Merge tag 'sched-urgent-2020-11-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Thomas Gleixner:
"A couple of scheduler fixes:
- Make the conditional update of the overutilized state work
correctly by caching the relevant flags state before overwriting
them and checking them afterwards.
- Fix a data race in the wakeup path which caused loadavg on ARM64
platforms to become a random number generator.
- Fix the ordering of the iowaiter accounting operations so it can't
be decremented before it is incremented.
- Fix a bug in the deadline scheduler vs. priority inheritance when a
non-deadline task A has inherited the parameters of a deadline task
B and then blocks on a non-deadline task C.
The second inheritance step used the static deadline parameters of
task A, which are usually 0, instead of further propagating task
B's parameters. The zero initialized parameters trigger a bug in
the deadline scheduler"
* tag 'sched-urgent-2020-11-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/deadline: Fix priority inheritance with multiple scheduling classes
sched: Fix rq->nr_iowait ordering
sched: Fix data-race in wakeup
sched/fair: Fix overutilized update in enqueue_task_fair()
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 063cd12..76cd21f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -552,7 +552,6 @@
* overruns.
*/
unsigned int dl_throttled : 1;
- unsigned int dl_boosted : 1;
unsigned int dl_yielded : 1;
unsigned int dl_non_contending : 1;
unsigned int dl_overrun : 1;
@@ -571,6 +570,15 @@
* time.
*/
struct hrtimer inactive_timer;
+
+#ifdef CONFIG_RT_MUTEXES
+ /*
+ * Priority Inheritance. When a DEADLINE scheduling entity is boosted
+ * pi_se points to the donor, otherwise points to the dl_se it belongs
+ * to (the original one/itself).
+ */
+ struct sched_dl_entity *pi_se;
+#endif
};
#ifdef CONFIG_UCLAMP_TASK
@@ -770,7 +778,6 @@
unsigned sched_reset_on_fork:1;
unsigned sched_contributes_to_load:1;
unsigned sched_migrated:1;
- unsigned sched_remote_wakeup:1;
#ifdef CONFIG_PSI
unsigned sched_psi_wake_requeue:1;
#endif
@@ -780,6 +787,21 @@
/* Unserialized, strictly 'current' */
+ /*
+ * This field must not be in the scheduler word above due to wakelist
+ * queueing no longer being serialized by p->on_cpu. However:
+ *
+ * p->XXX = X; ttwu()
+ * schedule() if (p->on_rq && ..) // false
+ * smp_mb__after_spinlock(); if (smp_load_acquire(&p->on_cpu) && //true
+ * deactivate_task() ttwu_queue_wakelist())
+ * p->on_rq = 0; p->sched_remote_wakeup = Y;
+ *
+ * guarantees all stores of 'current' are visible before
+ * ->sched_remote_wakeup gets used, so it can be in this word.
+ */
+ unsigned sched_remote_wakeup:1;
+
/* Bit to tell LSMs we're in execve(): */
unsigned in_execve:1;
unsigned in_iowait:1;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d2003a7..e7e4534 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2501,7 +2501,12 @@
#ifdef CONFIG_SMP
if (wake_flags & WF_MIGRATED)
en_flags |= ENQUEUE_MIGRATED;
+ else
#endif
+ if (p->in_iowait) {
+ delayacct_blkio_end(p);
+ atomic_dec(&task_rq(p)->nr_iowait);
+ }
activate_task(rq, p, en_flags);
ttwu_do_wakeup(rq, p, wake_flags, rf);
@@ -2888,11 +2893,6 @@
if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags))
goto unlock;
- if (p->in_iowait) {
- delayacct_blkio_end(p);
- atomic_dec(&task_rq(p)->nr_iowait);
- }
-
#ifdef CONFIG_SMP
/*
* Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
@@ -2963,6 +2963,11 @@
cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
if (task_cpu(p) != cpu) {
+ if (p->in_iowait) {
+ delayacct_blkio_end(p);
+ atomic_dec(&task_rq(p)->nr_iowait);
+ }
+
wake_flags |= WF_MIGRATED;
psi_ttwu_dequeue(p);
set_task_cpu(p, cpu);
@@ -4907,20 +4912,21 @@
if (!dl_prio(p->normal_prio) ||
(pi_task && dl_prio(pi_task->prio) &&
dl_entity_preempt(&pi_task->dl, &p->dl))) {
- p->dl.dl_boosted = 1;
+ p->dl.pi_se = pi_task->dl.pi_se;
queue_flag |= ENQUEUE_REPLENISH;
- } else
- p->dl.dl_boosted = 0;
+ } else {
+ p->dl.pi_se = &p->dl;
+ }
p->sched_class = &dl_sched_class;
} else if (rt_prio(prio)) {
if (dl_prio(oldprio))
- p->dl.dl_boosted = 0;
+ p->dl.pi_se = &p->dl;
if (oldprio < prio)
queue_flag |= ENQUEUE_HEAD;
p->sched_class = &rt_sched_class;
} else {
if (dl_prio(oldprio))
- p->dl.dl_boosted = 0;
+ p->dl.pi_se = &p->dl;
