From nobody Fri Nov 14 18:06:31 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1760814500160473.52637465849864; Sat, 18 Oct 2025 12:08:20 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vACHB-0006Yy-19; Sat, 18 Oct 2025 15:07:37 -0400 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 1vACH7-0006Tu-HJ; Sat, 18 Oct 2025 15:07:33 -0400 Received: from isrv.corpit.ru ([212.248.84.144]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vACH5-00016D-L6; Sat, 18 Oct 2025 15:07:33 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 17FB415F7A0; Sat, 18 Oct 2025 22:06:59 +0300 (MSK) Received: from think4mjt.tls.msk.ru (mjtthink.wg.tls.msk.ru [192.168.177.146]) by tsrv.corpit.ru (Postfix) with ESMTP id D581E2F0609; Sat, 18 Oct 2025 22:07:02 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Paolo Bonzini , Michael Tokarev Subject: [Stable-10.1.2 19/23] async: access bottom half flags with qatomic_read Date: Sat, 18 Oct 2025 22:06:54 +0300 Message-ID: <20251018190702.1178893-8-mjt@tls.msk.ru> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=212.248.84.144; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1760814503197158500 Content-Type: text/plain; charset="utf-8" From: Paolo Bonzini Running test-aio-multithread under TSAN reveals data races on bh->flags. Because bottom halves may be scheduled or canceled asynchronously, without taking a lock, adjust aio_compute_bh_timeout() and aio_ctx_check() to use a relaxed read to access the flags. Use an acquire load to ensure that anything that was written prior to qemu_bh_schedule() is visible. Closes: https://gitlab.com/qemu-project/qemu/-/issues/2749 Closes: https://gitlab.com/qemu-project/qemu/-/issues/851 Cc: qemu-stable@nongnu.org Signed-off-by: Paolo Bonzini (cherry picked from commit 5142397c79330aab9bef3230991c8ac0c251110f) Signed-off-by: Michael Tokarev diff --git a/util/async.c b/util/async.c index 2719c629ae..a736d2cd0d 100644 --- a/util/async.c +++ b/util/async.c @@ -256,8 +256,9 @@ static int64_t aio_compute_bh_timeout(BHList *head, int= timeout) QEMUBH *bh; =20 QSLIST_FOREACH_RCU(bh, head, next) { - if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) =3D=3D BH_SCHEDULED)= { - if (bh->flags & BH_IDLE) { + int flags =3D qatomic_load_acquire(&bh->flags); + if ((flags & (BH_SCHEDULED | BH_DELETED)) =3D=3D BH_SCHEDULED) { + if (flags & BH_IDLE) { /* idle bottom halves will be polled at least * every 10ms */ timeout =3D 10000000; @@ -335,14 +336,16 @@ aio_ctx_check(GSource *source) aio_notify_accept(ctx); =20 QSLIST_FOREACH_RCU(bh, &ctx->bh_list, next) { - if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) =3D=3D BH_SCHEDULED)= { + int flags =3D qatomic_load_acquire(&bh->flags); + if ((flags & (BH_SCHEDULED | BH_DELETED)) =3D=3D BH_SCHEDULED) { return true; } } =20 QSIMPLEQ_FOREACH(s, &ctx->bh_slice_list, next) { QSLIST_FOREACH_RCU(bh, &s->bh_list, next) { - if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) =3D=3D BH_SCHEDU= LED) { + int flags =3D qatomic_load_acquire(&bh->flags); + if ((flags & (BH_SCHEDULED | BH_DELETED)) =3D=3D BH_SCHEDULED)= { return true; } } --=20 2.47.3