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| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2009-05-05 17:50:25 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-05-05 20:18:32 +0200 |
| commit | 22c1558e51c210787c6cf75d8905246fc91ec030 (patch) | |
| tree | 40949ad88dcba74df009437a3270fda4e938cb3f /kernel/perf_counter.c | |
| parent | c5078f78b455fbf67ea71442c7e7ca8acf9ff095 (diff) | |
| download | lwn-22c1558e51c210787c6cf75d8905246fc91ec030.tar.gz lwn-22c1558e51c210787c6cf75d8905246fc91ec030.zip | |
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>
Diffstat (limited to 'kernel/perf_counter.c')
| -rw-r--r-- | 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 2d1342738305..c881afef997b 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; |