if (rt_prio(oldprio))
p->rt.timeout = 0;
p->sched_class = &fair_sched_class;
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index f232305..1d3c972 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -43,6 +43,28 @@
return !RB_EMPTY_NODE(&dl_se->rb_node);
}
+#ifdef CONFIG_RT_MUTEXES
+static inline struct sched_dl_entity *pi_of(struct sched_dl_entity *dl_se)
+{
+ return dl_se->pi_se;
+}
+
+static inline bool is_dl_boosted(struct sched_dl_entity *dl_se)
+{
+ return pi_of(dl_se) != dl_se;
+}
+#else
+static inline struct sched_dl_entity *pi_of(struct sched_dl_entity *dl_se)
+{
+ return dl_se;
+}
+
+static inline bool is_dl_boosted(struct sched_dl_entity *dl_se)
+{
+ return false;
+}
+#endif
+
#ifdef CONFIG_SMP
static inline struct dl_bw *dl_bw_of(int i)
{
@@ -698,7 +720,7 @@
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);
- WARN_ON(dl_se->dl_boosted);
+ WARN_ON(is_dl_boosted(dl_se));
WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
/*
@@ -736,21 +758,20 @@
* could happen are, typically, a entity voluntarily trying to overcome its
* runtime, or it just underestimated it during sched_setattr().
*/
-static void replenish_dl_entity(struct sched_dl_entity *dl_se,
- struct sched_dl_entity *pi_se)
+static void replenish_dl_entity(struct sched_dl_entity *dl_se)
{
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);
- BUG_ON(pi_se->dl_runtime <= 0);
+ BUG_ON(pi_of(dl_se)->dl_runtime <= 0);
/*
* This could be the case for a !-dl task that is boosted.
* Just go with full inherited parameters.
*/
if (dl_se->dl_deadline == 0) {
- dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
- dl_se->runtime = pi_se->dl_runtime;
+ dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
+ dl_se->runtime = pi_of(dl_se)->dl_runtime;
}
if (dl_se->dl_yielded && dl_se->runtime > 0)
@@ -763,8 +784,8 @@
* arbitrary large.
*/
while (dl_se->runtime <= 0) {
- dl_se->deadline += pi_se->dl_period;
- dl_se->runtime += pi_se->dl_runtime;
+ dl_se->deadline += pi_of(dl_se)->dl_period;
+ dl_se->runtime += pi_of(dl_se)->dl_runtime;
}
/*
@@ -778,8 +799,8 @@
*/
if (dl_time_before(dl_se->deadline, rq_clock(rq))) {
printk_deferred_once("sched: DL replenish lagged too much\n");
- dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
- dl_se->runtime = pi_se->dl_runtime;
+ dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
+ dl_se->runtime = pi_of(dl_se)->dl_runtime;
}
if (dl_se->dl_yielded)
@@ -812,8 +833,7 @@
* task with deadline equal to period this is the same of using
* dl_period instead of dl_deadline in the equation above.
*/
-static bool dl_entity_overflow(struct sched_dl_entity *dl_se,
- struct sched_dl_entity *pi_se, u64 t)
+static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
{
u64 left, right;
@@ -835,9 +855,9 @@
* of anything below microseconds resolution is actually fiction
* (but still we want to give the user that illusion >;).
*/
- left = (pi_se->dl_deadline >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
+ left = (pi_of(dl_se)->dl_deadline >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
right = ((dl_se->deadline - t) >> DL_SCALE) *
- (pi_se->dl_runtime >> DL_SCALE);
+ (pi_of(dl_se)->dl_runtime >> DL_SCALE);
return dl_time_before(right, left);
}
@@ -922,24 +942,23 @@
* Please refer to the comments update_dl_revised_wakeup() function to find
* more about the Revised CBS rule.
*/
-static void update_dl_entity(struct sched_dl_entity *dl_se,
- struct sched_dl_entity *pi_se)
+static void update_dl_entity(struct sched_dl_entity *dl_se)
{
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);
if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
- dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {
+ dl_entity_overflow(dl_se, rq_clock(rq))) {
if (unlikely(!dl_is_implicit(dl_se) &&
!dl_time_before(dl_se->deadline, rq_clock(rq)) &&
- !dl_se->dl_boosted)){
+ !is_dl_boosted(dl_se))) {
update_dl_revised_wakeup(dl_se, rq);
return;
}
- dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
- dl_se->runtime = pi_se->dl_runtime;
+ dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
+ dl_se->runtime = pi_of(dl_se)->dl_runtime;
}
}
@@ -1038,7 +1057,7 @@
* The task might have been boosted by someone else and might be in the
* boosting/deboosting path, its not throttled.
