linux-kernel - Re: [Regression] 2.6.24-git9: RT sched mishandles artswrapper (bisected)

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Message-ID: <b647ffbd0802051346k563a44f7t42739515c130124b@mail.gmail.com>
Date:	Tue, 5 Feb 2008 22:46:32 +0100
From:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Steven Rostedt" <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [Regression] 2.6.24-git9: RT sched mishandles artswrapper (bisected)

Rafael, any progress with this issue? (a few questions below).

> >
> > Does this artsmessage thing also run with RT priority?
>
> Well, it's in a strange state (after it's broken).  From top:
>
> PR = -51
> NI = 0
> S = R
> %CPU = 0.0
> %MEM = 0.0

cat /proc/$PID/stat ; sleep 3; cat /proc/$PID/stat ?
cat /proc/sched_debug; sleep 3 ; cat /proc/sched_debug

and also cat /proc/$PID/stat taken when this task still looks 'sane' :-/

Do you mean that only SCHED_NORMAL tasks can't run on this cpu or RT
tasks of high prio as well (so that maybe the scheduler is in
inconsistent state) ?
If the latter, the watchdog should have triggered after a while (if
enabled), I guess.

>
> Here's the corresponding trace from sysrq+t:
>
>  [<ffffffff8022fdb7>] ? try_to_wake_up+0x77/0x200
>  [<ffffffff8023573d>] __cond_resched+0x2d/0x60
>  [<ffffffff804ddce1>] _cond_resched+0x31/0x40
>  [<ffffffff804ddd24>] wait_for_common+0x34/0x170
>  [<ffffffff8022fdb7>] ? try_to_wake_up+0x77/0x200
>  [<ffffffff804ddec8>] wait_for_completion+0x18/0x20
> [ ... ]

does a stack trace always look like this?


-- 
Best regards,
Dmitry Adamushko
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