[GIT PULL] scheduler tree updates for v3.20

From: Ingo Molnar
Date: Mon Feb 09 2015 - 04:04:20 EST

Linus,

Please pull the latest sched-core-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-core-for-linus

# HEAD: 139b6fd26d85a65c4e0d2795b87b94f9505e5943 sched/Documentation: Remove unneeded word

The main scheduler changes in this cycle were:

- various sched/deadline fixes and enhancements

- rescheduling latency fixes/cleanups

- rework the rq->clock code to be more consistent and
more robust.

- minor micro-optimizations

- ->avg.decay_count fixes

- add a stack overflow check to might_sleep()

- idle-poll handler fix, possibly resulting in power savings

- misc smaller updates and fixes

Thanks,

Ingo

------------------>
Eric Sandeen (1):
sched/debug: Check for stack overflow in ___might_sleep()

Frederic Weisbecker (2):
sched: Fix missing preemption opportunity
sched: Pull resched loop to __schedule() callers

Johan Hedberg (1):
sched/wait: Introduce wait_on_bit_timeout()

Kirill Tkhai (1):
sched/fair: Fix sched_entity::avg::decay_count initialization

Peter Zijlstra (4):
sched/core: Validate rq_clock*() serialization
sched/core: Rework rq->clock update skips
sched/debug: Print rq->clock_task
sched/deadline: Fix stale yield state

Preeti U Murthy (1):
sched/idle: Add missing checks to the exit condition of cpu_idle_poll()

Sharon Dvir (1):
sched/Documentation: Remove unneeded word

Tetsuo Handa (1):
sched/debug: Fix potential call to __ffs(0) in sched_show_task()

Tim Chen (1):
sched/rt: Reduce rq lock contention by eliminating locking of non-feasible target

Wanpeng Li (3):
sched/deadline: Fix hrtick for a non-leftmost task
sched/deadline: Avoid pointless __setscheduler()
sched: Fix hrtick_start() on UP

Xunlei Pang (3):
sched/fair: Fix the dealing with decay_count in __synchronize_entity_decay()
sched/deadline: Modify cpudl::free_cpus to reflect rd->online
sched/deadline: Remove cpu_active_mask from cpudl_find()

Yao Dongdong (1):
sched/core: Remove check of p->sched_class


include/linux/wait.h | 26 +++++++++++
kernel/locking/mutex.c | 2 +-
kernel/sched/core.c | 107 +++++++++++++++++++++++++++++----------------
kernel/sched/cpudeadline.c | 27 ++++++++++--
kernel/sched/cpudeadline.h | 2 +
kernel/sched/deadline.c | 51 +++++++++++----------
kernel/sched/debug.c | 1 +
kernel/sched/fair.c | 7 ++-
kernel/sched/idle.c | 3 +-
kernel/sched/rt.c | 26 +++++++++--
kernel/sched/sched.h | 22 +++++++++-
11 files changed, 197 insertions(+), 77 deletions(-)

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 37423e0e1379..537d58eea8a0 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -990,6 +990,32 @@ wait_on_bit_io(void *word, int bit, unsigned mode)
}

/**
+ * wait_on_bit_timeout - wait for a bit to be cleared or a timeout elapses
+ * @word: the word being waited on, a kernel virtual address
+ * @bit: the bit of the word being waited on
+ * @mode: the task state to sleep in
+ * @timeout: timeout, in jiffies
+ *
+ * Use the standard hashed waitqueue table to wait for a bit
+ * to be cleared. This is similar to wait_on_bit(), except also takes a
+ * timeout parameter.
+ *
+ * Returned value will be zero if the bit was cleared before the
+ * @timeout elapsed, or non-zero if the @timeout elapsed or process
+ * received a signal and the mode permitted wakeup on that signal.
+ */
+static inline int
+wait_on_bit_timeout(void *word, int bit, unsigned mode, unsigned long timeout)
+{
+ might_sleep();
+ if (!test_bit(bit, word))
+ return 0;
+ return out_of_line_wait_on_bit_timeout(word, bit,
+ bit_wait_timeout,
+ mode, timeout);
+}
+
+/**
* wait_on_bit_action - wait for a bit to be cleared
* @word: the word being waited on, a kernel virtual address
* @bit: the bit of the word being waited on
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 454195194d4a..5b49f652a3cf 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -81,7 +81,7 @@ __visible void __sched __mutex_lock_slowpath(atomic_t *lock_count);
* The mutex must later on be released by the same task that
* acquired it. Recursive locking is not allowed. The task
* may not exit without first unlocking the mutex. Also, kernel
- * memory where the mutex resides mutex must not be freed with
+ * memory where the mutex resides must not be freed with
* the mutex still locked. The mutex must first be initialized
* (or statically defined) before it can be locked. memset()-ing
* the mutex to 0 is not allowed.
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9e838095beb8..b269e8a2a516 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -119,7 +119,9 @@ void update_rq_clock(struct rq *rq)
{
s64 delta;

