From: Anna-Maria Behnsen <anna-maria@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>,
John Stultz <john.stultz@linaro.org>,
Eric Dumazet <edumazet@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
linux-pm@vger.kernel.org, Arjan van de Ven <arjan@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Rik van Riel <riel@redhat.com>,
Anna-Maria Behnsen <anna-maria@linutronix.de>,
Richard Cochran <richardcochran@gmail.com>
Subject: [PATCH v3 17/17] timer: Always queue timers on the local CPU
Date: Tue, 25 Oct 2022 15:58:50 +0200 [thread overview]
Message-ID: <20221025135850.51044-18-anna-maria@linutronix.de> (raw)
In-Reply-To: <20221025135850.51044-1-anna-maria@linutronix.de>
The timer pull model is in place so we can remove the heuristics which try
to guess the best target CPU at enqueue/modification time.
All non pinned timers are queued on the local CPU in the seperate storage
and eventually pulled at expiry time to a remote CPU.
When a timer is added via add_timer_on(), TIMER_PINNED flag is required to
ensure it expires on the specified CPU. Otherwise it will be enqueued in
the global timer base which could be expired by a remote CPU. WARN_ONCE()
is added to prevent misuse.
Originally-by: Richard Cochran (linutronix GmbH) <richardcochran@gmail.com>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
---
kernel/time/timer.c | 17 +++++------------
1 file changed, 5 insertions(+), 12 deletions(-)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 67f9cc077ff7..f05e547e0c6c 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -947,17 +947,6 @@ static inline struct timer_base *get_timer_base(u32 tflags)
return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
}
-static inline struct timer_base *
-get_target_base(struct timer_base *base, unsigned tflags)
-{
-#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
- if (static_branch_likely(&timers_migration_enabled) &&
- !(tflags & TIMER_PINNED))
- return get_timer_cpu_base(tflags, get_nohz_timer_target());
-#endif
- return get_timer_this_cpu_base(tflags);
-}
-
static inline void forward_timer_base(struct timer_base *base)
{
unsigned long jnow = READ_ONCE(jiffies);
@@ -1093,7 +1082,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option
if (!ret && (options & MOD_TIMER_PENDING_ONLY))
goto out_unlock;
- new_base = get_target_base(base, timer->flags);
+ new_base = get_timer_this_cpu_base(timer->flags);
if (base != new_base) {
/*
@@ -1228,6 +1217,10 @@ void add_timer_on(struct timer_list *timer, int cpu)
BUG_ON(timer_pending(timer) || !timer->function);
+ WARN_ONCE(!(timer->flags & TIMER_PINNED), "TIMER_PINNED flag for "
+ "add_timer_on() is missing: timer=%p function=%ps",
+ timer, timer->function);
+
new_base = get_timer_cpu_base(timer->flags, cpu);
/*
--
2.30.2
next prev parent reply other threads:[~2022-10-25 14:01 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-25 13:58 [PATCH v3 00/17] timer: Move from a push remote at enqueue to a pull at expiry model Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 01/17] cpufreq: Prepare timer flags for hierarchical timer pull model Anna-Maria Behnsen
2022-10-26 13:54 ` Frederic Weisbecker
2022-10-31 15:22 ` Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 02/17] tick-sched: Warn when next tick seems to be in the past Anna-Maria Behnsen
2022-10-25 22:11 ` Frederic Weisbecker
2022-10-25 13:58 ` [PATCH v3 03/17] timer: Move store of next event into __next_timer_interrupt() Anna-Maria Behnsen
2022-10-26 9:33 ` Frederic Weisbecker
2022-10-25 13:58 ` [PATCH v3 04/17] timer: Split next timer interrupt logic Anna-Maria Behnsen
2022-10-26 9:40 ` Frederic Weisbecker
2022-10-25 13:58 ` [PATCH v3 05/17] timer: Rework idle logic Anna-Maria Behnsen
2022-10-26 13:27 ` Frederic Weisbecker
2022-10-25 13:58 ` [PATCH v3 06/17] timer: Keep the pinned timers separate from the others Anna-Maria Behnsen
2022-10-26 15:26 ` Frederic Weisbecker
2022-10-25 13:58 ` [PATCH v3 07/17] timer: Retrieve next expiry of pinned/non-pinned timers seperately Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 08/17] timer: Rename get_next_timer_interrupt() Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 09/17] timer: Split out "get next timer interrupt" functionality Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 10/17] timer: Add get next timer interrupt functionality for remote CPUs Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 11/17] timer: Restructure internal locking Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 12/17] timer: Check if timers base is handled already Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 13/17] tick/sched: Split out jiffies update helper function Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 14/17] timer: Implement the hierarchical pull model Anna-Maria Behnsen
2022-10-25 16:36 ` kernel test robot
2022-10-26 5:35 ` kernel test robot
2022-10-27 7:38 ` kernel test robot
2022-10-25 13:58 ` [PATCH v3 15/17] timer_migration: Add tracepoints Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 16/17] add_timer_on(): Make sure callers have TIMER_PINNED flag Anna-Maria Behnsen
2022-10-25 13:58 ` Anna-Maria Behnsen [this message]
2022-10-27 7:22 ` [PATCH v3 17/17] timer: Always queue timers on the local CPU kernel test robot
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