summaryrefslogtreecommitdiff
path: root/kernel
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2024-04-07 19:20:50 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2024-04-07 19:20:50 +0300
commit3520c35e5f0b00cfd6a774d04c1b3bb18edc428a (patch)
tree446e06cb35efcc5551ba35ae7c7a7647d9918295 /kernel
parente2948effa9063ae8bd0e7dd65ca4a0fa068c71a6 (diff)
parent7a96a84bfbee96871bb16c70ee3e93d564e190f4 (diff)
downloadlinux-3520c35e5f0b00cfd6a774d04c1b3bb18edc428a.tar.xz
Merge tag 'timers-urgent-2024-04-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fixes from Ingo Molnar: "Fix various timer bugs: - Fix a timer migration bug that may result in missed events - Fix timer migration group hierarchy event updates - Fix a PowerPC64 build warning - Fix a handful of DocBook annotation bugs" * tag 'timers-urgent-2024-04-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: timers/migration: Return early on deactivation timers/migration: Fix ignored event due to missing CPU update vdso: Use CONFIG_PAGE_SHIFT in vdso/datapage.h timers: Fix text inconsistencies and spelling tick/sched: Fix struct tick_sched doc warnings tick/sched: Fix various kernel-doc warnings timers: Fix kernel-doc format and add Return values time/timekeeping: Fix kernel-doc warnings and typos time/timecounter: Fix inline documentation
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/tick-sched.c18
-rw-r--r--kernel/time/tick-sched.h2
-rw-r--r--kernel/time/timer.c22
-rw-r--r--kernel/time/timer_migration.c32
4 files changed, 58 insertions, 16 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 269e21590df5..1331216a9cae 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -697,6 +697,7 @@ bool tick_nohz_tick_stopped_cpu(int cpu)
/**
* tick_nohz_update_jiffies - update jiffies when idle was interrupted
+ * @now: current ktime_t
*
* Called from interrupt entry when the CPU was idle
*
@@ -794,7 +795,7 @@ static u64 get_cpu_sleep_time_us(struct tick_sched *ts, ktime_t *sleeptime,
* This time is measured via accounting rather than sampling,
* and is as accurate as ktime_get() is.
*
- * This function returns -1 if NOHZ is not enabled.
+ * Return: -1 if NOHZ is not enabled, else total idle time of the @cpu
*/
u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
{
@@ -820,7 +821,7 @@ EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
* This time is measured via accounting rather than sampling,
* and is as accurate as ktime_get() is.
*
- * This function returns -1 if NOHZ is not enabled.
+ * Return: -1 if NOHZ is not enabled, else total iowait time of @cpu
*/
u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
{
@@ -1287,6 +1288,8 @@ void tick_nohz_irq_exit(void)
/**
* tick_nohz_idle_got_tick - Check whether or not the tick handler has run
+ *
+ * Return: %true if the tick handler has run, otherwise %false
*/
bool tick_nohz_idle_got_tick(void)
{
@@ -1305,6 +1308,8 @@ bool tick_nohz_idle_got_tick(void)
* stopped, it returns the next hrtimer.
*
* Called from power state control code with interrupts disabled
+ *
+ * Return: the next expiration time
*/
ktime_t tick_nohz_get_next_hrtimer(void)
{
@@ -1320,6 +1325,8 @@ ktime_t tick_nohz_get_next_hrtimer(void)
* The return value of this function and/or the value returned by it through the
* @delta_next pointer can be negative which must be taken into account by its
* callers.
+ *
+ * Return: the expected length of the current sleep
*/
ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next)
{
@@ -1357,8 +1364,11 @@ ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next)
/**
* tick_nohz_get_idle_calls_cpu - return the current idle calls counter value
* for a particular CPU.
+ * @cpu: target CPU number
*
* Called from the schedutil frequency scaling governor in scheduler context.
+ *
+ * Return: the current idle calls counter value for @cpu
*/
unsigned long tick_nohz_get_idle_calls_cpu(int cpu)
{
@@ -1371,6 +1381,8 @@ unsigned long tick_nohz_get_idle_calls_cpu(int cpu)
* tick_nohz_get_idle_calls - return the current idle calls counter value
*
* Called from the schedutil frequency scaling governor in scheduler context.
+ *
+ * Return: the current idle calls counter value for the current CPU
*/
unsigned long tick_nohz_get_idle_calls(void)
{
@@ -1559,7 +1571,7 @@ early_param("skew_tick", skew_tick);
/**
* tick_setup_sched_timer - setup the tick emulation timer
- * @mode: tick_nohz_mode to setup for
+ * @hrtimer: whether to use the hrtimer or not
*/
void tick_setup_sched_timer(bool hrtimer)
{
diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
index e11c4dc65bcb..b4a7822f495d 100644
--- a/kernel/time/tick-sched.h
+++ b/kernel/time/tick-sched.h
@@ -46,8 +46,8 @@ struct tick_device {
* @next_tick: Next tick to be fired when in dynticks mode.
* @idle_jiffies: jiffies at the entry to idle for idle time accounting
* @idle_waketime: Time when the idle was interrupted
+ * @idle_sleeptime_seq: sequence counter for data consistency
* @idle_entrytime: Time when the idle call was entered
- * @nohz_mode: Mode - one state of tick_nohz_mode
* @last_jiffies: Base jiffies snapshot when next event was last computed
* @timer_expires_base: Base time clock monotonic for @timer_expires
* @timer_expires: Anticipated timer expiration time (in case sched tick is stopped)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index dee29f1f5b75..3baf2fbe6848 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -64,15 +64,15 @@ EXPORT_SYMBOL(jiffies_64);
/*
* The timer wheel has LVL_DEPTH array levels. Each level provides an array of
- * LVL_SIZE buckets. Each level is driven by its own clock and therefor each
+ * LVL_SIZE buckets. Each level is driven by its own clock and therefore each
* level has a different granularity.
