LinuxLists.cc - [GIT PULL][PATCH 0/7] Timekeeping changes for 4.10 (take 2)

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Subject: [PATCH 1/7] selftests/timers: Fix spelling mistake "Asyncrhonous" -> "Asynchronous"

From: Colin Ian King <[email protected]>

Trivial fix to spelling mistake

Cc: Thomas Gleixner <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Signed-off-by: Colin Ian King <[email protected]>
Signed-off-by: John Stultz <[email protected]>
---
tools/testing/selftests/timers/skew_consistency.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/timers/skew_consistency.c b/tools/testing/selftests/timers/skew_consistency.c
index 5562f84..2a996e0 100644
--- a/tools/testing/selftests/timers/skew_consistency.c
+++ b/tools/testing/selftests/timers/skew_consistency.c
@@ -57,7 +57,7 @@ int main(int argv, char **argc)
pid_t pid;

- printf("Running Asyncrhonous Frequency Changing Tests...\n");
+ printf("Running Asynchronous Frequency Changing Tests...\n");

pid = fork();
if (!pid)
--
2.7.4

2016-11-28 22:35:52

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Subject: [PATCH 2/7] timekeeping: Ignore the bogus sleep time if pm_trace is enabled

From: Chen Yu <[email protected]>

Previously we encountered some memory overflow issues due to
the bogus sleep time brought by inconsistent rtc, which is
triggered when pm_trace is enabled, and we have fixed it
in recent kernel. However it's improper in the first place
to call __timekeeping_inject_sleeptime() in case that pm_trace
is enabled simply because that "hash" time value will wreckage
the timekeeping subsystem.

This patch is originally written by Thomas, which would bypass
the bogus rtc interval when pm_trace is enabled.
Meanwhile, if system succeed to resume back with pm_trace set, the
users are warned to adjust the bogus rtc either by 'ntpdate' or
'rdate', by resetting pm_trace_rtc_abused to false, otherwise above
tools might not work as expected.

Originally-from: Thomas Gleixner <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Xunlei Pang <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Len Brown <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Richard Cochran <[email protected]>
Acked-by: Pavel Machek <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Signed-off-by: Chen Yu <[email protected]>
[jstultz: Fixed up pr_warn formating, and implemented suggestions
from Ingo]
Signed-off-by: John Stultz <[email protected]>
---
v2: Added suggestions from Ingo
---
arch/x86/kernel/rtc.c | 9 +++++++++
drivers/base/power/trace.c | 26 ++++++++++++++++++++++++++
drivers/rtc/rtc-cmos.c | 7 +++++++
include/linux/mc146818rtc.h | 1 +
include/linux/pm-trace.h | 9 ++++++++-
5 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 79c6311c..3282a88 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -64,6 +64,15 @@ void mach_get_cmos_time(struct timespec *now)
unsigned int status, year, mon, day, hour, min, sec, century = 0;
unsigned long flags;

+ /*
+ * If pm_trace abused the RTC as storage set the timespec to 0
+ * which tells the caller that this RTC value is bogus.
+ */
+ if (!pm_trace_rtc_valid()) {
+ now->tv_sec = now->tv_nsec = 0;
+ return;
+ }
+
spin_lock_irqsave(&rtc_lock, flags);

/*
diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c
index efec10b..15563c4 100644
--- a/drivers/base/power/trace.c
+++ b/drivers/base/power/trace.c
@@ -10,6 +10,7 @@
#include <linux/pm-trace.h>
#include <linux/export.h>
#include <linux/rtc.h>
+#include <linux/suspend.h>

#include <linux/mc146818rtc.h>

@@ -74,6 +75,9 @@

#define DEVSEED (7919)

+bool pm_trace_rtc_abused __read_mostly;
+EXPORT_SYMBOL(pm_trace_rtc_abused);
+
static unsigned int dev_hash_value;

static int set_magic_time(unsigned int user, unsigned int file, unsigned int device)
@@ -104,6 +108,7 @@ static int set_magic_time(unsigned int user, unsigned int file, unsigned int dev
time.tm_min = (n % 20) * 3;
n /= 20;
mc146818_set_time(&time);
+ pm_trace_rtc_abused = true;
return n ? -1 : 0;
}

@@ -238,10 +243,31 @@ int show_trace_dev_match(char *buf, size_t size)
device_pm_unlock();
return ret;
}
+static int pm_trace_notify(struct notifier_block *nb,
+ unsigned long mode, void *_unused)
+{
+ switch (mode) {
+ case PM_POST_HIBERNATION:
+ case PM_POST_SUSPEND:
+ if (pm_trace_rtc_abused) {
+ pm_trace_rtc_abused = false;
+ pr_warn("Possible incorrect RTC due to pm_trace, please use 'ntpdate' or 'rdate' to reset.\n");
+ }
+ break;
+ default:
+ break;
+ }
+ return 0;
+}
+
+static struct notifier_block pm_trace_nb = {
+ .notifier_call = pm_trace_notify,
+};

static int early_resume_init(void)
{
hash_value_early_read = read_magic_time();
+ register_pm_notifier(&pm_trace_nb);
return 0;
}

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index dd3d598..9cf06b7 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -191,6 +191,13 @@ static inline void cmos_write_bank2(unsigned char val, unsigned char addr)

static int cmos_read_time(struct device *dev, struct rtc_time *t)
{
+ /*
+ * If pm_trace abused the RTC for storage tell the caller that it is
+ * unusable.
+ */
+ if (!pm_trace_rtc_valid())
+ return -EIO;
+
/* REVISIT: if the clock has a "century" register, use
* that instead of the heuristic in mc146818_get_time().
* That'll make Y3K compatility (year > 2070) easy!
diff --git a/include/linux/mc146818rtc.h b/include/linux/mc146818rtc.h
index a585b4b..0661af1 100644
--- a/include/linux/mc146818rtc.h
+++ b/include/linux/mc146818rtc.h
@@ -16,6 +16,7 @@
#include <asm/mc146818rtc.h> /* register access macros */
#include <linux/bcd.h>
#include <linux/delay.h>
+#include <linux/pm-trace.h>

#ifdef __KERNEL__
#include <linux/spinlock.h> /* spinlock_t */
diff --git a/include/linux/pm-trace.h b/include/linux/pm-trace.h
index ecbde7a..7b78793 100644
--- a/include/linux/pm-trace.h
+++ b/include/linux/pm-trace.h
@@ -1,11 +1,17 @@
#ifndef PM_TRACE_H
#define PM_TRACE_H

+#include <linux/types.h>
#ifdef CONFIG_PM_TRACE
#include <asm/pm-trace.h>
-#include <linux/types.h>

extern int pm_trace_enabled;
+extern bool pm_trace_rtc_abused;
+
+static inline bool pm_trace_rtc_valid(void)
+{
+ return !pm_trace_rtc_abused;
+}

static inline int pm_trace_is_enabled(void)
{
@@ -24,6 +30,7 @@ extern int show_trace_dev_match(char *buf, size_t size);

#else

+static inline bool pm_trace_rtc_valid(void) { return true; }
static inline int pm_trace_is_enabled(void) { return 0; }

#define TRACE_DEVICE(dev) do { } while (0)
--
2.7.4

2016-11-28 22:36:00

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Subject: [PATCH 3/7] timekeeping: clocksource_cyc2ns: Document intended range limitation

From: Chris Metcalf <[email protected]>

The "cycles" argument should not be an absolute clocksource cycle
value, as the implementation's arithmetic will overflow relatively
easily with wide (64 bit) clocksource counters.

For performance, the implementation is simple and fast, since the
function is intended for only relatively small delta values of
clocksource cycles.

Cc: Richard Cochran <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Chris Metcalf <[email protected]>
[jstultz: Fixed up to merge against HEAD & commit message tweaks,
also included rewording suggestion by Ingo]
Signed-off-by: John Stultz <[email protected]>
---
v2: Reworded comments as suggested by Ingo
---
include/linux/clocksource.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 0839818..65602d3 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -169,7 +169,10 @@ static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
* @mult: cycle to nanosecond multiplier
* @shift: cycle to nanosecond divisor (power of two)
*
- * Converts cycles to nanoseconds, using the given mult and shift.
+ * Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
+ * The code is optimized for performance and is not intended to work
+ * with absolute clocksource cycles (as those will easily overflow),
+ * but is only intended to be used with relative (delta) clocksource cycles.
*
* XXX - This could use some mult_lxl_ll() asm optimization
*/
--
2.7.4

2016-11-28 22:36:10

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Subject: [PATCH 4/7] time: alarmtimer: Add the tracepoints for alarmtimer

From: Baolin Wang <[email protected]>

For system debugging, we sometimes want to know who sets one
alarm timer, the time of the timer, when the timer started and
fired and so on. Thus adding tracepoints can help us trace the
alarmtimer information.

For example, when we debug the system supend/resume, if the
system is always resumed by RTC alarm, we can find out which
process set the alarm timer to resume system by below trace log:

......

Binder:3292_2-3304 [000] d..2 149.981123: alarmtimer_cancel:
alarmtimer:ffffffc1319a7800 type:REALTIME
expires:1325463120000000000 now:1325376810370370245

Binder:3292_2-3304 [000] d..2 149.981136: alarmtimer_start:
alarmtimer:ffffffc1319a7800 type:REALTIME
expires:1325376840000000000 now:1325376810370384591

Binder:3292_9-3953 [000] d..2 150.212991: alarmtimer_cancel:
alarmtimer:ffffffc1319a5a00 type:BOOTTIME
expires:179552000000 now:150154008122

Binder:3292_9-3953 [000] d..2 150.213006: alarmtimer_start:
alarmtimer:ffffffc1319a5a00 type:BOOTTIME
expires:179551000000 now:150154025622

......

system_server-3000 [002] ...1 162.701940: alarmtimer_suspend:
alarmtimer type:REALTIME expires:1325376839802714584

......

