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From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Austin Schuh <austin@peloton-tech.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Richard Weinberger <richard.weinberger@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	rt-users <linux-rt-users@vger.kernel.org>
Subject: Re: Filesystem lockup with CONFIG_PREEMPT_RT
Date: Fri, 27 Jun 2014 19:34:53 +0200	[thread overview]
Message-ID: <1403890493.5830.33.camel@marge.simpson.net> (raw)
In-Reply-To: <20140627100157.6b0143a5@gandalf.local.home>

On Fri, 2014-06-27 at 10:01 -0400, Steven Rostedt wrote:

> This seems like a lot of hacks.

It is exactly that, lacking proper pooper-scooper, show rt kernel how to
not step in it.

> I'm wondering if it would work if we
> just have the rt_spin_lock_slowlock not call schedule(), but call
> __schedule() directly. I mean it would keep with the mainline paradigm
> as spinlocks don't sleep there, and one going to sleep in the -rt
> kernel is similar to it being preempted by a very long NMI.

Problem being that we do sleep there, do need wakeup.  I have a hack
that turns them back into spinning locks, but it.. works too :)

> Does a spin_lock going to sleep really need to do all the presched and
> postsched work?

It would be lovely if we didn't have to do any of that.  On the IO bit,
I haven't seen hard evidence that the spinlock bit is absolutely
required (better not be, it doesn't guarantee anything), but the
combined hack did kill IO deadlock of multiple filesystems.

-Mike


  reply	other threads:[~2014-06-27 17:35 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-14  2:29 Filesystem lockup with CONFIG_PREEMPT_RT Austin Schuh
2014-05-14  2:29 ` Austin Schuh
2014-05-21  6:23 ` Austin Schuh
2014-05-21  6:23   ` Austin Schuh
2014-05-21  7:33   ` Richard Weinberger
2014-05-21  7:33     ` Richard Weinberger
2014-06-26 19:50     ` Austin Schuh
2014-06-26 22:35       ` Thomas Gleixner
2014-06-27  0:07         ` Austin Schuh
2014-06-27  3:22           ` Mike Galbraith
2014-06-27 12:57           ` Mike Galbraith
2014-06-27 14:01             ` Steven Rostedt
2014-06-27 17:34               ` Mike Galbraith [this message]
2014-06-27 17:54                 ` Steven Rostedt
2014-06-27 18:07                   ` Mike Galbraith
2014-06-27 18:19                     ` Steven Rostedt
2014-06-27 19:11                       ` Mike Galbraith
2014-06-28  1:18                       ` Austin Schuh
2014-06-28  3:32                         ` Mike Galbraith
2014-06-28  6:20                           ` Austin Schuh
2014-06-28  7:11                             ` Mike Galbraith
2014-06-27 14:24           ` Thomas Gleixner
2014-06-28  4:51             ` Mike Galbraith
2014-07-01  0:12             ` Austin Schuh
2014-07-01  0:53               ` Austin Schuh
2014-07-05 20:26                 ` Thomas Gleixner
2014-07-06  4:55                   ` Austin Schuh
2014-07-01  3:01             ` Austin Schuh
2014-07-01 19:32               ` Austin Schuh
2014-07-03 23:08                 ` Austin Schuh
2014-07-04  4:42                   ` Mike Galbraith
2014-05-21 19:30 John Blackwood
2014-05-21 19:30 ` John Blackwood
2014-05-21 21:59 ` Austin Schuh
2014-05-21 21:59   ` Austin Schuh
2014-07-05 20:36 ` Thomas Gleixner
2014-07-05 20:36   ` Thomas Gleixner
2014-07-05 19:30 Jan de Kruyf
2014-07-07  8:48 Jan de Kruyf
2014-07-07 13:00 ` Thomas Gleixner
2014-07-07 16:23 ` Austin Schuh
2014-07-08  8:03   ` Jan de Kruyf
2014-07-08 16:09     ` Austin Schuh

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