From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 99DD8283FEA; Mon, 23 Mar 2026 15:08:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774278481; cv=none; b=uMcaYGqfa4je1yLm3wih14bWbE4m0xJxQ1h5urmBySy2Tzv8hyqHfC7mFS1XKCV+f3MQldZRQfFFvTLWCV9jvdoFsuLEU76FBuHpjwvkCf2XhgtUpSwda4N65SmY9X36iH9Un5nk3Z+YMLfEcQ1UG99A6jD4EEMxCJbDw3pr1pI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774278481; c=relaxed/simple; bh=9PVVOY5NQk27j1jQXSYVWWeoLciYSJnLZGYoklOM0Io=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=t/GkFg5UipRqwB16IdBLNEfIfdohxa8SGO92KeBsRP4cOznsez5UqJTX+QdeMzgKMVga7AOXqhK9b3vNHaQYWIKqUuytGQ75jCdIQ/g8nnFNdNwM+E31J53VNd6WmGdd5WRIl79ymWGoepSBr9m+ZwcuCroWJ1HyvdQ85lcL0VA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gz/O/7gr; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="gz/O/7gr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 28F51C4CEF7; Mon, 23 Mar 2026 15:08:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774278481; bh=9PVVOY5NQk27j1jQXSYVWWeoLciYSJnLZGYoklOM0Io=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gz/O/7gry+rLOyL6UzililPn2h7NSWfTfqK9QOgj1XMm4kVLOnvzAjVQRApd9gDxq Tw0azePP+l2gaExhiToXLc5BQ3n1qZ96f7rY5Ot/1+bvyeKyhtSj25ZYT9z15tk2Gi 17VEdKI/u/sHUmVLsEqDMasidJq2cnLZR46deju0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Masami Hiramatsu , Mathieu Desnoyers , Huiwen He , "Steven Rostedt (Google)" Subject: [PATCH 6.6 319/567] tracing: Fix syscall events activation by ensuring refcount hits zero Date: Mon, 23 Mar 2026 14:43:59 +0100 Message-ID: <20260323134541.725958050@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260323134533.749096647@linuxfoundation.org> References: <20260323134533.749096647@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Huiwen He commit 0a663b764dbdf135a126284f454c9f01f95a87d4 upstream. When multiple syscall events are specified in the kernel command line (e.g., trace_event=syscalls:sys_enter_openat,syscalls:sys_enter_close), they are often not captured after boot, even though they appear enabled in the tracing/set_event file. The issue stems from how syscall events are initialized. Syscall tracepoints require the global reference count (sys_tracepoint_refcount) to transition from 0 to 1 to trigger the registration of the syscall work (TIF_SYSCALL_TRACEPOINT) for tasks, including the init process (pid 1). The current implementation of early_enable_events() with disable_first=true used an interleaved sequence of "Disable A -> Enable A -> Disable B -> Enable B". If multiple syscalls are enabled, the refcount never drops to zero, preventing the 0->1 transition that triggers actual registration. Fix this by splitting early_enable_events() into two distinct phases: 1. Disable all events specified in the buffer. 2. Enable all events specified in the buffer. This ensures the refcount hits zero before re-enabling, allowing syscall events to be properly activated during early boot. The code is also refactored to use a helper function to avoid logic duplication between the disable and enable phases. Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://patch.msgid.link/20260224023544.1250787-1-hehuiwen@kylinos.cn Fixes: ce1039bd3a89 ("tracing: Fix enabling of syscall events on the command line") Signed-off-by: Huiwen He Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_events.c | 52 +++++++++++++++++++++++++++++++------------- 1 file changed, 37 insertions(+), 15 deletions(-) --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -4140,26 +4140,22 @@ static __init int event_trace_memsetup(v return 0; } -__init void -early_enable_events(struct trace_array *tr, char *buf, bool disable_first) +/* + * Helper function to enable or disable a comma-separated list of events + * from the bootup buffer. + */ +static __init void __early_set_events(struct trace_array *tr, char *buf, bool enable) { char *token; - int ret; - - while (true) { - token = strsep(&buf, ","); - - if (!token) - break; + while ((token = strsep(&buf, ","))) { if (*token) { - /* Restarting syscalls requires that we stop them first */ - if (disable_first) + if (enable) { + if (ftrace_set_clr_event(tr, token, 1)) + pr_warn("Failed to enable trace event: %s\n", token); + } else { ftrace_set_clr_event(tr, token, 0); - - ret = ftrace_set_clr_event(tr, token, 1); - if (ret) - pr_warn("Failed to enable trace event: %s\n", token); + } } /* Put back the comma to allow this to be called again */ @@ -4168,6 +4164,32 @@ early_enable_events(struct trace_array * } } +/** + * early_enable_events - enable events from the bootup buffer + * @tr: The trace array to enable the events in + * @buf: The buffer containing the comma separated list of events + * @disable_first: If true, disable all events in @buf before enabling them + * + * This function enables events from the bootup buffer. If @disable_first + * is true, it will first disable all events in the buffer before enabling + * them. + * + * For syscall events, which rely on a global refcount to register the + * SYSCALL_WORK_SYSCALL_TRACEPOINT flag (especially for pid 1), we must + * ensure the refcount hits zero before re-enabling them. A simple + * "disable then enable" per-event is not enough if multiple syscalls are + * used, as the refcount will stay above zero. Thus, we need a two-phase + * approach: disable all, then enable all. + */ +__init void +early_enable_events(struct trace_array *tr, char *buf, bool disable_first) +{ + if (disable_first) + __early_set_events(tr, buf, false); + + __early_set_events(tr, buf, true); +} + static __init int event_trace_enable(void) { struct trace_array *tr = top_trace_array();