From nobody Thu Dec 18 06:33:16 2025 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (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 4D83E1EEA47; Tue, 11 Feb 2025 08:29:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739262566; cv=none; b=ptKoUhR2iDKrbpn97t3SnZJ2mKAns15+ECCuZMDYqioXuFGdwrbgu251UNtUCSKYrHChTv8/BjqVBiDg43Pc8fxgJCFD7uEorsKsQ+89IbaUY6tEkVHISYO3F7C+6SqiT9i02QZSzu4sfhS5EtdFnDyIEPrLyldRp9xHjCOMk0A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739262566; c=relaxed/simple; bh=5mLlG7UJKSNSJiUN+gLdBG8mvz50NDCZxBPd4G5dwuU=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=gaJLs1yqPLF6o1WrcV1BaPueZdJ0WeHnB1S3Ji0Mg+Ygis8coq8np0zoQGrMOabAM0Xk4V2Jo0ZnYsElNSnO60sk6kEYANsT1akEbKVP7TfIODlrKKvUYFCC6/+xPxYGCVQnpAzVVviJwdfP/p+S8y4aQYYuVS7aUv2iEW7QwOI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.235]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4YsZNL4kw6z4f3lCm; Tue, 11 Feb 2025 16:28:50 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.252]) by mail.maildlp.com (Postfix) with ESMTP id 55B631A0CA9; Tue, 11 Feb 2025 16:29:13 +0800 (CST) Received: from hulk-vt.huawei.com (unknown [10.67.174.121]) by APP3 (Coremail) with SMTP id _Ch0CgAHp8FICqtnfiPrDQ--.42730S2; Tue, 11 Feb 2025 16:29:13 +0800 (CST) From: Chen Ridong To: hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, akpm@linux-foundation.org Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, chenridong@huawei.com, wangweiyang2@huawei.com Subject: [PATCH] memcg: avoid dead loop when setting memory.max Date: Tue, 11 Feb 2025 08:18:19 +0000 Message-Id: <20250211081819.33307-1-chenridong@huaweicloud.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: _Ch0CgAHp8FICqtnfiPrDQ--.42730S2 X-Coremail-Antispam: 1UD129KBjvJXoWxJw1fZr4DXw15ZF4ftw1kXwb_yoW5Cw1DpF 13Jw1UGF48Jr1kXr4UJF1fWr15Ga1kCFy7JrW7ur1rA3ZxG3WUJ34rK3yUXryDXr1rZr1a vF1DJw4xtw4DJaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUv2b4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUGVWUXwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcxkI7VAKI48JM4IIrI8v6xkF7I0E8cxan2IY04v7MxkF7I0E n4kS14v26r1q6r43MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I 0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWU tVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcV CY1x0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAF wI0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa 7IUbmii3UUUUU== X-CM-SenderInfo: hfkh02xlgr0w46kxt4xhlfz01xgou0bp/ Content-Type: text/plain; charset="utf-8" From: Chen Ridong A softlockup issue was found with stress test: watchdog: BUG: soft lockup - CPU#27 stuck for 26s! [migration/27:181] CPU: 27 UID: 0 PID: 181 Comm: migration/27 6.14.0-rc2-next-20250210 #1 Stopper: multi_cpu_stop <- stop_machine_from_inactive_cpu RIP: 0010:stop_machine_yield+0x2/0x10 RSP: 0000:ff4a0dcecd19be48 EFLAGS: 00000246 RAX: ffffffff89c0108f RBX: ff4a0dcec03afe44 RCX: 0000000000000000 RDX: ff1cdaaf6eba5808 RSI: 0000000000000282 RDI: ff1cda80c1775a40 RBP: 0000000000000001 R08: 00000011620096c6 R09: 7fffffffffffffff R10: 0000000000000001 R11: 0000000000000100 R12: ff1cda80c1775a40 R13: 0000000000000000 R14: 0000000000000001 R15: ff4a0dcec03afe20 FS: 0000000000000000(0000) GS:ff1cdaaf6eb80000(0000) CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 00000025e2c2a001 CR4: 0000000000773ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: multi_cpu_stop+0x8f/0x100 cpu_stopper_thread+0x90/0x140 smpboot_thread_fn+0xad/0x150 kthread+0xc2/0x100 ret_from_fork+0x2d/0x50 The stress test involves CPU hotplug operations and memory control group (memcg) operations. The scenario can be described as follows: echo xx > memory.max cache_ap_online oom_reaper (CPU23) (CPU50) xx < usage stop_machine_from_inactive_cpu for(;;) // all active cpus trigger OOM queue_stop_cpus_work // waiting oom_reaper multi_cpu_stop(migration/xx) // sync all active cpus ack // waiting cpu23 ack // CPU50 loops in multi_cpu_stop waiting cpu50 Detailed explanation: 1. When the usage is larger than xx, an OOM may be triggered. If the process does not handle with ths kill signal immediately, it will loop in the memory_max_write. 2. When cache_ap_online is triggered, the multi_cpu_stop is queued to the active cpus. Within the multi_cpu_stop function, it attempts to synchronize the CPU states. However, the CPU23 didn't acknowledge because it is stuck in a loop within the for(;;). 3. The oom_reaper process is blocked because CPU50 is in a loop, waiting for CPU23 to acknowledge the synchronization request. 4. Finally, it formed cyclic dependency and lead to softlockup and dead loop. To fix this issue, add cond_resched() in the memory_max_write, so that it will not block migration task. Fixes: b6e6edcfa405 ("mm: memcontrol: reclaim and OOM kill when shrinking m= emory.max below usage") Signed-off-by: Chen Ridong Acked-by: Michal Hocko --- mm/memcontrol.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8d21c1a44220..16f3bdbd37d8 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4213,6 +4213,7 @@ static ssize_t memory_max_write(struct kernfs_open_fi= le *of, memcg_memory_event(memcg, MEMCG_OOM); if (!mem_cgroup_out_of_memory(memcg, GFP_KERNEL, 0)) break; + cond_resched(); } =20 memcg_wb_domain_size_changed(memcg); --=20 2.34.1