[PATCH 0/4] timers: Fix and improve tracing and documentation

[PATCH 0/4] timers: Fix and improve tracing and documentation

[Anna-Maria Gleixner]

Hi,

the patch series was developed during investigating timer problems and
timer improvements. It contains a struct documentation fix in tick-sched
and a fixes as well as an improvement for timer tracing.

Thanks,

        Anna-Maria


Anna-Maria Gleixner (4):
  tick-sched: Update tick_sched struct documentation
  timer: Move trace point to get proper index
  timer: Replace deprecated vsprintf pointer extension %pf by %ps
  trace/timer: Improve timer tracing

 include/trace/events/timer.h | 17 +++++++++++------
 kernel/time/tick-sched.h     | 13 ++++++++++---
 kernel/time/timer.c          | 30 +++++++++++++++++-------------
 3 files changed, 38 insertions(+), 22 deletions(-)

-- 
2.20.1

[PATCH 1/4] tick-sched: Update tick_sched struct documentation

[Anna-Maria Gleixner]

Adapt the documentation order of struct members to effective order of
struct members and add missing descriptions.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
---
 kernel/time/tick-sched.h | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
index 6de959a854b2..4fb06527cf64 100644
--- a/kernel/time/tick-sched.h
+++ b/kernel/time/tick-sched.h
@@ -24,12 +24,19 @@ enum tick_nohz_mode {
  * struct tick_sched - sched tick emulation and no idle tick control/stats
  * @sched_timer:	hrtimer to schedule the periodic tick in high
  *			resolution mode
+ * @check_clocks:	Notification mechanism about clocksource changes
+ * @nohz_mode:		Mode - one state of tick_nohz_mode
+ * @inidle:		Indicator that the CPU is in the tick idle mode
+ * @tick_stopped:	Indicator that the idle tick has been stopped
+ * @idle_active:	Indicator that the CPU is actively in the tick idle mode;
+ *			it is resetted during irq handling phases.
+ * @do_timer_lst:	CPU was the last one doing do_timer before going idle
+ * @got_idle_tick:	Tick timer function has run with @inidle set
  * @last_tick:		Store the last tick expiry time when the tick
  *			timer is modified for nohz sleeps. This is necessary
  *			to resume the tick timer operation in the timeline
  *			when the CPU returns from nohz sleep.
  * @next_tick:		Next tick to be fired when in dynticks mode.
- * @tick_stopped:	Indicator that the idle tick has been stopped
  * @idle_jiffies:	jiffies at the entry to idle for idle time accounting
  * @idle_calls:		Total number of idle calls
  * @idle_sleeps:	Number of idle calls, where the sched tick was stopped
@@ -40,8 +47,8 @@ enum tick_nohz_mode {
  * @iowait_sleeptime:	Sum of the time slept in idle with sched tick stopped, with IO outstanding
  * @timer_expires:	Anticipated timer expiration time (in case sched tick is stopped)
  * @timer_expires_base:	Base time clock monotonic for @timer_expires
- * @do_timer_lst:	CPU was the last one doing do_timer before going idle
- * @got_idle_tick:	Tick timer function has run with @inidle set
+ * @next_timer:		Expiry time of next expiring timer for debugging purpose only
+ * @tick_dep_mask:	Tick dependency mask - is set, if someone needs the tick
  */
 struct tick_sched {
 	struct hrtimer			sched_timer;
-- 
2.20.1

[PATCH 2/4] timer: Move trace point to get proper index

[Anna-Maria Gleixner]

When placing the timer_start trace point before timer wheel bucket
index is calculated, index information in trace point is useless.

It is not possible to simply move debug_activate() call after index
calculation, because debug_object_activate() function needs to be
called before touching the object.

