From: Russell King <rmk+lkml@arm.linux.org.uk>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Hubertus Franke <frankeh@watson.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@osdl.org>
Subject: Re: SMP BUG
Date: Thu, 16 Feb 2006 10:20:56 +0000 [thread overview]
Message-ID: <20060216102056.GA24741@flint.arm.linux.org.uk> (raw)
In-Reply-To: <Pine.LNX.4.64.0602151521320.22082@g5.osdl.org>
On Wed, Feb 15, 2006 at 03:23:02PM -0800, Linus Torvalds wrote:
> Does this fix the ARM oops?
It fixes that exact oops but only by preventing us getting that far
due to another oops.
We call cpu_up, which sends a CPU_UP_PREPARE event. This causes the
migration thread to be spawned, and rq->migration_thread to be set.
Eventually, we call the architecture __cpu_up(), which ends up
calling init_idle(). Due to this patch, init_idle() then NULLs out
rq->migration_thread.
Later, we send a CPU_ONLINE event, which then tries to do
wake_up_process(rq->migration_thread) - resulting in a NULL pointer
deref in try_to_wake_up().
Hence, with this patch, it looks like rq will be used prior to
initialisation. I could try commenting out the migration_thread
initialisation to NULL, but I suspect that there may be other
problems associated with this patch (eg, rq->migration_queue).
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
next prev parent reply other threads:[~2006-02-16 10:21 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-14 0:19 SMP BUG Hubertus Franke
2006-02-15 23:07 ` Russell King
2006-02-15 23:17 ` Andrew Morton
2006-02-15 23:34 ` Russell King
2006-02-15 23:23 ` Linus Torvalds
2006-02-15 23:30 ` Andrew Morton
2006-02-15 23:37 ` Russell King
2006-02-15 23:46 ` Andrew Morton
2006-02-16 0:14 ` Russell King
2006-02-16 0:28 ` Andrew Morton
2006-02-16 0:52 ` Linus Torvalds
2006-02-16 3:29 ` Nick Piggin
2006-02-16 8:37 ` Ingo Molnar
2006-02-16 10:20 ` Russell King [this message]
2006-02-16 15:54 ` Linus Torvalds
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