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Revert: Unify CLOCK_MONOTONIC and CLOCK_BOOTTIME

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Revert commits

92af4dcb4e ("tracing: Unify the "boot" and "mono" tracing clocks")
127bfa5f43 ("hrtimer: Unify MONOTONIC and BOOTTIME clock behavior")
7250a4047a ("posix-timers: Unify MONOTONIC and BOOTTIME clock behavior")
d6c7270e91 ("timekeeping: Remove boot time specific code")
f2d6fdbfd2 ("Input: Evdev - unify MONOTONIC and BOOTTIME clock behavior")
d6ed449afd ("timekeeping: Make the MONOTONIC clock behave like the BOOTTIME clock")
72199320d4 ("timekeeping: Add the new CLOCK_MONOTONIC_ACTIVE clock")

As stated in the pull request for the unification of CLOCK_MONOTONIC and
CLOCK_BOOTTIME, it was clear that we might have to revert the change.

As reported by several folks systemd and other applications rely on the
documented behaviour of CLOCK_MONOTONIC on Linux and break with the above
changes. After resume daemons time out and other timeout related issues are
observed. Rafael compiled this list:

* systemd kills daemons on resume, after >WatchdogSec seconds
  of suspending (Genki Sky).  [Verified that that's because systemd uses
  CLOCK_MONOTONIC and expects it to not include the suspend time.]

* systemd-journald misbehaves after resume:
  systemd-journald[7266]: File /var/log/journal/016627c3c4784cd4812d4b7e96a34226/system.journal
corrupted or uncleanly shut down, renaming and replacing.
  (Mike Galbraith).

* NetworkManager reports "networking disabled" and networking is broken
  after resume 50% of the time (Pavel).  [May be because of systemd.]

* MATE desktop dims the display and starts the screensaver right after
  system resume (Pavel).

* Full system hang during resume (me).  [May be due to systemd or NM or both.]

That happens on debian and open suse systems.

It's sad, that these problems were neither catched in -next nor by those
folks who expressed interest in this change.

Reported-by: Rafael J. Wysocki <rjw@rjwysocki.net>
Reported-by: Genki Sky <sky@genki.is>,
Reported-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kevin Easton <kevin@guarana.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Thomas Gleixner 2018-04-25 15:33:38 +02:00
parent 1f71addd34
commit a3ed0e4393
15 changed files with 114 additions and 104 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
Documentation/trace/ftrace.rst
View File

@ -461,9 +461,17 @@ of ftrace. Here is a list of some of the key files:
and ticks at the same rate as the hardware clocksource.
boot:
Same as mono. Used to be a separate clock which accounted
for the time spent in suspend while CLOCK_MONOTONIC did
not.
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::

7
drivers/input/evdev.c
View File

@ -31,6 +31,7 @@
enum evdev_clock_type {
EV_CLK_REAL = 0,
EV_CLK_MONO,
EV_CLK_BOOT,
EV_CLK_MAX
};
@ -197,10 +198,12 @@ static int evdev_set_clk_type(struct evdev_client *client, unsigned int clkid)
case CLOCK_REALTIME:
clk_type = EV_CLK_REAL;
break;
case CLOCK_BOOTTIME:
case CLOCK_MONOTONIC:
clk_type = EV_CLK_MONO;
break;
case CLOCK_BOOTTIME:
clk_type = EV_CLK_BOOT;
break;
default:
return -EINVAL;
}
@ -311,6 +314,8 @@ static void evdev_events(struct input_handle *handle,
ev_time[EV_CLK_MONO] = ktime_get();
ev_time[EV_CLK_REAL] = ktime_mono_to_real(ev_time[EV_CLK_MONO]);
ev_time[EV_CLK_BOOT] = ktime_mono_to_any(ev_time[EV_CLK_MONO],
TK_OFFS_BOOT);
rcu_read_lock();

