linux-kernel - Re: [PATCH] trace/osnoise: fix missed cpus_read

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Date:   Mon, 30 Aug 2021 19:26:43 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     qiang.zhang@...driver.com, rostedt@...dmis.org, bristot@...nel.org,
        mingo@...hat.com
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] trace/osnoise: fix missed cpus_read_unlock()

Hi Qiang,

On 8/29/21 7:52 AM, qiang.zhang@...driver.com wrote:
> From: "Qiang.zhang" <qiang.zhang@...driver.com>
set the Subject to:

trace/osnoise: Fix missed cpus_read_unlock() in start_per_cpu_kthreads()

> 
> When start_kthread() return error, the cpus_read_unlock() need
> to be called.
> 
> Signed-off-by: Qiang.zhang <qiang.zhang@...driver.com>

Add:

Fixes: c8895e271f79 ("trace/osnoise: Support hotplug operations")
Cc: <stable@...r.kernel.org> # v5.14+

> ---
>  kernel/trace/trace_osnoise.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
> index 65b08b8e5bf8..45d22d6f3acb 100644
> --- a/kernel/trace/trace_osnoise.c
> +++ b/kernel/trace/trace_osnoise.c
> @@ -1568,6 +1568,7 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
>  		retval = start_kthread(cpu);
>  		if (retval) {
>  			stop_per_cpu_kthreads();
> +			cpus_read_unlock();
>  			return retval;
>  		}
>  	}

Why not initialize retval = 0, and then remove the "return retval" from this if,
returning rteval at the end of the function?

-- Daniel