From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: mingo@kernel.org, linux-kernel@vger.kernel.org,
tglx@linutronix.de, qais.yousef@arm.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
bsegall@google.com, mgorman@suse.de, wim@linux-watchdog.org,
Christophe Leroy <christophe.leroy@c-s.fr>
Subject: Re: [PATCH 16/23] sched,watchdog: Convert to sched_set_fifo()
Date: Wed, 22 Apr 2020 15:24:48 +0200 [thread overview]
Message-ID: <20200422132448.GH20730@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200422085155.7549ca94@gandalf.local.home>
On Wed, Apr 22, 2020 at 08:51:55AM -0400, Steven Rostedt wrote:
> On Wed, 22 Apr 2020 13:27:35 +0200
> Peter Zijlstra <peterz@infradead.org> wrote:
>
> > Because SCHED_FIFO is a broken scheduler model (see previous patches)
> > take away the priority field, the kernel can't possibly make an
> > informed decision.
> >
> > Effectively changes prio from 99 to 50.
>
> Hmm, this being a watchdog, and looking at commit 38a1222ae4f364d
> ("watchdog: core: make sure the watchdog worker always works")
>
> I wonder if we should add a sched_set_high(), or have some other kind of
> watchdog handler that is guaranteed to trigger.
It's FIFO, it'll never win from either a deadline or a stop-task. After
that it doesn't matter.
fifo_high() is most definitely a bad idea, because then we're back into
the whole 'fifo priority' has meaning -- it does not. At least, it
doesn't until you've got system design information.
Maybe we should rename fifo_low to get away from that. I just drew a
blank on a better name there.
next prev parent reply other threads:[~2020-04-22 13:25 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-22 11:27 [PATCH 00/23] sched: Remove FIFO priorities from modules Peter Zijlstra
2020-04-22 11:27 ` [PATCH 01/23] sched: Provide sched_set_fifo() Peter Zijlstra
2020-04-22 13:11 ` Paul E. McKenney
2020-04-22 13:26 ` Peter Zijlstra
2020-04-22 15:50 ` Paul E. McKenney
2020-04-22 16:33 ` Steven Rostedt
2020-04-22 16:40 ` Paul E. McKenney
2020-04-22 16:46 ` Steven Rostedt
2020-04-22 17:45 ` Paul E. McKenney
2020-04-22 15:50 ` Paul E. McKenney
2020-04-27 17:04 ` Qais Yousef
2020-04-22 11:27 ` [PATCH 02/23] sched,bL_switcher: Convert to sched_set_fifo*() Peter Zijlstra
2020-04-22 13:27 ` Nicolas Pitre
2020-04-22 11:27 ` [PATCH 03/23] sched,crypto: " Peter Zijlstra
2020-04-22 13:33 ` Herbert Xu
2020-04-22 11:27 ` [PATCH 04/23] sched,acpi_pad: " Peter Zijlstra
2020-04-22 16:45 ` Dietmar Eggemann
2020-04-23 8:46 ` Peter Zijlstra
2020-04-22 11:27 ` [PATCH 05/23] sched,drbd: " Peter Zijlstra
2020-04-23 8:57 ` Peter Zijlstra
2020-04-22 11:27 ` [PATCH 06/23] sched,psci: " Peter Zijlstra
2020-04-22 11:55 ` Valentin Schneider
2020-04-22 14:06 ` Sudeep Holla
2020-04-27 16:35 ` Qais Yousef
2020-04-27 16:58 ` Valentin Schneider
2020-04-22 11:27 ` [PATCH 07/23] sched,msm: " Peter Zijlstra
2020-04-22 11:27 ` [PATCH 08/23] sched,drm/scheduler: " Peter Zijlstra
2020-04-22 11:27 ` [PATCH 09/23] sched,ivtv: " Peter Zijlstra
2020-04-22 12:53 ` Steven Rostedt
2020-04-22 13:26 ` Peter Zijlstra
2020-04-24 9:58 ` Hans Verkuil
2020-04-22 11:27 ` [PATCH 10/23] sched,mmc: " Peter Zijlstra
2020-04-22 16:59 ` Ulf Hansson
2020-04-23 8:59 ` Peter Zijlstra
2020-04-23 12:01 ` Ulf Hansson
2020-04-22 11:27 ` [PATCH 11/23] sched,spi: " Peter Zijlstra
2020-04-22 13:56 ` Mark Brown
2020-04-22 14:35 ` Doug Anderson
2020-04-22 15:47 ` Guenter Roeck
2020-04-22 16:41 ` Doug Anderson
2020-04-22 20:16 ` Guenter Roeck
2020-04-22 11:27 ` [PATCH 12/23] sched,powercap: " Peter Zijlstra
2020-04-22 11:27 ` [PATCH 13/23] sched,ion: Convert to sched_set_normal() Peter Zijlstra
2020-04-22 13:21 ` Vincent Guittot
2020-04-22 13:29 ` Peter Zijlstra
2020-04-22 13:36 ` Vincent Guittot
2020-04-22 13:59 ` Peter Zijlstra
2020-04-22 15:09 ` Vincent Guittot
2020-04-22 15:39 ` Peter Zijlstra
2020-04-22 15:52 ` Vincent Guittot
2020-04-22 15:38 ` Juri Lelli
2020-04-22 15:42 ` Peter Zijlstra
2020-04-22 11:27 ` [PATCH 14/23] sched,powerclamp: Convert to sched_set_fifo() Peter Zijlstra
2020-04-22 11:27 ` [PATCH 15/23] sched,serial: " Peter Zijlstra
2020-04-22 11:27 ` [PATCH 16/23] sched,watchdog: " Peter Zijlstra
2020-04-22 12:51 ` Steven Rostedt
2020-04-22 13:24 ` Peter Zijlstra [this message]
2025-05-16 8:42 ` Christophe Leroy
2025-05-16 12:42 ` Peter Zijlstra
2020-04-22 11:27 ` [PATCH 17/23] sched,irq: " Peter Zijlstra
2020-04-22 11:39 ` Peter Zijlstra
2020-04-22 11:27 ` [PATCH 18/23] sched,locktorture: " Peter Zijlstra
2020-04-22 15:51 ` Paul E. McKenney
2020-04-22 11:27 ` [PATCH 19/23] sched,rcuperf: Convert to sched_set_fifo_low() Peter Zijlstra
2020-04-22 15:51 ` Paul E. McKenney
2020-04-22 11:27 ` [PATCH 20/23] sched,rcutorture: " Peter Zijlstra
2020-04-22 15:51 ` Paul E. McKenney
2020-04-22 11:27 ` [PATCH 21/23] sched,psi: " Peter Zijlstra
2020-04-22 15:22 ` Johannes Weiner
2020-04-22 11:27 ` [PATCH 22/23] sched: Remove sched_setscheduler*() EXPORTs Peter Zijlstra
2020-04-22 11:27 ` [PATCH 23/23] sched: Remove sched_set_*() return value Peter Zijlstra
2020-04-22 14:25 ` Ingo Molnar
2020-04-22 16:16 ` Paul E. McKenney
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