>From the trace log, we can find out the 'Binder:3292_2' process
set one alarm timer which resumes the system.

Cc: Thomas Gleixner <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Steven Rostedt <[email protected]>
Signed-off-by: Baolin Wang <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Signed-off-by: John Stultz <[email protected]>
---
Changes since v4:
- Initialize 'type' to -1 and rename it in alarmtimer_suspend().
- Fix typo in subject line.

Changes since v3:
- Remove the "ALARM_" prefix in the string.
- Add the ACK by Steven Rostedt.

Changes since v2:
- Save time as s64 type.
- Remove 'process_name' parameter and add 'now' parameter.
- Rename the trace event name.
- Remove restart trace event.
- Other optimization.
---
include/trace/events/alarmtimer.h | 92 +++++++++++++++++++++++++++++++++++++++
kernel/time/alarmtimer.c | 16 ++++++-
2 files changed, 106 insertions(+), 2 deletions(-)
create mode 100644 include/trace/events/alarmtimer.h

diff --git a/include/trace/events/alarmtimer.h b/include/trace/events/alarmtimer.h
new file mode 100644
index 0000000..61ea556
--- /dev/null
+++ b/include/trace/events/alarmtimer.h
@@ -0,0 +1,92 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM alarmtimer
+
+#if !defined(_TRACE_ALARMTIMER_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_ALARMTIMER_H
+
+#include <linux/alarmtimer.h>
+#include <linux/rtc.h>
+#include <linux/tracepoint.h>
+
+TRACE_DEFINE_ENUM(ALARM_REALTIME);
+TRACE_DEFINE_ENUM(ALARM_BOOTTIME);
+
+#define show_alarm_type(type) __print_flags(type, " | ", \
+ { 1 << ALARM_REALTIME, "REALTIME" }, \
+ { 1 << ALARM_BOOTTIME, "BOOTTIME" })
+
+TRACE_EVENT(alarmtimer_suspend,
+
+ TP_PROTO(ktime_t expires, int flag),
+
+ TP_ARGS(expires, flag),
+
+ TP_STRUCT__entry(
+ __field(s64, expires)
+ __field(unsigned char, alarm_type)
+ ),
+
+ TP_fast_assign(
+ __entry->expires = expires.tv64;
+ __entry->alarm_type = flag;
+ ),
+
+ TP_printk("alarmtimer type:%s expires:%llu",
+ show_alarm_type((1 << __entry->alarm_type)),
+ __entry->expires
+ )
+);
+
+DECLARE_EVENT_CLASS(alarm_class,
+
+ TP_PROTO(struct alarm *alarm, ktime_t now),
+
+ TP_ARGS(alarm, now),
+
+ TP_STRUCT__entry(
+ __field(void *, alarm)
+ __field(unsigned char, alarm_type)
+ __field(s64, expires)
+ __field(s64, now)
+ ),
+
+ TP_fast_assign(
+ __entry->alarm = alarm;
+ __entry->alarm_type = alarm->type;
+ __entry->expires = alarm->node.expires.tv64;
+ __entry->now = now.tv64;
+ ),
+
+ TP_printk("alarmtimer:%p type:%s expires:%llu now:%llu",
+ __entry->alarm,
+ show_alarm_type((1 << __entry->alarm_type)),
+ __entry->expires,
+ __entry->now
+ )
+);
+
+DEFINE_EVENT(alarm_class, alarmtimer_fired,
+
+ TP_PROTO(struct alarm *alarm, ktime_t now),
+
+ TP_ARGS(alarm, now)
+);
+
+DEFINE_EVENT(alarm_class, alarmtimer_start,
+
+ TP_PROTO(struct alarm *alarm, ktime_t now),
+
+ TP_ARGS(alarm, now)
+);
+
+DEFINE_EVENT(alarm_class, alarmtimer_cancel,
+
+ TP_PROTO(struct alarm *alarm, ktime_t now),
+
+ TP_ARGS(alarm, now)
+);
+
+#endif /* _TRACE_ALARMTIMER_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 12dd190..4590f23 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -26,6 +26,9 @@
#include <linux/workqueue.h>
#include <linux/freezer.h>

+#define CREATE_TRACE_POINTS
+#include <trace/events/alarmtimer.h>
+
/**
* struct alarm_base - Alarm timer bases
* @lock: Lock for syncrhonized access to the base
@@ -194,6 +197,7 @@ static enum hrtimer_restart alarmtimer_fired(struct hrtimer *timer)
}
spin_unlock_irqrestore(&base->lock, flags);

+ trace_alarmtimer_fired(alarm, base->gettime());
return ret;

}
@@ -222,7 +226,7 @@ static int alarmtimer_suspend(struct device *dev)
ktime_t min, now;
unsigned long flags;
struct rtc_device *rtc;
- int i;
+ int i, min_type = -1;
int ret;

spin_lock_irqsave(&freezer_delta_lock, flags);
@@ -247,8 +251,10 @@ static int alarmtimer_suspend(struct device *dev)
if (!next)
continue;
delta = ktime_sub(next->expires, base->gettime());
- if (!min.tv64 || (delta.tv64 < min.tv64))
+ if (!min.tv64 || (delta.tv64 < min.tv64)) {
min = delta;
+ min_type = i;
+ }
}
if (min.tv64 == 0)
return 0;
@@ -264,6 +270,8 @@ static int alarmtimer_suspend(struct device *dev)
now = rtc_tm_to_ktime(tm);
now = ktime_add(now, min);

+ trace_alarmtimer_suspend(now, min_type);
+
/* Set alarm, if in the past reject suspend briefly to handle */
ret = rtc_timer_start(rtc, &rtctimer, now, ktime_set(0, 0));
if (ret < 0)
@@ -342,6 +350,8 @@ void alarm_start(struct alarm *alarm, ktime_t start)
alarmtimer_enqueue(base, alarm);
hrtimer_start(&alarm->timer, alarm->node.expires, HRTIMER_MODE_ABS);
spin_unlock_irqrestore(&base->lock, flags);
+
+ trace_alarmtimer_start(alarm, base->gettime());
}
EXPORT_SYMBOL_GPL(alarm_start);

@@ -390,6 +400,8 @@ int alarm_try_to_cancel(struct alarm *alarm)
if (ret >= 0)
alarmtimer_dequeue(base, alarm);
spin_unlock_irqrestore(&base->lock, flags);
+
+ trace_alarmtimer_cancel(alarm, base->gettime());
return ret;
}
EXPORT_SYMBOL_GPL(alarm_try_to_cancel);
--
2.7.4

2016-11-28 22:36:31

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Subject: [PATCH 6/7] trace: Add an option for boot clock as trace clock

From: Joel Fernandes <[email protected]>

Unlike monotonic clock, boot clock as a trace clock will account for
time spent in suspend useful for tracing suspend/resume. This uses
earlier introduced infrastructure for using the fast boot clock.

Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Signed-off-by: Joel Fernandes <[email protected]>
Signed-off-by: John Stultz <[email protected]>
---
kernel/trace/trace.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8696ce6..f7b64db 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1125,6 +1125,7 @@ static struct {
{ trace_clock, "perf", 1 },
{ ktime_get_mono_fast_ns, "mono", 1 },
{ ktime_get_raw_fast_ns, "mono_raw", 1 },
+ { ktime_get_boot_fast_ns, "boot", 1 },
ARCH_TRACE_CLOCKS
};

--
2.7.4

2016-11-28 22:36:19

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Subject: [PATCH 5/7] timekeeping: Add a fast and NMI safe boot clock

From: Joel Fernandes <[email protected]>

This boot clock can be used as a tracing clock and will account for
suspend time.

To keep it NMI safe since we're accessing from tracing, we're not using a
separate timekeeper with updates to monotonic clock and boot offset
protected with seqlocks. This has the following minor side effects:

(1) Its possible that a timestamp be taken after the boot offset is updated
but before the timekeeper is updated. If this happens, the new boot offset
is added to the old timekeeping making the clock appear to update slightly
earlier:
CPU 0 CPU 1
timekeeping_inject_sleeptime64()
__timekeeping_inject_sleeptime(tk, delta);
timestamp();
timekeeping_update(tk, TK_CLEAR_NTP...);

(2) On 32-bit systems, the 64-bit boot offset (tk->offs_boot) may be
partially updated. Since the tk->offs_boot update is a rare event, this
should be a rare occurrence which postprocessing should be able to handle.

Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Signed-off-by: Joel Fernandes <[email protected]>
Signed-off-by: John Stultz <[email protected]>
---
include/linux/timekeeping.h | 1 +
kernel/time/timekeeping.c | 29 +++++++++++++++++++++++++++++
2 files changed, 30 insertions(+)

diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 09168c5..361f8bf 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -249,6 +249,7 @@ static inline u64 ktime_get_raw_ns(void)

extern u64 ktime_get_mono_fast_ns(void);
extern u64 ktime_get_raw_fast_ns(void);
+extern u64 ktime_get_boot_fast_ns(void);

/*
* Timespec interfaces utilizing the ktime based ones
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 37dec7e..b2286e9 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -425,6 +425,35 @@ u64 ktime_get_raw_fast_ns(void)
}
EXPORT_SYMBOL_GPL(ktime_get_raw_fast_ns);

+/**
+ * ktime_get_boot_fast_ns - NMI safe and fast access to boot clock.
+ *
+ * To keep it NMI safe since we're accessing from tracing, we're not using a
+ * separate timekeeper with updates to monotonic clock and boot offset
+ * protected with seqlocks. This has the following minor side effects:
+ *
+ * (1) Its possible that a timestamp be taken after the boot offset is updated
+ * but before the timekeeper is updated. If this happens, the new boot offset
+ * is added to the old timekeeping making the clock appear to update slightly
+ * earlier:
+ * CPU 0 CPU 1
+ * timekeeping_inject_sleeptime64()
+ * __timekeeping_inject_sleeptime(tk, delta);
+ * timestamp();
+ * timekeeping_update(tk, TK_CLEAR_NTP...);
+ *
+ * (2) On 32-bit systems, the 64-bit boot offset (tk->offs_boot) may be
+ * partially updated. Since the tk->offs_boot update is a rare event, this
+ * should be a rare occurrence which postprocessing should be able to handle.
+ */
+u64 notrace ktime_get_boot_fast_ns(void)
+{
+ struct timekeeper *tk = &tk_core.timekeeper;
+
+ return (ktime_get_mono_fast_ns() + ktime_to_ns(tk->offs_boot));
+}
+EXPORT_SYMBOL_GPL(ktime_get_boot_fast_ns);
+
/* Suspend-time cycles value for halted fast timekeeper. */
static cycle_t cycles_at_suspend;

--
2.7.4

2016-11-28 22:36:41

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Subject: [PATCH 7/7] trace: Update documentation for mono, mono_raw and boot clock

From: Joel Fernandes <[email protected]>

Documentation was missing for mono and mono_raw, add them and also for
the boot clock introduced in this series.

Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Signed-off-by: Joel Fernandes <[email protected]>
Signed-off-by: John Stultz <[email protected]>
---
Documentation/trace/ftrace.txt | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 185c39f..5180b09 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -362,6 +362,26 @@ of ftrace. Here is a list of some of the key files:
to correlate events across hypervisor/guest if
tb_offset is known.

+ mono: This uses the fast monotonic clock (CLOCK_MONOTONIC)
+ which is monotonic and is subject to NTP rate adjustments.
+
+ mono_raw:
+ This is the raw monotonic clock (CLOCK_MONOTONIC_RAW)
+ which is montonic but is not subject to any rate adjustments
+ and ticks at the same rate as the hardware clocksource.
+
+ boot: This is the boot clock (CLOCK_BOOTTIME) and is based on the
+ fast monotonic clock, but also accounts for time spent in
+ suspend. Since the clock access is designed for use in
+ tracing in the suspend path, some side effects are possible
+ if clock is accessed after the suspend time is accounted before
+ the fast mono clock is updated. In this case, the clock update
+ appears to happen slightly sooner than it normally would have.
+ Also on 32-bit systems, its possible that the 64-bit boot offset
+ sees a partial update. These effects are rare and post
+ processing should be able to handle them. See comments on
+ ktime_get_boot_fast_ns function for more information.
+
To set a clock, simply echo the clock name into this file.

echo global > trace_clock
--
2.7.4

2016-11-28 23:06:46

by Steven Rostedt

[permalink] [raw]

Subject: Re: [PATCH 6/7] trace: Add an option for boot clock as trace clock

On Mon, 28 Nov 2016 14:35:23 -0800
John Stultz <[email protected]> wrote:

> From: Joel Fernandes <[email protected]>
>
> Unlike monotonic clock, boot clock as a trace clock will account for
> time spent in suspend useful for tracing suspend/resume. This uses
> earlier introduced infrastructure for using the fast boot clock.
>

Acked-by: Steven Rostedt <[email protected]>

-- Steve

> Cc: Steven Rostedt <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Richard Cochran <[email protected]>
> Cc: Prarit Bhargava <[email protected]>
> Reviewed-by: Thomas Gleixner <[email protected]>
> Signed-off-by: Joel Fernandes <[email protected]>
> Signed-off-by: John Stultz <[email protected]>
> ---
> kernel/trace/trace.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 8696ce6..f7b64db 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -1125,6 +1125,7 @@ static struct {
> { trace_clock, "perf", 1 },
> { ktime_get_mono_fast_ns, "mono", 1 },
> { ktime_get_raw_fast_ns, "mono_raw", 1 },
> + { ktime_get_boot_fast_ns, "boot", 1 },
> ARCH_TRACE_CLOCKS
> };
>

2016-11-28 23:07:27

by Steven Rostedt

[permalink] [raw]

Subject: Re: [PATCH 7/7] trace: Update documentation for mono, mono_raw and boot clock

On Mon, 28 Nov 2016 14:35:24 -0800
John Stultz <[email protected]> wrote:

> From: Joel Fernandes <[email protected]>
>
> Documentation was missing for mono and mono_raw, add them and also for
> the boot clock introduced in this series.
>
> Cc: Steven Rostedt <[email protected]>

Acked-by: Steven Rostedt <[email protected]>

-- Steve

> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Richard Cochran <[email protected]>
> Cc: Prarit Bhargava <[email protected]>
> Reviewed-by: Thomas Gleixner <[email protected]>
> Signed-off-by: Joel Fernandes <[email protected]>
> Signed-off-by: John Stultz <[email protected]>
> ---

2016-11-29 07:20:09

[permalink] [raw]

Subject: Re: [PATCH 2/7] timekeeping: Ignore the bogus sleep time if pm_trace is enabled

* John Stultz <[email protected]> wrote:

> From: Chen Yu <[email protected]>
>
> Previously we encountered some memory overflow issues due to
> the bogus sleep time brought by inconsistent rtc, which is
> triggered when pm_trace is enabled, and we have fixed it
> in recent kernel. However it's improper in the first place
> to call __timekeeping_inject_sleeptime() in case that pm_trace
> is enabled simply because that "hash" time value will wreckage
> the timekeeping subsystem.

s/

Previously we encountered memory overflow issues due to
bogus sleep time brought by an inconsistent RTC, which is
triggered when pm_trace is enabled, and we have fixed it
in recent kernels. However it's improper in the first place
to call __timekeeping_inject_sleeptime() in case pm_trace
is enabled simply because the "hash" time value will wreckage
the timekeeping subsystem.

Half a dozen typos ...

> This patch is originally written by Thomas, which would bypass
> the bogus rtc interval when pm_trace is enabled.
> Meanwhile, if system succeed to resume back with pm_trace set, the
> users are warned to adjust the bogus rtc either by 'ntpdate' or
> 'rdate', by resetting pm_trace_rtc_abused to false, otherwise above
> tools might not work as expected.

s/

This patch was originally written by Thomas, which would bypass
the bogus RTC interval when pm_trace is enabled.
Meanwhile, if the system succeeds to resume back with pm_trace set,
users are warned to adjust the bogus RTC either by 'ntpdate' or
'rdate', by resetting pm_trace_rtc_abused to false, otherwise above
tools might not work as expected.

> + /*
> + * If pm_trace abused the RTC as storage set the timespec to 0
> + * which tells the caller that this RTC value is bogus.
> + */

s/
/*
* If pm_trace abused the RTC as storage, set the timespec to 0,
* which tells the caller that this RTC value is bogus.
*/

> @@ -74,6 +75,9 @@
>
> #define DEVSEED (7919)
>
> +bool pm_trace_rtc_abused __read_mostly;
> +EXPORT_SYMBOL(pm_trace_rtc_abused);

EXPORT_SYMBOL_GPL()

> +static int pm_trace_notify(struct notifier_block *nb,
> + unsigned long mode, void *_unused)

Please no nonsensical linebreaks in the middle of an argument list.

> +{
> + switch (mode) {
> + case PM_POST_HIBERNATION:
> + case PM_POST_SUSPEND:
> + if (pm_trace_rtc_abused) {
> + pm_trace_rtc_abused = false;
> + pr_warn("Possible incorrect RTC due to pm_trace, please use 'ntpdate' or 'rdate' to reset.\n");

s/to reset./to reset it.

Thanks,

Ingo

2016-11-29 07:24:11

[permalink] [raw]

Subject: Re: [PATCH 4/7] time: alarmtimer: Add the tracepoints for alarmtimer

* John Stultz <[email protected]> wrote:

> From: Baolin Wang <[email protected]>
>
> For system debugging, we sometimes want to know who sets one
> alarm timer, the time of the timer, when the timer started and
> fired and so on. Thus adding tracepoints can help us trace the
> alarmtimer information.

s/one alarm timer/an alarm timer

> For example, when we debug the system supend/resume, if the
> system is always resumed by RTC alarm, we can find out which
> process set the alarm timer to resume system by below trace log:

s/when we debug the system/when we debug system
s/supend/suspend
s/resume system/resume the system
s/by below trace log/by the trace log below

> From the trace log, we can find out the 'Binder:3292_2' process
> set one alarm timer which resumes the system.

s/set one alarm timer/set an alarm timer

> Changes since v4:
> - Initialize 'type' to -1 and rename it in alarmtimer_suspend().
> - Fix typo in subject line.
>
> Changes since v3:
> - Remove the "ALARM_" prefix in the string.
> - Add the ACK by Steven Rostedt.
>
> Changes since v2:
> - Save time as s64 type.
> - Remove 'process_name' parameter and add 'now' parameter.
> - Rename the trace event name.
> - Remove restart trace event.
> - Other optimization.

