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 (file)
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -213,6 +213,8 @@ extern u64 hw_perf_save_disable(void);
 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_notify(struct pt_regs *regs)                { }
 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 (file)
--- 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 (file)
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -415,6 +415,9 @@ counter_sched_in(struct perf_counter *counter,
                 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 @@ void perf_counter_task_sched_in(struct task_struct *task, int cpu)
        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 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
  * @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 (file)
--- 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 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
                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;