Date: Tue, 27 Aug 2013 14:36:44 -0400
From: Tejun Heo <tj@kernel.org>
To: Gu Zheng <guz.fnst@cn.fujitsu.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Toshi Kani <toshi.kani@hp.com>, LKML <linux-kernel@vger.kernel.org>,
        Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Subject: Re: [PATCH] driver core / ACPI: Avoid device removal locking problems
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Hello,

On Tue, Aug 27, 2013 at 05:21:44PM +0800, Gu Zheng wrote:
> >> OK, so the patch below is quick and dirty and overkill, but it should make the
> >> splat go away at least.
> > 
> > And if this patch does make the splat go away for you, please also test the
> > appended one (Tejun, thanks for the hint!).
> > 
> > I'll address the ACPI part differently later.
> 
> What about changing device_hotplug_lock and acpi_scan_lock to rwsem? like the
> attached one(With a preliminary test, it also can make the splat go away).:)

Hmmm.. I don't get it.  How is introducing another rwlock whic may
cause the operation, even reading the status, to fail randomly a
better option?  It's harier and more brittle.  We probably want to
implement better solution in sysfs for files which interact with
device addition / removal paths but for now I think Rafael's patch is
the right direction.

Thanks.

-- 
tejun
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