From: peterz@infradead.org
To: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Qais Yousef <qais.yousef@arm.com>, Scott Wood <swood@redhat.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Ingo Molnar <mingo@kernel.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Vincent Donnefort <vincent.donnefort@arm.com>
Subject: Re: [patch 09/10] sched/core: Add migrate_disable/enable()
Date: Thu, 17 Sep 2020 17:54:10 +0200 [thread overview]
Message-ID: <20200917155410.GK1362448@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200917151341.2ilqamtnc6hperix@linutronix.de>
On Thu, Sep 17, 2020 at 05:13:41PM +0200, Sebastian Siewior wrote:
> On 2020-09-17 16:49:37 [+0200], peterz@infradead.org wrote:
> > I'm aware of the duct-tape :-) But I was under the impression that we
> > didn't want the duct-tape, and that there was lots of issues with the
> > FPU code, or was that another issue?
>
> Of course it would be better not to need the duct tape.
> Also symmetrical locking is what you want but clearly futex is one of
> a kind.
>
> I'm currently not aware of any issues in the FPU code in regard to this.
> A few weeks ago, I was looking for this kind of usage and only futex
> popped up.
I'm not sure what the problem with FPU was, I was throwing alternatives
at tglx to see what would stick, in part to (re)discover the design
constraints of this thing.
One reason for not allowing migrate_disable() to sleep was: FPU code.
Could it be it does something like:
preempt_disable();
spin_lock();
spin_unlock();
preempt_enable();
Where we'll never get preempted while migrate_disable()'d and thus never
trigger any of the sleep paths?
next prev parent reply other threads:[~2020-09-17 19:17 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-17 9:42 [patch 00/10] sched: Migrate disable support for RT Thomas Gleixner
2020-09-17 9:42 ` [patch 01/10] sched: Fix balance_callback() Thomas Gleixner
2020-09-17 9:42 ` [patch 02/10] sched/hotplug: Ensure only per-cpu kthreads run during hotplug Thomas Gleixner
2020-09-17 9:42 ` [patch 03/10] sched/core: Wait for tasks being pushed away on hotplug Thomas Gleixner
2020-09-17 9:42 ` [patch 04/10] sched/hotplug: Consolidate task migration on CPU unplug Thomas Gleixner
2020-09-17 9:42 ` [patch 05/10] sched/core: Split __set_cpus_allowed_ptr() Thomas Gleixner
2020-09-17 9:42 ` [patch 06/10] sched: Add task components for migration control Thomas Gleixner
2020-09-17 9:42 ` [patch 07/10] sched/core: Add mechanism to wait for affinity setting to complete Thomas Gleixner
2020-09-17 9:42 ` [patch 08/10] sched: Add update_migratory() callback to scheduler classes Thomas Gleixner
2020-09-17 9:42 ` [patch 09/10] sched/core: Add migrate_disable/enable() Thomas Gleixner
2020-09-17 14:24 ` peterz
2020-09-17 14:38 ` Sebastian Siewior
2020-09-17 14:49 ` peterz
2020-09-17 15:13 ` Sebastian Siewior
2020-09-17 15:54 ` peterz [this message]
2020-09-17 16:30 ` Sebastian Siewior
2020-09-18 8:22 ` peterz
2020-09-18 8:48 ` Sebastian Siewior
2020-09-18 7:00 ` Thomas Gleixner
2020-09-18 8:28 ` peterz
2020-09-17 9:42 ` [patch 10/10] sched/core: Make migrate disable and CPU hotplug cooperative Thomas Gleixner
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