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Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull timekeeping fixes from Thomas Gleixner:
 "Two fixes for timekeeping:

   - Revert to the previous kthread based update, which is unfortunately
     required due to lock ordering issues. The removal caused boot
     failures on old Core2 machines. Add a proper comment why the thread
     needs to stay to prevent accidental removal in the future.

   - Fix a silly typo in a function declaration"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  clocksource: Revert "Remove kthread"
  timekeeping: Fix declaration of read_persistent_wall_and_boot_offset()
This commit is contained in:
Linus Torvalds 2018-09-09 06:55:27 -07:00
commit 3567994a05
2 changed files with 32 additions and 12 deletions
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4
include/linux/timekeeping.h
View File

@ -258,8 +258,8 @@ extern void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot);
extern int persistent_clock_is_local; extern int persistent_clock_is_local;
extern void read_persistent_clock64(struct timespec64 *ts); extern void read_persistent_clock64(struct timespec64 *ts);
void read_persistent_clock_and_boot_offset(struct timespec64 *wall_clock, void read_persistent_wall_and_boot_offset(struct timespec64 *wall_clock,
struct timespec64 *boot_offset); struct timespec64 *boot_offset);
extern int update_persistent_clock64(struct timespec64 now); extern int update_persistent_clock64(struct timespec64 now);
/* /*

40
kernel/time/clocksource.c
View File

@ -133,19 +133,40 @@ static void inline clocksource_watchdog_unlock(unsigned long *flags)
spin_unlock_irqrestore(&watchdog_lock, *flags); spin_unlock_irqrestore(&watchdog_lock, *flags);
} }
static int clocksource_watchdog_kthread(void *data);
static void __clocksource_change_rating(struct clocksource *cs, int rating);
/* /*
* Interval: 0.5sec Threshold: 0.0625s * Interval: 0.5sec Threshold: 0.0625s
*/ */
#define WATCHDOG_INTERVAL (HZ >> 1) #define WATCHDOG_INTERVAL (HZ >> 1)
#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4) #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
static void clocksource_watchdog_work(struct work_struct *work)
{
/*
* We cannot directly run clocksource_watchdog_kthread() here, because
* clocksource_select() calls timekeeping_notify() which uses
* stop_machine(). One cannot use stop_machine() from a workqueue() due
* lock inversions wrt CPU hotplug.
*
* Also, we only ever run this work once or twice during the lifetime
* of the kernel, so there is no point in creating a more permanent
* kthread for this.
*
* If kthread_run fails the next watchdog scan over the
* watchdog_list will find the unstable clock again.
*/
kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
}
static void __clocksource_unstable(struct clocksource *cs) static void __clocksource_unstable(struct clocksource *cs)
{ {
cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG); cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
cs->flags |= CLOCK_SOURCE_UNSTABLE; cs->flags |= CLOCK_SOURCE_UNSTABLE;
/* /*
* If the clocksource is registered clocksource_watchdog_work() will * If the clocksource is registered clocksource_watchdog_kthread() will
* re-rate and re-select. * re-rate and re-select.
*/ */
if (list_empty(&cs->list)) { if (list_empty(&cs->list)) {
@ -156,7 +177,7 @@ static void __clocksource_unstable(struct clocksource *cs)
if (cs->mark_unstable) if (cs->mark_unstable)
cs->mark_unstable(cs); cs->mark_unstable(cs);
/* kick clocksource_watchdog_work() */ /* kick clocksource_watchdog_kthread() */
if (finished_booting) if (finished_booting)
schedule_work(&watchdog_work); schedule_work(&watchdog_work);
} }
@ -166,7 +187,7 @@ static void __clocksource_unstable(struct clocksource *cs)
* @cs: clocksource to be marked unstable * @cs: clocksource to be marked unstable
* *
* This function is called by the x86 TSC code to mark clocksources as unstable; * This function is called by the x86 TSC code to mark clocksources as unstable;
* it defers demotion and re-selection to a work. * it defers demotion and re-selection to a kthread.
*/ */
void clocksource_mark_unstable(struct clocksource *cs) void clocksource_mark_unstable(struct clocksource *cs)
{ {
@ -391,9 +412,7 @@ static void clocksource_dequeue_watchdog(struct clocksource *cs)
} }
} }
static void __clocksource_change_rating(struct clocksource *cs, int rating); static int __clocksource_watchdog_kthread(void)
static int __clocksource_watchdog_work(void)
{ {
struct clocksource *cs, *tmp; struct clocksource *cs, *tmp;
unsigned long flags; unsigned long flags;
@ -418,12 +437,13 @@ static int __clocksource_watchdog_work(void)
return select; return select;
} }
static void clocksource_watchdog_work(struct work_struct *work) static int clocksource_watchdog_kthread(void *data)
{ {
mutex_lock(&clocksource_mutex); mutex_lock(&clocksource_mutex);
if (__clocksource_watchdog_work()) if (__clocksource_watchdog_kthread())
clocksource_select(); clocksource_select();
mutex_unlock(&clocksource_mutex); mutex_unlock(&clocksource_mutex);
return 0;
} }
static bool clocksource_is_watchdog(struct clocksource *cs) static bool clocksource_is_watchdog(struct clocksource *cs)
@ -442,7 +462,7 @@ static void clocksource_enqueue_watchdog(struct clocksource *cs)
static void clocksource_select_watchdog(bool fallback) { } static void clocksource_select_watchdog(bool fallback) { }
static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { } static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
static inline void clocksource_resume_watchdog(void) { } static inline void clocksource_resume_watchdog(void) { }
static inline int __clocksource_watchdog_work(void) { return 0; } static inline int __clocksource_watchdog_kthread(void) { return 0; }
static bool clocksource_is_watchdog(struct clocksource *cs) { return false; } static bool clocksource_is_watchdog(struct clocksource *cs) { return false; }
void clocksource_mark_unstable(struct clocksource *cs) { } void clocksource_mark_unstable(struct clocksource *cs) { }
@ -810,7 +830,7 @@ static int __init clocksource_done_booting(void)
/* /*
* Run the watchdog first to eliminate unstable clock sources * Run the watchdog first to eliminate unstable clock sources
*/ */
__clocksource_watchdog_work(); __clocksource_watchdog_kthread();
clocksource_select(); clocksource_select();
mutex_unlock(&clocksource_mutex); mutex_unlock(&clocksource_mutex);
return 0; return 0;