From patchwork Tue Feb 20 13:10:14 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 875530 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3zm1GW2WsTz9ryl for ; Wed, 21 Feb 2018 00:11:31 +1100 (AEDT) Received: from localhost ([::1]:55418 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eo7hh-0003S3-Ee for incoming@patchwork.ozlabs.org; Tue, 20 Feb 2018 08:11:29 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38378) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eo7gw-0003Nw-RG for qemu-devel@nongnu.org; Tue, 20 Feb 2018 08:10:47 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eo7gv-0004Nx-6C for qemu-devel@nongnu.org; Tue, 20 Feb 2018 08:10:42 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:60466 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eo7gp-0004IX-Cb; Tue, 20 Feb 2018 08:10:35 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D771BEB705; Tue, 20 Feb 2018 13:10:23 +0000 (UTC) Received: from localhost (ovpn-117-78.ams2.redhat.com [10.36.117.78]) by smtp.corp.redhat.com (Postfix) with ESMTP id 85125AFD70; Tue, 20 Feb 2018 13:10:15 +0000 (UTC) From: Stefan Hajnoczi To: Date: Tue, 20 Feb 2018 13:10:14 +0000 Message-Id: <20180220131014.8998-1-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Tue, 20 Feb 2018 13:10:23 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Tue, 20 Feb 2018 13:10:23 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'stefanha@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [PATCH] vl: introduce vm_shutdown() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Fam Zheng , Stefan Hajnoczi , qemu-block@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" Commit 00d09fdbbae5f7864ce754913efc84c12fdf9f1a ("vl: pause vcpus before stopping iothreads") and commit dce8921b2baaf95974af8176406881872067adfa ("iothread: Stop threads before main() quits") tried to work around the fact that emulation was still active during termination by stopping iothreads. They suffer from race conditions: 1. virtio_scsi_handle_cmd_vq() racing with iothread_stop_all() hits the virtio_scsi_ctx_check() assertion failure because the BDS AioContext has been modified by iothread_stop_all(). 2. Guest vq kick racing with main loop termination leaves a readable ioeventfd that is handled by the next aio_poll() when external clients are enabled again, resulting in unwanted emulation activity. This patch obsoletes those commits by fully disabling emulation activity when vcpus are stopped. Use the new vm_shutdown() function instead of pause_all_vcpus() so that vm change state handlers are invoked too. Virtio devices will now stop their ioeventfds, preventing further emulation activity after vm_stop(). Note that vm_stop(RUN_STATE_SHUTDOWN) cannot be used because it emits a QMP STOP event that may affect existing clients. It is no longer necessary to call replay_disable_events() directly since vm_shutdown() does so already. Drop iothread_stop_all() since it is no longer used. Cc: Fam Zheng Cc: Kevin Wolf Signed-off-by: Stefan Hajnoczi --- include/sysemu/iothread.h | 1 - include/sysemu/sysemu.h | 1 + cpus.c | 16 +++++++++++++--- iothread.c | 31 ------------------------------- vl.c | 13 +++---------- 5 files changed, 17 insertions(+), 45 deletions(-) diff --git a/include/sysemu/iothread.h b/include/sysemu/iothread.h index 799614ffd2..8a7ac2c528 100644 --- a/include/sysemu/iothread.h +++ b/include/sysemu/iothread.h @@ -45,7 +45,6 @@ typedef struct { char *iothread_get_id(IOThread *iothread); IOThread *iothread_by_id(const char *id); AioContext *iothread_get_aio_context(IOThread *iothread); -void iothread_stop_all(void); GMainContext *iothread_get_g_main_context(IOThread *iothread); /* diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h index 77bb3da582..54f91dbc03 100644 --- a/include/sysemu/sysemu.h +++ b/include/sysemu/sysemu.h @@ -55,6 +55,7 @@ void vm_start(void); int vm_prepare_start(void); int vm_stop(RunState state); int vm_stop_force_state(RunState state); +int vm_shutdown(void); typedef enum WakeupReason { /* Always keep QEMU_WAKEUP_REASON_NONE = 0 */ diff --git a/cpus.c b/cpus.c index f298b659f4..90279f73fc 100644 --- a/cpus.c +++ b/cpus.c @@ -993,7 +993,7 @@ void cpu_synchronize_all_pre_loadvm(void) } } -static int do_vm_stop(RunState state) +static int do_vm_stop(RunState state, bool send_stop) { int ret = 0; @@ -1002,7 +1002,9 @@ static int do_vm_stop(RunState state) pause_all_vcpus(); runstate_set(state); vm_state_notify(0, state); - qapi_event_send_stop(&error_abort); + if (send_stop) { + qapi_event_send_stop(&error_abort); + } } bdrv_drain_all(); @@ -1012,6 +1014,14 @@ static int do_vm_stop(RunState state) return ret; } +/* Special vm_stop() variant for terminating the process. Historically clients + * did not expect a QMP STOP event and so we need to retain compatibility. + */ +int vm_shutdown(void) +{ + return do_vm_stop(RUN_STATE_SHUTDOWN, false); +} + static bool cpu_can_run(CPUState *cpu) { if (cpu->stop) { @@ -2007,7 +2017,7 @@ int vm_stop(RunState state) return 0; } - return do_vm_stop(state); + return do_vm_stop(state, true); } /** diff --git a/iothread.c b/iothread.c index 4b9bbde4cd..68d92086e3 100644 --- a/iothread.c +++ b/iothread.c @@ -101,18 +101,6 @@ void iothread_stop(IOThread *iothread) qemu_thread_join(&iothread->thread); } -static int iothread_stop_iter(Object *object, void *opaque) -{ - IOThread *iothread; - - iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD); - if (!iothread) { - return 0; - } - iothread_stop(iothread); - return 0; -} - static void iothread_instance_init(Object *obj) { IOThread *iothread = IOTHREAD(obj); @@ -333,25 +321,6 @@ IOThreadInfoList *qmp_query_iothreads(Error **errp) return head; } -void iothread_stop_all(void) -{ - Object *container = object_get_objects_root(); - BlockDriverState *bs; - BdrvNextIterator it; - - for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) { - AioContext *ctx = bdrv_get_aio_context(bs); - if (ctx == qemu_get_aio_context()) { - continue; - } - aio_context_acquire(ctx); - bdrv_set_aio_context(bs, qemu_get_aio_context()); - aio_context_release(ctx); - } - - object_child_foreach(container, iothread_stop_iter, NULL); -} - static gpointer iothread_g_main_context_init(gpointer opaque) { AioContext *ctx; diff --git a/vl.c b/vl.c index 81724f5f17..e7e7e13f86 100644 --- a/vl.c +++ b/vl.c @@ -4762,17 +4762,10 @@ int main(int argc, char **argv, char **envp) os_setup_post(); main_loop(); - replay_disable_events(); - /* The ordering of the following is delicate. Stop vcpus to prevent new - * I/O requests being queued by the guest. Then stop IOThreads (this - * includes a drain operation and completes all request processing). At - * this point emulated devices are still associated with their IOThreads - * (if any) but no longer have any work to do. Only then can we close - * block devices safely because we know there is no more I/O coming. - */ - pause_all_vcpus(); - iothread_stop_all(); + /* No more vcpu or device emulation activity beyond this point */ + vm_shutdown(); + bdrv_close_all(); res_free();