From mboxrd@z Thu Jan 1 00:00:00 1970 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 394583812F6; Tue, 9 Jun 2026 08:50:36 +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=1780995039; cv=none; b=pExrIaNrzxheAhNwkMViZDUroSF82Qk9U1MdFuEOYRjrDmlK/ubOgf3bpi5ck6yOgoUFLX3v4LSDIfLW3MzHsumD/41pXwIebNWXklTp9onXP7rjMpBwYVFkW1qMStdWI2p0u3l5jWaAphG2jV42+bcbnBj2vCrKFGA09X92EFk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780995039; c=relaxed/simple; bh=sFsCj8R0jEN1k2Y+Fu/trCTQWqQ/AKEkvKZ+ZH7ungA=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=L/P/kS3tZxS37ylJ/8LfwNTLNe+Lk+fxme64r18V3UlsSgcoPuZXRC0M6HK7s69NYc9CFRHiqq+eZ0oB2lvrgCFV1u1/q2tpMn+krc5j16qxJMW6JVdSiJfQ7EmrRcFITZTe/xjvOFOA3f0rUElHKqZMYIyHF7ky52bsAZo/RGw= 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 [172.19.163.198]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4gZN012mCPzYQtM7; Tue, 9 Jun 2026 16:50:09 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.75]) by mail.maildlp.com (Postfix) with ESMTP id F24EB40576; Tue, 9 Jun 2026 16:50:25 +0800 (CST) Received: from huawei.com (unknown [7.197.88.80]) by APP2 (Coremail) with SMTP id Syh0CgA3+n_L0ydqfvuqBA--.61309S2; Tue, 09 Jun 2026 16:50:24 +0800 (CST) From: Tengda Wu To: Masami Hiramatsu , Peter Zijlstra Cc: Steven Rostedt , Mathieu Desnoyers , Alexei Starovoitov , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, Tengda Wu Subject: [PATCH v3] rethook: Remove the running task check in rethook_find_ret_addr() Date: Tue, 9 Jun 2026 16:49:53 +0800 Message-Id: <20260609084953.901576-1-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: 8bit X-CM-TRANSID:Syh0CgA3+n_L0ydqfvuqBA--.61309S2 X-Coremail-Antispam: 1UD129KBjvJXoW7uw4fJw1fGw18tF4UJFyrWFg_yoW8CF1UpF 4xGwnYkFsFyr10yw1qvws3u345Zrs5Kw13WFsrGw1F9Fs8tw4UKrWSgw1YvFs0qr9rGa42 qr42vryqkanrZa7anT9S1TB71UUUUUDqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 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/ The current check in rethook_find_ret_addr() prevents obtaining a return address when the target task is marked as running. However, this condition is both insufficient for correctness and unnecessary for its intended purpose. The check is inherently racy: a task can begin running on another CPU immediately after task_is_running() returns false, potentially leading to concurrent modification of rethook data structures while the iteration is in progress. Rather than trying to fix this unreliable check deep in the unwinding path, simply remove it. The iteration is already safe from crashes because unwind_next_frame() holds RCU and rethook_node structures are RCU-freed; even if the iteration goes off the rails and returns invalid information, it will not crash. Callers that require consistency must provide a safe context themselves. Fixes: 54ecbe6f1ed5 ("rethook: Add a generic return hook") Acked-by: Peter Zijlstra (Intel) Signed-off-by: Tengda Wu --- v3: Improve commit message: clarify safety semantics and document that RCU guarantees no crash. v2: https://lore.kernel.org/all/20260609005728.458962-1-wutengda@huaweicloud.com/ v1: https://lore.kernel.org/all/20260525132253.1889726-1-wutengda@huaweicloud.com/ kernel/trace/rethook.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c index 5a8bdf88999a..f70f11bc6c91 100644 --- a/kernel/trace/rethook.c +++ b/kernel/trace/rethook.c @@ -250,9 +250,6 @@ unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame if (WARN_ON_ONCE(!cur)) return 0; - if (tsk != current && task_is_running(tsk)) - return 0; - do { ret = __rethook_find_ret_addr(tsk, cur); if (!ret) -- 2.34.1