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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 8AA7CCAC597 for ; Thu, 18 Sep 2025 06:49:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:Message-ID:Date:Subject:CC:To:From:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner; bh=xT01jm8M2HeKEr0vFkYwW8UybjwRjhTlEwa6HqPfnso=; b=e9HdPIlF1gU4y891tRajKCjMUy CndNndZ9UQ8wIlRD4FNb0rEuHnSF7gwMgNRiWXo0TUF/Yabe5ktqpmHYq2Ato5cmKWxMy1IGICTRO 3Uv/fdIANBEzWXH44cJUGVlr8tHSA4aozAzPqaodkGLnuLnpFsxSDMvdlqUn7gtNEStQG1pGIOTzl fNIdX/o/tAoHUELvsNaTe79WekiesOYmCgiYhRWqVaG0+p8VyZqF62m/OTe27Sor80LbabiSpHXzm ZGbDoPB+EoDDG+rgI1+TGgXRztbpgrOyJvpAK/MGya8F8HuFRC3bsZcB3rOBFNboB4ThGkaWhlDtS djv6idww==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uz8SY-0000000GSoh-3MSk; Thu, 18 Sep 2025 06:49:38 +0000 Received: from wxsgout04.xfusion.com ([36.139.87.180]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uz8SV-0000000GSlD-3wzd for linux-arm-kernel@lists.infradead.org; Thu, 18 Sep 2025 06:49:37 +0000 Received: from wuxpheds03048.xfusion.com (unknown [10.32.143.30]) by wxsgout04.xfusion.com (SkyGuard) with ESMTPS id 4cS5mf5HH7zB72Kv; Thu, 18 Sep 2025 14:47:46 +0800 (CST) Received: from DESKTOP-Q8I2N5U.xfusion.com (10.82.130.100) by wuxpheds03048.xfusion.com (10.32.143.30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_RSA_WITH_AES_128_CBC_SHA256) id 15.2.2562.20; Thu, 18 Sep 2025 14:49:16 +0800 From: shechenglong To: CC: , , , , , , shechenglong Subject: [PATCH] cpu: fix hard lockup triggered during stress-ng stress testing. Date: Thu, 18 Sep 2025 14:49:07 +0800 Message-ID: <20250918064907.1832-1-shechenglong@xfusion.com> X-Mailer: git-send-email 2.38.0.windows.1 MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.82.130.100] X-ClientProxiedBy: wuxpheds03045.xfusion.com (10.32.131.99) To wuxpheds03048.xfusion.com (10.32.143.30) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250917_234936_180800_160CACC5 X-CRM114-Status: GOOD ( 11.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Context of the Issue: In an ARM64 environment, the following steps were performed: 1. Repeatedly ran stress-ng to stress the CPU, memory, and I/O. 2. Cyclically executed test case pty06 from the LTP test suite. 3. Added mitigations=off to the GRUB parameters. After 1–2 hours of stress testing, a hardlockup occurred, causing a system crash. Root Cause of the Hardlockup: Each time stress-ng starts, it invokes the /sys/kernel/debug/clear_warn_once interface, which clears the values in the memory section from __start_once to __end_once. This caused functions like pr_info_once() — originally designed to print only once — to print again every time stress-ng was called. If the pty06 test case happened to be using the serial module at that same moment, it would sleep in waiter.list within the __down_common function. After pr_info_once() completed its output using the serial module, it invoked the semaphore up() function to wake up the process waiting in waiter.list. This sequence triggered an A-A deadlock, ultimately leading to a hardlockup and system crash. To prevent this, a local variable should be used to control and ensure the print operation occurs only once. Hard lockup call stack: _raw_spin_lock_nested+168 ttwu_queue+180 （rq_lock(rq, &rf); 2nd acquiring the rq->__lock） try_to_wake_up+548 wake_up_process+32 __up+88 up+100 __up_console_sem+96 console_unlock+696 vprintk_emit+428 vprintk_default+64 vprintk_func+220 printk+104 spectre_v4_enable_task_mitigation+344 __switch_to+100 __schedule+1028 (rq_lock(rq, &rf); 1st acquiring the rq->__lock) schedule_idle+48 do_idle+388 cpu_startup_entry+44 secondary_start_kernel+352 Signed-off-by: shechenglong --- arch/arm64/kernel/proton-pack.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c index edf1783ffc81..f8663157e041 100644 --- a/arch/arm64/kernel/proton-pack.c +++ b/arch/arm64/kernel/proton-pack.c @@ -424,8 +424,10 @@ static bool spectre_v4_mitigations_off(void) bool ret = cpu_mitigations_off() || __spectre_v4_policy == SPECTRE_V4_POLICY_MITIGATION_DISABLED; - if (ret) - pr_info_once("spectre-v4 mitigation disabled by command-line option\n"); + static atomic_t __printk_once = ATOMIC_INIT(0); + + if (ret && !atomic_cmpxchg(&__printk_once, 0, 1)) + pr_info("spectre-v4 mitigation disabled by command-line option\n"); return ret; } -- 2.33.0