[PATCH 3/7] perf_counter: ioctl(PERF_COUNTER_IOC_RESET)

[Peter Zijlstra]

Provide a way to reset an existing counter.

Similar to read() it doesn't collapse pending child counters.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 include/linux/perf_counter.h |    1 +
 kernel/perf_counter.c        |    8 ++++++++
 2 files changed, 9 insertions(+)

Index: linux-2.6/include/linux/perf_counter.h
===================================================================
--- linux-2.6.orig/include/linux/perf_counter.h
+++ linux-2.6/include/linux/perf_counter.h
@@ -160,6 +160,7 @@ struct perf_counter_hw_event {
 #define PERF_COUNTER_IOC_ENABLE		_IO ('$', 0)
 #define PERF_COUNTER_IOC_DISABLE	_IO ('$', 1)
 #define PERF_COUNTER_IOC_REFRESH	_IOW('$', 2, u32)
+#define PERF_COUNTER_IOC_RESET		_IO ('$', 3)
 
 /*
  * Structure of the page that can be mapped via mmap
Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/kernel/perf_counter.c
@@ -1288,6 +1288,11 @@ static unsigned int perf_poll(struct fil
 	return events;
 }
 
+static void perf_counter_reset(struct perf_counter *counter)
+{
+	atomic_set(&counter->count, 0);
+}
+
 static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	struct perf_counter *counter = file->private_data;
@@ -1303,6 +1308,9 @@ static long perf_ioctl(struct file *file
 	case PERF_COUNTER_IOC_REFRESH:
 		perf_counter_refresh(counter, arg);
 		break;
+	case PERF_COUNTER_IOC_RESET:
+		perf_counter_reset(counter);
+		break;
 	default:
 		err = -ENOTTY;
 	}

-- 

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