* [PATCH] perf: fix cmpxchg warning in perf_event_amd.c
@ 2010-05-18 20:43 Jason Baron
2010-05-19 6:32 ` Peter Zijlstra
0 siblings, 1 reply; 2+ messages in thread
From: Jason Baron @ 2010-05-18 20:43 UTC (permalink / raw)
To: eranian; +Cc: linux-kernel, a.p.zijlstra, mingo, paulus, perfmon2-devel
Hi,
I'm getting the following warnings:
In file included from arch/x86/kernel/cpu/perf_event.c:1343:
arch/x86/kernel/cpu/perf_event_amd.c: In function
‘amd_put_event_constraints’:
arch/x86/kernel/cpu/perf_event_amd.c:167: warning: value computed is not
used
Since cmpxchg returns a value, we need to use it. We can use it to test if its
equal to "event".
thanks,
-Jason
Signed-off-by: Jason Baron <jbaron@redhat.com>
---
arch/x86/kernel/cpu/perf_event_amd.c | 4 +---
1 files changed, 1 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_amd.c b/arch/x86/kernel/cpu/perf_event_amd.c
index 611df11..e13ce4a 100644
--- a/arch/x86/kernel/cpu/perf_event_amd.c
+++ b/arch/x86/kernel/cpu/perf_event_amd.c
@@ -163,10 +163,8 @@ static void amd_put_event_constraints(struct cpu_hw_events *cpuc,
* when we come here
*/
for (i = 0; i < x86_pmu.num_counters; i++) {
- if (nb->owners[i] == event) {
- cmpxchg(nb->owners+i, event, NULL);
+ if (cmpxchg(nb->owners+i, event, NULL) == event)
break;
- }
}
}
--
1.7.0.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] perf: fix cmpxchg warning in perf_event_amd.c
2010-05-18 20:43 [PATCH] perf: fix cmpxchg warning in perf_event_amd.c Jason Baron
@ 2010-05-19 6:32 ` Peter Zijlstra
0 siblings, 0 replies; 2+ messages in thread
From: Peter Zijlstra @ 2010-05-19 6:32 UTC (permalink / raw)
To: Jason Baron; +Cc: eranian, linux-kernel, mingo, paulus, perfmon2-devel
On Tue, 2010-05-18 at 16:43 -0400, Jason Baron wrote:
> Hi,
>
> I'm getting the following warnings:
>
> In file included from arch/x86/kernel/cpu/perf_event.c:1343:
> arch/x86/kernel/cpu/perf_event_amd.c: In function
> ‘amd_put_event_constraints’:
> arch/x86/kernel/cpu/perf_event_amd.c:167: warning: value computed is not
> used
>
> Since cmpxchg returns a value, we need to use it. We can use it to test if its
> equal to "event".
Should we:
a) add a WARN_ONCE() there and make use of the return value (it should
never happen)
or
b) replace the lot with: nb->owners[i] = NULL; which should I _think_
work.
> Signed-off-by: Jason Baron <jbaron@redhat.com>
> ---
> arch/x86/kernel/cpu/perf_event_amd.c | 4 +---
> 1 files changed, 1 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/perf_event_amd.c b/arch/x86/kernel/cpu/perf_event_amd.c
> index 611df11..e13ce4a 100644
> --- a/arch/x86/kernel/cpu/perf_event_amd.c
> +++ b/arch/x86/kernel/cpu/perf_event_amd.c
> @@ -163,10 +163,8 @@ static void amd_put_event_constraints(struct cpu_hw_events *cpuc,
> * when we come here
> */
> for (i = 0; i < x86_pmu.num_counters; i++) {
> - if (nb->owners[i] == event) {
> - cmpxchg(nb->owners+i, event, NULL);
> + if (cmpxchg(nb->owners+i, event, NULL) == event)
> break;
> - }
> }
> }
>
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