linux-kernel - Re: [BUG] kvm: dereference srcu-protected pointer without srcu_read

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Message-ID: <4BCC2B9D.8050008@redhat.com>
Date:	Mon, 19 Apr 2010 13:08:29 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Lai Jiangshan <laijs@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org
Subject: Re: [BUG] kvm: dereference srcu-protected pointer without srcu_read_lock()
 held

On 04/19/2010 12:58 PM, Lai Jiangshan wrote:
> Applied the patch I just sent and let CONFIG_PROVE_RCU=y,
> we can got the following dmesg. And we found that it is
> because some codes in KVM dereferences srcu-protected pointer without
> srcu_read_lock() held or update-side lock held.
>
> It is not hard to fix, the problem is that:
> Where is the most proper place to put a srcu_read_lock()?
>
> I can not determine the answer, so I report this bug
> instead of fixing it.
>
>    

I think the else branch in complete_pio() should work.  Marcelo?

Longer term I'd like to see the lock taken at the high levels (ioctls, 
in virt/kvm) and dropped only for guest entry and when we explicitly 
sleep (hlt emulation).

Note: complete_pio() is gone in the current code.

-- 
error compiling committee.c: too many arguments to function

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