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From: tip-bot for Anna-Maria Gleixner <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: torvalds@linux-foundation.org, tglx@linutronix.de, hch@lst.de,
	john.stultz@linaro.org, hpa@zytor.com, peterz@infradead.org,
	anna-maria@linutronix.de, mingo@kernel.org,
	linux-kernel@vger.kernel.org
Subject: [tip:timers/core] hrtimer: Make the remote enqueue check unconditional
Date: Mon, 15 Jan 2018 19:46:29 -0800	[thread overview]
Message-ID: <tip-07a9a7eae86abb796468b225586086d7c4cb59fc@git.kernel.org> (raw)
In-Reply-To: <20171221104205.7269-16-anna-maria@linutronix.de>

Commit-ID:  07a9a7eae86abb796468b225586086d7c4cb59fc
Gitweb:     https://git.kernel.org/tip/07a9a7eae86abb796468b225586086d7c4cb59fc
Author:     Anna-Maria Gleixner <anna-maria@linutronix.de>
AuthorDate: Thu, 21 Dec 2017 11:41:44 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 16 Jan 2018 02:35:47 +0100

hrtimer: Make the remote enqueue check unconditional

hrtimer_cpu_base.expires_next is used to cache the next event armed in the
timer hardware. The value is used to check whether an hrtimer can be
enqueued remotely. If the new hrtimer is expiring before expires_next, then
remote enqueue is not possible as the remote hrtimer hardware cannot be
accessed for reprogramming to an earlier expiry time.

The remote enqueue check is currently conditional on
CONFIG_HIGH_RES_TIMERS=y and hrtimer_cpu_base.hres_active. There is no
compelling reason to make this conditional.

Move hrtimer_cpu_base.expires_next out of the CONFIG_HIGH_RES_TIMERS=y
guarded area and remove the conditionals in hrtimer_check_target().

The check is currently a NOOP for the CONFIG_HIGH_RES_TIMERS=n and the
!hrtimer_cpu_base.hres_active case because in these cases nothing updates
hrtimer_cpu_base.expires_next yet. This will be changed with later patches
which further reduce the #ifdef zoo in this code.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: keescook@chromium.org
Link: http://lkml.kernel.org/r/20171221104205.7269-16-anna-maria@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/hrtimer.h |  6 +++---
 kernel/time/hrtimer.c   | 26 ++++++--------------------
 2 files changed, 9 insertions(+), 23 deletions(-)

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 22627b3..bb7270e 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -164,13 +164,13 @@ enum  hrtimer_base_type {
  * @hres_active:	State of high resolution mode
  * @in_hrtirq:		hrtimer_interrupt() is currently executing
  * @hang_detected:	The last hrtimer interrupt detected a hang
- * @expires_next:	absolute time of the next event, is required for remote
- *			hrtimer enqueue
  * @next_timer:		Pointer to the first expiring timer
  * @nr_events:		Total number of hrtimer interrupt events
  * @nr_retries:		Total number of hrtimer interrupt retries
  * @nr_hangs:		Total number of hrtimer interrupt hangs
  * @max_hang_time:	Maximum time spent in hrtimer_interrupt
+ * @expires_next:	absolute time of the next event, is required for remote
+ *			hrtimer enqueue
  * @clock_base:		array of clock bases for this cpu
  *
  * Note: next_timer is just an optimization for __remove_hrtimer().
@@ -186,13 +186,13 @@ struct hrtimer_cpu_base {
 #ifdef CONFIG_HIGH_RES_TIMERS
 	unsigned int			in_hrtirq	: 1,
 					hang_detected	: 1;
-	ktime_t				expires_next;
 	struct hrtimer			*next_timer;
 	unsigned int			nr_events;
 	unsigned short			nr_retries;
 	unsigned short			nr_hangs;
 	unsigned int			max_hang_time;
 #endif
+	ktime_t				expires_next;
 	struct hrtimer_clock_base	clock_base[HRTIMER_MAX_CLOCK_BASES];
 } ____cacheline_aligned;
 
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 5a624f9..a9ab67f 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -154,26 +154,21 @@ struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
 }
 
 /*
- * With HIGHRES=y we do not migrate the timer when it is expiring
- * before the next event on the target cpu because we cannot reprogram
- * the target cpu hardware and we would cause it to fire late.
+ * We do not migrate the timer when it is expiring before the next
+ * event on the target cpu. When high resolution is enabled, we cannot
+ * reprogram the target cpu hardware and we would cause it to fire
+ * late. To keep it simple, we handle the high resolution enabled and
+ * disabled case similar.
  *
  * Called with cpu_base->lock of target cpu held.
  */
 static int
 hrtimer_check_target(struct hrtimer *timer, struct hrtimer_clock_base *new_base)
 {
-#ifdef CONFIG_HIGH_RES_TIMERS
 	ktime_t expires;
 
