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printk: Use this_cpu_{read|write} api on printk_pending

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__get_cpu_var() is a bit inefficient, lets use __this_cpu_read() and
__this_cpu_write() to manipulate printk_pending.

printk_needs_cpu(cpu) is called only for the current cpu :
Use faster __this_cpu_read().

Remove the redundant unlikely on (cpu_is_offline(cpu)) test:

 # size kernel/printk.o*
   text	   data	    bss	    dec	    hex	filename
   9942	    756	 263488	 274186	  42f0a	kernel/printk.o.new
   9990	    756	 263488	 274234	  42f3a	kernel/printk.o.old

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1290788536.2855.237.camel@edumazet-laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Eric Dumazet 2010-11-26 17:22:16 +01:00 • committed by Ingo Molnar
commit 40dc11ffb3
1 changed files with 4 additions and 4 deletions
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8
kernel/printk.c
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@ -1074,17 +1074,17 @@ static DEFINE_PER_CPU(int, printk_pending);
void printk_tick(void)
{
if (__get_cpu_var(printk_pending)) {
__get_cpu_var(printk_pending) = 0;
if (__this_cpu_read(printk_pending)) {
__this_cpu_write(printk_pending, 0);
wake_up_interruptible(&log_wait);
}
}
int printk_needs_cpu(int cpu)
{
if (unlikely(cpu_is_offline(cpu)))
if (cpu_is_offline(cpu))
printk_tick();
return per_cpu(printk_pending, cpu);
return __this_cpu_read(printk_pending);
}
void wake_up_klogd(void)