Messages in this thread | | | Subject | Re: [PATCH] perf: fix cmpxchg warning in perf_event_amd.c | From | Peter Zijlstra <> | Date | Wed, 19 May 2010 08:32:56 +0200 |
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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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