[tip:perfcounters/core] perf_counter: convert perf_resource_mutex to a spinlock

tip-bot for Ingo Molnar
2009-05-04T17:35:37Z

Commit-ID: 1dce8d99b85aba6eddb8b8260baea944922e6fe7
Gitweb: http://git.kernel.org/tip/1dce8d99b85aba6eddb8b8260baea944922e6fe7
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Mon, 4 May 2009 19:23:18 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 4 May 2009 19:30:42 +0200

perf_counter: convert perf_resource_mutex to a spinlock

Now percpu counters can be initialized very early. But the init
sequence uses mutex_lock(). Fortunately, perf_resource_mutex should
be a spinlock anyway, so convert it.

[ Impact: fix crash due to early init mutex use ]

LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
kernel/perf_counter.c | 16 ++++++++--------
1 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index fcdafa2..5f86a11 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -46,9 +46,9 @@ static atomic_t nr_comm_tracking __read_mostly;
int sysctl_perf_counter_priv __read_mostly; /* do we need to be privileged */

/*
- * Mutex for (sysadmin-configurable) counter reservations:
+ * Lock for (sysadmin-configurable) counter reservations:
*/
-static DEFINE_MUTEX(perf_resource_mutex);
+static DEFINE_SPINLOCK(perf_resource_lock);

/*
* Architecture provided APIs - weak aliases:
@@ -3207,9 +3207,9 @@ static void __cpuinit perf_counter_init_cpu(int cpu)
cpuctx = &per_cpu(perf_cpu_context, cpu);
__perf_counter_init_context(&cpuctx->ctx, NULL);

- mutex_lock(&perf_resource_mutex);
+ spin_lock(&perf_resource_lock);
cpuctx->max_pertask = perf_max_counters - perf_reserved_percpu;
- mutex_unlock(&perf_resource_mutex);
+ spin_unlock(&perf_resource_lock);

hw_perf_counter_setup(cpu);
}
@@ -3292,7 +3292,7 @@ perf_set_reserve_percpu(struct sysdev_class *class,
if (val > perf_max_counters)
return -EINVAL;

- mutex_lock(&perf_resource_mutex);
+ spin_lock(&perf_resource_lock);
perf_reserved_percpu = val;
for_each_online_cpu(cpu) {
cpuctx = &per_cpu(perf_cpu_context, cpu);
@@ -3302,7 +3302,7 @@ perf_set_reserve_percpu(struct sysdev_class *class,
cpuctx->max_pertask = mpt;
spin_unlock_irq(&cpuctx->ctx.lock);
}
- mutex_unlock(&perf_resource_mutex);
+ spin_unlock(&perf_resource_lock);

return count;
}
@@ -3324,9 +3324,9 @@ perf_set_overcommit(struct sysdev_class *class, const char *buf, size_t count)
if (val > 1)
return -EINVAL;

- mutex_lock(&perf_resource_mutex);
+ spin_lock(&perf_resource_lock);
perf_overcommit = val;
- mutex_unlock(&perf_resource_mutex);
+ spin_unlock(&perf_resource_lock);

return count;
}