[tip:perfcounters/core] perf_counter: Add ioctl for changing the sample period/frequency

tip-bot for Peter Zijlstra
2009-06-02T20:18:29Z

Commit-ID: 08247e31ca79b8f02cce47b7e8120797a8726606
Gitweb: http://git.kernel.org/tip/08247e31ca79b8f02cce47b7e8120797a8726606
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Tue, 2 Jun 2009 16:46:57 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 2 Jun 2009 21:45:32 +0200

perf_counter: Add ioctl for changing the sample period/frequency

Reported-by: Stephane Eranian <eranian@googlemail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
include/linux/perf_counter.h | 9 +++++----
kernel/perf_counter.c | 41 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index c046f7d..45bdd3b 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -164,10 +164,11 @@ struct perf_counter_hw_event {
/*
* Ioctls that can be done on a perf counter fd:
*/
-#define PERF_COUNTER_IOC_ENABLE _IOW('$', 0, u32)
-#define PERF_COUNTER_IOC_DISABLE _IOW('$', 1, u32)
-#define PERF_COUNTER_IOC_REFRESH _IOW('$', 2, u32)
-#define PERF_COUNTER_IOC_RESET _IOW('$', 3, u32)
+#define PERF_COUNTER_IOC_ENABLE _IO ('$', 0)
+#define PERF_COUNTER_IOC_DISABLE _IO ('$', 1)
+#define PERF_COUNTER_IOC_REFRESH _IO ('$', 2)
+#define PERF_COUNTER_IOC_RESET _IO ('$', 3)
+#define PERF_COUNTER_IOC_PERIOD _IOW('$', 4, u64)

enum perf_counter_ioc_flags {
PERF_IOC_FLAG_GROUP = 1U << 0,
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 3f11a2b..abe2f3b 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1604,6 +1604,43 @@ static void perf_counter_for_each(struct perf_counter *counter,
mutex_unlock(&counter->child_mutex);
}

+static int perf_counter_period(struct perf_counter *counter, u64 __user *arg)
+{
+ struct perf_counter_context *ctx = counter->ctx;
+ unsigned long size;
+ int ret = 0;
+ u64 value;
+
+ if (!counter->hw_event.sample_period)
+ return -EINVAL;
+
+ size = copy_from_user(&value, arg, sizeof(value));
+ if (size != sizeof(value))
+ return -EFAULT;
+
+ if (!value)
+ return -EINVAL;
+
+ spin_lock_irq(&ctx->lock);
+ if (counter->hw_event.freq) {
+ if (value > sysctl_perf_counter_limit) {
+ ret = -EINVAL;
+ goto unlock;
+ }
+
+ counter->hw_event.sample_freq = value;
+ } else {
+ counter->hw_event.sample_period = value;
+ counter->hw.sample_period = value;
+
+ perf_log_period(counter, value);
+ }
+unlock:
+ spin_unlock_irq(&ctx->lock);
+
+ return ret;
+}
+
static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct perf_counter *counter = file->private_data;
@@ -1623,6 +1660,10 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

case PERF_COUNTER_IOC_REFRESH:
return perf_counter_refresh(counter, arg);
+
+ case PERF_COUNTER_IOC_PERIOD:
+ return perf_counter_period(counter, (u64 __user *)arg);
+
default:
return -ENOTTY;
}