From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A658E3A5E7D; Sat, 17 Oct 2026 17:31:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792258273; cv=none; b=ZOxsCpjB+ECIIbixE+T7Bi7MffRnG/56edVkj1kLmz96F0k2Gmy2LT1qE0nzCfCK9HqpDcoNOnAhC03VxMaCd9LOa00BomSPZsZq3SruODNWiNOUTB+zr6pHTyqOH3BF3uHrCc53ISFdtAs9cenULuBKCU4dnt8hnsE6pU2fCRw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792258273; c=relaxed/simple; bh=7qWtpK+48pHEkMuRN558Rt34VC5Pky8zyjB181vflXM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PV6sxQA8PXQhtne4xAuKXqjH+ItriPy+rYjHwZmNyZtQQ34N1WilOb/soE100r7BPQz56vpnHklI8bPGWc0S24W34FHNz3QkROqfLFW9elqrCXDOFIDwwqJ+GuTY2FbPcI9Wec9OKk22Kk8Ao9jn2cZcTebKv2erEKmYZZjqeEs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=l0iSUGYI; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="l0iSUGYI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 023321F000C4; Sat, 17 Oct 2026 17:31:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792258271; bh=7mZQqz8onhLirxfWax5VICmztJlbC1KNpXsTNGo9RKE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=l0iSUGYIncrpOOpIF53V7IetkuTiUDMgaG1gFu1bFPIQke8q4rH/HZACGLfx3cBbN aCo8nInY19qGmCSB/tntB51W0h+pQCkyLxLtVM6y9hMD0xZ1BBihiDN9TJGFV8vGp9 AwrTLH3TneQtCQBRGrNBJ1FQFn1RNSAyrCMDQgww= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yu Kuai , Song Liu , Sasha Levin Subject: [PATCH 6.6 0828/1674] md: fix stopping sync thread Date: Sat, 17 Oct 2026 17:51:40 +0200 Message-ID: <20261017160452.379518849@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160431.119607952@linuxfoundation.org> References: <20261017160431.119607952@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yu Kuai [ Upstream commit f52f5c71f3d4bb0992800139d2f35cf9f6f6e0ee ] Currently sync thread is stopped from multiple contex: - idle_sync_thread - frozen_sync_thread - __md_stop_writes - md_set_readonly - do_md_stop And there are some problems: 1) sync_work is flushed while reconfig_mutex is grabbed, this can deadlock because the work function will grab reconfig_mutex as well. 2) md_reap_sync_thread() can't be called directly while md_do_sync() is not finished yet, for example, commit 130443d60b1b ("md: refactor idle/frozen_sync_thread() to fix deadlock"). 3) If MD_RECOVERY_RUNNING is not set, there is no need to stop sync_thread at all because sync_thread must not be registered. Factor out a helper stop_sync_thread(), so that above contex will behave the same. Fix 1) by flushing sync_work after reconfig_mutex is released, before waiting for sync_thread to be done; Fix 2) bt letting daemon thread to unregister sync_thread; Fix 3) by always checking MD_RECOVERY_RUNNING first. Fixes: db5e653d7c9f ("md: delay choosing sync action to md_start_sync()") Signed-off-by: Yu Kuai Signed-off-by: Song Liu Link: https://lore.kernel.org/r/20231205094215.1824240-4-yukuai1@huaweicloud.com Stable-dep-of: 0dc76205549b ("md: fix rcu protection in md_wakeup_thread") Signed-off-by: Sasha Levin --- drivers/md/md.c | 90 ++++++++++++++++++++----------------------------- 1 file changed, 37 insertions(+), 53 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 3c605ba3801aa..4b2acf648d767 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -4832,25 +4832,29 @@ action_show(struct mddev *mddev, char *page) return sprintf(page, "%s\n", type); } -static void stop_sync_thread(struct mddev *mddev) +/** + * stop_sync_thread() - wait for sync_thread to stop if it's running. + * @mddev: the array. + * @locked: if set, reconfig_mutex will still be held after this function + * return; if not set, reconfig_mutex will be released after this + * function return. + * @check_seq: if set, only wait for curent running sync_thread to stop, noted + * that new sync_thread can still start. + */ +static void stop_sync_thread(struct mddev *mddev, bool locked, bool