- if (rq->skip_clock_update > 0)
+ lockdep_assert_held(&rq->lock);
+
+ if (rq->clock_skip_update & RQCF_ACT_SKIP)
return;

delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
@@ -490,6 +492,11 @@ static __init void init_hrtick(void)
*/
void hrtick_start(struct rq *rq, u64 delay)
{
+ /*
+ * Don't schedule slices shorter than 10000ns, that just
+ * doesn't make sense. Rely on vruntime for fairness.
+ */
+ delay = max_t(u64, delay, 10000LL);
__hrtimer_start_range_ns(&rq->hrtick_timer, ns_to_ktime(delay), 0,
HRTIMER_MODE_REL_PINNED, 0);
}
@@ -1046,7 +1053,7 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
* this case, we can save a useless back to back clock update.
*/
if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
- rq->skip_clock_update = 1;
+ rq_clock_skip_update(rq, true);
}

#ifdef CONFIG_SMP
@@ -1836,6 +1843,9 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
p->se.prev_sum_exec_runtime = 0;
p->se.nr_migrations = 0;
p->se.vruntime = 0;
+#ifdef CONFIG_SMP
+ p->se.avg.decay_count = 0;
+#endif
INIT_LIST_HEAD(&p->se.group_node);

#ifdef CONFIG_SCHEDSTATS
@@ -2755,6 +2765,10 @@ pick_next_task(struct rq *rq, struct task_struct *prev)
* - explicit schedule() call
* - return from syscall or exception to user-space
* - return from interrupt-handler to user-space
+ *
+ * WARNING: all callers must re-check need_resched() afterward and reschedule
+ * accordingly in case an event triggered the need for rescheduling (such as
+ * an interrupt waking up a task) while preemption was disabled in __schedule().
*/
static void __sched __schedule(void)
{
@@ -2763,7 +2777,6 @@ static void __sched __schedule(void)
struct rq *rq;
int cpu;

-need_resched:
preempt_disable();
cpu = smp_processor_id();
rq = cpu_rq(cpu);
@@ -2783,6 +2796,8 @@ static void __sched __schedule(void)
smp_mb__before_spinlock();
raw_spin_lock_irq(&rq->lock);

+ rq->clock_skip_update <<= 1; /* promote REQ to ACT */
+
switch_count = &prev->nivcsw;
if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
if (unlikely(signal_pending_state(prev->state, prev))) {
@@ -2807,13 +2822,13 @@ static void __sched __schedule(void)
switch_count = &prev->nvcsw;
}

- if (task_on_rq_queued(prev) || rq->skip_clock_update < 0)
+ if (task_on_rq_queued(prev))
update_rq_clock(rq);

next = pick_next_task(rq, prev);
clear_tsk_need_resched(prev);
clear_preempt_need_resched();
- rq->skip_clock_update = 0;
+ rq->clock_skip_update = 0;

if (likely(prev != next)) {
rq->nr_switches++;
@@ -2828,8 +2843,6 @@ static void __sched __schedule(void)
post_schedule(rq);

sched_preempt_enable_no_resched();
- if (need_resched())
- goto need_resched;
}

static inline void sched_submit_work(struct task_struct *tsk)
@@ -2849,7 +2862,9 @@ asmlinkage __visible void __sched schedule(void)
struct task_struct *tsk = current;

sched_submit_work(tsk);
- __schedule();
+ do {
+ __schedule();
+ } while (need_resched());
}
EXPORT_SYMBOL(schedule);

