From patchwork Mon Aug 21 09:13:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Tong Tiangen X-Patchwork-Id: 136393 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b82d:0:b0:3f2:4152:657d with SMTP id z13csp2995519vqi; Mon, 21 Aug 2023 06:14:11 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHL3ejYhXQsZuAfC806JjxT2d0HeTQrbU9e9CE1ja0frVPoo54KQ3CR9DFNniTDhJFVaJWm X-Received: by 2002:a2e:9bc5:0:b0:2bb:a06d:1d30 with SMTP id w5-20020a2e9bc5000000b002bba06d1d30mr4192746ljj.45.1692623651265; Mon, 21 Aug 2023 06:14:11 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1692623651; cv=none; d=google.com; s=arc-20160816; b=1IK0ziFIEZeJlPxKLw0u2vcPJ0RAwEaaBaoW6vnZFwY49pVnsKg36foGc4B2tI9nN7 3Wsy8afihdrG5uj4Q9Gepss9qfRdFbSAe/NPSAJ55GukELMIJqSKenLuDk/FOb+v3Xnp +kQEKJU5txoETj7XyHGPcl966//ccJu5qF3GoLA/rmWnGeCEjVxVnhsr5TpN1r+orhev yjZ3tWlcsc4dD3QFQ57oyLxR2nHVoV0pIK/l2dqfaMM1AOkYQ0D8OYh5X0AWWjyhWiLa I2jL3AjvBonuOauhxSiAVDGkQFhRgLV0KGf31FN7YWlGRhqT6mgwBli07AEL2mvowqPK HALg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :message-id:date:subject:cc:to:from; bh=G+HNfSj/RKbDIZE8b7A2cIZb/ltY7CJc09beoqnE3nA=; fh=fJ/pPzqKl2DdovjkwlgFt0A7lWhXaT5c9EaE9YrQUC0=; b=BVZwG27O/PIgDmets/EHz80uPiZ2nw2Oij6HDeZl93ZmRafDkkysnqCM8k6n9PaLdo ua5eseN9RwjN8PfbojCC/J+5ZmUz03iU/RtjbvZ3WaIoUEC4tEUrj3IqZcGq8Z1OUp1G JZCEqKPfmGatpxshM4vMR5+mRF5WAK3v+2f5gcD+iNDjM7R8hYTguetd0zQtlzQF1vYE 4Ciw3nx6ldnwaIC7blKnV2hw7CPnuYHvOZhGqZX0Nh7v7Hk28E2JXBjLpf5AN4iT9IGO zTD9gWyAcT25A8WaEK/DQ04/EH5XSpEYZidUJAeRa8bN7TBaGf9yOUGgvtg+lJBWZqwl aVxw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=huawei.com Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id yy10-20020a170906dc0a00b00992169858f2si5540986ejb.3.2023.08.21.06.13.29; Mon, 21 Aug 2023 06:14:11 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=huawei.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234052AbjHUJNU (ORCPT + 99 others); Mon, 21 Aug 2023 05:13:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231593AbjHUJNU (ORCPT ); Mon, 21 Aug 2023 05:13:20 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9D2A4BA for ; Mon, 21 Aug 2023 02:13:17 -0700 (PDT) Received: from kwepemm600017.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4RTmv81yWhz1L9FL; Mon, 21 Aug 2023 17:11:48 +0800 (CST) Received: from localhost.localdomain (10.175.112.125) by kwepemm600017.china.huawei.com (7.193.23.234) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Mon, 21 Aug 2023 17:13:14 +0800 From: Tong Tiangen To: Andrew Morton , Naoya Horiguchi , Miaohe Lin , CC: , , Tong Tiangen Subject: [PATCH v2] mm: memory-failure: use rcu lock instead of tasklist_lock when collect_procs() Date: Mon, 21 Aug 2023 17:13:12 +0800 Message-ID: <20230821091312.2034844-1-tongtiangen@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Originating-IP: [10.175.112.125] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To kwepemm600017.china.huawei.com (7.193.23.234) X-CFilter-Loop: Reflected X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1774819867424739136 X-GMAIL-MSGID: 1774844537797048778 We found a softlock issue in our test, analyzed the logs, and found that the relevant CPU call trace as follows: CPU0: _do_fork -> copy_process() -> write_lock_irq(&tasklist_lock) //Disable irq,waiting for //tasklist_lock CPU1: wp_page_copy() ->pte_offset_map_lock() -> spin_lock(&page->ptl); //Hold page->ptl -> ptep_clear_flush() -> flush_tlb_others() ... -> smp_call_function_many() -> arch_send_call_function_ipi_mask() -> csd_lock_wait() //Waiting for other CPUs respond //IPI CPU2: collect_procs_anon() -> read_lock(&tasklist_lock) //Hold tasklist_lock ->for_each_process(tsk) -> page_mapped_in_vma() -> page_vma_mapped_walk() -> map_pte() ->spin_lock(&page->ptl) //Waiting for page->ptl We can see that CPU1 waiting for CPU0 respond IPI，CPU0 waiting for CPU2 unlock tasklist_lock, CPU2 waiting for CPU1 unlock page->ptl. As a result, softlockup is triggered. For collect_procs_anon(), we will not modify the tasklist, but only perform read traversal. Therefore, we can use rcu lock