Commit-ID: 22c1558e51c210787c6cf75d8905246fc91ec030 Gitweb: http://git.kernel.org/tip/22c1558e51c210787c6cf75d8905246fc91ec030 Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> AuthorDate: Tue, 5 May 2009 17:50:25 +0200 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Tue, 5 May 2009 20:18:32 +0200 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@xxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx> LKML-Reference: <20090505155437.232686598@xxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- kernel/perf_counter.c | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index 2d13427..c881afe 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -1409,6 +1409,7 @@ static int perf_mmap_data_alloc(struct perf_counter *counter, int nr_pages) } data->nr_pages = nr_pages; + atomic_set(&data->lock, -1); rcu_assign_pointer(counter->data, data); @@ -1755,7 +1756,7 @@ static void perf_output_lock(struct perf_output_handle *handle) if (in_nmi() && atomic_read(&data->lock) == cpu) return; - while (atomic_cmpxchg(&data->lock, 0, cpu) != 0) + while (atomic_cmpxchg(&data->lock, -1, cpu) != -1) cpu_relax(); handle->locked = 1; @@ -1784,7 +1785,7 @@ again: * NMI can happen here, which means we can miss a done_head update. */ - cpu = atomic_xchg(&data->lock, 0); + cpu = atomic_xchg(&data->lock, -1); WARN_ON_ONCE(cpu != smp_processor_id()); /* @@ -1794,7 +1795,7 @@ again: /* * Since we had it locked, we can lock it again. */ - while (atomic_cmpxchg(&data->lock, 0, cpu) != 0) + while (atomic_cmpxchg(&data->lock, -1, cpu) != -1) cpu_relax(); goto again; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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