linux-kernel - Re: pci

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Date:	Wed, 1 Jul 2009 16:58:01 -0700
From:	Yinghai Lu <yhlu.kernel@...il.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, jbarnes@...tuousgeek.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-pci@...r.kernel.org, Marcelo Tosatti <mtosatti@...hat.com>,
	KVM list <kvm@...r.kernel.org>,
	Sheng Yang <sheng@...ux.intel.com>
Subject: Re: pci_stub and kvm

On Wed, Jul 1, 2009 at 12:49 AM, Avi Kivity<avi@...hat.com> wrote:
> On 07/01/2009 07:18 AM, Yinghai Lu wrote:
>>
>> [ 1966.343286]
>> [ 1966.343288] =======================================================
>> [ 1966.356756] [ INFO: possible circular locking dependency detected ]
>> [ 1966.356759] 2.6.31-rc1-tip-00978-g99123e5-dirty #438
>> [ 1966.356761] -------------------------------------------------------
>> [ 1966.356764] events/0/387 is trying to acquire lock:
>> [ 1966.356766]  (&kvm->lock){+.+.+.}, at: [<ffffffff8100af27>]
>> kvm_assigned_dev_interrupt_work_handler+0x42/0x13a
>> [ 1966.356786]
>> [ 1966.356787] but task is already holding lock:
>> [ 1966.356789]  (&match->interrupt_work){+.+...}, at:
>> [<ffffffff810986e9>] worker_thread+0x175/0x2f6
>> [ 1966.356797]
>> [ 1966.356798] which lock already depends on the new lock.
>> [ 1966.356799]
>> [ 1966.356800]
>> [ 1966.356801] the existing dependency chain (in reverse order) is:
>> [ 1966.356803]
>> [ 1966.356803] ->  #1 (&match->interrupt_work){+.+...}:
>> [ 1966.356809]        [<ffffffff810b3bf6>] __lock_acquire+0x1396/0x1710
>> [ 1966.356817]        [<ffffffff810b403c>] lock_acquire+0xcc/0x104
>> [ 1966.356821]        [<ffffffff810994a8>] __cancel_work_timer+0x121/0x247
>> [ 1966.356825]        [<ffffffff8109962c>] cancel_work_sync+0x23/0x39
>> [ 1966.356828]        [<ffffffff8100b280>] kvm_deassign_irq+0xf1/0x183
>> [ 1966.356832]        [<ffffffff8100db6c>] kvm_vm_ioctl+0x8c8/0xc1a
>> [ 1966.356837]        [<ffffffff81156e56>] vfs_ioctl+0x3e/0xa3
>> [ 1966.356846]        [<ffffffff8115741c>] do_vfs_ioctl+0x4be/0x511
>> [ 1966.356850]        [<ffffffff811574c5>] sys_ioctl+0x56/0x8d
>> [ 1966.356854]        [<ffffffff81034fdb>] system_call_fastpath+0x16/0x1b
>> [ 1966.356860]        [<ffffffffffffffff>] 0xffffffffffffffff
>> [ 1966.356869]
>> [ 1966.356870] ->  #0 (&kvm->lock){+.+.+.}:
>> [ 1966.356872]        [<ffffffff810b392b>] __lock_acquire+0x10cb/0x1710
>> [ 1966.356875]        [<ffffffff810b403c>] lock_acquire+0xcc/0x104
>> [ 1966.356878]        [<ffffffff81cde487>] mutex_lock_nested+0x75/0x2fa
>> [ 1966.356886]        [<ffffffff8100af27>]
>> kvm_assigned_dev_interrupt_work_handler+0x42/0x13a
>> [ 1966.356890]        [<ffffffff81098743>] worker_thread+0x1cf/0x2f6
>> [ 1966.356892]        [<ffffffff8109e335>] kthread+0xa8/0xb0
>> [ 1966.356899]        [<ffffffff8103609a>] child_rip+0xa/0x20
>> [ 1966.356906]        [<ffffffffffffffff>] 0xffffffffffffffff
>>
>
> This is already fixed in kvm.git.  I'm not sure about merging it to 2.6.30
> since the race is very rare and involves device assignment (which is not
> very mainstream), while the fix touches the core kvm parts.

tip/master merged with kvm/master doesn't have that warning.

YH
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