[v7] posix-timers: Cure the SIG_IGN mess

[patch V7 20/21] alarmtimers: Remove the throttle mechanism from alarm_forward_now()

Posted by Thomas Gleixner 2 weeks, 5 days ago

From: Thomas Gleixner <tglx@linutronix.de>

Now that ignored posix timer signals are requeued and the timers are
rearmed on signal delivery the workaround to keep such timers alive and
self rearm them is not longer required.

Remove the unused alarm timer parts.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/time/alarmtimer.c |   28 ++--------------------------
 1 file changed, 2 insertions(+), 26 deletions(-)
---

--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -467,35 +467,11 @@ u64 alarm_forward(struct alarm *alarm, k
 }
 EXPORT_SYMBOL_GPL(alarm_forward);
 
-static u64 __alarm_forward_now(struct alarm *alarm, ktime_t interval, bool throttle)
+u64 alarm_forward_now(struct alarm *alarm, ktime_t interval)
 {
 	struct alarm_base *base = &alarm_bases[alarm->type];
-	ktime_t now = base->get_ktime();
-
-	if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && throttle) {
-		/*
-		 * Same issue as with posix_timer_fn(). Timers which are
-		 * periodic but the signal is ignored can starve the system
-		 * with a very small interval. The real fix which was
-		 * promised in the context of posix_timer_fn() never
-		 * materialized, but someone should really work on it.
-		 *
-		 * To prevent DOS fake @now to be 1 jiffy out which keeps
-		 * the overrun accounting correct but creates an
-		 * inconsistency vs. timer_gettime(2).
-		 */
-		ktime_t kj = NSEC_PER_SEC / HZ;
 
-		if (interval < kj)
-			now = ktime_add(now, kj);
-	}
-
-	return alarm_forward(alarm, now, interval);
-}
-
-u64 alarm_forward_now(struct alarm *alarm, ktime_t interval)
-{
-	return __alarm_forward_now(alarm, interval, false);
+	return alarm_forward(alarm, base->get_ktime(), interval);
 }
 EXPORT_SYMBOL_GPL(alarm_forward_now);

Re: [patch V7 20/21] alarmtimers: Remove the throttle mechanism from alarm_forward_now()

Posted by Frederic Weisbecker 2 weeks, 5 days ago

Le Tue, Nov 05, 2024 at 09:14:56AM +0100, Thomas Gleixner a écrit :
> From: Thomas Gleixner <tglx@linutronix.de>
> 
> Now that ignored posix timer signals are requeued and the timers are
> rearmed on signal delivery the workaround to keep such timers alive and
> self rearm them is not longer required.
> 
> Remove the unused alarm timer parts.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

[tip: timers/core] alarmtimers: Remove the throttle mechanism from alarm_forward_now()

Posted by tip-bot2 for Thomas Gleixner 2 weeks, 3 days ago

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     6b0aa145786dab25c6b8e79ad70ac3382c381596
Gitweb:        https://git.kernel.org/tip/6b0aa145786dab25c6b8e79ad70ac3382c381596
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Tue, 05 Nov 2024 09:14:56 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 07 Nov 2024 02:14:45 +01:00

alarmtimers: Remove the throttle mechanism from alarm_forward_now()

Now that ignored posix timer signals are requeued and the timers are
rearmed on signal delivery the workaround to keep such timers alive and
self rearm them is not longer required.

Remove the unused alarm timer parts.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064214.252443020@linutronix.de

---
 kernel/time/alarmtimer.c | 28 ++--------------------------
 1 file changed, 2 insertions(+), 26 deletions(-)

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 8543d7f..593e7d5 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -467,35 +467,11 @@ u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval)
 }
 EXPORT_SYMBOL_GPL(alarm_forward);
 
-static u64 __alarm_forward_now(struct alarm *alarm, ktime_t interval, bool throttle)
+u64 alarm_forward_now(struct alarm *alarm, ktime_t interval)
 {
 	struct alarm_base *base = &alarm_bases[alarm->type];
-	ktime_t now = base->get_ktime();
-
-	if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && throttle) {
-		/*
-		 * Same issue as with posix_timer_fn(). Timers which are
-		 * periodic but the signal is ignored can starve the system
-		 * with a very small interval. The real fix which was
-		 * promised in the context of posix_timer_fn() never
-		 * materialized, but someone should really work on it.
-		 *
-		 * To prevent DOS fake @now to be 1 jiffy out which keeps
-		 * the overrun accounting correct but creates an
-		 * inconsistency vs. timer_gettime(2).
-		 */
-		ktime_t kj = NSEC_PER_SEC / HZ;
-
-		if (interval < kj)
-			now = ktime_add(now, kj);
-	}
-
-	return alarm_forward(alarm, now, interval);
-}
 
-u64 alarm_forward_now(struct alarm *alarm, ktime_t interval)
-{
-	return __alarm_forward_now(alarm, interval, false);
+	return alarm_forward(alarm, base->get_ktime(), interval);
 }
 EXPORT_SYMBOL_GPL(alarm_forward_now);