perf counters: protect them against CSTATE transitions

Impact: fix rare lost events problem

There are CPUs whose performance counters misbehave on CSTATE transitions,
so provide a way to just disable/enable them around deep idle methods.

(hw_perf_enable_all() is cheap on x86.)

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 22c4469abf44..5031b5614f25 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -156,6 +156,8 @@ extern void perf_counter_task_tick(struct task_struct *task, int cpu);
 extern void perf_counter_init_task(struct task_struct *task);
 extern void perf_counter_notify(struct pt_regs *regs);
 extern void perf_counter_print_debug(void);
+extern void hw_perf_restore_ctrl(u64 ctrl);
+extern u64 hw_perf_disable_all(void);
 #else
 static inline void
 perf_counter_task_sched_in(struct task_struct *task, int cpu)           { }
@@ -166,6 +168,8 @@ perf_counter_task_tick(struct task_struct *task, int cpu)		{ }
 static inline void perf_counter_init_task(struct task_struct *task)     { }
 static inline void perf_counter_notify(struct pt_regs *regs)            { }
 static inline void perf_counter_print_debug(void)                       { }
+static inline void hw_perf_restore_ctrl(u64 ctrl)                       { }
+static inline u64 hw_perf_disable_all(void)             { return 0; }
 #endif
 
 #endif /* _LINUX_PERF_COUNTER_H */