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: Fri, 18 Sep 2020 10:22:32 +0200 [thread overview]
Message-ID: <20200918082232.GL1362448@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200917163001.5ksl5vjwi35ozzsv@linutronix.de>
On Thu, Sep 17, 2020 at 06:30:01PM +0200, Sebastian Siewior wrote:
> On 2020-09-17 17:54:10 [+0200], peterz@infradead.org wrote:
> > 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.
>
> was this recent or distant in the time line?
The past few weeks :-) Thomas and me have been bickering about this
stuff on IRC on and off.
> > 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?
>
> I try to get rid of something like that. This doesn't work either way
> because the spin_lock() may block which it can't with disabled
> preemption.
Yeah, that obviously should have been migrate_disable/enable instead of
spin_lock/unlock :/
> Ah. We used to have migrate_disable() in pagefault_disable(). The x86
> FPU code does
> preempt_disable();
> …
> pagefault_disable();
>
> but that migrate_disable() was moved from pagefault_disable() to
> kmap_atomic(). We shouldn't have
> preempt_disable(); || local_irq_disable();
> kmap_atomic();
>
> on RT. I've been running around removing those. See
> a10dcebacdb0c ("fs/ntfs/aops.c: don't disable interrupts during kmap_atomic()")
> ce1e518190ea7 ("ide: don't disable interrupts during kmap_atomic()")
> f3a1075e5fc34 ("block: don't disable interrupts during kmap_atomic()")
Hmm, okay.
next prev parent reply other threads:[~2020-09-18 8:23 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
2020-09-17 16:30 ` Sebastian Siewior
2020-09-18 8:22 ` peterz [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200918082232.GL1362448@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=bigeasy@linutronix.de \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@kernel.org \
--cc=qais.yousef@arm.com \
--cc=rostedt@goodmis.org \
--cc=swood@redhat.com \
--cc=tglx@linutronix.de \
--cc=valentin.schneider@arm.com \
--cc=vincent.donnefort@arm.com \
--cc=vincent.guittot@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).