*
- * The level granularity is: LVL_CLK_DIV ^ lvl
+ * The level granularity is: LVL_CLK_DIV ^ level
* The level clock frequency is: HZ / (LVL_CLK_DIV ^ level)
*
* The array level of a newly armed timer depends on the relative expiry
* time. The farther the expiry time is away the higher the array level and
- * therefor the granularity becomes.
+ * therefore the granularity becomes.
*
* Contrary to the original timer wheel implementation, which aims for 'exact'
* expiry of the timers, this implementation removes the need for recascading
@@ -207,7 +207,7 @@ EXPORT_SYMBOL(jiffies_64);
* struct timer_base - Per CPU timer base (number of base depends on config)
* @lock: Lock protecting the timer_base
* @running_timer: When expiring timers, the lock is dropped. To make
- * sure not to race agains deleting/modifying a
+ * sure not to race against deleting/modifying a
* currently running timer, the pointer is set to the
* timer, which expires at the moment. If no timer is
* running, the pointer is NULL.
@@ -737,7 +737,7 @@ static bool timer_is_static_object(void *addr)
}
/*
- * fixup_init is called when:
+ * timer_fixup_init is called when:
* - an active object is initialized
*/
static bool timer_fixup_init(void *addr, enum debug_obj_state state)
@@ -761,7 +761,7 @@ static void stub_timer(struct timer_list *unused)
}
/*
- * fixup_activate is called when:
+ * timer_fixup_activate is called when:
* - an active object is activated
* - an unknown non-static object is activated
*/
@@ -783,7 +783,7 @@ static bool timer_fixup_activate(void *addr, enum debug_obj_state state)
}
/*
- * fixup_free is called when:
+ * timer_fixup_free is called when:
* - an active object is freed
*/
static bool timer_fixup_free(void *addr, enum debug_obj_state state)
@@ -801,7 +801,7 @@ static bool timer_fixup_free(void *addr, enum debug_obj_state state)
}
/*
- * fixup_assert_init is called when:
+ * timer_fixup_assert_init is called when:
* - an untracked/uninit-ed object is found
*/
static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state)
@@ -914,7 +914,7 @@ static void do_init_timer(struct timer_list *timer,
* @key: lockdep class key of the fake lock used for tracking timer
* sync lock dependencies
*
- * init_timer_key() must be done to a timer prior calling *any* of the
+ * init_timer_key() must be done to a timer prior to calling *any* of the
* other timer functions.
*/
void init_timer_key(struct timer_list *timer,
@@ -1417,7 +1417,7 @@ static int __timer_delete(struct timer_list *timer, bool shutdown)
* If @shutdown is set then the lock has to be taken whether the
* timer is pending or not to protect against a concurrent rearm
* which might hit between the lockless pending check and the lock
- * aquisition. By taking the lock it is ensured that such a newly
+ * acquisition. By taking the lock it is ensured that such a newly
* enqueued timer is dequeued and cannot end up with
* timer->function == NULL in the expiry code.
*
@@ -2306,7 +2306,7 @@ static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 basem,
/*
* When timer base is not set idle, undo the effect of
- * tmigr_cpu_deactivate() to prevent inconsitent states - active
+ * tmigr_cpu_deactivate() to prevent inconsistent states - active
* timer base but inactive timer migration hierarchy.
*
* When timer base was already marked idle, nothing will be
diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index c63a0afdcebe..ccba875d2234 100644
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -751,6 +751,33 @@ bool tmigr_update_events(struct tmigr_group *group, struct tmigr_group *child,
first_childevt = evt = data->evt;
+ /*
+ * Walking the hierarchy is required in any case when a
+ * remote expiry was done before. This ensures to not lose
+ * already queued events in non active groups (see section
+ * "Required event and timerqueue update after a remote
+ * expiry" in the documentation at the top).
+ *
+ * The two call sites which are executed without a remote expiry
+ * before, are not prevented from propagating changes through
+ * the hierarchy by the return:
+ * - When entering this path by tmigr_new_timer(), @evt->ignore
+ * is never set.
+ * - tmigr_inactive_up() takes care of the propagation by
+ * itself and ignores the return value. But an immediate
+ * return is possible if there is a parent, sparing group
+ * locking at this level, because the upper walking call to
+ * the parent will take care about removing this event from
+ * within the group and update next_expiry accordingly.
+ *
+ * However if there is no parent, ie: the hierarchy has only a
+ * single level so @group is the top level group, make sure the
+ * first event information of the group is updated properly and
+ * also handled properly, so skip this fast return path.
+ */
+ if (evt->ignore && !remote && group->parent)
+ return true;
+
raw_spin_lock(&group->lock);
childstate.state = 0;
@@ -762,8 +789,11 @@ bool tmigr_update_events(struct tmigr_group *group, struct tmigr_group *child,
* queue when the expiry time changed only or when it could be ignored.
*/
if (timerqueue_node_queued(&evt->nextevt)) {
- if ((evt->nextevt.expires == nextexp) && !evt->ignore)
+ if ((evt->nextevt.expires == nextexp) && !evt->ignore) {
+ /* Make sure not to miss a new CPU event with the same expiry */
+ evt->cpu = first_childevt->cpu;
goto check_toplvl;
+ }
if (!timerqueue_del(&group->events, &evt->nextevt))
WRITE_ONCE(group->next_expiry, KTIME_MAX);