@@ -2884,6 +2899,21 @@ void __sched schedule_preempt_disabled(void)
preempt_disable();
}

+static void preempt_schedule_common(void)
+{
+ do {
+ __preempt_count_add(PREEMPT_ACTIVE);
+ __schedule();
+ __preempt_count_sub(PREEMPT_ACTIVE);
+
+ /*
+ * Check again in case we missed a preemption opportunity
+ * between schedule and now.
+ */
+ barrier();
+ } while (need_resched());
+}
+
#ifdef CONFIG_PREEMPT
/*
* this is the entry point to schedule() from in-kernel preemption
@@ -2899,17 +2929,7 @@ asmlinkage __visible void __sched notrace preempt_schedule(void)
if (likely(!preemptible()))
return;

- do {
- __preempt_count_add(PREEMPT_ACTIVE);
- __schedule();
- __preempt_count_sub(PREEMPT_ACTIVE);
-
- /*
- * Check again in case we missed a preemption opportunity
- * between schedule and now.
- */
- barrier();
- } while (need_resched());
+ preempt_schedule_common();
}
NOKPROBE_SYMBOL(preempt_schedule);
EXPORT_SYMBOL(preempt_schedule);
@@ -3405,6 +3425,20 @@ static bool check_same_owner(struct task_struct *p)
return match;
}

+static bool dl_param_changed(struct task_struct *p,
+ const struct sched_attr *attr)
+{
+ struct sched_dl_entity *dl_se = &p->dl;
+
+ if (dl_se->dl_runtime != attr->sched_runtime ||
+ dl_se->dl_deadline != attr->sched_deadline ||
+ dl_se->dl_period != attr->sched_period ||
+ dl_se->flags != attr->sched_flags)
+ return true;
+
+ return false;
+}
+
static int __sched_setscheduler(struct task_struct *p,
const struct sched_attr *attr,
bool user)
@@ -3533,7 +3567,7 @@ static int __sched_setscheduler(struct task_struct *p,
goto change;
if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
goto change;
- if (dl_policy(policy))
+ if (dl_policy(policy) && dl_param_changed(p, attr))
goto change;

p->sched_reset_on_fork = reset_on_fork;
@@ -4225,17 +4259,10 @@ SYSCALL_DEFINE0(sched_yield)
return 0;
}

-static void __cond_resched(void)
-{
- __preempt_count_add(PREEMPT_ACTIVE);
- __schedule();
- __preempt_count_sub(PREEMPT_ACTIVE);
-}
-
int __sched _cond_resched(void)
{
if (should_resched()) {
- __cond_resched();
+ preempt_schedule_common();
return 1;
}
return 0;
@@ -4260,7 +4287,7 @@ int __cond_resched_lock(spinlock_t *lock)
if (spin_needbreak(lock) || resched) {
spin_unlock(lock);
if (resched)
- __cond_resched();
+ preempt_schedule_common();
else
cpu_relax();
ret = 1;
@@ -4276,7 +4303,7 @@ int __sched __cond_resched_softirq(void)

if (should_resched()) {
local_bh_enable();
- __cond_resched();
+ preempt_schedule_common();
local_bh_disable();
return 1;
}
@@ -4531,9 +4558,10 @@ void sched_show_task(struct task_struct *p)
{
unsigned long free = 0;
int ppid;
- unsigned state;
+ unsigned long state = p->state;

- state = p->state ? __ffs(p->state) + 1 : 0;
+ if (state)
+ state = __ffs(state) + 1;
printk(KERN_INFO "%-15.15s %c", p->comm,
state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
#if BITS_PER_LONG == 32
@@ -4766,7 +4794,7 @@ static struct rq *move_queued_task(struct task_struct *p, int new_cpu)

void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
{
- if (p->sched_class && p->sched_class->set_cpus_allowed)
+ if (p->sched_class->set_cpus_allowed)
p->sched_class->set_cpus_allowed(p, new_mask);

cpumask_copy(&p->cpus_allowed, new_mask);
@@ -7276,6 +7304,11 @@ void __init sched_init(void)
enter_lazy_tlb(&init_mm, current);

