forked from Minki/linux
perf_counter: fix the output lock
Use -1 instead of 0 as unlocked, since 0 is a valid cpu number. ( This is not an issue right now but will be once we allow multiple counters to output to the same mmap area. ) [ Impact: prepare code for multi-counter profile output ] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> LKML-Reference: <20090505155437.232686598@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -1409,6 +1409,7 @@ static int perf_mmap_data_alloc(struct perf_counter *counter, int nr_pages)
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}
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data->nr_pages = nr_pages;
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atomic_set(&data->lock, -1);
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rcu_assign_pointer(counter->data, data);
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@ -1755,7 +1756,7 @@ static void perf_output_lock(struct perf_output_handle *handle)
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if (in_nmi() && atomic_read(&data->lock) == cpu)
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return;
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while (atomic_cmpxchg(&data->lock, 0, cpu) != 0)
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while (atomic_cmpxchg(&data->lock, -1, cpu) != -1)
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cpu_relax();
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handle->locked = 1;
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@ -1784,7 +1785,7 @@ again:
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* NMI can happen here, which means we can miss a done_head update.
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*/
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cpu = atomic_xchg(&data->lock, 0);
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cpu = atomic_xchg(&data->lock, -1);
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WARN_ON_ONCE(cpu != smp_processor_id());
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/*
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@ -1794,7 +1795,7 @@ again:
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/*
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* Since we had it locked, we can lock it again.
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*/
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while (atomic_cmpxchg(&data->lock, 0, cpu) != 0)
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while (atomic_cmpxchg(&data->lock, -1, cpu) != -1)
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cpu_relax();
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goto again;
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