Therefore split debug_activate() function and move trace point into
timer enqueue after index calculation. debug_object_activate() call
remains at the original place.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
---
 kernel/time/timer.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 2fce056f8a49..8d7918ae4d0c 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -536,6 +536,8 @@ static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
 	hlist_add_head(&timer->entry, base->vectors + idx);
 	__set_bit(idx, base->pending_map);
 	timer_set_idx(timer, idx);
+
+	trace_timer_start(timer, timer->expires, timer->flags);
 }
 
 static void
@@ -757,13 +759,6 @@ static inline void debug_init(struct timer_list *timer)
 	trace_timer_init(timer);
 }
 
-static inline void
-debug_activate(struct timer_list *timer, unsigned long expires)
-{
-	debug_timer_activate(timer);
-	trace_timer_start(timer, expires, timer->flags);
-}
-
 static inline void debug_deactivate(struct timer_list *timer)
 {
 	debug_timer_deactivate(timer);
@@ -1037,7 +1032,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option
 		}
 	}
 
-	debug_activate(timer, expires);
+	debug_timer_activate(timer);
 
 	timer->expires = expires;
 	/*
@@ -1171,7 +1166,7 @@ void add_timer_on(struct timer_list *timer, int cpu)
 	}
 	forward_timer_base(base);
 
-	debug_activate(timer, timer->expires);
+	debug_timer_activate(timer);
 	internal_add_timer(base, timer);
 	raw_spin_unlock_irqrestore(&base->lock, flags);
 }
-- 
2.20.1

[PATCH 3/4] timer: Replace deprecated vsprintf pointer extension %pf by %ps

[Anna-Maria Gleixner]

Since commit 04b8eb7a4ccd ("symbol lookup: introduce
dereference_symbol_descriptor()") %pf is deprecated, because %ps is smart
enough to handle function pointer dereference on platforms where such
dereference is required.

While at it shorten touched lines not to contain more than 80 characters.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
---
 include/trace/events/timer.h | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index a57e4ee989d6..da975d69c453 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -73,7 +73,7 @@ TRACE_EVENT(timer_start,
 		__entry->flags		= flags;
 	),
 
-	TP_printk("timer=%p function=%pf expires=%lu [timeout=%ld] cpu=%u idx=%u flags=%s",
+	TP_printk("timer=%p function=%ps expires=%lu [timeout=%ld] cpu=%u idx=%u flags=%s",
 		  __entry->timer, __entry->function, __entry->expires,
 		  (long)__entry->expires - __entry->now,
 		  __entry->flags & TIMER_CPUMASK,
@@ -105,7 +105,8 @@ TRACE_EVENT(timer_expire_entry,
 		__entry->function	= timer->function;
 	),
 
-	TP_printk("timer=%p function=%pf now=%lu", __entry->timer, __entry->function,__entry->now)
+	TP_printk("timer=%p function=%ps now=%lu",
+		  __entry->timer, __entry->function, __entry->now)
 );
 
 /**
@@ -210,7 +211,7 @@ TRACE_EVENT(hrtimer_start,
 		__entry->mode		= mode;
 	),
 
-	TP_printk("hrtimer=%p function=%pf expires=%llu softexpires=%llu "
+	TP_printk("hrtimer=%p function=%ps expires=%llu softexpires=%llu "
 		  "mode=%s", __entry->hrtimer, __entry->function,
 		  (unsigned long long) __entry->expires,
 		  (unsigned long long) __entry->softexpires,
@@ -243,7 +244,8 @@ TRACE_EVENT(hrtimer_expire_entry,
 		__entry->function	= hrtimer->function;
 	),
 
-	TP_printk("hrtimer=%p function=%pf now=%llu", __entry->hrtimer, __entry->function,
+	TP_printk("hrtimer=%p function=%ps now=%llu",
+		  __entry->hrtimer, __entry->function,
 		  (unsigned long long) __entry->now)
 );
 
-- 
2.20.1

[PATCH 4/4] trace/timer: Improve timer tracing

[Anna-Maria Gleixner]

Timers are added to the timer wheel off by one. This is required in
case a timer is queued directly before incrementing jiffies to prevent
early timer expiry.

When reading a timer trace and relying only on the expiry time of the
timer in timer_start trace point and on the now in timer_expiry_entry
trace point, it seems that the timer fires late. With the current
timer_expiry_entry trace point information only now=jiffies is printed
but not the value of base->clk. This makes it impossible to draw a
conclusion to the index of base->clk and makes it impossible to
examine timer problems without additional trace points.

