Message-ID: <21a188b3-d3f9-ac13-4e9b-d870401b074f@kernel.org>
Date:   Fri, 10 Mar 2023 14:52:34 +0100
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Subject: Re: [PATCHv2 2/2] trace/hwlat: Do not start per-cpu thread if it is
 already running
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To:     Tero Kristo <tero.kristo@linux.intel.com>, rostedt@goodmis.org,
        mhiramat@kernel.org
Cc:     linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org
References: <20230310100451.3948583-1-tero.kristo@linux.intel.com>
 <20230310100451.3948583-3-tero.kristo@linux.intel.com>
From:   Daniel Bristot de Oliveira <bristot@kernel.org>
In-Reply-To: <20230310100451.3948583-3-tero.kristo@linux.intel.com>
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On 3/10/23 11:04, Tero Kristo wrote:
> 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.
> 
> Signed-off-by: Tero Kristo <tero.kristo@linux.intel.com>

Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>

-- Daniel