2
include/linux/hrtimer.h
View File

@ -161,9 +161,11 @@ struct hrtimer_clock_base {
enum hrtimer_base_type {
HRTIMER_BASE_MONOTONIC,
HRTIMER_BASE_REALTIME,
HRTIMER_BASE_BOOTTIME,
HRTIMER_BASE_TAI,
HRTIMER_BASE_MONOTONIC_SOFT,
HRTIMER_BASE_REALTIME_SOFT,
HRTIMER_BASE_BOOTTIME_SOFT,
HRTIMER_BASE_TAI_SOFT,
HRTIMER_MAX_CLOCK_BASES,
};

2
include/linux/timekeeper_internal.h
View File

@ -52,7 +52,6 @@ struct tk_read_base {
* @offs_real: Offset clock monotonic -> clock realtime
* @offs_boot: Offset clock monotonic -> clock boottime
* @offs_tai: Offset clock monotonic -> clock tai
* @time_suspended: Accumulated suspend time
* @tai_offset: The current UTC to TAI offset in seconds
* @clock_was_set_seq: The sequence number of clock was set events
* @cs_was_changed_seq: The sequence number of clocksource change events
@ -95,7 +94,6 @@ struct timekeeper {
ktime_t offs_real;
ktime_t offs_boot;
ktime_t offs_tai;
ktime_t time_suspended;
s32 tai_offset;
unsigned int clock_was_set_seq;
u8 cs_was_changed_seq;

37
include/linux/timekeeping.h
View File

@ -33,25 +33,20 @@ extern void ktime_get_ts64(struct timespec64 *ts);
extern time64_t ktime_get_seconds(void);
extern time64_t __ktime_get_real_seconds(void);
extern time64_t ktime_get_real_seconds(void);
extern void ktime_get_active_ts64(struct timespec64 *ts);
extern int __getnstimeofday64(struct timespec64 *tv);
extern void getnstimeofday64(struct timespec64 *tv);
extern void getboottime64(struct timespec64 *ts);
#define ktime_get_real_ts64(ts) getnstimeofday64(ts)
/* Clock BOOTTIME compatibility wrappers */
static inline void get_monotonic_boottime64(struct timespec64 *ts)
{
ktime_get_ts64(ts);
}
#define ktime_get_real_ts64(ts) getnstimeofday64(ts)
/*
* ktime_t based interfaces
*/
enum tk_offsets {
TK_OFFS_REAL,
TK_OFFS_BOOT,
TK_OFFS_TAI,
TK_OFFS_MAX,
};
@ -62,10 +57,6 @@ extern ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs);
extern ktime_t ktime_get_raw(void);
extern u32 ktime_get_resolution_ns(void);
/* Clock BOOTTIME compatibility wrappers */
static inline ktime_t ktime_get_boottime(void) { return ktime_get(); }
static inline u64 ktime_get_boot_ns(void) { return ktime_get(); }
/**
* ktime_get_real - get the real (wall-) time in ktime_t format
*/
@ -74,6 +65,17 @@ static inline ktime_t ktime_get_real(void)
return ktime_get_with_offset(TK_OFFS_REAL);
}
/**
* ktime_get_boottime - Returns monotonic time since boot in ktime_t format
*
* This is similar to CLOCK_MONTONIC/ktime_get, but also includes the
* time spent in suspend.
*/
static inline ktime_t ktime_get_boottime(void)
{
return ktime_get_with_offset(TK_OFFS_BOOT);
}
/**
* ktime_get_clocktai - Returns the TAI time of day in ktime_t format
*/
@ -100,6 +102,11 @@ static inline u64 ktime_get_real_ns(void)
return ktime_to_ns(ktime_get_real());
}
static inline u64 ktime_get_boot_ns(void)
{
return ktime_to_ns(ktime_get_boottime());
}
static inline u64 ktime_get_tai_ns(void)
{
return ktime_to_ns(ktime_get_clocktai());
@ -112,11 +119,17 @@ 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);
extern u64 ktime_get_real_fast_ns(void);
/*
* timespec64 interfaces utilizing the ktime based ones
*/
static inline void get_monotonic_boottime64(struct timespec64 *ts)
{
*ts = ktime_to_timespec64(ktime_get_boottime());
}
static inline void timekeeping_clocktai64(struct timespec64 *ts)
{
*ts = ktime_to_timespec64(ktime_get_clocktai());

