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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2009-05-05 17:50:25 +0200
committerIngo Molnar <mingo@elte.hu>2009-05-05 20:18:32 +0200
commit22c1558e51c210787c6cf75d8905246fc91ec030 (patch)
tree40949ad88dcba74df009437a3270fda4e938cb3f /kernel/perf_counter.c
parentc5078f78b455fbf67ea71442c7e7ca8acf9ff095 (diff)
downloadlwn-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.c7
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;