perf counters: add prctl interface to disable/enable counters
Add a way for self-monitoring tasks to disable/enable counters summarily,
via a prctl:
PR_TASK_PERF_COUNTERS_DISABLE 31
PR_TASK_PERF_COUNTERS_ENABLE 32
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 30c0ec8..97d86c2 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -213,6 +213,8 @@
extern void hw_perf_restore(u64 ctrl);
extern void atomic64_counter_set(struct perf_counter *counter, u64 val64);
extern u64 atomic64_counter_read(struct perf_counter *counter);
+extern int perf_counter_task_disable(void);
+extern int perf_counter_task_enable(void);
#else
static inline void
@@ -226,6 +228,8 @@
static inline void perf_counter_print_debug(void) { }
static inline void hw_perf_restore(u64 ctrl) { }
static inline u64 hw_perf_save_disable(void) { return 0; }
+static inline int perf_counter_task_disable(void) { return -EINVAL; }
+static inline int perf_counter_task_enable(void) { return -EINVAL; }
#endif
#endif /* _LINUX_PERF_COUNTER_H */
diff --git a/include/linux/prctl.h b/include/linux/prctl.h
index 48d887e..b00df4c 100644
--- a/include/linux/prctl.h
+++ b/include/linux/prctl.h
@@ -85,4 +85,7 @@
#define PR_SET_TIMERSLACK 29
#define PR_GET_TIMERSLACK 30
+#define PR_TASK_PERF_COUNTERS_DISABLE 31
+#define PR_TASK_PERF_COUNTERS_ENABLE 32
+
#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index a0fe847..4e679b9 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -415,6 +415,9 @@
struct perf_counter_context *ctx,
int cpu)
{
+ if (counter->active == -1)
+ return;
+
counter->hw_ops->hw_perf_counter_enable(counter);
counter->active = 1;
counter->oncpu = cpu; /* TODO: put 'cpu' into cpuctx->cpu */
@@ -479,6 +482,79 @@
cpuctx->task_ctx = ctx;
}
+int perf_counter_task_disable(void)
+{
+ struct task_struct *curr = current;
+ struct perf_counter_context *ctx = &curr->perf_counter_ctx;
+ struct perf_counter *counter;
+ u64 perf_flags;
+ int cpu;
+
+ if (likely(!ctx->nr_counters))
+ return 0;
+
+ local_irq_disable();
+ cpu = smp_processor_id();
+
+ perf_counter_task_sched_out(curr, cpu);
+
+ spin_lock(&ctx->lock);
+
+ /*
+ * Disable all the counters:
+ */
+ perf_flags = hw_perf_save_disable();
+
+ list_for_each_entry(counter, &ctx->counter_list, list_entry) {
+ WARN_ON_ONCE(counter->active == 1);
+ counter->active = -1;
+ }
+ hw_perf_restore(perf_flags);
+
+ spin_unlock(&ctx->lock);
+
+ local_irq_enable();
+
+ return 0;
+}
+
+int perf_counter_task_enable(void)
+{
+ struct task_struct *curr = current;
+ struct perf_counter_context *ctx = &curr->perf_counter_ctx;
+ struct perf_counter *counter;
+ u64 perf_flags;
+ int cpu;
+
+ if (likely(!ctx->nr_counters))
+ return 0;
+
+ local_irq_disable();
+ cpu = smp_processor_id();
+
+ spin_lock(&ctx->lock);
+
+ /*
+ * Disable all the counters:
+ */
+ perf_flags = hw_perf_save_disable();
+
+ list_for_each_entry(counter, &ctx->counter_list, list_entry) {
+ if (counter->active != -1)
+ continue;
+ counter->active = 0;
+ }
+ hw_perf_restore(perf_flags);
+
+ spin_unlock(&ctx->lock);
+
+ perf_counter_task_sched_in(curr, cpu);
+
+ local_irq_enable();
+
+ return 0;
+}
+
void perf_counter_task_tick(struct task_struct *curr, int cpu)
{
struct perf_counter_context *ctx = &curr->perf_counter_ctx;
@@ -951,13 +1027,9 @@
* @cpu: target cpu
* @group_fd: group leader counter fd
*/
-asmlinkage int sys_perf_counter_open(
-
- struct perf_counter_hw_event *hw_event_uptr __user,
- pid_t pid,
- int cpu,
- int group_fd)
-
+asmlinkage int
+sys_perf_counter_open(struct perf_counter_hw_event *hw_event_uptr __user,
+ pid_t pid, int cpu, int group_fd)
{
struct perf_counter *counter, *group_leader;
struct perf_counter_hw_event hw_event;
diff --git a/kernel/sys.c b/kernel/sys.c
index 31deba8..0f66633 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -14,6 +14,7 @@
#include <linux/prctl.h>
#include <linux/highuid.h>
#include <linux/fs.h>
+#include <linux/perf_counter.h>
#include <linux/resource.h>
#include <linux/kernel.h>
#include <linux/kexec.h>
@@ -1716,6 +1717,12 @@
case PR_SET_TSC:
error = SET_TSC_CTL(arg2);
break;
+ case PR_TASK_PERF_COUNTERS_DISABLE:
+ error = perf_counter_task_disable();
+ break;
+ case PR_TASK_PERF_COUNTERS_ENABLE:
+ error = perf_counter_task_enable();
+ break;
case PR_GET_TIMERSLACK:
error = current->timer_slack_ns;
break;