/*
+ * During early bootup we pretend to be a normal task:
+ */
+ current->sched_class = &fair_sched_class;
+
+ /*
* Make us the idle thread. Technically, schedule() should not be
* called from this thread, however somewhere below it might be,
* but because we are the idle thread, we just pick up running again
@@ -7285,11 +7318,6 @@ void __init sched_init(void)

calc_load_update = jiffies + LOAD_FREQ;

- /*
- * During early bootup we pretend to be a normal task:
- */
- current->sched_class = &fair_sched_class;
-
#ifdef CONFIG_SMP
zalloc_cpumask_var(&sched_domains_tmpmask, GFP_NOWAIT);
/* May be allocated at isolcpus cmdline parse time */
@@ -7351,6 +7379,9 @@ void ___might_sleep(const char *file, int line, int preempt_offset)
in_atomic(), irqs_disabled(),
current->pid, current->comm);

+ if (task_stack_end_corrupted(current))
+ printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
+
debug_show_held_locks(current);
if (irqs_disabled())
print_irqtrace_events(current);
diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 539ca3ce071b..c6acb07466bb 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -107,7 +107,8 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
int best_cpu = -1;
const struct sched_dl_entity *dl_se = &p->dl;

- if (later_mask && cpumask_and(later_mask, later_mask, cp->free_cpus)) {
+ if (later_mask &&
+ cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
best_cpu = cpumask_any(later_mask);
goto out;
} else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
@@ -186,6 +187,26 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
}

/*
+ * cpudl_set_freecpu - Set the cpudl.free_cpus
+ * @cp: the cpudl max-heap context
+ * @cpu: rd attached cpu
+ */
+void cpudl_set_freecpu(struct cpudl *cp, int cpu)
+{
+ cpumask_set_cpu(cpu, cp->free_cpus);
+}
+
+/*
+ * cpudl_clear_freecpu - Clear the cpudl.free_cpus
+ * @cp: the cpudl max-heap context
+ * @cpu: rd attached cpu
+ */
+void cpudl_clear_freecpu(struct cpudl *cp, int cpu)
+{
+ cpumask_clear_cpu(cpu, cp->free_cpus);
+}
+
+/*
* cpudl_init - initialize the cpudl structure
* @cp: the cpudl max-heap context
*/
@@ -203,7 +224,7 @@ int cpudl_init(struct cpudl *cp)
if (!cp->elements)
return -ENOMEM;

- if (!alloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
+ if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
kfree(cp->elements);
return -ENOMEM;
}
@@ -211,8 +232,6 @@ int cpudl_init(struct cpudl *cp)
for_each_possible_cpu(i)
cp->elements[i].idx = IDX_INVALID;

- cpumask_setall(cp->free_cpus);
-
return 0;
}

diff --git a/kernel/sched/cpudeadline.h b/kernel/sched/cpudeadline.h
index 020039bd1326..1a0a6ef2fbe1 100644
--- a/kernel/sched/cpudeadline.h
+++ b/kernel/sched/cpudeadline.h
@@ -24,6 +24,8 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
struct cpumask *later_mask);
void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid);
int cpudl_init(struct cpudl *cp);
+void cpudl_set_freecpu(struct cpudl *cp, int cpu);
+void cpudl_clear_freecpu(struct cpudl *cp, int cpu);
void cpudl_cleanup(struct cpudl *cp);
#endif /* CONFIG_SMP */

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 726470d47f87..a027799ae130 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -350,6 +350,11 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se,
dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
dl_se->runtime = pi_se->dl_runtime;
}
+
+ if (dl_se->dl_yielded)
+ dl_se->dl_yielded = 0;
+ if (dl_se->dl_throttled)
+ dl_se->dl_throttled = 0;
}

/*
@@ -536,23 +541,19 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)

sched_clock_tick();
update_rq_clock(rq);
- dl_se->dl_throttled = 0;
- dl_se->dl_yielded = 0;
- if (task_on_rq_queued(p)) {
- enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
- if (dl_task(rq->curr))
- check_preempt_curr_dl(rq, p, 0);
- else
- resched_curr(rq);
+ enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
+ if (dl_task(rq->curr))
+ check_preempt_curr_dl(rq, p, 0);
+ else
+ resched_curr(rq);
#ifdef CONFIG_SMP
- /*
- * Queueing this task back might have overloaded rq,
- * check if we need to kick someone away.
- */
- if (has_pushable_dl_tasks(rq))
- push_dl_task(rq);
+ /*
+ * Queueing this task back might have overloaded rq,
+ * check if we need to kick someone away.
+ */
+ if (has_pushable_dl_tasks(rq))
+ push_dl_task(rq);
#endif
- }
unlock:
raw_spin_unlock(&rq->lock);