I find it really sad that a patch that has gone through 4 iterations still has so
many typos and grammar errors in its changelog :-(

Thanks,

Ingo

2016-11-29 07:27:04

[permalink] [raw]

Subject: Re: [PATCH 7/7] trace: Update documentation for mono, mono_raw and boot clock

* John Stultz <[email protected]> wrote:

> + boot: This is the boot clock (CLOCK_BOOTTIME) and is based on the
> + fast monotonic clock, but also accounts for time spent in
> + suspend. Since the clock access is designed for use in
> + tracing in the suspend path, some side effects are possible
> + if clock is accessed after the suspend time is accounted before
> + the fast mono clock is updated. In this case, the clock update
> + appears to happen slightly sooner than it normally would have.
> + Also on 32-bit systems, its possible that the 64-bit boot offset
> + sees a partial update. These effects are rare and post
> + processing should be able to handle them. See comments on
> + ktime_get_boot_fast_ns function for more information.

s/its possible/it's possible
s/comments on ktime_get_boost_fast_ns function/comments in the ktime_get_boost_fast_ns() function

Thanks,

Ingo

2016-11-29 08:23:31

[permalink] [raw]

Subject: Re: [PATCH 4/7] time: alarmtimer: Add the tracepoints for alarmtimer

On 29 November 2016 at 15:23, Ingo Molnar <[email protected]> wrote:
>
> * John Stultz <[email protected]> wrote:
>
>> From: Baolin Wang <[email protected]>
>>
>> For system debugging, we sometimes want to know who sets one
>> alarm timer, the time of the timer, when the timer started and
>> fired and so on. Thus adding tracepoints can help us trace the
>> alarmtimer information.
>
> s/one alarm timer/an alarm timer
>
>> For example, when we debug the system supend/resume, if the
>> system is always resumed by RTC alarm, we can find out which
>> process set the alarm timer to resume system by below trace log:
>
> s/when we debug the system/when we debug system
> s/supend/suspend
> s/resume system/resume the system
> s/by below trace log/by the trace log below
>
>> From the trace log, we can find out the 'Binder:3292_2' process
>> set one alarm timer which resumes the system.
>
> s/set one alarm timer/set an alarm timer
>
>> Changes since v4:
>> - Initialize 'type' to -1 and rename it in alarmtimer_suspend().
>> - Fix typo in subject line.
>>
>> Changes since v3:
>> - Remove the "ALARM_" prefix in the string.
>> - Add the ACK by Steven Rostedt.
>>
>> Changes since v2:
>> - Save time as s64 type.
>> - Remove 'process_name' parameter and add 'now' parameter.
>> - Rename the trace event name.
>> - Remove restart trace event.
>> - Other optimization.
>
> I find it really sad that a patch that has gone through 4 iterations still has so
> many typos and grammar errors in its changelog :-(

Really sorry for these elementary errors, I will fix these errors in
new patch. Sorry for troubles again.

--
Baolin.wang
Best Regards

2016-11-29 09:13:14

[permalink] [raw]

Subject: Re: [PATCH 4/7] time: alarmtimer: Add the tracepoints for alarmtimer

* Baolin Wang <[email protected]> wrote:

> On 29 November 2016 at 15:23, Ingo Molnar <[email protected]> wrote:
> >
> > * John Stultz <[email protected]> wrote:
> >
> >> From: Baolin Wang <[email protected]>
> >>
> >> For system debugging, we sometimes want to know who sets one
> >> alarm timer, the time of the timer, when the timer started and
> >> fired and so on. Thus adding tracepoints can help us trace the
> >> alarmtimer information.
> >
> > s/one alarm timer/an alarm timer
> >
> >> For example, when we debug the system supend/resume, if the
> >> system is always resumed by RTC alarm, we can find out which
> >> process set the alarm timer to resume system by below trace log:
> >
> > s/when we debug the system/when we debug system
> > s/supend/suspend
> > s/resume system/resume the system
> > s/by below trace log/by the trace log below
> >
> >> From the trace log, we can find out the 'Binder:3292_2' process
> >> set one alarm timer which resumes the system.
> >
> > s/set one alarm timer/set an alarm timer
> >
> >> Changes since v4:
> >> - Initialize 'type' to -1 and rename it in alarmtimer_suspend().
> >> - Fix typo in subject line.
> >>
> >> Changes since v3:
> >> - Remove the "ALARM_" prefix in the string.
> >> - Add the ACK by Steven Rostedt.
> >>
> >> Changes since v2:
> >> - Save time as s64 type.
> >> - Remove 'process_name' parameter and add 'now' parameter.
> >> - Rename the trace event name.
> >> - Remove restart trace event.
> >> - Other optimization.
> >
> > I find it really sad that a patch that has gone through 4 iterations still has so
> > many typos and grammar errors in its changelog :-(
>
> Really sorry for these elementary errors, I will fix these errors in
> new patch. Sorry for troubles again.

No problem - the code looks fine to me, so we can fix this when applying the
patches.

Thanks,

Ingo

2016-11-29 09:29:36

by Chen Yu

[permalink] [raw]

Subject: Re: [PATCH 2/7] timekeeping: Ignore the bogus sleep time if pm_trace is enabled

On Tue, Nov 29, 2016 at 08:19:55AM +0100, Ingo Molnar wrote:
>
> * John Stultz <[email protected]> wrote:
>
> > From: Chen Yu <[email protected]>
> >
> > Previously we encountered some memory overflow issues due to
> > the bogus sleep time brought by inconsistent rtc, which is
> > triggered when pm_trace is enabled, and we have fixed it
> > in recent kernel. However it's improper in the first place
> > to call __timekeeping_inject_sleeptime() in case that pm_trace
> > is enabled simply because that "hash" time value will wreckage
> > the timekeeping subsystem.
>
> s/
>
> Previously we encountered memory overflow issues due to
> bogus sleep time brought by an inconsistent RTC, which is
> triggered when pm_trace is enabled, and we have fixed it
> in recent kernels. However it's improper in the first place
> to call __timekeeping_inject_sleeptime() in case pm_trace
> is enabled simply because the "hash" time value will wreckage
> the timekeeping subsystem.
>
> Half a dozen typos ...
>
> > This patch is originally written by Thomas, which would bypass
> > the bogus rtc interval when pm_trace is enabled.
> > Meanwhile, if system succeed to resume back with pm_trace set, the
> > users are warned to adjust the bogus rtc either by 'ntpdate' or
> > 'rdate', by resetting pm_trace_rtc_abused to false, otherwise above
> > tools might not work as expected.
>
> s/
>
> This patch was originally written by Thomas, which would bypass
> the bogus RTC interval when pm_trace is enabled.
> Meanwhile, if the system succeeds to resume back with pm_trace set,
> users are warned to adjust the bogus RTC either by 'ntpdate' or
> 'rdate', by resetting pm_trace_rtc_abused to false, otherwise above
> tools might not work as expected.
>
> > + /*
> > + * If pm_trace abused the RTC as storage set the timespec to 0
> > + * which tells the caller that this RTC value is bogus.
> > + */
>
> s/
> /*
> * If pm_trace abused the RTC as storage, set the timespec to 0,
> * which tells the caller that this RTC value is bogus.
> */
>
> > @@ -74,6 +75,9 @@
> >
> > #define DEVSEED (7919)
> >
> > +bool pm_trace_rtc_abused __read_mostly;
> > +EXPORT_SYMBOL(pm_trace_rtc_abused);
>
> EXPORT_SYMBOL_GPL()
>
> > +static int pm_trace_notify(struct notifier_block *nb,
> > + unsigned long mode, void *_unused)
>
> Please no nonsensical linebreaks in the middle of an argument list.
>
> > +{
> > + switch (mode) {
> > + case PM_POST_HIBERNATION:
> > + case PM_POST_SUSPEND:
> > + if (pm_trace_rtc_abused) {
> > + pm_trace_rtc_abused = false;
> > + pr_warn("Possible incorrect RTC due to pm_trace, please use 'ntpdate' or 'rdate' to reset.\n");
>
>
> s/to reset./to reset it.
>
> Thanks,
>
> Ingo
Thanks Ingo, I've sent out a new versin based on your comments.
Yu

2016-11-29 11:52:36

[permalink] [raw]

Subject: Re: [PATCH 4/7] time: alarmtimer: Add the tracepoints for alarmtimer

On 29 November 2016 at 17:12, Ingo Molnar <[email protected]> wrote:
>
> * Baolin Wang <[email protected]> wrote:
>
>> On 29 November 2016 at 15:23, Ingo Molnar <[email protected]> wrote:
>> >
>> > * John Stultz <[email protected]> wrote:
>> >
>> >> From: Baolin Wang <[email protected]>
>> >>
>> >> For system debugging, we sometimes want to know who sets one
>> >> alarm timer, the time of the timer, when the timer started and
>> >> fired and so on. Thus adding tracepoints can help us trace the
>> >> alarmtimer information.
>> >
>> > s/one alarm timer/an alarm timer
>> >
>> >> For example, when we debug the system supend/resume, if the
>> >> system is always resumed by RTC alarm, we can find out which
>> >> process set the alarm timer to resume system by below trace log:
>> >
>> > s/when we debug the system/when we debug system
>> > s/supend/suspend
>> > s/resume system/resume the system
>> > s/by below trace log/by the trace log below
>> >
>> >> From the trace log, we can find out the 'Binder:3292_2' process
>> >> set one alarm timer which resumes the system.
>> >
>> > s/set one alarm timer/set an alarm timer
>> >
>> >> Changes since v4:
>> >> - Initialize 'type' to -1 and rename it in alarmtimer_suspend().
>> >> - Fix typo in subject line.
>> >>
>> >> Changes since v3:
>> >> - Remove the "ALARM_" prefix in the string.
>> >> - Add the ACK by Steven Rostedt.
>> >>
>> >> Changes since v2:
>> >> - Save time as s64 type.
>> >> - Remove 'process_name' parameter and add 'now' parameter.
>> >> - Rename the trace event name.
>> >> - Remove restart trace event.
>> >> - Other optimization.
>> >
>> > I find it really sad that a patch that has gone through 4 iterations still has so
>> > many typos and grammar errors in its changelog :-(
>>
>> Really sorry for these elementary errors, I will fix these errors in
>> new patch. Sorry for troubles again.
>
> No problem - the code looks fine to me, so we can fix this when applying the
> patches.

Okay, thanks a lot.