1
include/uapi/linux/time.h
View File

@ -73,7 +73,6 @@ struct __kernel_old_timeval {
*/
#define CLOCK_SGI_CYCLE 10
#define CLOCK_TAI 11
#define CLOCK_MONOTONIC_ACTIVE 12
#define MAX_CLOCKS 16
#define CLOCKS_MASK (CLOCK_REALTIME | CLOCK_MONOTONIC)

16
kernel/time/hrtimer.c
View File

@ -90,6 +90,11 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
.clockid = CLOCK_REALTIME,
.get_time = &ktime_get_real,
},
{
.index = HRTIMER_BASE_BOOTTIME,
.clockid = CLOCK_BOOTTIME,
.get_time = &ktime_get_boottime,
},
{
.index = HRTIMER_BASE_TAI,
.clockid = CLOCK_TAI,
@ -105,6 +110,11 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
.clockid = CLOCK_REALTIME,
.get_time = &ktime_get_real,
},
{
.index = HRTIMER_BASE_BOOTTIME_SOFT,
.clockid = CLOCK_BOOTTIME,
.get_time = &ktime_get_boottime,
},
{
.index = HRTIMER_BASE_TAI_SOFT,
.clockid = CLOCK_TAI,
@ -119,7 +129,7 @@ static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = {
[CLOCK_REALTIME] = HRTIMER_BASE_REALTIME,
[CLOCK_MONOTONIC] = HRTIMER_BASE_MONOTONIC,
[CLOCK_BOOTTIME] = HRTIMER_BASE_MONOTONIC,
[CLOCK_BOOTTIME] = HRTIMER_BASE_BOOTTIME,
[CLOCK_TAI] = HRTIMER_BASE_TAI,
};
@ -571,12 +581,14 @@ __hrtimer_get_next_event(struct hrtimer_cpu_base *cpu_base, unsigned int active_
static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
{
ktime_t *offs_real = &base->clock_base[HRTIMER_BASE_REALTIME].offset;
ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;
ktime_t *offs_tai = &base->clock_base[HRTIMER_BASE_TAI].offset;
ktime_t now = ktime_get_update_offsets_now(&base->clock_was_set_seq,
offs_real, offs_tai);
offs_real, offs_boot, offs_tai);
base->clock_base[HRTIMER_BASE_REALTIME_SOFT].offset = *offs_real;
base->clock_base[HRTIMER_BASE_BOOTTIME_SOFT].offset = *offs_boot;
base->clock_base[HRTIMER_BASE_TAI_SOFT].offset = *offs_tai;
return now;

2
kernel/time/posix-stubs.c
View File

@ -83,8 +83,6 @@ int do_clock_gettime(clockid_t which_clock, struct timespec64 *tp)
case CLOCK_BOOTTIME:
get_monotonic_boottime64(tp);
break;
case CLOCK_MONOTONIC_ACTIVE:
ktime_get_active_ts64(tp);
default:
return -EINVAL;
}