instead of spin lock tasklist_lock, from this, we can break the softlock chain above. The same logic can also be applied to: - collect_procs_file() - collect_procs_fsdax() - collect_procs_ksm() Signed-off-by: Tong Tiangen Acked-by: Naoya Horiguchi --- Since v1: - 1. According to Matthew's suggestion, only the comments of find_early_kill_thread() are modified, no need to hold the rcu lock. Changes since RFC[1]: - 1. According to Naoya's suggestion, modify the tasklist_lock in the comment about locking order in mm/filemap.c. - 2. According to Kefeng's suggestion, optimize the implementation of find_early_kill_thread() without functional changes. - 3. Modify the title description. [1] https://lore.kernel.org/lkml/20230815130154.1100779-1-tongtiangen@huawei.com/ --- mm/filemap.c | 3 --- mm/ksm.c | 4 ++-- mm/memory-failure.c | 16 ++++++++-------- 3 files changed, 10 insertions(+), 13 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 014b73eb96a1..dfade1ef1765 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -121,9 +121,6 @@ * bdi.wb->list_lock (zap_pte_range->set_page_dirty) * ->inode->i_lock (zap_pte_range->set_page_dirty) * ->private_lock (zap_pte_range->block_dirty_folio) - * - * ->i_mmap_rwsem - * ->tasklist_lock (memory_failure, collect_procs_ao) */ static void page_cache_delete(struct address_space *mapping, diff --git a/mm/ksm.c b/mm/ksm.c index 8d6aee05421d..981af9c72e7a 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2925,7 +2925,7 @@ void collect_procs_ksm(struct page *page, struct list_head *to_kill, struct anon_vma *av = rmap_item->anon_vma; anon_vma_lock_read(av); - read_lock(&tasklist_lock); + rcu_read_lock(); for_each_process(tsk) { struct anon_vma_chain *vmac; unsigned long addr; @@ -2944,7 +2944,7 @@ void collect_procs_ksm(struct page *page, struct list_head *to_kill, } } } - read_unlock(&tasklist_lock); + rcu_read_unlock(); anon_vma_unlock_read(av); } } diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 7b01fffe7a79..4d6e43c88489 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -547,8 +547,8 @@ static void kill_procs(struct list_head *to_kill, int forcekill, bool fail, * on behalf of the thread group. Return task_struct of the (first found) * dedicated thread if found, and return NULL otherwise. * - * We already hold read_lock(&tasklist_lock) in the caller, so we don't - * have to call rcu_read_lock/unlock() in this function. + * We already hold rcu lock in the caller, so we don't have to call + * rcu_read_lock/unlock() in this function. */ static struct task_struct *find_early_kill_thread(struct task_struct *tsk) { @@ -609,7 +609,7 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill, return; pgoff = page_to_pgoff(page); - read_lock(&tasklist_lock); + rcu_read_lock(); for_each_process(tsk) { struct anon_vma_chain *vmac; struct task_struct *t = task_early_kill(tsk, force_early); @@ -626,7 +626,7 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill, add_to_kill_anon_file(t, page, vma, to_kill); } } - read_unlock(&tasklist_lock); + rcu_read_unlock(); anon_vma_unlock_read(av); } @@ -642,7 +642,7 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill, pgoff_t pgoff; i_mmap_lock_read(mapping); - read_lock(&tasklist_lock); + rcu_read_lock(); pgoff = page_to_pgoff(page); for_each_process(tsk) { struct task_struct *t = task_early_kill(tsk, force_early); @@ -662,7 +662,7 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill, add_to_kill_anon_file(t, page, vma, to_kill); } } - read_unlock(&tasklist_lock); + rcu_read_unlock(); i_mmap_unlock_read(mapping); } @@ -685,7 +685,7 @@ static void collect_procs_fsdax(struct page *page, struct task_struct *tsk; i_mmap_lock_read(mapping); - read_lock(&tasklist_lock); + rcu_read_lock(); for_each_process(tsk) { struct task_struct *t = task_early_kill(tsk, true); @@ -696,7 +696,7 @@ static void collect_procs_fsdax(struct page *page, add_to_kill_fsdax(t, page, vma, to_kill, pgoff); } } - read_unlock(&tasklist_lock); + rcu_read_unlock(); i_mmap_unlock_read(mapping); } #endif /* CONFIG_FS_DAX */