--
Baolin.wang
Best Regards

2016-11-29 12:09:28

by Thomas Gleixner

[permalink] [raw]

Subject: Re: [PATCH 4/7] time: alarmtimer: Add the tracepoints for alarmtimer

On Mon, 28 Nov 2016, John Stultz wrote:

> From: Baolin Wang <[email protected]>
>
> For system debugging, we sometimes want to know who sets one
> alarm timer, the time of the timer, when the timer started and
> fired and so on. Thus adding tracepoints can help us trace the
> alarmtimer information.
>
> For example, when we debug the system supend/resume, if the
> system is always resumed by RTC alarm, we can find out which
> process set the alarm timer to resume system by below trace log:
>
> ......
>
> Binder:3292_2-3304 [000] d..2 149.981123: alarmtimer_cancel:
> alarmtimer:ffffffc1319a7800 type:REALTIME
> expires:1325463120000000000 now:1325376810370370245
>
> Binder:3292_2-3304 [000] d..2 149.981136: alarmtimer_start:
> alarmtimer:ffffffc1319a7800 type:REALTIME
> expires:1325376840000000000 now:1325376810370384591
>
> Binder:3292_9-3953 [000] d..2 150.212991: alarmtimer_cancel:
> alarmtimer:ffffffc1319a5a00 type:BOOTTIME
> expires:179552000000 now:150154008122
>
> Binder:3292_9-3953 [000] d..2 150.213006: alarmtimer_start:
> alarmtimer:ffffffc1319a5a00 type:BOOTTIME
> expires:179551000000 now:150154025622
>
> ......
>
> system_server-3000 [002] ...1 162.701940: alarmtimer_suspend:
> alarmtimer type:REALTIME expires:1325376839802714584
> ......
>
> >From the trace log, we can find out the 'Binder:3292_2' process
> set one alarm timer which resumes the system.

To be honest. I have a hard time to figure out that Binder:3292_2 armed the
timer.

suspend: expires:1325376839802714584
Binder start: expires:1325376840000000000

That does not make any sense at all. And this is a result of how that
suspend tracepoint got glued into alarmtimer_suspend():

> @@ -222,7 +226,7 @@ static int alarmtimer_suspend(struct device *dev)
> ktime_t min, now;
> unsigned long flags;
> struct rtc_device *rtc;
> - int i;
> + int i, min_type = -1;
> int ret;
>
> spin_lock_irqsave(&freezer_delta_lock, flags);
> @@ -247,8 +251,10 @@ static int alarmtimer_suspend(struct device *dev)
> if (!next)
> continue;
> delta = ktime_sub(next->expires, base->gettime());
> - if (!min.tv64 || (delta.tv64 < min.tv64))
> + if (!min.tv64 || (delta.tv64 < min.tv64)) {
> min = delta;
> + min_type = i;
> + }
> }
> if (min.tv64 == 0)
> return 0;
> @@ -264,6 +270,8 @@ static int alarmtimer_suspend(struct device *dev)
> now = rtc_tm_to_ktime(tm);
> now = ktime_add(now, min);
>
> + trace_alarmtimer_suspend(now, min_type);

So first we calculate the relative expiry time from now, add it to the RTC
and then print out the sum. That's utter crap especially if the first
expiring timer is based on CLOCK_BOOTTIME. Even with CLOCK_REALTIME you do
not get matching expiry time as you can see above.

Now looking at the other possibility to arm the resume time: freezer_delta.
That's even more undebuggable because the freezer time is stored as
relative timeout without any type information. How is one supposed to map
that back to an alarm timer start?

Find below a revamped version (untested) of this including a proper written
changelog.

Thanks,

tglx

8<--------------
Subject: time/alarmtimer: Add tracepoints for alarmtimer
From: John Stultz <[email protected]>
Date: Mon, 28 Nov 2016 14:35:21 -0800

From: Baolin Wang <[email protected]>

Alarm timers are one of the mechanisms to wake up a system from suspend,
but there exist no tracepoints to analyse which process/thread armed an
alarmtimer.

Add tracepoints for start/cancel/expire of individual alarm timers and one
for tracing the suspend time decision when to resume the system.

The following trace excerpt illustrates the new mechanism:

Binder:3292_2-3304 [000] d..2 149.981123: alarmtimer_cancel:
alarmtimer:ffffffc1319a7800 type:REALTIME
expires:1325463120000000000 now:1325376810370370245

Binder:3292_2-3304 [000] d..2 149.981136: alarmtimer_start:
alarmtimer:ffffffc1319a7800 type:REALTIME
expires:1325376840000000000 now:1325376810370384591

Binder:3292_9-3953 [000] d..2 150.212991: alarmtimer_cancel:
alarmtimer:ffffffc1319a5a00 type:BOOTTIME
expires:179552000000 now:150154008122

Binder:3292_9-3953 [000] d..2 150.213006: alarmtimer_start:
alarmtimer:ffffffc1319a5a00 type:BOOTTIME
expires:179551000000 now:150154025622

system_server-3000 [002] ...1 162.701940: alarmtimer_suspend:
alarmtimer type:REALTIME expires:1325376840000000000

The wakeup time which is selected at suspend time allows to map it back to
the task arming the timer: Binder:3292_2.

[ tglx: Store real alarm timer expiry time instead of some useless RTC
relative information, add proper type information for wakeups which
are handled via the clock_nanosleep/freezer and massage the
changelog. ]

Signed-off-by: Baolin Wang <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Richard Cochran <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

---
Changes since v4:
- Initialize 'type' to -1 and rename it in alarmtimer_suspend().
- Fix typo in subject line.

Changes since v3:
- Remove the "ALARM_" prefix in the string.
- Add the ACK by Steven Rostedt.

Changes since v2:
- Save time as s64 type.
- Remove 'process_name' parameter and add 'now' parameter.
- Rename the trace event name.
- Remove restart trace event.
- Other optimization.
---
include/linux/alarmtimer.h | 5 +
include/trace/events/alarmtimer.h | 96 ++++++++++++++++++++++++++++++++++++++
kernel/time/alarmtimer.c | 53 +++++++++++++++++---
3 files changed, 144 insertions(+), 10 deletions(-)
create mode 100644 include/trace/events/alarmtimer.h

--- a/include/linux/alarmtimer.h
+++ b/include/linux/alarmtimer.h
@@ -10,7 +10,12 @@ enum alarmtimer_type {
ALARM_REALTIME,
ALARM_BOOTTIME,

+ /* Supported types end here */
ALARM_NUMTYPE,
+
+ /* Used for tracing information. No usable types. */
+ ALARM_REALTIME_FREEZER,
+ ALARM_BOOTTIME_FREEZER,
};

enum alarmtimer_restart {
--- /dev/null
+++ b/include/trace/events/alarmtimer.h
@@ -0,0 +1,96 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM alarmtimer
+
+#if !defined(_TRACE_ALARMTIMER_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_ALARMTIMER_H
+
+#include <linux/alarmtimer.h>
+#include <linux/rtc.h>
+#include <linux/tracepoint.h>
+
+TRACE_DEFINE_ENUM(ALARM_REALTIME);
+TRACE_DEFINE_ENUM(ALARM_BOOTTIME);
+TRACE_DEFINE_ENUM(ALARM_REALTIME_FREEZER);
+TRACE_DEFINE_ENUM(ALARM_BOOTTIME_FREEZER);
+
+#define show_alarm_type(type) __print_flags(type, " | ", \
+ { 1 << ALARM_REALTIME, "REALTIME" }, \
+ { 1 << ALARM_BOOTTIME, "BOOTTIME" }, \
+ { 1 << ALARM_REALTIME_FREEZER, "REALTIME Freezer" }, \
+ { 1 << ALARM_BOOTTIME_FREEZER, "BOOTTIME Freezer" })
+
+TRACE_EVENT(alarmtimer_suspend,
+
+ TP_PROTO(ktime_t expires, int flag),
+
+ TP_ARGS(expires, flag),
+
+ TP_STRUCT__entry(
+ __field(s64, expires)
+ __field(unsigned char, alarm_type)
+ ),
+
+ TP_fast_assign(
+ __entry->expires = expires.tv64;
+ __entry->alarm_type = flag;
+ ),
+
+ TP_printk("alarmtimer type:%s expires:%llu",
+ show_alarm_type((1 << __entry->alarm_type)),
+ __entry->expires
+ )
+);
+
+DECLARE_EVENT_CLASS(alarm_class,
+
+ TP_PROTO(struct alarm *alarm, ktime_t now),
+
+ TP_ARGS(alarm, now),
+
+ TP_STRUCT__entry(
+ __field(void *, alarm)
+ __field(unsigned char, alarm_type)
+ __field(s64, expires)
+ __field(s64, now)
+ ),
+
+ TP_fast_assign(
+ __entry->alarm = alarm;
+ __entry->alarm_type = alarm->type;
+ __entry->expires = alarm->node.expires.tv64;
+ __entry->now = now.tv64;
+ ),
+
+ TP_printk("alarmtimer:%p type:%s expires:%llu now:%llu",
+ __entry->alarm,
+ show_alarm_type((1 << __entry->alarm_type)),
+ __entry->expires,
+ __entry->now
+ )
+);
+
+DEFINE_EVENT(alarm_class, alarmtimer_fired,
+
+ TP_PROTO(struct alarm *alarm, ktime_t now),
+
+ TP_ARGS(alarm, now)
+);
+
+DEFINE_EVENT(alarm_class, alarmtimer_start,
+
+ TP_PROTO(struct alarm *alarm, ktime_t now),
+
+ TP_ARGS(alarm, now)
+);
+
+DEFINE_EVENT(alarm_class, alarmtimer_cancel,
+
+ TP_PROTO(struct alarm *alarm, ktime_t now),
+
+ TP_ARGS(alarm, now)
+);
+
+#endif /* _TRACE_ALARMTIMER_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -26,6 +26,9 @@
#include <linux/workqueue.h>
#include <linux/freezer.h>

+#define CREATE_TRACE_POINTS
+#include <trace/events/alarmtimer.h>
+
/**
* struct alarm_base - Alarm timer bases
* @lock: Lock for syncrhonized access to the base
@@ -40,7 +43,9 @@ static struct alarm_base {
clockid_t base_clockid;
} alarm_bases[ALARM_NUMTYPE];

-/* freezer delta & lock used to handle clock_nanosleep triggered wakeups */
+/* freezer information to handle clock_nanosleep triggered wakeups */
+static enum alarmtimer_type freezer_alarmtype;
+static ktime_t freezer_expires;
static ktime_t freezer_delta;
static DEFINE_SPINLOCK(freezer_delta_lock);