26
kernel/time/posix-timers.c
View File

@ -252,16 +252,15 @@ static int posix_get_coarse_res(const clockid_t which_clock, struct timespec64 *
return 0;
}
static int posix_get_tai(clockid_t which_clock, struct timespec64 *tp)
static int posix_get_boottime(const clockid_t which_clock, struct timespec64 *tp)
{
timekeeping_clocktai64(tp);
get_monotonic_boottime64(tp);
return 0;
}
static int posix_get_monotonic_active(clockid_t which_clock,
struct timespec64 *tp)
static int posix_get_tai(clockid_t which_clock, struct timespec64 *tp)
{
ktime_get_active_ts64(tp);
timekeeping_clocktai64(tp);
return 0;
}
@ -1317,9 +1316,19 @@ static const struct k_clock clock_tai = {
.timer_arm = common_hrtimer_arm,
};
static const struct k_clock clock_monotonic_active = {
static const struct k_clock clock_boottime = {
.clock_getres = posix_get_hrtimer_res,
.clock_get = posix_get_monotonic_active,
.clock_get = posix_get_boottime,
.nsleep = common_nsleep,
.timer_create = common_timer_create,
.timer_set = common_timer_set,
.timer_get = common_timer_get,
.timer_del = common_timer_del,
.timer_rearm = common_hrtimer_rearm,
.timer_forward = common_hrtimer_forward,
.timer_remaining = common_hrtimer_remaining,
.timer_try_to_cancel = common_hrtimer_try_to_cancel,
.timer_arm = common_hrtimer_arm,
};
static const struct k_clock * const posix_clocks[] = {
@ -1330,11 +1339,10 @@ static const struct k_clock * const posix_clocks[] = {
[CLOCK_MONOTONIC_RAW] = &clock_monotonic_raw,
[CLOCK_REALTIME_COARSE] = &clock_realtime_coarse,
[CLOCK_MONOTONIC_COARSE] = &clock_monotonic_coarse,
[CLOCK_BOOTTIME] = &clock_monotonic,
[CLOCK_BOOTTIME] = &clock_boottime,
[CLOCK_REALTIME_ALARM] = &alarm_clock,
[CLOCK_BOOTTIME_ALARM] = &alarm_clock,
[CLOCK_TAI] = &clock_tai,
[CLOCK_MONOTONIC_ACTIVE] = &clock_monotonic_active,
};
static const struct k_clock *clockid_to_kclock(const clockid_t id)

15
kernel/time/tick-common.c
View File

@ -419,19 +419,6 @@ void tick_suspend_local(void)
clockevents_shutdown(td->evtdev);
}
static void tick_forward_next_period(void)
{
ktime_t delta, now = ktime_get();
u64 n;
delta = ktime_sub(now, tick_next_period);
n = ktime_divns(delta, tick_period);
tick_next_period += n * tick_period;
if (tick_next_period < now)
tick_next_period += tick_period;
tick_sched_forward_next_period();
}
/**
* tick_resume_local - Resume the local tick device
*
@ -444,8 +431,6 @@ void tick_resume_local(void)
struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
bool broadcast = tick_resume_check_broadcast();
tick_forward_next_period();
clockevents_tick_resume(td->evtdev);
if (!broadcast) {
if (td->mode == TICKDEV_MODE_PERIODIC)

6
kernel/time/tick-internal.h
View File

@ -141,12 +141,6 @@ static inline void tick_check_oneshot_broadcast_this_cpu(void) { }
static inline bool tick_broadcast_oneshot_available(void) { return tick_oneshot_possible(); }
#endif /* !(BROADCAST && ONESHOT) */
#if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS)
extern void tick_sched_forward_next_period(void);
#else
static inline void tick_sched_forward_next_period(void) { }
#endif
/* NO_HZ_FULL internal */
#ifdef CONFIG_NO_HZ_FULL
extern void tick_nohz_init(void);

9
kernel/time/tick-sched.c
View File

@ -51,15 +51,6 @@ struct tick_sched *tick_get_tick_sched(int cpu)
*/
static ktime_t last_jiffies_update;
/*
* Called after resume. Make sure that jiffies are not fast forwarded due to
* clock monotonic being forwarded by the suspended time.
*/
void tick_sched_forward_next_period(void)
{
last_jiffies_update = tick_next_period;
}
/*
* Must be called with interrupts disabled !
*/

