[GIT pull] timers/core for 5.19-rc1

From: Thomas Gleixner
Date: Mon May 23 2022 - 04:02:43 EST

Linus,

please pull the latest timers/core branch from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-core-2022-05-23

up to: 317f29c14d0c: timers: Provide a better debugobjects hint for delayed works


Updates for timers and timekeeping core code:

- Expose CLOCK_TAI to instrumentation to aid with TSN debugging.

- Ensure that the clockevent is stopped when there is no timer armed to
avoid pointless wakeups.

- Make the sched clock frequency handling and rounding consistent.

- Provide a better debugobject hint for delayed works. The timer callback
is always the same, which makes it difficult to identify the underlying
work. Use the work function as a hint instead.

- Move the timer specific sysctl code into the timer subsystem.

- The usual set of improvements and cleanups

Thanks,

tglx

------------------>
Anna-Maria Behnsen (3):
timers: Fix warning condition in __run_timers()
timers: Initialize base::next_expiry_recalc in timers_prepare_cpu()
tracing/timer: Add missing argument documentation of trace points

Jakob Koschel (1):
clockevents: Use dedicated list iterator variable

Kurt Kanzenbach (1):
timekeeping: Introduce fast accessor to clock tai

Maciej W. Rozycki (3):
time/sched_clock: Round the frequency reported to nearest rather than down
time/sched_clock: Use Hz as the unit for clock rate reporting below 4kHz
time/sched_clock: Fix formatting of frequency reporting code

Nicholas Piggin (1):
timers/nohz: Switch to ONESHOT_STOPPED in the low-res handler when the tick is stopped

Stephen Boyd (1):
timers: Provide a better debugobjects hint for delayed works

Thomas Gleixner (3):
timers: Simplify calc_index()
timekeeping: Annotate ktime_get_boot_fast_ns() with data_race()
timekeeping: Consolidate fast timekeeper

Yury Norov (1):
clocksource: Replace cpumask_weight() with cpumask_empty()

tangmeng (1):
timers: Move timer sysctl into the timer code


Documentation/core-api/timekeeping.rst | 1 +
include/linux/timekeeping.h | 1 +
include/linux/timer.h | 8 ---
include/trace/events/timer.h | 5 +-
kernel/sysctl.c | 11 ----
kernel/time/clockevents.c | 9 ++--
kernel/time/clocksource.c | 2 +-
kernel/time/sched_clock.c | 13 +++--
kernel/time/tick-sched.c | 12 ++++-
kernel/time/timekeeping.c | 39 ++++++++++----
kernel/time/timer.c | 99 ++++++++++++++++++++++++++--------
11 files changed, 134 insertions(+), 66 deletions(-)

diff --git a/Documentation/core-api/timekeeping.rst b/Documentation/core-api/timekeeping.rst
index 729e24864fe7..22ec68f24421 100644
--- a/Documentation/core-api/timekeeping.rst
+++ b/Documentation/core-api/timekeeping.rst
@@ -132,6 +132,7 @@ Some additional variants exist for more specialized cases:
.. c:function:: u64 ktime_get_mono_fast_ns( void )
u64 ktime_get_raw_fast_ns( void )
u64 ktime_get_boot_fast_ns( void )
+ u64 ktime_get_tai_fast_ns( void )
u64 ktime_get_real_fast_ns( void )

These variants are safe to call from any context, including from
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 78a98bdff76d..fe1e467ba046 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -177,6 +177,7 @@ 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);
+extern u64 ktime_get_tai_fast_ns(void);
extern u64 ktime_get_real_fast_ns(void);

/*
diff --git a/include/linux/timer.h b/include/linux/timer.h
index fda13c9d1256..648f00105f58 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -196,14 +196,6 @@ extern void init_timers(void);
struct hrtimer;
extern enum hrtimer_restart it_real_fn(struct hrtimer *);

-#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
-struct ctl_table;
-
-extern unsigned int sysctl_timer_migration;
-int timer_migration_handler(struct ctl_table *table, int write,
- void *buffer, size_t *lenp, loff_t *ppos);
-#endif
-
unsigned long __round_jiffies(unsigned long j, int cpu);
unsigned long __round_jiffies_relative(unsigned long j, int cpu);
unsigned long round_jiffies(unsigned long j);
diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index 6ad031c71be7..2e713a7d9aa3 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -48,6 +48,7 @@ DEFINE_EVENT(timer_class, timer_init,
* timer_start - called when the timer is started
* @timer: pointer to struct timer_list
* @expires: the timers expiry time
+ * @flags: the timers flags
*/
TRACE_EVENT(timer_start,

@@ -84,6 +85,7 @@ TRACE_EVENT(timer_start,
/**
* timer_expire_entry - called immediately before the timer callback
* @timer: pointer to struct timer_list
+ * @baseclk: value of timer_base::clk when timer expires
*
* Allows to determine the timer latency.
*/
@@ -190,7 +192,8 @@ TRACE_EVENT(hrtimer_init,

/**
* hrtimer_start - called when the hrtimer is started
- * @hrtimer: pointer to struct hrtimer
+ * @hrtimer: pointer to struct hrtimer
+ * @mode: the hrtimers mode
*/
TRACE_EVENT(hrtimer_start,

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 830aaf8ca08e..5b7b1a82ae6a 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2288,17 +2288,6 @@ static struct ctl_table kern_table[] = {
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
-#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
- {
- .procname = "timer_migration",
- .data = &sysctl_timer_migration,
- .maxlen = sizeof(unsigned int),
- .mode = 0644,
- .proc_handler = timer_migration_handler,
- .extra1 = SYSCTL_ZERO,
- .extra2 = SYSCTL_ONE,
- },
-#endif
#ifdef CONFIG_BPF_SYSCALL
{
.procname = "unprivileged_bpf_disabled",
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 003ccf338d20..5d85014d59b5 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -690,7 +690,7 @@ static ssize_t unbind_device_store(struct device *dev,
{
char name[CS_NAME_LEN];
ssize_t ret = sysfs_get_uname(buf, name, count);
- struct clock_event_device *ce;
+ struct clock_event_device *ce = NULL, *iter;

if (ret < 0)
return ret;
@@ -698,9 +698,10 @@ static ssize_t unbind_device_store(struct device *dev,
ret = -ENODEV;
mutex_lock(&clockevents_mutex);
raw_spin_lock_irq(&clockevents_lock);
- list_for_each_entry(ce, &clockevent_devices, list) {
- if (!strcmp(ce->name, name)) {
- ret = __clockevents_try_unbind(ce, dev->id);
+ list_for_each_entry(iter, &clockevent_devices, list) {
+ if (!strcmp(iter->name, name)) {
+ ret = __clockevents_try_unbind(iter, dev->id);
+ ce = iter;
break;
}
}
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 95d7ca35bdf2..cee5da1e54c4 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -343,7 +343,7 @@ void clocksource_verify_percpu(struct clocksource *cs)
cpus_read_lock();
preempt_disable();
clocksource_verify_choose_cpus();
- if (cpumask_weight(&cpus_chosen) == 0) {
+ if (cpumask_empty(&cpus_chosen)) {
preempt_enable();
cpus_read_unlock();
pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name);
diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
index b1b9b12899f5..8464c5acc913 100644
--- a/kernel/time/sched_clock.c
+++ b/kernel/time/sched_clock.c
@@ -8,6 +8,7 @@
#include <linux/jiffies.h>
#include <linux/ktime.h>
#include <linux/kernel.h>
+#include <linux/math.h>
#include <linux/moduleparam.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
@@ -199,15 +200,13 @@ sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)

r = rate;
if (r >= 4000000) {
- r /= 1000000;
+ r = DIV_ROUND_CLOSEST(r, 1000000);
r_unit = 'M';
+ } else if (r >= 4000) {
+ r = DIV_ROUND_CLOSEST(r, 1000);
+ r_unit = 'k';
} else {
- if (r >= 1000) {
- r /= 1000;
- r_unit = 'k';
- } else {
- r_unit = ' ';
- }
+ r_unit = ' ';
}

/* Calculate the ns resolution of this counter */
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 2d76c91b85de..b1b105db31eb 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -928,6 +928,8 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu)
if (unlikely(expires == KTIME_MAX)) {
if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
hrtimer_cancel(&ts->sched_timer);
+ else
+ tick_program_event(KTIME_MAX, 1);
return;
}