@@ -613,10 +614,9 @@ static void update_curr_dl(struct rq *rq)

dl_se->runtime -= dl_se->dl_yielded ? 0 : delta_exec;
if (dl_runtime_exceeded(rq, dl_se)) {
+ dl_se->dl_throttled = 1;
__dequeue_task_dl(rq, curr, 0);
- if (likely(start_dl_timer(dl_se, curr->dl.dl_boosted)))
- dl_se->dl_throttled = 1;
- else
+ if (unlikely(!start_dl_timer(dl_se, curr->dl.dl_boosted)))
enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);

if (!is_leftmost(curr, &rq->dl))
@@ -853,7 +853,7 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
* its rq, the bandwidth timer callback (which clearly has not
* run yet) will take care of this.
*/
- if (p->dl.dl_throttled)
+ if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH))
return;

enqueue_dl_entity(&p->dl, pi_se, flags);
@@ -1073,7 +1073,13 @@ static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
{
update_curr_dl(rq);

- if (hrtick_enabled(rq) && queued && p->dl.runtime > 0)
+ /*
+ * Even when we have runtime, update_curr_dl() might have resulted in us
+ * not being the leftmost task anymore. In that case NEED_RESCHED will
+ * be set and schedule() will start a new hrtick for the next task.
+ */
+ if (hrtick_enabled(rq) && queued && p->dl.runtime > 0 &&
+ is_leftmost(p, &rq->dl))
start_hrtick_dl(rq, p);
}

@@ -1166,9 +1172,6 @@ static int find_later_rq(struct task_struct *task)
* We have to consider system topology and task affinity
* first, then we can look for a suitable cpu.
*/
- cpumask_copy(later_mask, task_rq(task)->rd->span);
- cpumask_and(later_mask, later_mask, cpu_active_mask);
- cpumask_and(later_mask, later_mask, &task->cpus_allowed);
best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
task, later_mask);
if (best_cpu == -1)
@@ -1563,6 +1566,7 @@ static void rq_online_dl(struct rq *rq)
if (rq->dl.overloaded)
dl_set_overload(rq);

+ cpudl_set_freecpu(&rq->rd->cpudl, rq->cpu);
if (rq->dl.dl_nr_running > 0)
cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr, 1);
}
@@ -1574,6 +1578,7 @@ static void rq_offline_dl(struct rq *rq)
dl_clear_overload(rq);

cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);
+ cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
}

void init_sched_dl_class(void)
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 92cc52001e74..8baaf858d25c 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -305,6 +305,7 @@ do { \
PN(next_balance);
SEQ_printf(m, " .%-30s: %ld\n", "curr->pid", (long)(task_pid_nr(rq->curr)));
PN(clock);
+ PN(clock_task);
P(cpu_load[0]);
P(cpu_load[1]);
P(cpu_load[2]);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index fe331fc391f5..7ce18f3c097a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -676,7 +676,6 @@ void init_task_runnable_average(struct task_struct *p)
{
u32 slice;

- p->se.avg.decay_count = 0;
slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
p->se.avg.runnable_avg_sum = slice;
p->se.avg.runnable_avg_period = slice;
@@ -2574,11 +2573,11 @@ static inline u64 __synchronize_entity_decay(struct sched_entity *se)
u64 decays = atomic64_read(&cfs_rq->decay_counter);

decays -= se->avg.decay_count;
+ se->avg.decay_count = 0;
if (!decays)
return 0;

se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
- se->avg.decay_count = 0;

return decays;
}
@@ -5157,7 +5156,7 @@ static void yield_task_fair(struct rq *rq)
* so we don't do microscopic update in schedule()
* and double the fastpath cost.
*/
- rq->skip_clock_update = 1;
+ rq_clock_skip_update(rq, true);
}

set_skip_buddy(se);
@@ -5949,8 +5948,8 @@ static unsigned long scale_rt_capacity(int cpu)
*/
age_stamp = ACCESS_ONCE(rq->age_stamp);
avg = ACCESS_ONCE(rq->rt_avg);
+ delta = __rq_clock_broken(rq) - age_stamp;

