From mboxrd@z Thu Jan 1 00:00:00 1970 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 lists1p.gnu.org (lists1p.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 7161AFA1FCE for ; Wed, 22 Apr 2026 16:13:04 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wFaBd-0000Pz-LU; Wed, 22 Apr 2026 12:12:25 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wFaBZ-0000PG-RP for qemu-devel@nongnu.org; Wed, 22 Apr 2026 12:12:22 -0400 Received: from mail-pf1-x434.google.com ([2607:f8b0:4864:20::434]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1wFaBX-0005P1-3b for qemu-devel@nongnu.org; Wed, 22 Apr 2026 12:12:20 -0400 Received: by mail-pf1-x434.google.com with SMTP id d2e1a72fcca58-82f8b60e54dso3743296b3a.2 for ; Wed, 22 Apr 2026 09:12:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1776874335; x=1777479135; darn=nongnu.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=XkwnlAaIhmzRWKnpfKUMWyjcWDJ6wWPYevSxB2grds0=; b=cPkWmns+ER0PU3gWQU4st5iCvQouQtBk8Pb1K7E6hXOcYNhlB482Cy8cKuBL5q9NQt pwmARcGBy5WVk8bbqNTKpywOEc5OIoxm/6pw/P51SjogkmOndV87pY8cb0zQtbsWptFF g8gN2cE9rLdz+6td5fnS2lcHt8EndrfjiGWdgX4CPjGWFvgb85aqqzAyzVlclEC+dnWX fiZCc8gUXbvjZ5gAhFDVQmjjV3pMreUA3ha3Sy/t8Y0ec5QoD0qZmsC2ZxXBTLiDttXc S6keIpYqj5Mt0G0vu/sd7KkqT7ZjC+m04Rx7YUwfT41J2e/Z+AMaYgNFDCeXE4gGLgYk raOA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776874335; x=1777479135; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=XkwnlAaIhmzRWKnpfKUMWyjcWDJ6wWPYevSxB2grds0=; b=L2oWLIdQhc6qHu8C4N+ZkOQ6bqZeXk+n/U2WEtOubuBwUQGokr7iHjXE6UjhJhTc5F 93Om+fLIsWf7BZTKjKbyEyXMza0OWrB9jpiYw+nl3D76kmc88BqkXpVJ6YxViVaS2Qj0 eP+rq7dGfy2hfdMLbdj+6ULhSe/jJmgZfiH8TU0+QeSJPGs62aw5WpyD28jGhmOW6tEJ rXdFxUj8Cgq9zXgXMuRAINj5mlEHB1HAKEVKqYefxEs0YKRd5O1IYDOjgNdMWzr7S5qu oAGYQi60M/PnA5VU1HmfpdW5DouQ67P3CqIG+dRbBUSv4QFtg7d15lGDAo9+Q9MNXrtb 1Q4w== X-Gm-Message-State: AOJu0YztzxbyEdqgqLBibzNQuiiCgIC/km3TKe2dHoUQEn7NZE37h1DB ylpLJHf5en/YSe85YASauD88TN8dCLhMLOi9UWV/QV5rwwOakfZzXz14c5DLxw== X-Gm-Gg: AeBDiesqWeMwsBu4cyY85BmTHEL30KGKECMCQvbL47Ix8Ucbu/57asVP0SznDZn6Fol C7potUqadeS3g62IftxN01txibtK1qMmCJQ9KSmxe0FI30JKVXoR8hAvp/TOnjL/V9ik73c8Jlx KoKrJl/mJJ615mhHQWOKAv64qROfpmut4iK7MwAXuqRkiTM2dYAyVsh4k8zG0TwKYCdqK/kKsLE J5K4ahvipbGb1DNlCyW+WIzhcGWiee0mYcsI73TcLDJj/oA1QECPGIdIl1y77tQpKFkdebI6WXs 8djQNXfGfsf87ARCfPrBZHmbQmhojaWCDezfwYnq2B76+tV8V7UpSi7CbfmohNJREcUt5kb5bMq WsUtqG2X1UOeB4QmuKXFAh4OecZlT0U//zSQSyu3yNCBQTX4elS3ZDtL3WoKrcK68tILiaWnXAz COQj78gDahuPyXH7HmJTTBsdsnQfwWaibuexPr06+CDiQk4FdtExSO3vgwiA== X-Received: by 2002:a05:6a00:2da2:b0:829:8942:2c85 with SMTP id d2e1a72fcca58-82f8c86b594mr23653843b3a.17.1776874334657; Wed, 22 Apr 2026 09:12:14 -0700 (PDT) Received: from localhost.localdomain ([42.114.219.141]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82f8e9cbb28sm16558138b3a.13.2026.04.22.09.12.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Apr 2026 09:12:13 -0700 (PDT) From: Trieu Huynh X-Google-Original-From: Trieu Huynh To: qemu-devel@nongnu.org Cc: Trieu Huynh Subject: [PATCH 0/1] migration/multifd: fix channel count TOCTOU race on cancel and retry Date: Wed, 22 Apr 2026 23:12:01 +0700 Message-ID: <20260422161202.34150-1-viking4@gmail.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::434; envelope-from=vikingtc4@gmail.com; helo=mail-pf1-x434.google.com X-Spam_score_int: -17 X-Spam_score: -1.8 X-Spam_bar: - X-Spam_report: (-1.8 / 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, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, 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: qemu development 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: Trieu Huynh QEMU aborts on src during multifd migration when multifd-channels is changed after migrate_cancel: ~ # qemu-system-x86_64: ../util/yank.c:107: yank_unregister_instance: Assertion `QLIST_EMPTY(&entry->yankfns)' failed. Aborted (core dumped) Below is the backtrace: #7 yank_unregister_instance (instance=0x7fffffffd870) at ../util/yank.c:107 #8 migration_cleanup (s=0x555557649d10) at ../migration/migration.c:1338 #9 migration_cleanup_bh (opaque=0x555557649d10) at ../migration/migration.c:1345 #10 migration_bh_dispatch_bh (opaque=0x7ffe500051d0) at ../migration/migration.c:350 #11 aio_bh_call (bh=0x7ffe5006d670) at ../util/async.c:173 #12 aio_bh_poll (ctx=0x555557649210) at ../util/async.c:220 #13 aio_dispatch (ctx=0x555557649210) at ../util/aio-posix.c:390 #14 aio_ctx_dispatch (source=0x555557649210) at ../util/async.c:365 ... Steps to reproduce: * 1. Start VM on src ./qemu-system-x86_64 \ - * 2. Start dest with -incoming defer ./qemu-system-x86_64 \ -incoming defer \ - * 3. Enable multifd with 4 channels on both src and dest { "execute": "qmp_capabilities" } { "execute": "migrate-set-capabilities", "arguments": {"capabilities": [{"capability": "multifd", "state": true}]} } { "execute": "migrate-set-parameters", "arguments": {"multifd-channels": 4} } { "execute": "migrate-incoming", "arguments": {"uri": "tcp:0:4444"} } * 4. Trigger migration ** dest: { "execute": "migrate-incoming", "arguments": {"uri": "tcp:0:4444"} } ** src: { "execute": "migrate", "arguments": {"uri": "tcp:127.0.0.1:4444"} } * 5. Cancel migration on src while status is active { "execute": "migrate_cancel" } * 6. Immediately change multifd-channels to 2 on src { "execute": "migrate-set-parameters", "arguments": {"multifd-channels": 2} } QEMU aborts as shown above Trieu Huynh (1): migration/multifd: fix channel count TOCTOU race on cancel and retry migration/multifd.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) -- 2.43.0