From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [kvm.git & 2.6.37-rc1] KVM deadlock with CONFIG_PREEMPT host Date: Mon, 08 Nov 2010 11:28:02 +0100 Message-ID: <4CD7D0B2.80600@siemens.com> References: <4CD7BD00.2020703@siemens.com> <20101108091849.GC3975@arch.trippelsdorf.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: kvm , Linux Kernel Mailing List , Avi Kivity , Marcelo Tosatti , "Paul E. McKenney" To: Markus Trippelsdorf Return-path: In-Reply-To: <20101108091849.GC3975@arch.trippelsdorf.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Am 08.11.2010 10:18, Markus Trippelsdorf wrote: > On Mon, Nov 08, 2010 at 10:04:00AM +0100, Jan Kiszka wrote: >> Hi, >> >> I'm seeing lock-ups of the QEMU process on kvm.git as well as current >> upstream kernels. This is a backtrace of the hanging VCPU thread: >> >> [] __stop_cpus+0x184/0x1a7 >> [] try_stop_cpus+0x40/0x59 >> [] synchronize_sched_expedited+0x84/0x9d >> [] __synchronize_srcu+0x33/0x72 >> [] synchronize_srcu_expedited+0x15/0x17 >> [] __kvm_set_memory_region+0x6a3/0x782 [kvm] >> [] kvm_set_memory_region+0x37/0x50 [kvm] >> [] kvm_vm_ioctl_set_memory_region+0x18/0x1a [kvm] >> [] kvm_vm_ioctl+0x22d/0x3b1 [kvm] >> [] do_vfs_ioctl+0x5a1/0x5e2 >> [] sys_ioctl+0x56/0x79 >> [] system_call_fastpath+0x16/0x1b >> [] 0xffffffffffffffff >> >> This issue disappears when disabling CONFIG_PREEMPT on the host. >> According to some rough bisecting, it was imported into kvm.git with >> merge 146d3bb06b. Given that RCU is involved, I also tried >> force-enabling non-preemptible CONFIG_TREE_RCU again, but that made no >> difference as long as PREEMPT is on. >> >> Can anyone confirm this or does someone have an idea what goes wrong? Of >> course, .config will be provided if required. > > This patch should help (,it fixes the problem in my case): > http://article.gmane.org/gmane.linux.kernel/1058018 Yeah, that works here as well. Would be a nice-to-have in kvm.git until it's pull via the next upstream merge. At least for me this bug triggers at every VM boot. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux