linux-kernel - Re: [PATCH 1/3] hotplug: Optimize {get,put}_online

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Date:	Thu, 3 Oct 2013 16:01:50 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc:	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] hotplug: Optimize {get,put}_online_cpus()

On Wed, Oct 02, 2013 at 04:56:56PM +0200, Peter Zijlstra wrote:
> +	if (atomic_dec_and_test(&cpuhp_waitcount))
> +		wake_up(&cpuhp_writer);
> +
> +	goto again:
>  }

> +
> +#define per_cpu_sum(var)						\
> +({ 									\
> + 	typeof(var) __sum = 0;						\
> + 	int cpu;							\
> + 	for_each_possible_cpu(cpu)					\
> + 		__sum += per_cpu(var, cpu);				\
> + 	__sum;								\
> +)}
>  

I just noticed I forgot a refresh..


+++ b/kernel/cpu.c
@@ -120,7 +120,7 @@ void __get_online_cpus(void)
        if (atomic_dec_and_test(&cpuhp_waitcount))
                wake_up(&cpuhp_writer);
 
-       goto again:
+       goto again;
 }
 EXPORT_SYMBOL_GPL(__get_online_cpus);
 
@@ -146,7 +146,7 @@ EXPORT_SYMBOL_GPL(__put_online_cpus);
        for_each_possible_cpu(cpu)                                      \
                __sum += per_cpu(var, cpu);                             \
        __sum;                                                          \
-)}
+})
 
 /*
  * See srcu_readers_active_idx_check() for a rather more detailed explanation.
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