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Date: Thu, 10 Sep 2009 11:25:49 +0800
Message-ID: <d82e647a0909092025q377729fau88e39214c349d746@mail.gmail.com>
Subject: Re: [2.6.31-rc9] hotplug SATA vs lockdep: false positive?
From: Ming Lei <tom.leiming@gmail.com>
To: Daniel J Blueman <daniel.blueman@gmail.com>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>, linux-acpi@vger.kernel.org
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2009/9/10 Daniel J Blueman <daniel.blueman@gmail.com>:
> When hot-plugging my SATA DVD drive into my laptop, I see a lockdep
> warning [1]. On closer inspection, both flush_workqueue() and
> worker_thread() do tricks with lockdep maps. False positive?

> Call Trace:
> ?[<ffffffff8108c8a7>] print_circular_bug_tail+0xa7/0x100
> ?[<ffffffff8108ebe1>] __lock_acquire+0xef1/0x1240
> ?[<ffffffff8108a808>] ? add_lock_to_list+0x58/0xf0
> ?[<ffffffff8108f04e>] lock_acquire+0x11e/0x170
> ?[<ffffffff81073a70>] ? flush_workqueue+0x0/0xf0 (workqueue.c:397)
> ?[<ffffffff812f6ebd>] ? acpi_os_execute_hp_deferred+0x0/0x3e
> ?[<ffffffff81073acc>] flush_workqueue+0x5c/0xf0 (workqueue.c:403)

The lockdep warning is caused by calling flush_workqueue() from the
work function of
acpi_os_execute_hp_deferred. I don't know if it is safe to do that.

> ?[<ffffffff81073a70>] ? flush_workqueue+0x0/0xf0 (workqueue.c:397)
> ?[<ffffffff812f6eaf>] acpi_os_wait_events_complete+0x10/0x1e drivers/acpi/osl.c
> ?[<ffffffff812f6ee7>] acpi_os_execute_hp_deferred+0x2a/0x3e
> ?[<ffffffff81072a98>] worker_thread+0x248/0x3c0 (workqueue.c:292)
> ?[<ffffffff81072a42>] ? worker_thread+0x1f2/0x3c0
> ?[<ffffffff81077900>] ? autoremove_wake_function+0x0/0x40
> ?[<ffffffff81072850>] ? worker_thread+0x0/0x3c0
> ?[<ffffffff81077456>] kthread+0xa6/0xc0
> ?[<ffffffff8100d29a>] child_rip+0xa/0x20
> ?[<ffffffff8100cbd4>] ? restore_args+0x0/0x30
> ?[<ffffffff810773b0>] ? kthread+0x0/0xc0
> ?[<ffffffff8100d290>] ? child_rip+0x0/0x20
>

-- 
Lei Ming
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