- delta = rq_clock(rq) - age_stamp;
if (unlikely(delta < 0))
delta = 0;

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index c47fce75e666..aaf1c1d5cf5d 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -47,7 +47,8 @@ static inline int cpu_idle_poll(void)
rcu_idle_enter();
trace_cpu_idle_rcuidle(0, smp_processor_id());
local_irq_enable();
- while (!tif_need_resched())
+ while (!tif_need_resched() &&
+ (cpu_idle_force_poll || tick_check_broadcast_expired()))
cpu_relax();
trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
rcu_idle_exit();
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index ee15f5a0d1c1..f4d4b077eba0 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -831,11 +831,14 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
enqueue = 1;

/*
- * Force a clock update if the CPU was idle,
- * lest wakeup -> unthrottle time accumulate.
+ * When we're idle and a woken (rt) task is
+ * throttled check_preempt_curr() will set
+ * skip_update and the time between the wakeup
+ * and this unthrottle will get accounted as
+ * 'runtime'.
*/
if (rt_rq->rt_nr_running && rq->curr == rq->idle)
- rq->skip_clock_update = -1;
+ rq_clock_skip_update(rq, false);
}
if (rt_rq->rt_time || rt_rq->rt_nr_running)
idle = 0;
@@ -1337,7 +1340,12 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
curr->prio <= p->prio)) {
int target = find_lowest_rq(p);

- if (target != -1)
+ /*
+ * Don't bother moving it if the destination CPU is
+ * not running a lower priority task.
+ */
+ if (target != -1 &&
+ p->prio < cpu_rq(target)->rt.highest_prio.curr)
cpu = target;
}
rcu_read_unlock();
@@ -1614,6 +1622,16 @@ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)

lowest_rq = cpu_rq(cpu);

+ if (lowest_rq->rt.highest_prio.curr <= task->prio) {
+ /*
+ * Target rq has tasks of equal or higher priority,
+ * retrying does not release any lock and is unlikely
+ * to yield a different result.
+ */
+ lowest_rq = NULL;
+ break;
+ }
+
/* if the prio of this runqueue changed, try again */
if (double_lock_balance(rq, lowest_rq)) {
/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 9a2a45c970e7..0870db23d79c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -558,8 +558,6 @@ struct rq {
#ifdef CONFIG_NO_HZ_FULL
unsigned long last_sched_tick;
#endif
- int skip_clock_update;
-
/* capture load from *all* tasks on this cpu: */
struct load_weight load;
unsigned long nr_load_updates;
@@ -588,6 +586,7 @@ struct rq {
unsigned long next_balance;
struct mm_struct *prev_mm;

+ unsigned int clock_skip_update;
u64 clock;
u64 clock_task;

@@ -687,16 +686,35 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
#define cpu_curr(cpu) (cpu_rq(cpu)->curr)
#define raw_rq() raw_cpu_ptr(&runqueues)

+static inline u64 __rq_clock_broken(struct rq *rq)
+{
+ return ACCESS_ONCE(rq->clock);
+}
+
static inline u64 rq_clock(struct rq *rq)
{
+ lockdep_assert_held(&rq->lock);
return rq->clock;
}

static inline u64 rq_clock_task(struct rq *rq)
{
+ lockdep_assert_held(&rq->lock);
return rq->clock_task;
}

+#define RQCF_REQ_SKIP 0x01
+#define RQCF_ACT_SKIP 0x02
+
+static inline void rq_clock_skip_update(struct rq *rq, bool skip)
+{
+ lockdep_assert_held(&rq->lock);
+ if (skip)
+ rq->clock_skip_update |= RQCF_REQ_SKIP;
+ else
+ rq->clock_skip_update &= ~RQCF_REQ_SKIP;
+}
+
#ifdef CONFIG_NUMA
enum numa_topology_type {
NUMA_DIRECT,
--
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