Messages in this thread Patch in this message | | | From | Robert Richter <> | Subject | [PATCH 09/12] perf/core, x86: use test_and_set_bit() to when grabbing a counter | Date | Fri, 22 Jan 2010 15:22:04 +0100 |
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Using test_and_set_bit() in the generic counter allocator makes this atomic. Otherwise a counter could have been allocated twice.
Signed-off-by: Robert Richter <robert.richter@amd.com> --- arch/x86/kernel/cpu/perf_event.c | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index 4eb0355..3f81f91 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -1395,8 +1395,13 @@ gen_get_event_idx(struct cpu_hw_events *cpuc, struct hw_perf_event *hwc) { int idx; +again: idx = find_first_zero_bit(cpuc->used_mask, x86_pmu.num_counters); - return idx == x86_pmu.num_counters ? -1 : idx; + if (idx == x86_pmu.num_counters) + return -1; + if (test_and_set_bit(idx, cpuc->used_mask)) + goto again; + return idx; } /* @@ -1465,7 +1470,6 @@ try_generic: if (idx == -1) return -EAGAIN; - set_bit(idx, cpuc->used_mask); hwc->idx = idx; } hwc->config_base = x86_pmu.eventsel; -- 1.6.6
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