Therefore add the base->clk value to the timer_expire_entry trace
point, to be able to calculate the index the timer base is located at
during collecting expired timers.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
---
 include/trace/events/timer.h | 11 +++++++----
 kernel/time/timer.c          | 17 +++++++++++++----
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index da975d69c453..dade735657ef 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -89,24 +89,27 @@ TRACE_EVENT(timer_start,
  */
 TRACE_EVENT(timer_expire_entry,
 
-	TP_PROTO(struct timer_list *timer),
+	TP_PROTO(struct timer_list *timer, unsigned long baseclk),
 
-	TP_ARGS(timer),
+	TP_ARGS(timer, baseclk),
 
 	TP_STRUCT__entry(
 		__field( void *,	timer	)
 		__field( unsigned long,	now	)
 		__field( void *,	function)
+		__field( unsigned long,	baseclk	)
 	),
 
 	TP_fast_assign(
 		__entry->timer		= timer;
 		__entry->now		= jiffies;
 		__entry->function	= timer->function;
+		__entry->baseclk	= baseclk;
 	),
 
-	TP_printk("timer=%p function=%ps now=%lu",
-		  __entry->timer, __entry->function, __entry->now)
+	TP_printk("timer=%p function=%ps now=%lu base->clk=%lu",
+		  __entry->timer, __entry->function, __entry->now,
+		  __entry->baseclk)
 );
 
 /**
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 8d7918ae4d0c..c0233c1a4ccb 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1293,7 +1293,8 @@ int del_timer_sync(struct timer_list *timer)
 EXPORT_SYMBOL(del_timer_sync);
 #endif
 
-static void call_timer_fn(struct timer_list *timer, void (*fn)(struct timer_list *))
+static void call_timer_fn(unsigned long baseclk, struct timer_list *timer,
+			  void (*fn)(struct timer_list *))
 {
 	int count = preempt_count();
 
@@ -1316,7 +1317,7 @@ static void call_timer_fn(struct timer_list *timer, void (*fn)(struct timer_list
 	 */
 	lock_map_acquire(&lockdep_map);
 
-	trace_timer_expire_entry(timer);
+	trace_timer_expire_entry(timer, baseclk);
 	fn(timer);
 	trace_timer_expire_exit(timer);
 
@@ -1337,6 +1338,14 @@ static void call_timer_fn(struct timer_list *timer, void (*fn)(struct timer_list
 
 static void expire_timers(struct timer_base *base, struct hlist_head *head)
 {
+	/*
+	 * this value is required for tracing only
+	 *
+	 * base->clk was incremented directly before expire_timers was
+	 * called. But expiry is related to the old base->clk value.
+	 */
+	unsigned long baseclk = base->clk - 1;
+
 	while (!hlist_empty(head)) {
 		struct timer_list *timer;
 		void (*fn)(struct timer_list *);
@@ -1350,11 +1359,11 @@ static void expire_timers(struct timer_base *base, struct hlist_head *head)
 
 		if (timer->flags & TIMER_IRQSAFE) {
 			raw_spin_unlock(&base->lock);
-			call_timer_fn(timer, fn);
+			call_timer_fn(baseclk, timer, fn);
 			raw_spin_lock(&base->lock);
 		} else {
 			raw_spin_unlock_irq(&base->lock);
-			call_timer_fn(timer, fn);
+			call_timer_fn(baseclk, timer, fn);
 			raw_spin_lock_irq(&base->lock);
 		}
 	}
-- 
2.20.1

[tip:timers/core] tick/sched: Update tick_sched struct documentation

[tip-bot for Anna-Maria Gleixner]

Commit-ID:  d6b87eaf10bd061914f6d277d7428b3285d8850e
Gitweb:     https://git.kernel.org/tip/d6b87eaf10bd061914f6d277d7428b3285d8850e
Author:     Anna-Maria Gleixner <anna-maria@linutronix.de>
AuthorDate: Thu, 21 Mar 2019 13:09:18 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 24 Mar 2019 20:29:32 +0100

tick/sched: Update tick_sched struct documentation

Adapt the documentation order of struct members to the effective order of
struct members and add missing descriptions.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: fweisbec@gmail.com
Cc: peterz@infradead.org
Link: https://lkml.kernel.org/r/20190321120921.16463-2-anna-maria@linutronix.de