-	if (!new_base->cpu_base->hres_active)
-		return 0;
-
 	expires = ktime_sub(hrtimer_get_expires(timer), new_base->offset);
 	return expires <= new_base->cpu_base->expires_next;
-#else
-	return 0;
-#endif
 }
 
 static inline
@@ -657,14 +652,6 @@ static void hrtimer_reprogram(struct hrtimer *timer,
 }
 
 /*
- * Initialize the high resolution related parts of cpu_base
- */
-static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base)
-{
-	base->expires_next = KTIME_MAX;
-}
-
-/*
  * Retrigger next event is called after clock was set
  *
  * Called with interrupts disabled via on_each_cpu()
@@ -729,7 +716,6 @@ static inline int hrtimer_reprogram(struct hrtimer *timer,
 {
 	return 0;
 }
-static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base) { }
 static inline void retrigger_next_event(void *arg) { }
 
 #endif /* CONFIG_HIGH_RES_TIMERS */
@@ -1599,7 +1585,7 @@ int hrtimers_prepare_cpu(unsigned int cpu)
 
 	cpu_base->cpu = cpu;
 	cpu_base->hres_active = 0;
-	hrtimer_init_hres(cpu_base);
+	cpu_base->expires_next = KTIME_MAX;
 	return 0;
 }
 

