linux-kernel - Re: [patch V2 01/29] tracing: Cleanup stack trace code

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Date:   Thu, 18 Apr 2019 18:19:38 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Alexander Potapenko <glider@...gle.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pekka Enberg <penberg@...nel.org>, linux-mm@...ck.org,
        David Rientjes <rientjes@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        kasan-dev@...glegroups.com,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Akinobu Mita <akinobu.mita@...il.com>,
        iommu@...ts.linux-foundation.org,
        Robin Murphy <robin.murphy@....com>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        David Sterba <dsterba@...e.com>, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>,
        linux-btrfs@...r.kernel.org, dm-devel@...hat.com,
        Mike Snitzer <snitzer@...hat.com>,
        Alasdair Kergon <agk@...hat.com>,
        intel-gfx@...ts.freedesktop.org,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        linux-arch@...r.kernel.org
Subject: Re: [patch V2 01/29] tracing: Cleanup stack trace code

On Thu, 18 Apr 2019 10:41:20 +0200
Thomas Gleixner <tglx@...utronix.de> wrote:


> @@ -412,23 +404,20 @@ stack_trace_sysctl(struct ctl_table *tab
>  		   void __user *buffer, size_t *lenp,
>  		   loff_t *ppos)
>  {
> -	int ret;
> +	int ret, was_enabled;

One small nit. Could this be:

	int was_enabled;
	int ret;

I prefer only joining variables that are related on the same line.
Makes it look cleaner IMO.

>  
>  	mutex_lock(&stack_sysctl_mutex);
> +	was_enabled = !!stack_tracer_enabled;
>  

Bah, not sure why I didn't do it this way to begin with. I think I
copied something else that couldn't do it this way for some reason and
didn't put any brain power behind the copy. :-/ But that was back in
2008 so I blame it on being "young and stupid" ;-)

Other then the above nit and removing the unneeded +1 in max_entries:

Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve


>  	ret = proc_dointvec(table, write, buffer, lenp, ppos);
>  
> -	if (ret || !write ||
> -	    (last_stack_tracer_enabled == !!stack_tracer_enabled))
> +	if (ret || !write || (was_enabled == !!stack_tracer_enabled))
>  		goto out;
>  
> -	last_stack_tracer_enabled = !!stack_tracer_enabled;
> -
>  	if (stack_tracer_enabled)
>  		register_ftrace_function(&trace_ops);
>  	else
>  		unregister_ftrace_function(&trace_ops);
> -
>   out:
>  	mutex_unlock(&stack_sysctl_mutex);
>  	return ret;
> @@ -444,7 +433,6 @@ static __init int enable_stacktrace(char
>  		strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE);
>  
>  	stack_tracer_enabled = 1;
> -	last_stack_tracer_enabled = 1;
>  	return 1;
>  }
>  __setup("stacktrace", enable_stacktrace);
>