---
 kernel/time/tick-sched.h | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
index 6de959a854b2..4fb06527cf64 100644
--- a/kernel/time/tick-sched.h
+++ b/kernel/time/tick-sched.h
@@ -24,12 +24,19 @@ enum tick_nohz_mode {
  * struct tick_sched - sched tick emulation and no idle tick control/stats
  * @sched_timer:	hrtimer to schedule the periodic tick in high
  *			resolution mode
+ * @check_clocks:	Notification mechanism about clocksource changes
+ * @nohz_mode:		Mode - one state of tick_nohz_mode
+ * @inidle:		Indicator that the CPU is in the tick idle mode
+ * @tick_stopped:	Indicator that the idle tick has been stopped
+ * @idle_active:	Indicator that the CPU is actively in the tick idle mode;
+ *			it is resetted during irq handling phases.
+ * @do_timer_lst:	CPU was the last one doing do_timer before going idle
+ * @got_idle_tick:	Tick timer function has run with @inidle set
  * @last_tick:		Store the last tick expiry time when the tick
  *			timer is modified for nohz sleeps. This is necessary
  *			to resume the tick timer operation in the timeline
  *			when the CPU returns from nohz sleep.
  * @next_tick:		Next tick to be fired when in dynticks mode.
- * @tick_stopped:	Indicator that the idle tick has been stopped
  * @idle_jiffies:	jiffies at the entry to idle for idle time accounting
  * @idle_calls:		Total number of idle calls
  * @idle_sleeps:	Number of idle calls, where the sched tick was stopped
@@ -40,8 +47,8 @@ enum tick_nohz_mode {
  * @iowait_sleeptime:	Sum of the time slept in idle with sched tick stopped, with IO outstanding
  * @timer_expires:	Anticipated timer expiration time (in case sched tick is stopped)
  * @timer_expires_base:	Base time clock monotonic for @timer_expires
- * @do_timer_lst:	CPU was the last one doing do_timer before going idle
- * @got_idle_tick:	Tick timer function has run with @inidle set
+ * @next_timer:		Expiry time of next expiring timer for debugging purpose only
+ * @tick_dep_mask:	Tick dependency mask - is set, if someone needs the tick
  */
 struct tick_sched {
 	struct hrtimer			sched_timer;

[tip:timers/core] timer: Move trace point to get proper index

[tip-bot for Anna-Maria Gleixner]

Commit-ID:  dc1e7dc5ac6254ba0502323381a7ec847e408f1d
Gitweb:     https://git.kernel.org/tip/dc1e7dc5ac6254ba0502323381a7ec847e408f1d
Author:     Anna-Maria Gleixner <anna-maria@linutronix.de>
AuthorDate: Thu, 21 Mar 2019 13:09:19 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 24 Mar 2019 20:29:32 +0100

timer: Move trace point to get proper index

When placing the timer_start trace point before the timer wheel bucket
index is calculated, the index information in the trace point is useless.

It is not possible to simply move the debug_activate() call after the index
calculation, because debug_object_activate() needs to be called before
touching the object.

Therefore split debug_activate() and move the trace point into
enqueue_timer() after the new index has been calculated. The
debug_object_activate() call remains at the original place.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: fweisbec@gmail.com
Cc: peterz@infradead.org
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/20190321120921.16463-3-anna-maria@linutronix.de

---
 kernel/time/timer.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 2fce056f8a49..8d7918ae4d0c 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -536,6 +536,8 @@ static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
 	hlist_add_head(&timer->entry, base->vectors + idx);
 	__set_bit(idx, base->pending_map);
 	timer_set_idx(timer, idx);
+
+	trace_timer_start(timer, timer->expires, timer->flags);
 }
 
 static void
@@ -757,13 +759,6 @@ static inline void debug_init(struct timer_list *timer)
 	trace_timer_init(timer);
 }
 
-static inline void
-debug_activate(struct timer_list *timer, unsigned long expires)
-{
-	debug_timer_activate(timer);
-	trace_timer_start(timer, expires, timer->flags);
-}
-
 static inline void debug_deactivate(struct timer_list *timer)
 {
 	debug_timer_deactivate(timer);
@@ -1037,7 +1032,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option
 		}
 	}
 
-	debug_activate(timer, expires);
+	debug_timer_activate(timer);
 
 	timer->expires = expires;
 	/*
@@ -1171,7 +1166,7 @@ void add_timer_on(struct timer_list *timer, int cpu)
 	}
 	forward_timer_base(base);
 
-	debug_activate(timer, timer->expires);
+	debug_timer_activate(timer);
 	internal_add_timer(base, timer);
 	raw_spin_unlock_irqrestore(&base->lock, flags);
 }

[tip:timers/core] timer/trace: Replace deprecated vsprintf pointer extension %pf by %ps

