From: Ralf Baechle <ralf@linux-mips.org>
To: maksim.rayskiy@gmail.com
Cc: linux-mips@linux-mips.org, Maksim Rayskiy <mrayskiy@broadcom.com>
Subject: Re: [PATCH] MIPS: clear idle task mm pointer when hotplugging cpu
Date: Wed, 9 Feb 2011 13:02:09 +0100 [thread overview]
Message-ID: <20110209120209.GA21796@linux-mips.org> (raw)
In-Reply-To: <1297210687-14589-1-git-send-email-maksim.rayskiy@gmail.com>
On Tue, Feb 08, 2011 at 04:18:07PM -0800, maksim.rayskiy@gmail.com wrote:
> If kernel starts with maxcpus= option which does not bring all
> available cpus online at boot time, idle tasks for offline cpus
> are not created. If later offline cpus are hotplugged through sysfs,
> __cpu_up is called in the context of the user task, and fork_idle
> copies its non-zero mm pointer. This causes BUG() in per_cpu_trap_init.
>
> To avoid this, release mm for idle task and reset the pointer after
> fork_idle().
Nice catch, applied.
x86 avoid this problem by forking the idle threads in a worker thread which
also avoids other potencial issues; we probably should take the same
path.
Ralf
prev parent reply other threads:[~2011-02-09 12:01 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-09 0:18 [PATCH] MIPS: clear idle task mm pointer when hotplugging cpu maksim.rayskiy
2011-02-09 12:02 ` Ralf Baechle [this message]
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