timerfd: Manage cancelable timers in timerfd

Peter is concerned about the extra scan of CLOCK_REALTIME_COS in the
timer interrupt. Yes, I did not think about it, because the solution
was so elegant. I didn't like the extra list in timerfd when it was
proposed some time ago, but with a rcu based list the list walk it's
less horrible than the original global lock, which was held over the
list iteration.

Requested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>

3 files changed, 7 insertions, 9 deletions

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index eda4ccde0730..925c8c01db7b 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -155,7 +155,6 @@ enum  hrtimer_base_type {
         HRTIMER_BASE_REALTIME,
         HRTIMER_BASE_MONOTONIC,
         HRTIMER_BASE_BOOTTIME,
-        HRTIMER_BASE_REALTIME_COS,
         HRTIMER_MAX_CLOCK_BASES,
 };
 
@@ -306,6 +305,11 @@ static inline int hrtimer_is_hres_active(struct hrtimer *timer)
 #endif
 
 extern void clock_was_set(void);
+#ifdef CONFIG_TIMERFD
+extern void timerfd_clock_was_set(void);
+#else
+static inline void timerfd_clock_was_set(void) { }
+#endif
 extern void hrtimers_resume(void);
 
 extern ktime_t ktime_get(void);
diff --git a/include/linux/time.h b/include/linux/time.h
index a9242773eb24..b3061782dec3 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -302,12 +302,6 @@ struct itimerval {
  * The IDs of various hardware clocks:
  */
 #define CLOCK_SGI_CYCLE                 10
-
-#ifdef __KERNEL__
-/* This clock is not exposed to user space */
-#define CLOCK_REALTIME_COS              15
-#endif
-
 #define MAX_CLOCKS                      16
 #define CLOCKS_MASK                     (CLOCK_REALTIME | CLOCK_MONOTONIC)
 #define CLOCKS_MONO                     CLOCK_MONOTONIC
diff --git a/include/linux/timerfd.h b/include/linux/timerfd.h
index e9571fc8f1a0..d3b57fa12225 100644
--- a/include/linux/timerfd.h
+++ b/include/linux/timerfd.h
@@ -19,7 +19,7 @@
  * shared O_* flags.
  */
 #define TFD_TIMER_ABSTIME (1 << 0)
-#define TFD_TIMER_CANCELON_SET (1 << 1)
+#define TFD_TIMER_CANCEL_ON_SET (1 << 1)
 #define TFD_CLOEXEC O_CLOEXEC
 #define TFD_NONBLOCK O_NONBLOCK
 
@@ -27,6 +27,6 @@
 /* Flags for timerfd_create.  */
 #define TFD_CREATE_FLAGS TFD_SHARED_FCNTL_FLAGS
 /* Flags for timerfd_settime.  */
-#define TFD_SETTIME_FLAGS (TFD_TIMER_ABSTIME | TFD_TIMER_CANCELON_SET)
+#define TFD_SETTIME_FLAGS (TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET)
 
 #endif /* _LINUX_TIMERFD_H */