[tip-bot for Anna-Maria Gleixner]

Commit-ID:  6849cbb0f9a8dbc1ba56e9abc6955613103e01e3
Gitweb:     https://git.kernel.org/tip/6849cbb0f9a8dbc1ba56e9abc6955613103e01e3
Author:     Anna-Maria Gleixner <anna-maria@linutronix.de>
AuthorDate: Thu, 21 Mar 2019 13:09:20 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 24 Mar 2019 20:29:33 +0100

timer/trace: Replace deprecated vsprintf pointer extension %pf by %ps

Since commit 04b8eb7a4ccd ("symbol lookup: introduce
dereference_symbol_descriptor()") %pf is deprecated, because %ps is smart
enough to handle function pointer dereference on platforms where such a
dereference is required.

While at it add proper line breaks to stay in the 80 character limit.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: fweisbec@gmail.com
Cc: peterz@infradead.org
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/20190321120921.16463-4-anna-maria@linutronix.de

---
 include/trace/events/timer.h | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index a57e4ee989d6..da975d69c453 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -73,7 +73,7 @@ TRACE_EVENT(timer_start,
 		__entry->flags		= flags;
 	),
 
-	TP_printk("timer=%p function=%pf expires=%lu [timeout=%ld] cpu=%u idx=%u flags=%s",
+	TP_printk("timer=%p function=%ps expires=%lu [timeout=%ld] cpu=%u idx=%u flags=%s",
 		  __entry->timer, __entry->function, __entry->expires,
 		  (long)__entry->expires - __entry->now,
 		  __entry->flags & TIMER_CPUMASK,
@@ -105,7 +105,8 @@ TRACE_EVENT(timer_expire_entry,
 		__entry->function	= timer->function;
 	),
 
-	TP_printk("timer=%p function=%pf now=%lu", __entry->timer, __entry->function,__entry->now)
+	TP_printk("timer=%p function=%ps now=%lu",
+		  __entry->timer, __entry->function, __entry->now)
 );
 
 /**
@@ -210,7 +211,7 @@ TRACE_EVENT(hrtimer_start,
 		__entry->mode		= mode;
 	),
 
-	TP_printk("hrtimer=%p function=%pf expires=%llu softexpires=%llu "
+	TP_printk("hrtimer=%p function=%ps expires=%llu softexpires=%llu "
 		  "mode=%s", __entry->hrtimer, __entry->function,
 		  (unsigned long long) __entry->expires,
 		  (unsigned long long) __entry->softexpires,
@@ -243,7 +244,8 @@ TRACE_EVENT(hrtimer_expire_entry,
 		__entry->function	= hrtimer->function;
 	),
 
-	TP_printk("hrtimer=%p function=%pf now=%llu", __entry->hrtimer, __entry->function,
+	TP_printk("hrtimer=%p function=%ps now=%llu",
+		  __entry->hrtimer, __entry->function,
 		  (unsigned long long) __entry->now)
 );
 

[tip:timers/core] timer/trace: Improve timer tracing

[tip-bot for Anna-Maria Gleixner]

Commit-ID:  f28d3d5346e97e60c81f933ac89ccf015430e5cf
Gitweb:     https://git.kernel.org/tip/f28d3d5346e97e60c81f933ac89ccf015430e5cf
Author:     Anna-Maria Gleixner <anna-maria@linutronix.de>
AuthorDate: Thu, 21 Mar 2019 13:09:21 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 24 Mar 2019 20:29:33 +0100

timer/trace: Improve timer tracing

Timers are added to the timer wheel off by one. This is required in
case a timer is queued directly before incrementing jiffies to prevent
early timer expiry.

When reading a timer trace and relying only on the expiry time of the timer
in the timer_start trace point and on the now in the timer_expiry_entry
trace point, it seems that the timer fires late. With the current
timer_expiry_entry trace point information only now=jiffies is printed but
not the value of base->clk. This makes it impossible to draw a conclusion
to the index of base->clk and makes it impossible to examine timer problems
without additional trace points.