@@ -194,6 +199,7 @@ static enum hrtimer_restart alarmtimer_f
}
spin_unlock_irqrestore(&base->lock, flags);

+ trace_alarmtimer_fired(alarm, base->gettime());
return ret;

}
@@ -218,15 +224,16 @@ EXPORT_SYMBOL_GPL(alarm_expires_remainin
*/
static int alarmtimer_suspend(struct device *dev)
{
- struct rtc_time tm;
- ktime_t min, now;
- unsigned long flags;
+ ktime_t min, now, expires;
+ int i, ret, type;
struct rtc_device *rtc;
- int i;
- int ret;
+ unsigned long flags;
+ struct rtc_time tm;

spin_lock_irqsave(&freezer_delta_lock, flags);
min = freezer_delta;
+ expires = freezer_expires;
+ type = freezer_alarmtype;
freezer_delta = ktime_set(0, 0);
spin_unlock_irqrestore(&freezer_delta_lock, flags);

@@ -247,8 +254,11 @@ static int alarmtimer_suspend(struct dev
if (!next)
continue;
delta = ktime_sub(next->expires, base->gettime());
- if (!min.tv64 || (delta.tv64 < min.tv64))
+ if (!min.tv64 || (delta.tv64 < min.tv64)) {
+ expires = next->expires;
min = delta;
+ type = i;
+ }
}
if (min.tv64 == 0)
return 0;
@@ -258,6 +268,8 @@ static int alarmtimer_suspend(struct dev
return -EBUSY;
}

+ trace_alarmtimer_suspend(expires, type);
+
/* Setup an rtc timer to fire that far in the future */
rtc_timer_cancel(rtc, &rtctimer);
rtc_read_time(rtc, &tm);
@@ -295,15 +307,32 @@ static int alarmtimer_resume(struct devi

static void alarmtimer_freezerset(ktime_t absexp, enum alarmtimer_type type)
{
- ktime_t delta;
+ struct alarm_base *base;
unsigned long flags;
- struct alarm_base *base = &alarm_bases[type];
+ ktime_t delta;
+
+ switch(type) {
+ case ALARM_REALTIME:
+ base = &alarm_bases[ALARM_REALTIME];
+ type = ALARM_REALTIME_FREEZER;
+ break;
+ case ALARM_BOOTTIME:
+ base = &alarm_bases[ALARM_BOOTTIME];
+ type = ALARM_BOOTTIME_FREEZER;
+ break;
+ default:
+ WARN_ONCE(1, "Invalid alarm type: %d\n", type);
+ return;
+ }

delta = ktime_sub(absexp, base->gettime());

spin_lock_irqsave(&freezer_delta_lock, flags);
- if (!freezer_delta.tv64 || (delta.tv64 < freezer_delta.tv64))
+ if (!freezer_delta.tv64 || (delta.tv64 < freezer_delta.tv64)) {
freezer_delta = delta;
+ freezer_expires = absexp;
+ freezer_alarmtype = type;
+ }
spin_unlock_irqrestore(&freezer_delta_lock, flags);
}

@@ -342,6 +371,8 @@ void alarm_start(struct alarm *alarm, kt
alarmtimer_enqueue(base, alarm);
hrtimer_start(&alarm->timer, alarm->node.expires, HRTIMER_MODE_ABS);
spin_unlock_irqrestore(&base->lock, flags);
+
+ trace_alarmtimer_start(alarm, base->gettime());
}
EXPORT_SYMBOL_GPL(alarm_start);

@@ -390,6 +421,8 @@ int alarm_try_to_cancel(struct alarm *al
if (ret >= 0)
alarmtimer_dequeue(base, alarm);
spin_unlock_irqrestore(&base->lock, flags);
+
+ trace_alarmtimer_cancel(alarm, base->gettime());
return ret;
}
EXPORT_SYMBOL_GPL(alarm_try_to_cancel);

2016-11-29 16:10:39

by Joel Fernandes

[permalink] [raw]

Subject: Re: [PATCH 7/7] trace: Update documentation for mono, mono_raw and boot clock

On Mon, Nov 28, 2016 at 11:26 PM, Ingo Molnar <[email protected]> wrote:
>
> * John Stultz <[email protected]> wrote:
>
>> + boot: This is the boot clock (CLOCK_BOOTTIME) and is based on the
>> + fast monotonic clock, but also accounts for time spent in
>> + suspend. Since the clock access is designed for use in
>> + tracing in the suspend path, some side effects are possible
>> + if clock is accessed after the suspend time is accounted before
>> + the fast mono clock is updated. In this case, the clock update
>> + appears to happen slightly sooner than it normally would have.
>> + Also on 32-bit systems, its possible that the 64-bit boot offset
>> + sees a partial update. These effects are rare and post
>> + processing should be able to handle them. See comments on
>> + ktime_get_boot_fast_ns function for more information.
>
> s/its possible/it's possible
> s/comments on ktime_get_boost_fast_ns function/comments in the ktime_get_boost_fast_ns() function
>

Thanks, I'll fix these up and repost.

Regards,
Joel

> Thanks,
>
> Ingo

2016-11-29 16:14:06

by Thomas Gleixner

[permalink] [raw]

Subject: Re: [PATCH 7/7] trace: Update documentation for mono, mono_raw and boot clock

On Tue, 29 Nov 2016, Joel Fernandes wrote:
> On Mon, Nov 28, 2016 at 11:26 PM, Ingo Molnar <[email protected]> wrote:
> >
> > * John Stultz <[email protected]> wrote:
> >
> >> + boot: This is the boot clock (CLOCK_BOOTTIME) and is based on the
> >> + fast monotonic clock, but also accounts for time spent in
> >> + suspend. Since the clock access is designed for use in
> >> + tracing in the suspend path, some side effects are possible
> >> + if clock is accessed after the suspend time is accounted before
> >> + the fast mono clock is updated. In this case, the clock update
> >> + appears to happen slightly sooner than it normally would have.
> >> + Also on 32-bit systems, its possible that the 64-bit boot offset
> >> + sees a partial update. These effects are rare and post
> >> + processing should be able to handle them. See comments on
> >> + ktime_get_boot_fast_ns function for more information.
> >
> > s/its possible/it's possible
> > s/comments on ktime_get_boost_fast_ns function/comments in the ktime_get_boost_fast_ns() function
> >
>
> Thanks, I'll fix these up and repost.

Don't bother. I have fixed it up locally already.

Thanks,

tglx

2016-11-29 17:10:41

[permalink] [raw]

Subject: [tip:timers/core] selftests/timers: Fix spelling mistake "Asyncrhonous" -> "Asynchronous"

Commit-ID: a109ded26c8c85c17872c8f61e8979c5d650004d
Gitweb: http://git.kernel.org/tip/a109ded26c8c85c17872c8f61e8979c5d650004d
Author: Colin Ian King <[email protected]>
AuthorDate: Mon, 28 Nov 2016 14:35:18 -0800
Committer: Thomas Gleixner <[email protected]>
CommitDate: Tue, 29 Nov 2016 18:02:57 +0100

selftests/timers: Fix spelling mistake "Asyncrhonous" -> "Asynchronous"

Trivial fix to spelling mistake

Signed-off-by: Colin Ian King <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Shuah Khan <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

---
tools/testing/selftests/timers/skew_consistency.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/timers/skew_consistency.c b/tools/testing/selftests/timers/skew_consistency.c
index 5562f84..2a996e0 100644
--- a/tools/testing/selftests/timers/skew_consistency.c
+++ b/tools/testing/selftests/timers/skew_consistency.c
@@ -57,7 +57,7 @@ int main(int argv, char **argc)
pid_t pid;

- printf("Running Asyncrhonous Frequency Changing Tests...\n");
+ printf("Running Asynchronous Frequency Changing Tests...\n");

pid = fork();
if (!pid)

2016-11-29 17:11:43

[permalink] [raw]

Subject: [tip:timers/core] timekeeping: Ignore the bogus sleep time if pm_trace is enabled

Commit-ID: ba58d1020a54933c6b087a3107661c8513556cb8
Gitweb: http://git.kernel.org/tip/ba58d1020a54933c6b087a3107661c8513556cb8
Author: Chen Yu <[email protected]>
AuthorDate: Mon, 28 Nov 2016 14:35:19 -0800
Committer: Thomas Gleixner <[email protected]>
CommitDate: Tue, 29 Nov 2016 18:02:58 +0100

timekeeping: Ignore the bogus sleep time if pm_trace is enabled

Power management suspend/resume tracing (ab)uses the RTC to store
suspend/resume information persistently. As a consequence the RTC value is
clobbered when timekeeping is resumed and tries to inject the sleep time.

Commit a4f8f6667f09 ("timekeeping: Cap array access in timekeeping_debug")
plugged a out of bounds array access in the timekeeping debug code which
was caused by the clobbered RTC value, but we still use the clobbered RTC
value for sleep time injection into kernel timekeeping, which will result
in random adjustments depending on the stored "hash" value.

To prevent this keep track of the RTC clobbering and ignore the invalid RTC
timestamp at resume. If the system resumed successfully clear the flag,
which marks the RTC as unusable, warn the user about the RTC clobber and
recommend to adjust the RTC with 'ntpdate' or 'rdate'.

