From patchwork Thu Jan 16 08:43:32 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 13941466 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 38B0CC02180 for ; Thu, 16 Jan 2025 08:44:06 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tYLTq-0006qb-47; Thu, 16 Jan 2025 03:43:58 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tYLTm-0006p0-83; Thu, 16 Jan 2025 03:43:54 -0500 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tYLTg-0006nn-Np; Thu, 16 Jan 2025 03:43:53 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=tjqHi7zeaRi1ZPcfAv+eUnMUtGpd7kq8NDwOvC3nsVk=; b=bSv6dzL1vdg3gqEa+FP0eVjouM j1nwqH+kRmJ+mY1u3/gaLep/NqlwSpdMpOcYt1dytUykeQJVgUuDnW4v49K4RgJNc1dx01+0jassk JhfKQKY5znnu+hthvlM4rlvAL7lOcloj9F/r3RlWMgiPSzFm/nh/QaAZWfD39v3o2hNz6zOeabUBz iOU0OF5os3V/ZMvjShsLmfv83KQ99Fhq7pJ/v1xsw+hZYc7c0qoRIKFqE2/q5yXXsUWMrvUMsP4l4 VDN+WWnfDRy1TysjP3lpzq4ulph49cnnjXzdy+j4ZY6W56keXvTz9FkFo8EXnhsclB1dGNdfwLaZO I9gZjIXw==; Received: from [2001:8b0:10b:1::ebe] (helo=i7.infradead.org) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tYLTd-0000000Akbc-0hzA; Thu, 16 Jan 2025 08:43:45 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tYLTc-00000007pIP-3i2w; Thu, 16 Jan 2025 08:43:44 +0000 From: David Woodhouse To: Stefan Hajnoczi , qemu-devel@nongnu.org Cc: Stefano Stabellini , Anthony PERARD , Paul Durrant , "Edgar E. Iglesias" , Kevin Wolf , Hanna Reitz , =?utf-8?q?M?= =?utf-8?q?arc-Andr=C3=A9_Lureau?= , Paolo Bonzini , Jason Wang , xen-devel@lists.xenproject.org, qemu-block@nongnu.org, Phil Dennis-Jordan , David Woodhouse Subject: [PULL 8/8] system/runstate: Fix regression, clarify BQL status of exit notifiers Date: Thu, 16 Jan 2025 08:43:32 +0000 Message-ID: <20250116084332.1864967-9-dwmw2@infradead.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20250116084332.1864967-1-dwmw2@infradead.org> References: <20250116084332.1864967-1-dwmw2@infradead.org> MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Received-SPF: none client-ip=2001:8b0:10b:1236::1; envelope-from=BATV+cabf69696ff47aa9dee2+7816+infradead.org+dwmw2@casper.srs.infradead.org; helo=casper.infradead.org X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Phil Dennis-Jordan By changing the way the main QEMU event loop is invoked, I inadvertently changed the BQL status of exit notifiers: some of them implicitly assumed they would be called with the BQL held; the BQL is however not held during the exit(status) call in qemu_default_main(). Instead of attempting to ensuring we always call exit() from the BQL - including any transitive calls - this change adds a BQL lock guard to qemu_run_exit_notifiers, ensuring the BQL will always be held in the exit notifiers. Additionally, the BQL promise is now documented at the qemu_{add,remove}_exit_notifier() declarations. Fixes: f5ab12caba4f ("ui & main loop: Redesign of system-specific main thread event handling") Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2771 Reported-by: David Woodhouse Signed-off-by: Phil Dennis-Jordan Tested-by: David Woodhouse Signed-off-by: David Woodhouse --- include/system/system.h | 1 + system/runstate.c | 1 + 2 files changed, 2 insertions(+) diff --git a/include/system/system.h b/include/system/system.h index 5364ad4f27..0cbb43ec30 100644 --- a/include/system/system.h +++ b/include/system/system.h @@ -15,6 +15,7 @@ extern bool qemu_uuid_set; const char *qemu_get_vm_name(void); +/* Exit notifiers will run with BQL held. */ void qemu_add_exit_notifier(Notifier *notify); void qemu_remove_exit_notifier(Notifier *notify); diff --git a/system/runstate.c b/system/runstate.c index 3a8fe866bc..272801d307 100644 --- a/system/runstate.c +++ b/system/runstate.c @@ -850,6 +850,7 @@ void qemu_remove_exit_notifier(Notifier *notify) static void qemu_run_exit_notifiers(void) { + BQL_LOCK_GUARD(); notifier_list_notify(&exit_notifiers, NULL); }