@@ -1364,9 +1366,15 @@ static void tick_nohz_handler(struct clock_event_device *dev)
tick_sched_do_timer(ts, now);
tick_sched_handle(ts, regs);

- /* No need to reprogram if we are running tickless */
- if (unlikely(ts->tick_stopped))
+ if (unlikely(ts->tick_stopped)) {
+ /*
+ * The clockevent device is not reprogrammed, so change the
+ * clock event device to ONESHOT_STOPPED to avoid spurious
+ * interrupts on devices which might not be truly one shot.
+ */
+ tick_program_event(KTIME_MAX, 1);
return;
+ }

hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index dcdcb85121e4..8895ff20f82d 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -429,6 +429,14 @@ static void update_fast_timekeeper(const struct tk_read_base *tkr,
memcpy(base + 1, base, sizeof(*base));
}

+static __always_inline u64 fast_tk_get_delta_ns(struct tk_read_base *tkr)
+{
+ u64 delta, cycles = tk_clock_read(tkr);
+
+ delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
+ return timekeeping_delta_to_ns(tkr, delta);
+}
+
static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
{
struct tk_read_base *tkr;
@@ -439,12 +447,7 @@ static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
seq = raw_read_seqcount_latch(&tkf->seq);
tkr = tkf->base + (seq & 0x01);
now = ktime_to_ns(tkr->base);
-
- now += timekeeping_delta_to_ns(tkr,
- clocksource_delta(
- tk_clock_read(tkr),
- tkr->cycle_last,
- tkr->mask));
+ now += fast_tk_get_delta_ns(tkr);
} while (read_seqcount_latch_retry(&tkf->seq, seq));

return now;
@@ -528,10 +531,27 @@ 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));
+ return (ktime_get_mono_fast_ns() + ktime_to_ns(data_race(tk->offs_boot)));
}
EXPORT_SYMBOL_GPL(ktime_get_boot_fast_ns);

+/**
+ * ktime_get_tai_fast_ns - NMI safe and fast access to tai clock.
+ *
+ * The same limitations as described for ktime_get_boot_fast_ns() apply. The
+ * mono time and the TAI offset are not read atomically which may yield wrong
+ * readouts. However, an update of the TAI offset is an rare event e.g., caused
+ * by settime or adjtimex with an offset. The user of this function has to deal
+ * with the possibility of wrong timestamps in post processing.
+ */
+u64 notrace ktime_get_tai_fast_ns(void)
+{
+ struct timekeeper *tk = &tk_core.timekeeper;
+
+ return (ktime_get_mono_fast_ns() + ktime_to_ns(data_race(tk->offs_tai)));
+}
+EXPORT_SYMBOL_GPL(ktime_get_tai_fast_ns);
+
static __always_inline u64 __ktime_get_real_fast(struct tk_fast *tkf, u64 *mono)
{
struct tk_read_base *tkr;
@@ -543,10 +563,7 @@ static __always_inline u64 __ktime_get_real_fast(struct tk_fast *tkf, u64 *mono)
tkr = tkf->base + (seq & 0x01);
basem = ktime_to_ns(tkr->base);
baser = ktime_to_ns(tkr->base_real);
-
- delta = timekeeping_delta_to_ns(tkr,
- clocksource_delta(tk_clock_read(tkr),
- tkr->cycle_last, tkr->mask));
+ delta = fast_tk_get_delta_ns(tkr);
} while (read_seqcount_latch_retry(&tkf->seq, seq));

if (mono)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 85f1021ad459..a0666d948147 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -44,6 +44,7 @@
#include <linux/slab.h>
#include <linux/compat.h>
#include <linux/random.h>
+#include <linux/sysctl.h>

#include <linux/uaccess.h>
#include <asm/unistd.h>
@@ -223,7 +224,7 @@ static void timer_update_keys(struct work_struct *work);
static DECLARE_WORK(timer_update_work, timer_update_keys);

#ifdef CONFIG_SMP
-unsigned int sysctl_timer_migration = 1;
+static unsigned int sysctl_timer_migration = 1;

DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);

