[PATCH 09/24] timekeeping: Move timekeeper_lock into tk_core

Anna-Maria Behnsen
2024-09-11T13:30:07Z

timekeeper_lock protects updates to struct tk_core but is not part of
struct tk_core. As long as there is only a single timekeeper, this is not a
problem. But when the timekeeper infrastructure will be reused for per ptp
clock timekeepers, timekeeper_lock needs to be part of tk_core.

Move the lock into tk_core, move initialisation of the lock and sequence
counter into timekeeping_init() and update all users of timekeeper_lock.

As this is touching all lock sites, convert them to use:

guard(raw_spinlock_irqsave)(&tk_core.lock);

instead of lock/unlock functions whenever possible.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
---
kernel/time/timekeeping.c | 77 +++++++++++++++++++++--------------------------
1 file changed, 34 insertions(+), 43 deletions(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e0b6d088a33b..f8ffab5bb790 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -41,8 +41,6 @@ enum timekeeping_adv_mode {
TK_ADV_FREQ
};

-static DEFINE_RAW_SPINLOCK(timekeeper_lock);
-
/*
* The most important data for readout fits into a single 64 byte
* cache line.
@@ -51,10 +49,8 @@ static struct {
seqcount_raw_spinlock_t seq;
struct timekeeper timekeeper;
struct timekeeper shadow_timekeeper;
-} tk_core ____cacheline_aligned = {
- .seq = SEQCNT_RAW_SPINLOCK_ZERO(tk_core.seq, &timekeeper_lock),
-};
-
+ raw_spinlock_t lock;
+} tk_core ____cacheline_aligned;

/* flag for if timekeeping is suspended */
int __read_mostly timekeeping_suspended;
@@ -118,13 +114,13 @@ unsigned long timekeeper_lock_irqsave(void)
{
unsigned long flags;

- raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ raw_spin_lock_irqsave(&tk_core.lock, flags);
return flags;
}

void timekeeper_unlock_irqrestore(unsigned long flags)
{
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+ raw_spin_unlock_irqrestore(&tk_core.lock, flags);
}

static inline void tk_normalize_xtime(struct timekeeper *tk)
@@ -197,7 +193,7 @@ static inline void tk_update_sleep_time(struct timekeeper *tk, ktime_t delta)
* the tkr's clocksource may change between the read reference, and the
* clock reference passed to the read function. This can cause crashes if
* the wrong clocksource is passed to the wrong read function.
- * This isn't necessary to use when holding the timekeeper_lock or doing
+ * This isn't necessary to use when holding the tk_core.lock or doing
* a read of the fast-timekeeper tkrs (which is protected by its own locking
* and update logic).
*/
@@ -689,13 +685,11 @@ static void update_pvclock_gtod(struct timekeeper *tk, bool was_set)
int pvclock_gtod_register_notifier(struct notifier_block *nb)
{
struct timekeeper *tk = &tk_core.timekeeper;
- unsigned long flags;
int ret;

- raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ guard(raw_spinlock_irqsave)(&tk_core.lock);
ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);
update_pvclock_gtod(tk, true);
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

return ret;
}
@@ -708,14 +702,8 @@ EXPORT_SYMBOL_GPL(pvclock_gtod_register_notifier);
*/
int pvclock_gtod_unregister_notifier(struct notifier_block *nb)
{
- unsigned long flags;
- int ret;
-
- raw_spin_lock_irqsave(&timekeeper_lock, flags);
- ret = raw_notifier_chain_unregister(&pvclock_gtod_chain, nb);
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
-
- return ret;
+ guard(raw_spinlock_irqsave)(&tk_core.lock);
+ return raw_notifier_chain_unregister(&pvclock_gtod_chain, nb);
}
EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);

@@ -763,7 +751,7 @@ static inline void tk_update_ktime_data(struct timekeeper *tk)
tk->tkr_raw.base = ns_to_ktime(tk->raw_sec * NSEC_PER_SEC);
}

-/* must hold timekeeper_lock */
+/* must hold tk_core.lock */
static void timekeeping_update(struct timekeeper *tk, unsigned int action)
{
if (action & TK_CLEAR_NTP) {
@@ -1460,7 +1448,7 @@ int do_settimeofday64(const struct timespec64 *ts)
if (!timespec64_valid_settod(ts))
return -EINVAL;

- raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ raw_spin_lock_irqsave(&tk_core.lock, flags);
write_seqcount_begin(&tk_core.seq);

timekeeping_forward_now(tk);
@@ -1480,7 +1468,7 @@ int do_settimeofday64(const struct timespec64 *ts)
timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);

write_seqcount_end(&tk_core.seq);
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+ raw_spin_unlock_irqrestore(&tk_core.lock, flags);

/* Signal hrtimers about time change */
clock_was_set(CLOCK_SET_WALL);
@@ -1510,7 +1498,7 @@ static int timekeeping_inject_offset(const struct timespec64 *ts)
if (ts->tv_nsec < 0 || ts->tv_nsec >= NSEC_PER_SEC)
return -EINVAL;

- raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ raw_spin_lock_irqsave(&tk_core.lock, flags);
write_seqcount_begin(&tk_core.seq);

timekeeping_forward_now(tk);
@@ -1530,7 +1518,7 @@ static int timekeeping_inject_offset(const struct timespec64 *ts)
timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);

write_seqcount_end(&tk_core.seq);
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+ raw_spin_unlock_irqrestore(&tk_core.lock, flags);