[jstultz: Fixed up pr_warn formating, and implemented suggestions from Ingo]
[ tglx: Rewrote changelog ]

Originally-from: Thomas Gleixner <[email protected]>
Signed-off-by: Chen Yu <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Acked-by: Pavel Machek <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Xunlei Pang <[email protected]>
Cc: Len Brown <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

---
arch/x86/kernel/rtc.c | 9 +++++++++
drivers/base/power/trace.c | 27 +++++++++++++++++++++++++++
drivers/rtc/rtc-cmos.c | 7 +++++++
include/linux/mc146818rtc.h | 1 +
include/linux/pm-trace.h | 9 ++++++++-
5 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 79c6311c..5b21cb7 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -64,6 +64,15 @@ void mach_get_cmos_time(struct timespec *now)
unsigned int status, year, mon, day, hour, min, sec, century = 0;
unsigned long flags;

+ /*
+ * If pm_trace abused the RTC as storage, set the timespec to 0,
+ * which tells the caller that this RTC value is unusable.
+ */
+ if (!pm_trace_rtc_valid()) {
+ now->tv_sec = now->tv_nsec = 0;
+ return;
+ }
+
spin_lock_irqsave(&rtc_lock, flags);

/*
diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c
index efec10b..1cda505 100644
--- a/drivers/base/power/trace.c
+++ b/drivers/base/power/trace.c
@@ -10,6 +10,7 @@
#include <linux/pm-trace.h>
#include <linux/export.h>
#include <linux/rtc.h>
+#include <linux/suspend.h>

#include <linux/mc146818rtc.h>

@@ -74,6 +75,9 @@

#define DEVSEED (7919)

+bool pm_trace_rtc_abused __read_mostly;
+EXPORT_SYMBOL_GPL(pm_trace_rtc_abused);
+
static unsigned int dev_hash_value;

static int set_magic_time(unsigned int user, unsigned int file, unsigned int device)
@@ -104,6 +108,7 @@ static int set_magic_time(unsigned int user, unsigned int file, unsigned int dev
time.tm_min = (n % 20) * 3;
n /= 20;
mc146818_set_time(&time);
+ pm_trace_rtc_abused = true;
return n ? -1 : 0;
}

@@ -239,9 +244,31 @@ int show_trace_dev_match(char *buf, size_t size)
return ret;
}

+static int
+pm_trace_notify(struct notifier_block *nb, unsigned long mode, void *_unused)
+{
+ switch (mode) {
+ case PM_POST_HIBERNATION:
+ case PM_POST_SUSPEND:
+ if (pm_trace_rtc_abused) {
+ pm_trace_rtc_abused = false;
+ pr_warn("Possible incorrect RTC due to pm_trace, please use 'ntpdate' or 'rdate' to reset it.\n");
+ }
+ break;
+ default:
+ break;
+ }
+ return 0;
+}
+
+static struct notifier_block pm_trace_nb = {
+ .notifier_call = pm_trace_notify,
+};
+
static int early_resume_init(void)
{
hash_value_early_read = read_magic_time();
+ register_pm_notifier(&pm_trace_nb);
return 0;
}

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index dd3d598..b27a189 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -191,6 +191,13 @@ static inline void cmos_write_bank2(unsigned char val, unsigned char addr)

static int cmos_read_time(struct device *dev, struct rtc_time *t)
{
+ /*
+ * If pm_trace abused the RTC for storage, set the timespec to 0,
+ * which tells the caller that this RTC value is unusable.
+ */
+ if (!pm_trace_rtc_valid())
+ return -EIO;
+
/* REVISIT: if the clock has a "century" register, use
* that instead of the heuristic in mc146818_get_time().
* That'll make Y3K compatility (year > 2070) easy!
diff --git a/include/linux/mc146818rtc.h b/include/linux/mc146818rtc.h
index a585b4b..0661af1 100644
--- a/include/linux/mc146818rtc.h
+++ b/include/linux/mc146818rtc.h
@@ -16,6 +16,7 @@
#include <asm/mc146818rtc.h> /* register access macros */
#include <linux/bcd.h>
#include <linux/delay.h>
+#include <linux/pm-trace.h>

#ifdef __KERNEL__
#include <linux/spinlock.h> /* spinlock_t */
diff --git a/include/linux/pm-trace.h b/include/linux/pm-trace.h
index ecbde7a..7b78793 100644
--- a/include/linux/pm-trace.h
+++ b/include/linux/pm-trace.h
@@ -1,11 +1,17 @@
#ifndef PM_TRACE_H
#define PM_TRACE_H

+#include <linux/types.h>
#ifdef CONFIG_PM_TRACE
#include <asm/pm-trace.h>
-#include <linux/types.h>

extern int pm_trace_enabled;
+extern bool pm_trace_rtc_abused;
+
+static inline bool pm_trace_rtc_valid(void)
+{
+ return !pm_trace_rtc_abused;
+}

static inline int pm_trace_is_enabled(void)
{
@@ -24,6 +30,7 @@ extern int show_trace_dev_match(char *buf, size_t size);

#else

+static inline bool pm_trace_rtc_valid(void) { return true; }
static inline int pm_trace_is_enabled(void) { return 0; }

#define TRACE_DEVICE(dev) do { } while (0)

2016-11-29 17:11:55

[permalink] [raw]

Subject: [tip:timers/core] timekeeping/clocksource_cyc2ns: Document intended range limitation

Commit-ID: ec4101e8903e318b9fd4e3bbf72b1eaba53c64e1
Gitweb: http://git.kernel.org/tip/ec4101e8903e318b9fd4e3bbf72b1eaba53c64e1
Author: Chris Metcalf <[email protected]>
AuthorDate: Mon, 28 Nov 2016 14:35:20 -0800
Committer: Thomas Gleixner <[email protected]>
CommitDate: Tue, 29 Nov 2016 18:02:58 +0100

timekeeping/clocksource_cyc2ns: Document intended range limitation

The "cycles" argument should not be an absolute clocksource cycle
value, as the implementation's arithmetic will overflow relatively
easily with wide (64 bit) clocksource counters.

For performance, the implementation is simple and fast, since the
function is intended for only relatively small delta values of
clocksource cycles.

[jstultz: Fixed up to merge against HEAD & commit message tweaks,
also included rewording suggestion by Ingo]
Signed-off-by: Chris Metcalf <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Richard Cochran <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

---
include/linux/clocksource.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 0839818..65602d3 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -169,7 +169,10 @@ static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
* @mult: cycle to nanosecond multiplier
* @shift: cycle to nanosecond divisor (power of two)
*
- * Converts cycles to nanoseconds, using the given mult and shift.
+ * Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
+ * The code is optimized for performance and is not intended to work
+ * with absolute clocksource cycles (as those will easily overflow),
+ * but is only intended to be used with relative (delta) clocksource cycles.
*
* XXX - This could use some mult_lxl_ll() asm optimization
*/

2016-11-29 17:12:16

[permalink] [raw]

Subject: [tip:timers/core] timekeeping: Add a fast and NMI safe boot clock

Commit-ID: 948a5312f41658f7b76a598a139ef1f4dea09ca9
Gitweb: http://git.kernel.org/tip/948a5312f41658f7b76a598a139ef1f4dea09ca9
Author: Joel Fernandes <[email protected]>
AuthorDate: Mon, 28 Nov 2016 14:35:22 -0800
Committer: Thomas Gleixner <[email protected]>
CommitDate: Tue, 29 Nov 2016 18:02:59 +0100

timekeeping: Add a fast and NMI safe boot clock

This boot clock can be used as a tracing clock and will account for
suspend time.

To keep it NMI safe since we're accessing from tracing, we're not using a
separate timekeeper with updates to monotonic clock and boot offset
protected with seqlocks. This has the following minor side effects:

(1) Its possible that a timestamp be taken after the boot offset is updated
but before the timekeeper is updated. If this happens, the new boot offset
is added to the old timekeeping making the clock appear to update slightly
earlier:
CPU 0 CPU 1
timekeeping_inject_sleeptime64()
__timekeeping_inject_sleeptime(tk, delta);
timestamp();
timekeeping_update(tk, TK_CLEAR_NTP...);

(2) On 32-bit systems, the 64-bit boot offset (tk->offs_boot) may be
partially updated. Since the tk->offs_boot update is a rare event, this
should be a rare occurrence which postprocessing should be able to handle.

Signed-off-by: Joel Fernandes <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Steven Rostedt <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

---
include/linux/timekeeping.h | 1 +
kernel/time/timekeeping.c | 29 +++++++++++++++++++++++++++++
2 files changed, 30 insertions(+)

diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 09168c5..361f8bf 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -249,6 +249,7 @@ static inline u64 ktime_get_raw_ns(void)

extern u64 ktime_get_mono_fast_ns(void);
extern u64 ktime_get_raw_fast_ns(void);
+extern u64 ktime_get_boot_fast_ns(void);

/*
* Timespec interfaces utilizing the ktime based ones
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 37dec7e..b2286e9 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -425,6 +425,35 @@ u64 ktime_get_raw_fast_ns(void)
}
EXPORT_SYMBOL_GPL(ktime_get_raw_fast_ns);

+/**
+ * ktime_get_boot_fast_ns - NMI safe and fast access to boot clock.
+ *
+ * To keep it NMI safe since we're accessing from tracing, we're not using a
+ * separate timekeeper with updates to monotonic clock and boot offset
+ * protected with seqlocks. This has the following minor side effects:
+ *
+ * (1) Its possible that a timestamp be taken after the boot offset is updated
+ * but before the timekeeper is updated. If this happens, the new boot offset
+ * is added to the old timekeeping making the clock appear to update slightly
+ * earlier:
+ * CPU 0 CPU 1
+ * timekeeping_inject_sleeptime64()
+ * __timekeeping_inject_sleeptime(tk, delta);
+ * timestamp();
+ * timekeeping_update(tk, TK_CLEAR_NTP...);
+ *
+ * (2) On 32-bit systems, the 64-bit boot offset (tk->offs_boot) may be
+ * partially updated. Since the tk->offs_boot update is a rare event, this
+ * should be a rare occurrence which postprocessing should be able to handle.
+ */
+u64 notrace ktime_get_boot_fast_ns(void)
+{
+ struct timekeeper *tk = &tk_core.timekeeper;
+
+ return (ktime_get_mono_fast_ns() + ktime_to_ns(tk->offs_boot));
+}
+EXPORT_SYMBOL_GPL(ktime_get_boot_fast_ns);
+
/* Suspend-time cycles value for halted fast timekeeper. */
static cycle_t cycles_at_suspend;

2016-11-29 17:12:54

[permalink] [raw]

Subject: [tip:timers/core] trace: Add an option for boot clock as trace clock

Commit-ID: 80ec3552107ac16a836dbff4cf3c23fdd3256ee3
Gitweb: http://git.kernel.org/tip/80ec3552107ac16a836dbff4cf3c23fdd3256ee3
Author: Joel Fernandes <[email protected]>
AuthorDate: Mon, 28 Nov 2016 14:35:23 -0800
Committer: Thomas Gleixner <[email protected]>
CommitDate: Tue, 29 Nov 2016 18:02:59 +0100

trace: Add an option for boot clock as trace clock

Unlike monotonic clock, boot clock as a trace clock will account for
time spent in suspend useful for tracing suspend/resume. This uses
earlier introduced infrastructure for using the fast boot clock.