@@ -234,7 +235,42 @@ static void timers_update_migration(void)
else
static_branch_disable(&timers_migration_enabled);
}
-#else
+
+#ifdef CONFIG_SYSCTL
+static int timer_migration_handler(struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ int ret;
+
+ mutex_lock(&timer_keys_mutex);
+ ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+ if (!ret && write)
+ timers_update_migration();
+ mutex_unlock(&timer_keys_mutex);
+ return ret;
+}
+
+static struct ctl_table timer_sysctl[] = {
+ {
+ .procname = "timer_migration",
+ .data = &sysctl_timer_migration,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = timer_migration_handler,
+ .extra1 = SYSCTL_ZERO,
+ .extra2 = SYSCTL_ONE,
+ },
+ {}
+};
+
+static int __init timer_sysctl_init(void)
+{
+ register_sysctl("kernel", timer_sysctl);
+ return 0;
+}
+device_initcall(timer_sysctl_init);
+#endif /* CONFIG_SYSCTL */
+#else /* CONFIG_SMP */
static inline void timers_update_migration(void) { }
#endif /* !CONFIG_SMP */

@@ -251,19 +287,6 @@ void timers_update_nohz(void)
schedule_work(&timer_update_work);
}

-int timer_migration_handler(struct ctl_table *table, int write,
- void *buffer, size_t *lenp, loff_t *ppos)
-{
- int ret;
-
- mutex_lock(&timer_keys_mutex);
- ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
- if (!ret && write)
- timers_update_migration();
- mutex_unlock(&timer_keys_mutex);
- return ret;
-}
-
static inline bool is_timers_nohz_active(void)
{
return static_branch_unlikely(&timers_nohz_active);
@@ -502,7 +525,7 @@ static inline unsigned calc_index(unsigned long expires, unsigned lvl,
*
* Round up with level granularity to prevent this.
*/
- expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
+ expires = (expires >> LVL_SHIFT(lvl)) + 1;
*bucket_expiry = expires << LVL_SHIFT(lvl);
return LVL_OFFS(lvl) + (expires & LVL_MASK);
}
@@ -615,9 +638,39 @@ static void internal_add_timer(struct timer_base *base, struct timer_list *timer

static const struct debug_obj_descr timer_debug_descr;

+struct timer_hint {
+ void (*function)(struct timer_list *t);
+ long offset;
+};
+
+#define TIMER_HINT(fn, container, timr, hintfn) \
+ { \
+ .function = fn, \
+ .offset = offsetof(container, hintfn) - \
+ offsetof(container, timr) \
+ }
+
+static const struct timer_hint timer_hints[] = {
+ TIMER_HINT(delayed_work_timer_fn,
+ struct delayed_work, timer, work.func),
+ TIMER_HINT(kthread_delayed_work_timer_fn,
+ struct kthread_delayed_work, timer, work.func),
+};
+
static void *timer_debug_hint(void *addr)
{
- return ((struct timer_list *) addr)->function;
+ struct timer_list *timer = addr;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(timer_hints); i++) {
+ if (timer_hints[i].function == timer->function) {
+ void (**fn)(void) = addr + timer_hints[i].offset;
+
+ return *fn;
+ }
+ }
+
+ return timer->function;
}

static bool timer_is_static_object(void *addr)
@@ -1722,11 +1775,14 @@ static inline void __run_timers(struct timer_base *base)
time_after_eq(jiffies, base->next_expiry)) {
levels = collect_expired_timers(base, heads);
/*
- * The only possible reason for not finding any expired
- * timer at this clk is that all matching timers have been
- * dequeued.
+ * The two possible reasons for not finding any expired
+ * timer at this clk are that all matching timers have been
+ * dequeued or no timer has been queued since
+ * base::next_expiry was set to base::clk +
+ * NEXT_TIMER_MAX_DELTA.
*/
- WARN_ON_ONCE(!levels && !base->next_expiry_recalc);
+ WARN_ON_ONCE(!levels && !base->next_expiry_recalc
+ && base->timers_pending);
base->clk++;
base->next_expiry = __next_timer_interrupt(base);

@@ -1950,6 +2006,7 @@ int timers_prepare_cpu(unsigned int cpu)
base = per_cpu_ptr(&timer_bases[b], cpu);
base->clk = jiffies;
base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
+ base->next_expiry_recalc = false;
base->timers_pending = false;
base->is_idle = false;
}