  reply	other threads:[~2018-01-16  3:49 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-21 10:41 [PATCH v4 00/36] hrtimer: Provide softirq context hrtimers Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 01/36] timers: Use static keys for migrate_enable/nohz_active Anna-Maria Gleixner
2017-12-22 15:45   ` [PATCH v5 " Sebastian Andrzej Siewior
2018-01-14 22:13     ` Thomas Gleixner
2018-01-14 22:30       ` [PATCH v6 " Thomas Gleixner
2018-01-11  4:25   ` [PATCH v4 " Frederic Weisbecker
2018-01-16  3:40   ` [tip:timers/core] hrtimer: Optimize the hrtimer code by using static keys for migration_enable/nohz_active tip-bot for Thomas Gleixner
2017-12-21 10:41 ` [PATCH v4 02/36] hrtimer: Correct blantanly wrong comment Anna-Maria Gleixner
2018-01-11 18:28   ` Frederic Weisbecker
2018-01-16  1:02   ` Ingo Molnar
2018-01-16  3:40   ` [tip:timers/core] hrtimer: Correct blatantly incorrect comment tip-bot for Thomas Gleixner
2017-12-21 10:41 ` [PATCH v4 03/36] hrtimer: Fix kerneldoc for struct hrtimer_cpu_base Anna-Maria Gleixner
2018-01-16  3:41   ` [tip:timers/core] hrtimer: Fix kerneldoc syntax for 'struct hrtimer_cpu_base' tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 04/36] hrtimer: Cleanup clock argument in schedule_hrtimeout_range_clock() Anna-Maria Gleixner
2018-01-16  3:41   ` [tip:timers/core] hrtimer: Clean up the 'int clock' parameter of schedule_hrtimeout_range_clock() tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 05/36] hrtimer: Fix hrtimer function description Anna-Maria Gleixner
2018-01-16  3:42   ` [tip:timers/core] hrtimer: Fix hrtimer_start[_range_ns]() function descriptions tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 06/36] hrtimer: Ensure POSIX compliance (relative CLOCK_REALTIME hrtimers) Anna-Maria Gleixner
2018-01-16  3:42   ` [tip:timers/core] " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 07/36] hrtimer: Cleanup hrtimer_mode enum Anna-Maria Gleixner
2018-01-16  3:43   ` [tip:timers/core] hrtimer: Clean up 'enum hrtimer_mode' tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 08/36] tracing/hrtimer: Take all clock bases and modes into account Anna-Maria Gleixner
2018-01-16  3:43   ` [tip:timers/core] tracing/hrtimer: Fix tracing bugs by taking " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 09/36] tracing/hrtimer: Print hrtimer mode in hrtimer_start tracepoint Anna-Maria Gleixner
2018-01-16  3:43   ` [tip:timers/core] tracing/hrtimer: Print the hrtimer mode in the 'hrtimer_start' tracepoint tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 10/36] hrtimer: Switch for loop to _ffs() evaluation Anna-Maria Gleixner
2018-01-16  3:44   ` [tip:timers/core] hrtimer: Switch 'for' " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 11/36] hrtimer: Store running timer in hrtimer_clock_base Anna-Maria Gleixner
2018-01-16  3:44   ` [tip:timers/core] " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 12/36] hrtimer: Make room in struct hrtimer_cpu_base Anna-Maria Gleixner
2018-01-16  3:45   ` [tip:timers/core] hrtimer: Make room in 'struct hrtimer_cpu_base' tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 13/36] hrtimer: Reduce conditional code (hres_active) Anna-Maria Gleixner
2018-01-16  3:45   ` [tip:timers/core] hrtimer: Make the hrtimer_cpu_base::hres_active field unconditional, to simplify the code tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 14/36] hrtimer: Use accesor functions instead of direct access Anna-Maria Gleixner
2018-01-16  3:46   ` [tip:timers/core] " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 15/36] hrtimer: Make the remote enqueue check unconditional Anna-Maria Gleixner
2018-01-16  3:46   ` tip-bot for Anna-Maria Gleixner [this message]
2017-12-21 10:41 ` [PATCH v4 16/36] hrtimer: Make hrtimer_cpu_base.next_timer handling unconditional Anna-Maria Gleixner
2018-01-16  3:46   ` [tip:timers/core] " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 17/36] hrtimer: Make hrtimer_reprogramm() unconditional Anna-Maria Gleixner
2018-01-16  3:47   ` [tip:timers/core] " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 18/36] hrtimer: Make hrtimer_force_reprogramm() unconditionally available Anna-Maria Gleixner
2018-01-16  3:47   ` [tip:timers/core] " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 19/36] hrtimer: Unify handling of hrtimer remove Anna-Maria Gleixner
2018-01-16  3:48   ` [tip:timers/core] hrtimer: Unify hrtimer removal handling tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 20/36] hrtimer: Unify handling of remote enqueue Anna-Maria Gleixner
2018-01-16  3:48   ` [tip:timers/core] hrtimer: Unify remote enqueue handling tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 21/36] hrtimer: Make remote enqueue decision less restrictive Anna-Maria Gleixner
2018-01-16  3:49   ` [tip:timers/core] " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 22/36] hrtimer: Remove base argument from hrtimer_reprogram() Anna-Maria Gleixner
2018-01-16  3:49   ` [tip:timers/core] hrtimer: Remove the 'base' parameter " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 23/36] hrtimer: Split hrtimer_start_range_ns() Anna-Maria Gleixner
2018-01-16  3:49   ` [tip:timers/core] hrtimer: Factor out __hrtimer_start_range_ns() tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 24/36] hrtimer: Split __hrtimer_get_next_event() Anna-Maria Gleixner
2018-01-16  3:50   ` [tip:timers/core] hrtimer: Factor out __hrtimer_next_event_base() tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 25/36] hrtimer: Use irqsave/irqrestore around __run_hrtimer() Anna-Maria Gleixner
2018-01-16  3:50   ` [tip:timers/core] " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 26/36] hrtimer: Add clock bases and hrtimer mode for soft irq context Anna-Maria Gleixner
2018-01-16  3:51   ` [tip:timers/core] hrtimer: Add clock bases and hrtimer mode for softirq context tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 27/36] hrtimer: Prepare handling of hard and softirq based hrtimers Anna-Maria Gleixner
2018-01-16  3:51   ` [tip:timers/core] " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 28/36] hrtimer: Implement support for " Anna-Maria Gleixner
2018-01-16 10:22   ` [tip:timers/core] " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 29/36] hrtimer: Implement SOFT/HARD clock base selection Anna-Maria Gleixner
2018-01-16 10:22   ` [tip:timers/core] " tip-bot for Anna-Maria Gleixner
2017-12-21 10:41 ` [PATCH v4 30/36] can/bcm: Replace hrtimer_tasklet with softirq based hrtimer Anna-Maria Gleixner
2017-12-21 10:42 ` [PATCH v4 31/36] mac80211_hwsim: Replace hrtimer tasklet with softirq hrtimer Anna-Maria Gleixner
2018-01-04 15:12   ` Johannes Berg
2018-01-04 15:18     ` Thomas Gleixner
2017-12-21 10:42 ` [PATCH v4 32/36] xfrm: " Anna-Maria Gleixner
2017-12-21 10:42 ` [PATCH v4 33/36] softirq: Remove tasklet_hrtimer Anna-Maria Gleixner
2017-12-21 10:42 ` [PATCH v4 34/36] ALSA/dummy: Replace tasklet with softirq hrtimer Anna-Maria Gleixner
2018-01-16 10:23   ` [tip:timers/core] " tip-bot for Thomas Gleixner
2017-12-21 10:42 ` [PATCH v4 35/36] usb/gadget/NCM: " Anna-Maria Gleixner
2018-01-16 10:23   ` [tip:timers/core] " tip-bot for Thomas Gleixner
2017-12-21 10:42 ` [PATCH v4 36/36] net/mvpp2: " Anna-Maria Gleixner
2018-01-16  1:39 ` [PATCH v4 00/36] hrtimer: Provide softirq context hrtimers Ingo Molnar
2018-01-16  2:03   ` Ingo Molnar

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