Therefore add the base->clk value to the timer_expire_entry trace
point, to be able to calculate the index the timer base is located at
during collecting expired timers.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: fweisbec@gmail.com
Cc: peterz@infradead.org
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/20190321120921.16463-5-anna-maria@linutronix.de

---
 include/trace/events/timer.h | 11 +++++++----
 kernel/time/timer.c          | 17 +++++++++++++----
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index da975d69c453..b7a904825e7d 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -89,24 +89,27 @@ TRACE_EVENT(timer_start,
  */
 TRACE_EVENT(timer_expire_entry,
 
-	TP_PROTO(struct timer_list *timer),
+	TP_PROTO(struct timer_list *timer, unsigned long baseclk),
 
-	TP_ARGS(timer),
+	TP_ARGS(timer, baseclk),
 
 	TP_STRUCT__entry(
 		__field( void *,	timer	)
 		__field( unsigned long,	now	)
 		__field( void *,	function)
+		__field( unsigned long,	baseclk	)
 	),
 
 	TP_fast_assign(
 		__entry->timer		= timer;
 		__entry->now		= jiffies;
 		__entry->function	= timer->function;
+		__entry->baseclk	= baseclk;
 	),
 
-	TP_printk("timer=%p function=%ps now=%lu",
-		  __entry->timer, __entry->function, __entry->now)
+	TP_printk("timer=%p function=%ps now=%lu baseclk=%lu",
+		  __entry->timer, __entry->function, __entry->now,
+		  __entry->baseclk)
 );
 
 /**
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 8d7918ae4d0c..a9b1bbc2d88d 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1293,7 +1293,9 @@ int del_timer_sync(struct timer_list *timer)
 EXPORT_SYMBOL(del_timer_sync);
 #endif
 
-static void call_timer_fn(struct timer_list *timer, void (*fn)(struct timer_list *))
+static void call_timer_fn(struct timer_list *timer,
+			  void (*fn)(struct timer_list *),
+			  unsigned long baseclk)
 {
 	int count = preempt_count();
 
@@ -1316,7 +1318,7 @@ static void call_timer_fn(struct timer_list *timer, void (*fn)(struct timer_list
 	 */
 	lock_map_acquire(&lockdep_map);
 
-	trace_timer_expire_entry(timer);
+	trace_timer_expire_entry(timer, baseclk);
 	fn(timer);
 	trace_timer_expire_exit(timer);
 
@@ -1337,6 +1339,13 @@ static void call_timer_fn(struct timer_list *timer, void (*fn)(struct timer_list
 
 static void expire_timers(struct timer_base *base, struct hlist_head *head)
 {
+	/*
+	 * This value is required only for tracing. base->clk was
+	 * incremented directly before expire_timers was called. But expiry
+	 * is related to the old base->clk value.
+	 */
+	unsigned long baseclk = base->clk - 1;
+
 	while (!hlist_empty(head)) {
 		struct timer_list *timer;
 		void (*fn)(struct timer_list *);
@@ -1350,11 +1359,11 @@ static void expire_timers(struct timer_base *base, struct hlist_head *head)
 
 		if (timer->flags & TIMER_IRQSAFE) {
 			raw_spin_unlock(&base->lock);
-			call_timer_fn(timer, fn);
+			call_timer_fn(timer, fn, baseclk);
 			raw_spin_lock(&base->lock);
 		} else {
 			raw_spin_unlock_irq(&base->lock);
-			call_timer_fn(timer, fn);
+			call_timer_fn(timer, fn, baseclk);
 			raw_spin_lock_irq(&base->lock);
 		}
 	}

Re: [PATCH 0/4] timers: Fix and improve tracing and documentation

[Peter Zijlstra]

On Thu, Mar 21, 2019 at 01:09:17PM +0100, Anna-Maria Gleixner wrote:
> Hi,
> 
> the patch series was developed during investigating timer problems and
> timer improvements. It contains a struct documentation fix in tick-sched
> and a fixes as well as an improvement for timer tracing.
> 
> Thanks,
> 
>         Anna-Maria
> 
> 
> Anna-Maria Gleixner (4):
>   tick-sched: Update tick_sched struct documentation
>   timer: Move trace point to get proper index
>   timer: Replace deprecated vsprintf pointer extension %pf by %ps
>   trace/timer: Improve timer tracing
> 
>  include/trace/events/timer.h | 17 +++++++++++------
>  kernel/time/tick-sched.h     | 13 ++++++++++---
>  kernel/time/timer.c          | 30 +++++++++++++++++-------------
>  3 files changed, 38 insertions(+), 22 deletions(-)

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>