From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=36345 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Ppei2-0003Kx-Ug for qemu-devel@nongnu.org; Wed, 16 Feb 2011 05:34:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ppei1-0000t2-Q6 for qemu-devel@nongnu.org; Wed, 16 Feb 2011 05:34:10 -0500 Received: from david.siemens.de ([192.35.17.14]:31443) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ppei1-0000sc-DG for qemu-devel@nongnu.org; Wed, 16 Feb 2011 05:34:09 -0500 Message-ID: <4D5BA81D.1080205@siemens.com> Date: Wed, 16 Feb 2011 11:34:05 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <20110215175410.GA13487@amt.cnet> <4D5ACCED.1080906@siemens.com> <20110215200446.GA15802@amt.cnet> <4D5AE2FC.4020309@web.de> <20110215205504.GA16527@amt.cnet> <20110215205631.GA16579@amt.cnet> <4D5B99A9.1010404@redhat.com> <4D5B9CFC.1030503@siemens.com> <4D5B9F8B.3000306@redhat.com> <4D5BA128.9060909@siemens.com> <4D5BA6A2.9080701@redhat.com> In-Reply-To: <4D5BA6A2.9080701@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [PATCH] fix halt emulation with icount and CONFIG_IOTHREAD (v2) List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: "Edgar E. Iglesias" , Marcelo Tosatti , "qemu-devel@nongnu.org" On 2011-02-16 11:27, Paolo Bonzini wrote: > On 02/16/2011 11:04 AM, Jan Kiszka wrote: >> On 2011-02-16 10:57, Paolo Bonzini wrote: >>> On 02/16/2011 10:46 AM, Jan Kiszka wrote: >>>> What should this be good for? The iothread already kicks the vcpu if it >>>> wants to acquire the contended global mutex. >>> >>> Assuming the VCPU is in the timedwait that Marcelo changed, the global >>> mutex is free and the iothread will not kick the VCPU. >> >> Then why should it kick it at all? > > To make it notice something changed in all_cpu_threads_idle---but that's > wrong, it should have been kicked in cpu_interrupt. > >> If we change the halt condition, we should not kick the vcpus but only >> signal the condition variable. Actually, I've a patch queued that skips >> pointless qemu_thread_signal in qemu_cpu_kick for TCG. > > Yes, I was kicking just because that's the wrapper that is used to > signal the condition variable---just like I was kicking in my patches to > eliminate timedwait. > >>> So, perhaps the correct fix is to kick the cpu in cpu_interrupt, and all >>> I wrote about timeouts and timers is wrong. My patch would band-aid it. >> >> That's my strong suspect. We really need to understand what goes wrong. > > I agree on both counts. > FWIW, I've rebased most of your patches on top of my outstanding ones and pushed them to git://git.kiszka.org/qemu-kvm.git queues/kvm-upstream Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux