Date: Wed, 16 Oct 2013 08:59:28 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Joe Perches <joe@perches.com>, Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Liu Chuansheng <chuansheng.liu@intel.com>,
        Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 2/3] core: Convert printk_once to use DO_ONCE
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On Wed, 16 Oct 2013 13:53:56 +0200
Frederic Weisbecker <fweisbec@gmail.com> wrote:

 
> static int done;
> 
> if (!done) {
>     trace_printk(something);
>     trace_printk(something else);
>     trace_dump_stack();
>     done = 1;
> }
> 
> Having a DO_ONCE() would help a lot I think.
> 
> Now we can rename it to __DO_ONCE() and put a big fat comment to avoid it
> to be misused.

I wonder if we should make it just ONCE(), with no arguments that
should go into an if statement.


if (ONCE())
	do_this_function_once();


Where ONCE() is:

({
	static int __once;
	int __old_once = __once;

	__once = 1;
	__old_once;
})

Or the xchg version:

({
	static int __once;

	if (!__once)
		xchg(&__once, 1);
	else
		1;
})

-- Steve
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