From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [BUG] kvm: dereference srcu-protected pointer without srcu_read_lock() held Date: Mon, 19 Apr 2010 13:08:29 +0300 Message-ID: <4BCC2B9D.8050008@redhat.com> References: <4BCC2543.7050104@cn.fujitsu.com> <4BCC295D.1040807@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , "Paul E. McKenney" , LKML , kvm@vger.kernel.org To: Lai Jiangshan Return-path: In-Reply-To: <4BCC295D.1040807@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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