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

Thomas Gleixner
2019-08-19T15:47:57Z

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 <tglx@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;