Signed-off-by: Joel Fernandes <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Richard Cochran <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

---
kernel/trace/trace.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8696ce6..f7b64db 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1125,6 +1125,7 @@ static struct {
{ trace_clock, "perf", 1 },
{ ktime_get_mono_fast_ns, "mono", 1 },
{ ktime_get_raw_fast_ns, "mono_raw", 1 },
+ { ktime_get_boot_fast_ns, "boot", 1 },
ARCH_TRACE_CLOCKS
};

2016-11-29 17:13:30

[permalink] [raw]

Subject: [tip:timers/core] trace: Update documentation for mono, mono_raw and boot clock

Commit-ID: 2924ecd441f3c12da59b297daade265f49d0831b
Gitweb: http://git.kernel.org/tip/2924ecd441f3c12da59b297daade265f49d0831b
Author: Joel Fernandes <[email protected]>
AuthorDate: Mon, 28 Nov 2016 14:35:24 -0800
Committer: Thomas Gleixner <[email protected]>
CommitDate: Tue, 29 Nov 2016 18:03:00 +0100

trace: Update documentation for mono, mono_raw and boot clock

Documentation was missing for mono and mono_raw, add them and also for
the boot clock introduced in this series.

Signed-off-by: Joel Fernandes <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Richard Cochran <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

---
Documentation/trace/ftrace.txt | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 185c39f..5596e2d 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -362,6 +362,26 @@ of ftrace. Here is a list of some of the key files:
to correlate events across hypervisor/guest if
tb_offset is known.

+ mono: This uses the fast monotonic clock (CLOCK_MONOTONIC)
+ which is monotonic and is subject to NTP rate adjustments.
+
+ mono_raw:
+ This is the raw monotonic clock (CLOCK_MONOTONIC_RAW)
+ which is montonic but is not subject to any rate adjustments
+ and ticks at the same rate as the hardware clocksource.
+
+ boot: This is the boot clock (CLOCK_BOOTTIME) and is based on the
+ fast monotonic clock, but also accounts for time spent in
+ suspend. Since the clock access is designed for use in
+ tracing in the suspend path, some side effects are possible
+ if clock is accessed after the suspend time is accounted before
+ the fast mono clock is updated. In this case, the clock update
+ appears to happen slightly sooner than it normally would have.
+ Also on 32-bit systems, it's possible that the 64-bit boot offset
+ sees a partial update. These effects are rare and post
+ processing should be able to handle them. See comments in the
+ ktime_get_boot_fast_ns() function for more information.
+
To set a clock, simply echo the clock name into this file.

echo global > trace_clock

2016-11-30 11:43:28

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Subject: Re: [PATCH 4/7] time: alarmtimer: Add the tracepoints for alarmtimer

2016-12-01 02:34:24

[permalink] [raw]

Subject: Re: [PATCH 4/7] time: alarmtimer: Add the tracepoints for alarmtimer

On 29 November 2016 at 20:06, Thomas Gleixner <[email protected]> wrote:
> On Mon, 28 Nov 2016, John Stultz wrote:
>
>> From: Baolin Wang <[email protected]>
>>
>> For system debugging, we sometimes want to know who sets one
>> alarm timer, the time of the timer, when the timer started and
>> fired and so on. Thus adding tracepoints can help us trace the
>> alarmtimer information.
>>
>> For example, when we debug the system supend/resume, if the
>> system is always resumed by RTC alarm, we can find out which
>> process set the alarm timer to resume system by below trace log:
>>
>> ......
>>
>> Binder:3292_2-3304 [000] d..2 149.981123: alarmtimer_cancel:
>> alarmtimer:ffffffc1319a7800 type:REALTIME
>> expires:1325463120000000000 now:1325376810370370245
>>
>> Binder:3292_2-3304 [000] d..2 149.981136: alarmtimer_start:
>> alarmtimer:ffffffc1319a7800 type:REALTIME
>> expires:1325376840000000000 now:1325376810370384591
>>
>> Binder:3292_9-3953 [000] d..2 150.212991: alarmtimer_cancel:
>> alarmtimer:ffffffc1319a5a00 type:BOOTTIME
>> expires:179552000000 now:150154008122
>>
>> Binder:3292_9-3953 [000] d..2 150.213006: alarmtimer_start:
>> alarmtimer:ffffffc1319a5a00 type:BOOTTIME
>> expires:179551000000 now:150154025622
>>
>> ......
>>
>> system_server-3000 [002] ...1 162.701940: alarmtimer_suspend:
>> alarmtimer type:REALTIME expires:1325376839802714584
>> ......
>>
>> >From the trace log, we can find out the 'Binder:3292_2' process
>> set one alarm timer which resumes the system.
>
> To be honest. I have a hard time to figure out that Binder:3292_2 armed the
> timer.
>
> suspend: expires:1325376839802714584
> Binder start: expires:1325376840000000000
>
> That does not make any sense at all. And this is a result of how that
> suspend tracepoint got glued into alarmtimer_suspend():
>
>> @@ -222,7 +226,7 @@ static int alarmtimer_suspend(struct device *dev)
>> ktime_t min, now;
>> unsigned long flags;
>> struct rtc_device *rtc;
>> - int i;
>> + int i, min_type = -1;
>> int ret;
>>
>> spin_lock_irqsave(&freezer_delta_lock, flags);
>> @@ -247,8 +251,10 @@ static int alarmtimer_suspend(struct device *dev)
>> if (!next)
>> continue;
>> delta = ktime_sub(next->expires, base->gettime());
>> - if (!min.tv64 || (delta.tv64 < min.tv64))
>> + if (!min.tv64 || (delta.tv64 < min.tv64)) {
>> min = delta;
>> + min_type = i;
>> + }
>> }
>> if (min.tv64 == 0)
>> return 0;
>> @@ -264,6 +270,8 @@ static int alarmtimer_suspend(struct device *dev)
>> now = rtc_tm_to_ktime(tm);
>> now = ktime_add(now, min);
>>
>> + trace_alarmtimer_suspend(now, min_type);
>
> So first we calculate the relative expiry time from now, add it to the RTC
> and then print out the sum. That's utter crap especially if the first
> expiring timer is based on CLOCK_BOOTTIME. Even with CLOCK_REALTIME you do
> not get matching expiry time as you can see above.
>
> Now looking at the other possibility to arm the resume time: freezer_delta.
> That's even more undebuggable because the freezer time is stored as
> relative timeout without any type information. How is one supposed to map
> that back to an alarm timer start?
>
> Find below a revamped version (untested) of this including a proper written
> changelog.
>
> Thanks,
>
> tglx
>
> 8<--------------
> Subject: time/alarmtimer: Add tracepoints for alarmtimer
> From: John Stultz <[email protected]>
> Date: Mon, 28 Nov 2016 14:35:21 -0800
>
> From: Baolin Wang <[email protected]>
>
> Alarm timers are one of the mechanisms to wake up a system from suspend,
> but there exist no tracepoints to analyse which process/thread armed an
> alarmtimer.
>
> Add tracepoints for start/cancel/expire of individual alarm timers and one
> for tracing the suspend time decision when to resume the system.
>
> The following trace excerpt illustrates the new mechanism:
>
> Binder:3292_2-3304 [000] d..2 149.981123: alarmtimer_cancel:
> alarmtimer:ffffffc1319a7800 type:REALTIME
> expires:1325463120000000000 now:1325376810370370245
>
> Binder:3292_2-3304 [000] d..2 149.981136: alarmtimer_start:
> alarmtimer:ffffffc1319a7800 type:REALTIME
> expires:1325376840000000000 now:1325376810370384591
>
> Binder:3292_9-3953 [000] d..2 150.212991: alarmtimer_cancel:
> alarmtimer:ffffffc1319a5a00 type:BOOTTIME
> expires:179552000000 now:150154008122
>
> Binder:3292_9-3953 [000] d..2 150.213006: alarmtimer_start:
> alarmtimer:ffffffc1319a5a00 type:BOOTTIME
> expires:179551000000 now:150154025622
>
> system_server-3000 [002] ...1 162.701940: alarmtimer_suspend:
> alarmtimer type:REALTIME expires:1325376840000000000
>
> The wakeup time which is selected at suspend time allows to map it back to
> the task arming the timer: Binder:3292_2.
>
> [ tglx: Store real alarm timer expiry time instead of some useless RTC
> relative information, add proper type information for wakeups which
> are handled via the clock_nanosleep/freezer and massage the
> changelog. ]
>
> Signed-off-by: Baolin Wang <[email protected]>
> Signed-off-by: John Stultz <[email protected]>
> Acked-by: Steven Rostedt <[email protected]>
> Cc: Prarit Bhargava <[email protected]>
> Cc: Richard Cochran <[email protected]>
> Link: http://lkml.kernel.org/r/[email protected]
> Signed-off-by: Thomas Gleixner <[email protected]>

Tested-by: Baolin Wang <[email protected]>

--
Baolin.wang
Best Regards

2016-12-01 13:52:28