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Message-Id: <20090130090835.416e7662.akpm@linux-foundation.org>
Date: Fri, 30 Jan 2009 09:08:35 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Ingo Molnar <mingo@...e.hu>
Cc: Rusty Russell <rusty@...tcorp.com.au>,
Mike Travis <travis@....com>, Ingo Molnar <mingo@...hat.com>,
Dave Jones <davej@...hat.com>, cpufreq@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] work_on_cpu: Use our own workqueue.
On Fri, 30 Jan 2009 14:49:35 +0100 Ingo Molnar <mingo@...e.hu> wrote:
> > So we still don't have any non-buggy proposal.
>
> Current upstream code is not pretty (due to the extra workqueue) but not
> buggy either. You'd be right to point out that it is easy to insert a bug
> into it and thus it's not pleasant (more of a workaround than a real fix)
> but if it's outright buggy then please talk up.
OK, so we're not aware of anything in there which will trigger the bug
yet. Although allocate_threshold_blocks() takes about half the locks in
the kernel - it can run an ext3 commit, it does netlink tx, synchronous
process exec, etc.
Why not give up and kill the whole work_on_cpu() thing? afaict the
only caller which cannot be immediately switched to use an IPI is
mce_amd_64's allocate_threshold_blocks(), and it looks like that can be
trivially fixed by moving the entire function except for one rdmsr() up
into the caller.
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