printk: Use this_cpu_{read|write} api on printk_pending
__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>
diff --git a/kernel/printk.c b/kernel/printk.c
index a23315d..ab3ffc5 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1074,17 +1074,17 @@
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)