check_seq) { - if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) - return; + int sync_seq; - if (mddev_lock(mddev)) - return; + if (check_seq) + sync_seq = atomic_read(&mddev->sync_seq); - /* - * Check again in case MD_RECOVERY_RUNNING is cleared before lock is - * held. - */ if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) { - mddev_unlock(mddev); + if (!locked) + mddev_unlock(mddev); return; } - if (work_pending(&mddev->sync_work)) - flush_workqueue(md_misc_wq); + mddev_unlock(mddev); set_bit(MD_RECOVERY_INTR, &mddev->recovery); /* @@ -4858,21 +4862,28 @@ static void stop_sync_thread(struct mddev *mddev) * never happen */ md_wakeup_thread_directly(mddev->sync_thread); + if (work_pending(&mddev->sync_work)) + flush_work(&mddev->sync_work); - mddev_unlock(mddev); + wait_event(resync_wait, + !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) || + (check_seq && sync_seq != atomic_read(&mddev->sync_seq))); + + if (locked) + mddev_lock_nointr(mddev); } static void idle_sync_thread(struct mddev *mddev) { - int sync_seq = atomic_read(&mddev->sync_seq); - mutex_lock(&mddev->sync_mutex); clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); - stop_sync_thread(mddev); - wait_event(resync_wait, sync_seq != atomic_read(&mddev->sync_seq) || - !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)); + if (mddev_lock(mddev)) { + mutex_unlock(&mddev->sync_mutex); + return; + } + stop_sync_thread(mddev, false, true); mutex_unlock(&mddev->sync_mutex); } @@ -4880,11 +4891,13 @@ static void frozen_sync_thread(struct mddev *mddev) { mutex_lock(&mddev->sync_mutex); set_bit(MD_RECOVERY_FROZEN, &mddev->recovery); - stop_sync_thread(mddev); - wait_event(resync_wait, mddev->sync_thread == NULL && - !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)); + if (mddev_lock(mddev)) { + mutex_unlock(&mddev->sync_mutex); + return; + } + stop_sync_thread(mddev, false, false); mutex_unlock(&mddev->sync_mutex); } @@ -6305,14 +6318,7 @@ static void md_clean(struct mddev *mddev) static void __md_stop_writes(struct mddev *mddev) { - set_bit(MD_RECOVERY_FROZEN, &mddev->recovery); - if (work_pending(&mddev->sync_work)) - flush_workqueue(md_misc_wq); - if (mddev->sync_thread) { - set_bit(MD_RECOVERY_INTR, &mddev->recovery); - md_reap_sync_thread(mddev); - } - + stop_sync_thread(mddev, true, false); del_timer_sync(&mddev->safemode_timer); if (mddev->pers && mddev->pers->quiesce) { @@ -6406,18 +6412,8 @@ static int md_set_readonly(struct mddev *mddev, struct block_device *bdev) set_bit(MD_RECOVERY_FROZEN, &mddev->recovery); md_wakeup_thread(mddev->thread); } - if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) - set_bit(MD_RECOVERY_INTR, &mddev->recovery); - - /* - * Thread might be blocked waiting for metadata update which will now - * never happen - */ - md_wakeup_thread_directly(mddev->sync_thread); - mddev_unlock(mddev); - wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING, - &mddev->recovery)); + stop_sync_thread(mddev, false, false); wait_event(mddev->sb_wait, !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)); mddev_lock_nointr(mddev); @@ -6471,20 +6467,8 @@ static int do_md_stop(struct mddev *mddev, int mode, set_bit(MD_RECOVERY_FROZEN, &mddev->recovery); md_wakeup_thread(mddev->thread); } - if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) - set_bit(MD_RECOVERY_INTR, &mddev->recovery); - /* - * Thread might be blocked waiting for metadata update which will now - * never happen - */ - md_wakeup_thread_directly(mddev->sync_thread); - - mddev_unlock(mddev); - wait_event(resync_wait, (mddev->sync_thread == NULL && - !test_bit(MD_RECOVERY_RUNNING, - &mddev->recovery))); - mddev_lock_nointr(mddev); + stop_sync_thread(mddev, true, false); mutex_lock(&mddev->open_mutex); if ((mddev->pers && atomic_read(&mddev->openers) > !!bdev) || -- 2.53.0