*/
- if (dl_se->dl_boosted)
+ if (is_dl_boosted(dl_se))
goto unlock;
/*
@@ -1066,7 +1085,7 @@
* but do not enqueue -- wait for our wakeup to do that.
*/
if (!task_on_rq_queued(p)) {
- replenish_dl_entity(dl_se, dl_se);
+ replenish_dl_entity(dl_se);
goto unlock;
}
@@ -1156,7 +1175,7 @@
if (dl_time_before(dl_se->deadline, rq_clock(rq)) &&
dl_time_before(rq_clock(rq), dl_next_period(dl_se))) {
- if (unlikely(dl_se->dl_boosted || !start_dl_timer(p)))
+ if (unlikely(is_dl_boosted(dl_se) || !start_dl_timer(p)))
return;
dl_se->dl_throttled = 1;
if (dl_se->runtime > 0)
@@ -1287,7 +1306,7 @@
dl_se->dl_overrun = 1;
__dequeue_task_dl(rq, curr, 0);
- if (unlikely(dl_se->dl_boosted || !start_dl_timer(curr)))
+ if (unlikely(is_dl_boosted(dl_se) || !start_dl_timer(curr)))
enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
if (!is_leftmost(curr, &rq->dl))
@@ -1481,8 +1500,7 @@
}
static void
-enqueue_dl_entity(struct sched_dl_entity *dl_se,
- struct sched_dl_entity *pi_se, int flags)
+enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
{
BUG_ON(on_dl_rq(dl_se));
@@ -1493,9 +1511,9 @@
*/
if (flags & ENQUEUE_WAKEUP) {
task_contending(dl_se, flags);
- update_dl_entity(dl_se, pi_se);
+ update_dl_entity(dl_se);
} else if (flags & ENQUEUE_REPLENISH) {
- replenish_dl_entity(dl_se, pi_se);
+ replenish_dl_entity(dl_se);
} else if ((flags & ENQUEUE_RESTORE) &&
dl_time_before(dl_se->deadline,
rq_clock(rq_of_dl_rq(dl_rq_of_se(dl_se))))) {
@@ -1512,19 +1530,7 @@
static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
{
- struct task_struct *pi_task = rt_mutex_get_top_task(p);
- struct sched_dl_entity *pi_se = &p->dl;
-
- /*
- * Use the scheduling parameters of the top pi-waiter task if:
- * - we have a top pi-waiter which is a SCHED_DEADLINE task AND
- * - our dl_boosted is set (i.e. the pi-waiter's (absolute) deadline is
- * smaller than our deadline OR we are a !SCHED_DEADLINE task getting
- * boosted due to a SCHED_DEADLINE pi-waiter).
- * Otherwise we keep our runtime and deadline.
- */
- if (pi_task && dl_prio(pi_task->normal_prio) && p->dl.dl_boosted) {
- pi_se = &pi_task->dl;
+ if (is_dl_boosted(&p->dl)) {
/*
* Because of delays in the detection of the overrun of a
* thread's runtime, it might be the case that a thread
@@ -1557,7 +1563,7 @@
* the throttle.
*/
p->dl.dl_throttled = 0;
- BUG_ON(!p->dl.dl_boosted || flags != ENQUEUE_REPLENISH);
+ BUG_ON(!is_dl_boosted(&p->dl) || flags != ENQUEUE_REPLENISH);
return;
}
@@ -1594,7 +1600,7 @@
return;
}
- enqueue_dl_entity(&p->dl, pi_se, flags);
+ enqueue_dl_entity(&p->dl, flags);
if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
enqueue_pushable_dl_task(rq, p);
@@ -2787,11 +2793,14 @@
dl_se->dl_bw = 0;
dl_se->dl_density = 0;
- dl_se->dl_boosted = 0;
dl_se->dl_throttled = 0;
dl_se->dl_yielded = 0;
dl_se->dl_non_contending = 0;
dl_se->dl_overrun = 0;
+
+#ifdef CONFIG_RT_MUTEXES
+ dl_se->pi_se = dl_se;
+#endif
}
bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8917d2d..ae7ceba 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5477,6 +5477,7 @@
struct cfs_rq *cfs_rq;
struct sched_entity *se = &p->se;
int idle_h_nr_running = task_has_idle_policy(p);
+ int task_new = !(flags & ENQUEUE_WAKEUP);
/*
* The code below (indirectly) updates schedutil which looks at
@@ -5549,7 +5550,7 @@
* into account, but that is not straightforward to implement,
* and the following generally works well enough in practice.
*/
- if (flags & ENQUEUE_WAKEUP)
+ if (!task_new)
update_overutilized_status(rq);
enqueue_throttle:
