Commit ff5a6a35 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

Merge branch 'timers/urgent' of... 

Merge branch 'timers/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into timers/urgent

Pull dyntick fixes from Frederic Weisbecker:

  - Fix a rearm race in the posix cpu timer code
  - Handle get_next_timer_interrupt() correctly when no timers are pending

Link: https://lore.kernel.org/r/20210715104218.81276-1-frederic@kernel.org
parents 2734d6c1 aebacb7f

kernel/time/posix-cpu-timers.c

+5 −5
Original line number Diff line number Diff line
@@ -991,6 +991,11 @@ static void posix_cpu_timer_rearm(struct k_itimer *timer) 
	if (!p)

		goto out;



	/* Protect timer list r/w in arm_timer() */

	sighand = lock_task_sighand(p, &flags);

	if (unlikely(sighand == NULL))

		goto out;



	/*

	 * Fetch the current sample and update the timer's expiry time.

	 */
@@ -1001,11 +1006,6 @@ static void posix_cpu_timer_rearm(struct k_itimer *timer) 


	bump_cpu_timer(timer, now);



	/* Protect timer list r/w in arm_timer() */

	sighand = lock_task_sighand(p, &flags);

	if (unlikely(sighand == NULL))

		goto out;



	/*

	 * Now re-arm for the new expiry time.

	 */

kernel/time/timer.c

+5 −3
Original line number Diff line number Diff line
@@ -207,6 +207,7 @@ struct timer_base { 
	unsigned int		cpu;

	bool			next_expiry_recalc;

	bool			is_idle;

	bool			timers_pending;

	DECLARE_BITMAP(pending_map, WHEEL_SIZE);

	struct hlist_head	vectors[WHEEL_SIZE];

} ____cacheline_aligned;
@@ -595,6 +596,7 @@ static void enqueue_timer(struct timer_base *base, struct timer_list *timer, 
		 * can reevaluate the wheel:

		 */

		base->next_expiry = bucket_expiry;

		base->timers_pending = true;

		base->next_expiry_recalc = false;

		trigger_dyntick_cpu(base, timer);

	}
@@ -1582,6 +1584,7 @@ static unsigned long __next_timer_interrupt(struct timer_base *base) 
	}



	base->next_expiry_recalc = false;

	base->timers_pending = !(next == base->clk + NEXT_TIMER_MAX_DELTA);



	return next;

}
@@ -1633,7 +1636,6 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) 
	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);

	u64 expires = KTIME_MAX;

	unsigned long nextevt;

	bool is_max_delta;



	/*

	 * Pretend that there is no timer pending if the cpu is offline.
@@ -1646,7 +1648,6 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) 
	if (base->next_expiry_recalc)

		base->next_expiry = __next_timer_interrupt(base);

	nextevt = base->next_expiry;

	is_max_delta = (nextevt == base->clk + NEXT_TIMER_MAX_DELTA);



	/*

	 * We have a fresh next event. Check whether we can forward the
@@ -1664,7 +1665,7 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) 
		expires = basem;

		base->is_idle = false;

	} else {

		if (!is_max_delta)

		if (base->timers_pending)

			expires = basem + (u64)(nextevt - basej) * TICK_NSEC;

		/*

		 * If we expect to sleep more than a tick, mark the base idle.
@@ -1947,6 +1948,7 @@ int timers_prepare_cpu(unsigned int cpu) 
		base = per_cpu_ptr(&timer_bases[b], cpu);

		base->clk = jiffies;

		base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;

		base->timers_pending = false;

		base->is_idle = false;

	}

	return 0;