboeuf
2022-05-09 19:10 ` Rik van Riel
2022-05-09 19:17 ` Josh Poimboeuf
2022-05-09 19:49 ` Rik van Riel
2022-05-09 20:09 ` Josh Poimboeuf [this message]
2022-05-10 0:32 ` Song Liu
2022-05-10 9:35 ` Peter Zijlstra
2022-05-10 1:48 ` Rik van Riel
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