From nobody Wed Dec 17 10:52:37 2025 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 392E0293B42 for ; Fri, 9 May 2025 13:13:02 +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=1746796382; cv=none; b=jD520gbHMaLCe/evHUmk+mDxTx09TZI4rm5nHnf+h4GAUkc+EHwEsvL9wyMn5LM/vEJtj9jo7Xi6yWZTwJ8sYPPpr7eB84qgc9YuVDATNukUpoOo9eT54Zfgp13PPxlv/fgcxzIVgzyJWn5NjxNGPqnBtmIMmPq3TIqsEhEf4rU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746796382; c=relaxed/simple; bh=qPP3CvHK8t4fr7gLX3mL04NCQ8w/oQ01akHffgDkhj8=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=L/1U8flERSuUo/pi6RSAY77dCr4FI9GX6YcNI1K3X8fv2vOZFB55uflFuQnW+KZ6tgAVELYV4qqDqAkcjLqQcGf+fw6WmzZQY225Sspa+6WtBBWfgkdeTvyTijZDFVfuGAhVy5Xl6tz0it8qvTUdS8aifCT1lJfRnDIF1tD5xkk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 20324C4CEF1; Fri, 9 May 2025 13:13:02 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.98.2) (envelope-from ) id 1uDNXR-00000002bzn-2nIO; Fri, 09 May 2025 09:13:17 -0400 Message-ID: <20250509131317.512092358@goodmis.org> User-Agent: quilt/0.68 Date: Fri, 09 May 2025 09:13:13 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton Subject: [for-next][PATCH 24/31] tracing: Use atomic_inc_return() for updating "disabled" counter in irqsoff tracer References: <20250509131249.340302366@goodmis.org> 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 Content-Type: text/plain; charset="utf-8" From: Steven Rostedt The irqsoff tracer uses the per CPU "disabled" field to prevent corruption of the accounting when it starts to trace interrupts disabled, but there's a slight race that could happen if for some reason it was called twice. Use atomic_inc_return() instead. Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Link: https://lore.kernel.org/20250505212236.567884756@goodmis.org Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace_irqsoff.c | 29 ++++++++++++++++++----------- 1 file changed, 18 insertions(+), 11 deletions(-) diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c index 0b6d932a931e..5496758b6c76 100644 --- a/kernel/trace/trace_irqsoff.c +++ b/kernel/trace/trace_irqsoff.c @@ -397,6 +397,7 @@ start_critical_timing(unsigned long ip, unsigned long p= arent_ip) int cpu; struct trace_array *tr =3D irqsoff_trace; struct trace_array_cpu *data; + long disabled; =20 if (!tracer_enabled || !tracing_is_enabled()) return; @@ -411,15 +412,17 @@ start_critical_timing(unsigned long ip, unsigned long= parent_ip) if (unlikely(!data) || local_read(&data->disabled)) return; =20 - local_inc(&data->disabled); + disabled =3D local_inc_return(&data->disabled); =20 - data->critical_sequence =3D max_sequence; - data->preempt_timestamp =3D ftrace_now(cpu); - data->critical_start =3D parent_ip ? : ip; + if (disabled =3D=3D 1) { + data->critical_sequence =3D max_sequence; + data->preempt_timestamp =3D ftrace_now(cpu); + data->critical_start =3D parent_ip ? : ip; =20 - __trace_function(tr, ip, parent_ip, tracing_gen_ctx()); + __trace_function(tr, ip, parent_ip, tracing_gen_ctx()); =20 - per_cpu(tracing_cpu, cpu) =3D 1; + per_cpu(tracing_cpu, cpu) =3D 1; + } =20 local_dec(&data->disabled); } @@ -431,6 +434,7 @@ stop_critical_timing(unsigned long ip, unsigned long pa= rent_ip) struct trace_array *tr =3D irqsoff_trace; struct trace_array_cpu *data; unsigned int trace_ctx; + long disabled; =20 cpu =3D raw_smp_processor_id(); /* Always clear the tracing cpu on stopping the trace */ @@ -448,12 +452,15 @@ stop_critical_timing(unsigned long ip, unsigned long = parent_ip) !data->critical_start || local_read(&data->disabled)) return; =20 - local_inc(&data->disabled); + disabled =3D local_inc_return(&data->disabled); + + if (disabled =3D=3D 1) { + trace_ctx =3D tracing_gen_ctx(); + __trace_function(tr, ip, parent_ip, trace_ctx); + check_critical_timing(tr, data, parent_ip ? : ip, cpu); + data->critical_start =3D 0; + } =20 - trace_ctx =3D tracing_gen_ctx(); - __trace_function(tr, ip, parent_ip, trace_ctx); - check_critical_timing(tr, data, parent_ip ? : ip, cpu); - data->critical_start =3D 0; local_dec(&data->disabled); } =20 --=20 2.47.2