From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>,
Luca Tettamanti <kronos.it@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Fix SMP alternatives : use mutex instead of spinlock, text_poke is sleepable
Date: Thu, 1 May 2008 16:08:59 -0400 [thread overview]
Message-ID: <20080501200858.GA12246@Krystal> (raw)
In-Reply-To: <alpine.LFD.1.10.0805011151521.5994@woody.linux-foundation.org>
* Linus Torvalds (torvalds@linux-foundation.org) wrote:
>
>
> On Thu, 1 May 2008, Mathieu Desnoyers wrote:
> >
> > Yep. I think using a mutex should fix it. There is no reason to use a
> > spinlock rather than a mutex here.
>
> Is there any reason to do any locking what-so-ever?
>
> If this code could possibly race with something else, that sounds like a
> bug in itself, no?
>
> Linus
The smp_alt mutex taken in
alternatives_smp_module_add/alternatives_smp_module_del seems required
because this code will run at module load/free, even in SMP context (not
within stop_machine_run).
As for alternatives_smp_switch, which is called when switching between
UP and SMP, always in UP context, I guess we should assume it could be
executed concurrently wrt the module_load/free, even in UP on a
CONFIG_PREEMPT kernel.
Mathieu
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
next prev parent reply other threads:[~2008-05-01 20:09 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-30 19:51 [BUG] smp alternatives: sleeping function called from invalid context Luca Tettamanti
2008-05-01 13:04 ` Mathieu Desnoyers
2008-05-01 15:02 ` Luca Tettamanti
2008-05-01 16:44 ` Luca Tettamanti
2008-05-01 18:46 ` [PATCH] Fix SMP alternatives : use mutex instead of spinlock, text_poke is sleepable Mathieu Desnoyers
2008-05-01 18:52 ` Linus Torvalds
2008-05-01 20:08 ` Mathieu Desnoyers [this message]
[not found] <20080413224207.4430a09c@daedalus.pq.iki.fi>
2008-04-13 20:05 ` [BUG/PATCH] x86 mmiotrace: dynamically disable non-boot CPUs Pekka Paalanen
2008-04-14 6:57 ` Ingo Molnar
2008-04-19 15:41 ` [BUG] kmalloc_node(GFP_KERNEL) while smp_alt spinlocked Pekka Paalanen
2008-04-19 16:19 ` [PATCH] Fix SMP alternatives : use mutex instead of spinlock, text_poke is sleepable Mathieu Desnoyers
2008-04-19 21:06 ` Pekka Paalanen
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