From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v2] fix qemu-kvm sigsegv at exit Date: Wed, 28 Oct 2009 11:42:56 +0200 Message-ID: <4AE81220.2000102@redhat.com> References: <20091026184602.GB6016@amt.cnet> <20091026185849.GA5930@redhat.com> <20091027153346.GA9730@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , kvm To: Marcelo Tosatti Return-path: Received: from mx1.redhat.com ([209.132.183.28]:25716 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751247AbZJ1Jmy (ORCPT ); Wed, 28 Oct 2009 05:42:54 -0400 Received: from int-mx08.intmail.prod.int.phx2.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id n9S9gxnC008328 for ; Wed, 28 Oct 2009 05:42:59 -0400 In-Reply-To: <20091027153346.GA9730@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: On 10/27/2009 05:33 PM, Marcelo Tosatti wrote: > Michael reported a qemu-kvm SIGSEGV at shutdown: > > Program received signal SIGSEGV, Segmentation fault. > [Switching to Thread 0x411d0940 (LWP 14446)] > 0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0, > expire_time=62275467335) > at /home/mst/scm/qemu-kvm/vl.c:1009 > 1009 if ((alarm_timer->flags& ALARM_FLAG_EXPIRED) == 0) > { > (gdb) l > 1004 ts->next = *pt; > 1005 *pt = ts; > 1006 > 1007 /* Rearm if necessary */ > 1008 if (pt ==&active_timers[ts->clock->type]) { > 1009 if ((alarm_timer->flags& ALARM_FLAG_EXPIRED) == 0) > { > 1010 qemu_rearm_alarm_timer(alarm_timer); > 1011 } > 1012 /* Interrupt execution to force deadline > recalculation. */ > 1013 if (use_icount) > (gdb) p alarm_timer > $1 = (struct qemu_alarm_timer *) 0x0 > > Problem is kvm_main_loop_wait(env, 0) can process the stop request > (signalling iothread that vcpu is stopped, so its OK to exit) and > continue to kvm_cpu_exec. > > Reorder kvm_main_loop_wait and kvm_cpu_exec, as suggested by Gleb. > > Signed-off-by: Marcelo Tosatti > Reported-by: "Michael S. Tsirkin" > > diff --git a/qemu-kvm.c b/qemu-kvm.c > index 4c13628..809fd65 100644 > --- a/qemu-kvm.c > +++ b/qemu-kvm.c > @@ -1867,8 +1867,8 @@ static int kvm_main_loop_cpu(CPUState *env) > run_cpu = !env->halted; > } > if (run_cpu) { > - kvm_main_loop_wait(env, 0); > kvm_cpu_exec(env); > + kvm_main_loop_wait(env, 0); > } else { > kvm_main_loop_wait(env, 1000); > } > This will miss an event at the very beginning of the loop (powerdown requested before we had a chance to spin up?). I think it should be fine since there will be a pending signal which will break us out of kvm_cpu_exec() before it has a chance to do anything (i.e. spin in the guest). So, I think it's fine, but please double check the above. -- error compiling committee.c: too many arguments to function