From: Manfred Spraul <manfred@colorfullife.com>
To: linux-kernel@vger.kernel.org, Andrea Arcangeli <andrea@suse.de>,
David Mosberger <davidm@hpl.hp.com>
Subject: Re: [patch] proposed fix for ptrace() SMP race
Date: Mon, 10 Sep 2001 19:54:51 +0200 [thread overview]
Message-ID: <3B9CFE6B.1563125D@colorfullife.com> (raw)
>
> BTW, checking this stuff I found two bugs, one is the check for
> cpus_allowed before calling reschedule_idle,
The call in linux/kernel.c, around line 348?
348 if (!synchronous || !(p->cpus_allowed & (1 << smp_processor_id())))
349 reschedule_idle(p);
The test was added for wake_up_{,interruptible_}sync(): if the woken up
task is not permitted to run on the current cpu, reschedule() is
necessary, otherwise skip the reschedule.
If ptrace sets cpus_allowed to 0 between wake_up_sync() and schedule(),
the reschedule is lost. But always rescheduling would defeat the purpose
of wake_up_sync().
--
Manfred
next reply other threads:[~2001-09-10 17:55 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-09-10 17:54 Manfred Spraul [this message]
-- strict thread matches above, loose matches on Subject: below --
2001-09-06 23:00 [patch] proposed fix for ptrace() SMP race David Mosberger
2001-09-07 0:19 ` Andrea Arcangeli
2001-09-07 0:40 ` David Mosberger
2001-09-07 1:28 ` Andrea Arcangeli
2001-09-07 1:41 ` Alan Cox
2001-09-07 13:34 ` Andrea Arcangeli
2001-09-07 5:21 ` David Mosberger
2001-09-07 13:28 ` Andrea Arcangeli
2001-09-07 15:35 ` David Mosberger
2001-09-08 17:11 ` Andrea Arcangeli
2001-09-10 17:20 ` David Mosberger
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