[patch 03/44] posix-timer: Use a callback for cancel synchronization

[Thomas Gleixner]

Cleanup timer_wait_running() by using a kclock callback. Get's rid of the
ifdeffery and the odd conditionals. Should have thought about this right
away.

Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
 kernel/time/alarmtimer.c   |   14 ++++++++++++++
 kernel/time/posix-timers.c |   32 ++++++++++++--------------------
 kernel/time/posix-timers.h |    1 +
 3 files changed, 27 insertions(+), 20 deletions(-)

--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -606,6 +606,19 @@ static int alarm_timer_try_to_cancel(str
 }
 
 /**
+ * alarm_timer_wait_running - Posix timer callback to wait for a timer
+ * @timr:      Pointer to the posixtimer data struct
+ *
+ * Called from the core code when timer cancel detected that the callback
+ * is running. @timr is unlocked and rcu read lock is held to prevent it
+ * from being freed.
+ */
+static void alarm_timer_wait_running(struct k_itimer *timr)
+{
+       hrtimer_cancel_wait_running(&timr->it.alarm.alarmtimer.timer);
+}
+
+/**
  * alarm_timer_arm - Posix timer callback to arm a timer
  * @timr:      Pointer to the posixtimer data struct
  * @expires:   The new expiry time
@@ -834,6 +847,7 @@ const struct k_clock alarm_clock = {
        .timer_forward          = alarm_timer_forward,
        .timer_remaining        = alarm_timer_remaining,
        .timer_try_to_cancel    = alarm_timer_try_to_cancel,
+       .timer_wait_running     = alarm_timer_wait_running,
        .nsleep                 = alarm_timer_nsleep,
 };
 #endif /* CONFIG_POSIX_TIMERS */
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -805,7 +805,11 @@ static int common_hrtimer_try_to_cancel(
        return hrtimer_try_to_cancel(&timr->it.real.timer);
 }
 
-#ifdef CONFIG_PREEMPT_RT
+static void common_timer_wait_running(struct k_itimer *timer)
+{
+       hrtimer_cancel_wait_running(&timer->it.real.timer);
+}
+
 static struct k_itimer *timer_wait_running(struct k_itimer *timer,
                                           unsigned long *flags)
 {
@@ -816,29 +820,13 @@ static struct k_itimer *timer_wait_runni
        rcu_read_lock();
        unlock_timer(timer, *flags);
 
-       if (kc->timer_arm == common_hrtimer_arm)
-               hrtimer_cancel_wait_running(&timer->it.real.timer);
-       else if (kc == &alarm_clock)
-               hrtimer_cancel_wait_running(&timer->it.alarm.alarmtimer.timer);
-       else
-               WARN_ON_ONCE(1);
-       rcu_read_unlock();
-
-       /* Relock the timer. It might be not longer hashed. */
-       return lock_timer(timer_id, flags);
-}
-#else
-static struct k_itimer *timer_wait_running(struct k_itimer *timer,
-                                          unsigned long *flags)
-{
-       timer_t timer_id = READ_ONCE(timer->it_id);
+       if (!WARN_ON_ONCE(kc->timer_wait_running))
+               kc->timer_wait_running(timer);
 
-       unlock_timer(timer, *flags);
-       cpu_relax();
+       rcu_read_unlock();
        /* Relock the timer. It might be not longer hashed. */
        return lock_timer(timer_id, flags);
 }
-#endif
 
 /* Set a POSIX.1b interval timer. */
 int common_timer_set(struct k_itimer *timr, int flags,
@@ -1279,6 +1267,7 @@ static const struct k_clock clock_realti
        .timer_forward          = common_hrtimer_forward,
        .timer_remaining        = common_hrtimer_remaining,
        .timer_try_to_cancel    = common_hrtimer_try_to_cancel,
+       .timer_wait_running     = common_timer_wait_running,
        .timer_arm              = common_hrtimer_arm,
 };
 
@@ -1294,6 +1283,7 @@ static const struct k_clock clock_monoto
        .timer_forward          = common_hrtimer_forward,
        .timer_remaining        = common_hrtimer_remaining,
        .timer_try_to_cancel    = common_hrtimer_try_to_cancel,
+       .timer_wait_running     = common_timer_wait_running,
        .timer_arm              = common_hrtimer_arm,
 };
 
@@ -1324,6 +1314,7 @@ static const struct k_clock clock_tai =
        .timer_forward          = common_hrtimer_forward,
        .timer_remaining        = common_hrtimer_remaining,
        .timer_try_to_cancel    = common_hrtimer_try_to_cancel,
+       .timer_wait_running     = common_timer_wait_running,
        .timer_arm              = common_hrtimer_arm,
 };
 
@@ -1339,6 +1330,7 @@ static const struct k_clock clock_bootti
        .timer_forward          = common_hrtimer_forward,
        .timer_remaining        = common_hrtimer_remaining,
        .timer_try_to_cancel    = common_hrtimer_try_to_cancel,
+       .timer_wait_running     = common_timer_wait_running,
        .timer_arm              = common_hrtimer_arm,
 };
 
--- a/kernel/time/posix-timers.h
+++ b/kernel/time/posix-timers.h
@@ -24,6 +24,7 @@ struct k_clock {
        int     (*timer_try_to_cancel)(struct k_itimer *timr);
        void    (*timer_arm)(struct k_itimer *timr, ktime_t expires,
                             bool absolute, bool sigev_none);
+       void    (*timer_wait_running)(struct k_itimer *timr);
 };
 
 extern const struct k_clock clock_posix_cpu;