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Subject[PATCH 3/7] perf_counter: ioctl(PERF_COUNTER_IOC_RESET)
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@chello.nl>
---
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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