/* Signal hrtimers about time change */
clock_was_set(CLOCK_SET_WALL);
@@ -1606,7 +1594,7 @@ static int change_clocksource(void *data)
return 0;
}

- raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ raw_spin_lock_irqsave(&tk_core.lock, flags);
write_seqcount_begin(&tk_core.seq);

timekeeping_forward_now(tk);
@@ -1615,7 +1603,7 @@ static int change_clocksource(void *data)
timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);

write_seqcount_end(&tk_core.seq);
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+ raw_spin_unlock_irqrestore(&tk_core.lock, flags);

if (old) {
if (old->disable)
@@ -1744,6 +1732,12 @@ read_persistent_wall_and_boot_offset(struct timespec64 *wall_time,
*boot_offset = ns_to_timespec64(local_clock());
}

+static __init void tkd_basic_setup(struct tk_data *tkd)
+{
+ raw_spin_lock_init(&tkd->lock);
+ seqcount_raw_spinlock_init(&tkd->seq, &tkd->lock);
+}
+
/*
* Flag reflecting whether timekeeping_resume() has injected sleeptime.
*
@@ -1770,7 +1764,8 @@ void __init timekeeping_init(void)
struct timespec64 wall_time, boot_offset, wall_to_mono;
struct timekeeper *tk = &tk_core.timekeeper;
struct clocksource *clock;
- unsigned long flags;
+
+ tkd_basic_setup(&tk_core);

read_persistent_wall_and_boot_offset(&wall_time, &boot_offset);
if (timespec64_valid_settod(&wall_time) &&
@@ -1790,7 +1785,7 @@ void __init timekeeping_init(void)
*/
wall_to_mono = timespec64_sub(boot_offset, wall_time);

- raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ guard(raw_spinlock_irqsave)(&tk_core.lock);
write_seqcount_begin(&tk_core.seq);
ntp_init();

@@ -1807,7 +1802,6 @@ void __init timekeeping_init(void)
timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);

write_seqcount_end(&tk_core.seq);
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
}

/* time in seconds when suspend began for persistent clock */
@@ -1888,7 +1882,7 @@ void timekeeping_inject_sleeptime64(const struct timespec64 *delta)
struct timekeeper *tk = &tk_core.timekeeper;
unsigned long flags;

- raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ raw_spin_lock_irqsave(&tk_core.lock, flags);
write_seqcount_begin(&tk_core.seq);

suspend_timing_needed = false;
@@ -1900,7 +1894,7 @@ void timekeeping_inject_sleeptime64(const struct timespec64 *delta)
timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);

write_seqcount_end(&tk_core.seq);
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+ raw_spin_unlock_irqrestore(&tk_core.lock, flags);

/* Signal hrtimers about time change */
clock_was_set(CLOCK_SET_WALL | CLOCK_SET_BOOT);
@@ -1924,7 +1918,7 @@ void timekeeping_resume(void)
clockevents_resume();
clocksource_resume();

- raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ raw_spin_lock_irqsave(&tk_core.lock, flags);
write_seqcount_begin(&tk_core.seq);

/*
@@ -1962,7 +1956,7 @@ void timekeeping_resume(void)
timekeeping_suspended = 0;
timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
write_seqcount_end(&tk_core.seq);
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+ raw_spin_unlock_irqrestore(&tk_core.lock, flags);

touch_softlockup_watchdog();

@@ -1993,7 +1987,7 @@ int timekeeping_suspend(void)

suspend_timing_needed = true;

- raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ raw_spin_lock_irqsave(&tk_core.lock, flags);
write_seqcount_begin(&tk_core.seq);
timekeeping_forward_now(tk);
timekeeping_suspended = 1;
@@ -2032,7 +2026,7 @@ int timekeeping_suspend(void)
timekeeping_update(tk, TK_MIRROR);
halt_fast_timekeeper(tk);
write_seqcount_end(&tk_core.seq);
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+ raw_spin_unlock_irqrestore(&tk_core.lock, flags);

tick_suspend();
clocksource_suspend();
@@ -2292,7 +2286,7 @@ static bool timekeeping_advance(enum timekeeping_adv_mode mode)
int shift = 0, maxshift;
u64 offset;

- guard(raw_spinlock_irqsave)(&timekeeper_lock);
+ guard(raw_spinlock_irqsave)(&tk_core.lock);

/* Make sure we're fully resumed: */
if (unlikely(timekeeping_suspended))
@@ -2587,7 +2581,7 @@ int do_adjtimex(struct __kernel_timex *txc)
ktime_get_real_ts64(&ts);
add_device_randomness(&ts, sizeof(ts));

- raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ raw_spin_lock_irqsave(&tk_core.lock, flags);
write_seqcount_begin(&tk_core.seq);

orig_tai = tai = tk->tai_offset;
@@ -2602,7 +2596,7 @@ int do_adjtimex(struct __kernel_timex *txc)
}

write_seqcount_end(&tk_core.seq);
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+ raw_spin_unlock_irqrestore(&tk_core.lock, flags);

audit_ntp_log(&ad);

@@ -2626,11 +2620,8 @@ int do_adjtimex(struct __kernel_timex *txc)
*/
void hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
{
- unsigned long flags;
-
- raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ guard(raw_spinlock_irqsave)(&tk_core.lock);
__hardpps(phase_ts, raw_ts);
- raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
}
EXPORT_SYMBOL(hardpps);
#endif /* CONFIG_NTP_PPS */

--
2.39.2