78
kernel/time/timekeeping.c
View File

@ -138,12 +138,7 @@ static void tk_set_wall_to_mono(struct timekeeper *tk, struct timespec64 wtm)
static inline void tk_update_sleep_time(struct timekeeper *tk, ktime_t delta)
{
/* Update both bases so mono and raw stay coupled. */
tk->tkr_mono.base += delta;
tk->tkr_raw.base += delta;
/* Accumulate time spent in suspend */
tk->time_suspended += delta;
tk->offs_boot = ktime_add(tk->offs_boot, delta);
}
/*
@ -473,6 +468,36 @@ 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);
/*
* See comment for __ktime_get_fast_ns() vs. timestamp ordering
*/
@ -764,6 +789,7 @@ EXPORT_SYMBOL_GPL(ktime_get_resolution_ns);
static ktime_t *offsets[TK_OFFS_MAX] = {
[TK_OFFS_REAL] = &tk_core.timekeeper.offs_real,
[TK_OFFS_BOOT] = &tk_core.timekeeper.offs_boot,
[TK_OFFS_TAI] = &tk_core.timekeeper.offs_tai,
};
@ -860,39 +886,6 @@ void ktime_get_ts64(struct timespec64 *ts)
}
EXPORT_SYMBOL_GPL(ktime_get_ts64);
/**
* ktime_get_active_ts64 - Get the active non-suspended monotonic clock
* @ts: pointer to timespec variable
*
* The function calculates the monotonic clock from the realtime clock and
* the wall_to_monotonic offset, subtracts the accumulated suspend time and
* stores the result in normalized timespec64 format in the variable
* pointed to by @ts.
*/
void ktime_get_active_ts64(struct timespec64 *ts)
{
struct timekeeper *tk = &tk_core.timekeeper;
struct timespec64 tomono, tsusp;
u64 nsec, nssusp;
unsigned int seq;
WARN_ON(timekeeping_suspended);
do {
seq = read_seqcount_begin(&tk_core.seq);
ts->tv_sec = tk->xtime_sec;
nsec = timekeeping_get_ns(&tk->tkr_mono);
tomono = tk->wall_to_monotonic;
nssusp = tk->time_suspended;
} while (read_seqcount_retry(&tk_core.seq, seq));
ts->tv_sec += tomono.tv_sec;
ts->tv_nsec = 0;
timespec64_add_ns(ts, nsec + tomono.tv_nsec);
tsusp = ns_to_timespec64(nssusp);
*ts = timespec64_sub(*ts, tsusp);
}
/**
* ktime_get_seconds - Get the seconds portion of CLOCK_MONOTONIC
*
@ -1593,6 +1586,7 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
return;
}
tk_xtime_add(tk, delta);
tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *delta));
tk_update_sleep_time(tk, timespec64_to_ktime(*delta));
tk_debug_account_sleep_time(delta);
}
@ -2125,7 +2119,7 @@ out:
void getboottime64(struct timespec64 *ts)
{
struct timekeeper *tk = &tk_core.timekeeper;
ktime_t t = ktime_sub(tk->offs_real, tk->time_suspended);
ktime_t t = ktime_sub(tk->offs_real, tk->offs_boot);
*ts = ktime_to_timespec64(t);
}
@ -2188,6 +2182,7 @@ void do_timer(unsigned long ticks)
* ktime_get_update_offsets_now - hrtimer helper
* @cwsseq: pointer to check and store the clock was set sequence number
* @offs_real: pointer to storage for monotonic -> realtime offset
* @offs_boot: pointer to storage for monotonic -> boottime offset
* @offs_tai: pointer to storage for monotonic -> clock tai offset
*
* Returns current monotonic time and updates the offsets if the
@ -2197,7 +2192,7 @@ void do_timer(unsigned long ticks)
* Called from hrtimer_interrupt() or retrigger_next_event()
*/
ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq, ktime_t *offs_real,
ktime_t *offs_tai)
ktime_t *offs_boot, ktime_t *offs_tai)
{
struct timekeeper *tk = &tk_core.timekeeper;
unsigned int seq;
@ -2214,6 +2209,7 @@ ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq, ktime_t *offs_real,
if (*cwsseq != tk->clock_was_set_seq) {
*cwsseq = tk->clock_was_set_seq;
*offs_real = tk->offs_real;
*offs_boot = tk->offs_boot;
*offs_tai = tk->offs_tai;
}

1
kernel/time/timekeeping.h
View File

@ -6,6 +6,7 @@
*/
extern ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq,
ktime_t *offs_real,
ktime_t *offs_boot,
ktime_t *offs_tai);
extern int timekeeping_valid_for_hres(void);

2
kernel/trace/trace.c
View File

@ -1165,7 +1165,7 @@ static struct {
{ trace_clock, "perf", 1 },
{ ktime_get_mono_fast_ns, "mono", 1 },
{ ktime_get_raw_fast_ns, "mono_raw", 1 },
{ ktime_get_mono_fast_ns, "boot", 1 },
{ ktime_get_boot_fast_ns, "boot", 1 },
ARCH_TRACE_CLOCKS
};