From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <vschneid@redhat.com>,
linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Tomas Glozar <tglozar@redhat.com>
Subject: Re: [PATCH] sched/fair: Make the BW replenish timer expire in hardirq context for PREEMPT_RT
Date: Thu, 2 Nov 2023 17:19:49 +0100 [thread overview]
Message-ID: <20231102161949.IdSqSK2E@linutronix.de> (raw)
In-Reply-To: <20231031160120.GE15024@noisy.programming.kicks-ass.net>
On 2023-10-31 17:01:20 [+0100], Peter Zijlstra wrote:
> On Mon, Oct 30, 2023 at 03:51:04PM +0100, Valentin Schneider wrote:
> > task would get PI'd to FIFO1 (ktimers' default priority). Unfortunately,
> > rwlocks cannot sanely do PI as they allow multiple readers.
…
> I'm thinking working on that is saner than adding this O(n) cgroup loop
> to hard-irq context. Hmm?
I have plans to get rid of the softirq issue and the argument for "bad"
or inefficient rwlocks is usually "get rid of rwlocks then". So…
Then I looked at the patch and it only swapped the flag nothing else and
this hardly works. So I looked at sched_cfs_period_timer():
| static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
| {
…
| raw_spin_lock_irqsave(&cfs_b->lock, flags);
…
| raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
|
| return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
|}
Judging by this, the whole callback runs already with disabled
interrupts. At least now it enabled interrupts if multiple callbacks are
invoked…
Sebastian
prev parent reply other threads:[~2023-11-02 16:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-30 14:51 [PATCH] sched/fair: Make the BW replenish timer expire in hardirq context for PREEMPT_RT Valentin Schneider
2023-10-31 16:01 ` Peter Zijlstra
2023-11-02 16:19 ` Sebastian Andrzej Siewior [this message]
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