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perf_counter: kerneltop: simplify data_head read

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Now that the kernel side changed, match up again.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171023.327144324@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-03-30 19:07:04 +02:00 committed by Ingo Molnar
parent 38ff667b32
commit 1955643902
1 changed files with 1 additions and 13 deletions
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14
Documentation/perf_counter/kerneltop.c
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@ -1125,22 +1125,10 @@ struct mmap_data {
static unsigned int mmap_read_head(struct mmap_data *md) static unsigned int mmap_read_head(struct mmap_data *md)
{ {
struct perf_counter_mmap_page *pc = md->base; struct perf_counter_mmap_page *pc = md->base;
unsigned int seq, head; int head;
repeat:
rmb();
seq = pc->lock;
if (unlikely(seq & 1)) {
cpu_relax();
goto repeat;
}
head = pc->data_head; head = pc->data_head;
rmb(); rmb();
if (pc->lock != seq)
goto repeat;
return head; return head;
} }