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 09B7C8BEB for ; Tue, 28 Mar 2023 15:05:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7DBA1C4339C; Tue, 28 Mar 2023 15:05:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1680015952; bh=nOai4my4CkFgclSU7YAKhG/cMS9uXMRuAyvl2wCF208=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1gT47i92ZeqX8FEB0AP7MfxPlvqkYmcOpqbvja3QjHoxUx9cxp9gtYXcROpeCZhhc qHZPhUO0rIqPEca2SX7uqaSd4MA+zxRBhaNTBwg9v+H98Aht8w637YLPLM84AWigVt qa+WXFc28RJxFq1WWFnEQxfSBFdKlVr90dFuhNhY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tero Kristo , Daniel Bristot de Oliveira , "Steven Rostedt (Google)" , Sasha Levin Subject: [PATCH 5.15 012/146] trace/hwlat: Do not start per-cpu thread if it is already running Date: Tue, 28 Mar 2023 16:41:41 +0200 Message-Id: <20230328142603.220384449@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230328142602.660084725@linuxfoundation.org> References: <20230328142602.660084725@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Tero Kristo [ Upstream commit 08697bca9bbba15f2058fdbd9f970bd5f6a8a2e8 ] The hwlatd tracer will end up starting multiple per-cpu threads with the following script: #!/bin/sh cd /sys/kernel/debug/tracing echo 0 > tracing_on echo hwlat > current_tracer echo per-cpu > hwlat_detector/mode echo 100000 > hwlat_detector/width echo 200000 > hwlat_detector/window echo 1 > tracing_on To fix the issue, check if the hwlatd thread for the cpu is already running, before starting a new one. Along with the previous patch, this avoids running multiple instances of the same CPU thread on the system. Link: https://lore.kernel.org/all/20230302113654.2984709-1-tero.kristo@linux.intel.com/ Link: https://lkml.kernel.org/r/20230310100451.3948583-3-tero.kristo@linux.intel.com Cc: stable@vger.kernel.org Fixes: f46b16520a087 ("trace/hwlat: Implement the per-cpu mode") Signed-off-by: Tero Kristo Acked-by: Daniel Bristot de Oliveira Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin --- kernel/trace/trace_hwlat.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c index 72eeab938f1de..9ec032f22531c 100644 --- a/kernel/trace/trace_hwlat.c +++ b/kernel/trace/trace_hwlat.c @@ -492,6 +492,10 @@ static int start_cpu_kthread(unsigned int cpu) { struct task_struct *kthread; + /* Do not start a new hwlatd thread if it is already running */ + if (per_cpu(hwlat_per_cpu_data, cpu).kthread) + return 0; + kthread = kthread_run_on_cpu(kthread_fn, NULL, cpu, "hwlatd/%u"); if (IS_ERR(kthread)) { pr_err(BANNER "could not start sampling thread\n"); -- 2.39.2