From nobody Tue Feb 10 12:40:00 2026 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 209BD246762; Mon, 9 Feb 2026 09:31:19 +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=1770629481; cv=none; b=mpKFD89CWpCO27YYrHoz1/UhXXuQYVGkBxcjFi4j8z6OVGk5mHeJwER8Zs571qGCdYEprGJWh8sgbaS+VNL37F62YH0ZTuRABkf+8ywyp89MOom/vZ+NBGERSqnaOXW39C3J01cJPH8UpbXEu0ZK8p+GsO5ZkPh+YEdi+SsNjF4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770629481; c=relaxed/simple; bh=dWPIyAinjJJgLyRH3NRk8yFrvm44VyykuKnYZ554Ovw=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=Sv0N+vaQrwj8F9fWqotSZt+XCQA1zLU/d7vEuyyD/PqC3CmwCc7A0Z1fPN8ci4t9Bc/swRq1ZOC2x8sLJRxJTBPgha7XLLe46MLw9qrr/rlnkSYNgZr6mwuhR0FrIEdhfpcwCu+I4hhX+UEZaj9+N4UCGkWOzzzG53P+H9cTO/s= 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 [172.19.163.177]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4f8fYm1mpszYQtnh; Mon, 9 Feb 2026 17:30:20 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id 83B9A4058A; Mon, 9 Feb 2026 17:31:17 +0800 (CST) Received: from huawei.com (unknown [7.197.88.80]) by APP1 (Coremail) with SMTP id cCh0CgCHPuRZqYlp5UrVGg--.57503S2; Mon, 09 Feb 2026 17:31:17 +0800 (CST) From: Tengda Wu To: Steven Rostedt , Masami Hiramatsu Cc: Mathieu Desnoyers , Ingo Molnar , Thomas Gleixner , Arnaldo Carvalho de Melo , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, Tengda Wu Subject: [PATCH] tracing: Fix soft lockup when lseeking trace file Date: Mon, 9 Feb 2026 17:31:01 +0800 Message-Id: <20260209093101.1623454-1-wutengda@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: cCh0CgCHPuRZqYlp5UrVGg--.57503S2 X-Coremail-Antispam: 1UD129KBjvJXoW7AryxAFWDJF1DXw1DZry7ZFb_yoW8Gw1rpF Za9FZxGr4UGF4jyFWF9F4xWryavwnFg347KF9rGw4FvFyDJr15ursFgF1Yg3y5ur9Yy34a vFWYv34UWwnrZFJanT9S1TB71UUUUUDqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkC14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26w1j6s0DM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4U JVWxJr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gc CE3s1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E 2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJV W8JwACjcxG0xvY0x0EwIxGrwACjI8F5VA0II8E6IAqYI8I648v4I1lc7CjxVAaw2AFwI0_ Jw0_GFyl42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67 AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43MIIY rxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14 v26r1j6r4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJVW8 JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjfUonmRUU UUU X-CM-SenderInfo: pzxwv0hjgdqx5xdzvxpfor3voofrz/ Content-Type: text/plain; charset="utf-8" A soft lockup may occur when accessing trace file via lseek while tracing is active and a large offset is provided. The call trace is shown below: watchdog: BUG: soft lockup - CPU#3 stuck for 26s! [poc:141] CPU: 3 UID: 0 PID: 141 Comm: poc Not tainted 6.19.0 #1 PREEMPT(none) Call Trace: ring_buffer_iter_peek peek_next_entry __find_next_entry trace_find_next_entry_inc s_next traverse.part.0 seq_lseek tracing_lseek __x64_sys_lseek do_syscall_64 entry_SYSCALL_64_after_hwframe The root cause is that the lseek implementation for trace files is based on seq_lseek, which contains a loop that repeatedly calls show() and next() functions until the position reaches the target offset. Since no scheduling point is set within this loop, a large offset can cause the CPU to be stuck in the loop for an extended period, triggering the soft lockup detector. Fixed by adding cond_resched() in s_next(). Fixes: bc0c38d139ec ("ftrace: latency tracer infrastructure") Signed-off-by: Tengda Wu --- kernel/trace/trace.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8bd4ec08fb36..3afe148ef683 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3928,6 +3928,8 @@ static void *s_next(struct seq_file *m, void *v, loff= _t *pos) =20 iter->pos =3D *pos; =20 + cond_resched(); + return ent; } =20 --=20 2.34.1