* [PATCH v3 1/5] sched: Wrapper for checking task_struct::on_rq
2014-07-30 21:42 [PATCH v3 0/5] sched: Add on_rq states and remove several double rq locks Kirill Tkhai
@ 2014-07-30 21:42 ` Kirill Tkhai
2014-07-30 21:42 ` [PATCH v3 2/5] sched: Teach scheduler to understand ONRQ_MIGRATING state Kirill Tkhai
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Kirill Tkhai @ 2014-07-30 21:42 UTC (permalink / raw)
To: linux-kernel
Cc: nicolas.pitre, peterz, pjt, oleg, rostedt, umgwanakikbuti, ktkhai,
tim.c.chen, mingo
Implement task_queued() and use it everywhere instead of on_rq check.
No functional changes.
The only exception is we do not use the wrapper in check_for_tasks(),
because it requires to export task_queued() in global header files.
Next patch in series would return it back, so it doesn't matter.
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
---
kernel/sched/core.c | 82 +++++++++++++++++++++++-----------------------
kernel/sched/deadline.c | 14 ++++----
kernel/sched/fair.c | 22 ++++++------
kernel/sched/rt.c | 16 ++++-----
kernel/sched/sched.h | 7 ++++
kernel/sched/stop_task.c | 2 +
6 files changed, 75 insertions(+), 68 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2676866..26aa7bc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1043,7 +1043,7 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
* A queue event has occurred, and we're going to schedule. In
* this case, we can save a useless back to back clock update.
*/
- if (rq->curr->on_rq && test_tsk_need_resched(rq->curr))
+ if (task_queued(rq->curr) && test_tsk_need_resched(rq->curr))
rq->skip_clock_update = 1;
}
@@ -1088,7 +1088,7 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
static void __migrate_swap_task(struct task_struct *p, int cpu)
{
- if (p->on_rq) {
+ if (task_queued(p)) {
struct rq *src_rq, *dst_rq;
src_rq = task_rq(p);
@@ -1214,7 +1214,7 @@ static int migration_cpu_stop(void *data);
unsigned long wait_task_inactive(struct task_struct *p, long match_state)
{
unsigned long flags;
- int running, on_rq;
+ int running, queued;
unsigned long ncsw;
struct rq *rq;
@@ -1252,7 +1252,7 @@ unsigned long wait_task_inactive(struct task_struct *p, long match_state)
rq = task_rq_lock(p, &flags);
trace_sched_wait_task(p);
running = task_running(rq, p);
- on_rq = p->on_rq;
+ queued = task_queued(p);
ncsw = 0;
if (!match_state || p->state == match_state)
ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
@@ -1284,7 +1284,7 @@ unsigned long wait_task_inactive(struct task_struct *p, long match_state)
* running right now), it's preempted, and we should
* yield - it could be a while.
*/
- if (unlikely(on_rq)) {
+ if (unlikely(queued)) {
ktime_t to = ktime_set(0, NSEC_PER_SEC/HZ);
set_current_state(TASK_UNINTERRUPTIBLE);
@@ -1478,7 +1478,7 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
{
activate_task(rq, p, en_flags);
- p->on_rq = 1;
+ p->on_rq = ONRQ_QUEUED;
/* if a worker is waking up, notify workqueue */
if (p->flags & PF_WQ_WORKER)
@@ -1537,7 +1537,7 @@ static int ttwu_remote(struct task_struct *p, int wake_flags)
int ret = 0;
rq = __task_rq_lock(p);
- if (p->on_rq) {
+ if (task_queued(p)) {
/* check_preempt_curr() may use rq clock */
update_rq_clock(rq);
ttwu_do_wakeup(rq, p, wake_flags);
@@ -1678,7 +1678,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
success = 1; /* we're going to change ->state */
cpu = task_cpu(p);
- if (p->on_rq && ttwu_remote(p, wake_flags))
+ if (task_queued(p) && ttwu_remote(p, wake_flags))
goto stat;
#ifdef CONFIG_SMP
@@ -1742,7 +1742,7 @@ static void try_to_wake_up_local(struct task_struct *p)
if (!(p->state & TASK_NORMAL))
goto out;
- if (!p->on_rq)
+ if (!task_queued(p))
ttwu_activate(rq, p, ENQUEUE_WAKEUP);
ttwu_do_wakeup(rq, p, 0);
@@ -2095,7 +2095,7 @@ void wake_up_new_task(struct task_struct *p)
init_task_runnable_average(p);
rq = __task_rq_lock(p);
activate_task(rq, p, 0);
- p->on_rq = 1;
+ p->on_rq = ONRQ_QUEUED;
trace_sched_wakeup_new(p, true);
check_preempt_curr(rq, p, WF_FORK);
#ifdef CONFIG_SMP
@@ -2444,7 +2444,7 @@ static u64 do_task_delta_exec(struct task_struct *p, struct rq *rq)
* project cycles that may never be accounted to this
* thread, breaking clock_gettime().
*/
- if (task_current(rq, p) && p->on_rq) {
+ if (task_current(rq, p) && task_queued(p)) {
update_rq_clock(rq);
ns = rq_clock_task(rq) - p->se.exec_start;
if ((s64)ns < 0)
@@ -2490,7 +2490,7 @@ unsigned long long task_sched_runtime(struct task_struct *p)
* If we see ->on_cpu without ->on_rq, the task is leaving, and has
* been accounted, so we're correct here as well.
*/
- if (!p->on_cpu || !p->on_rq)
+ if (!p->on_cpu || !task_queued(p))
return p->se.sum_exec_runtime;
#endif
@@ -2794,7 +2794,7 @@ static void __sched __schedule(void)
switch_count = &prev->nvcsw;
}
- if (prev->on_rq || rq->skip_clock_update < 0)
+ if (task_queued(prev) || rq->skip_clock_update < 0)
update_rq_clock(rq);
next = pick_next_task(rq, prev);
@@ -2959,7 +2959,7 @@ EXPORT_SYMBOL(default_wake_function);
*/
void rt_mutex_setprio(struct task_struct *p, int prio)
{
- int oldprio, on_rq, running, enqueue_flag = 0;
+ int oldprio, queued, running, enqueue_flag = 0;
struct rq *rq;
const struct sched_class *prev_class;
@@ -2988,9 +2988,9 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
trace_sched_pi_setprio(p, prio);
oldprio = p->prio;
prev_class = p->sched_class;
- on_rq = p->on_rq;
+ queued = task_queued(p);
running = task_current(rq, p);
- if (on_rq)
+ if (queued)
dequeue_task(rq, p, 0);
if (running)
p->sched_class->put_prev_task(rq, p);
@@ -3030,7 +3030,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
if (running)
p->sched_class->set_curr_task(rq);
- if (on_rq)
+ if (queued)
enqueue_task(rq, p, enqueue_flag);
check_class_changed(rq, p, prev_class, oldprio);
@@ -3041,7 +3041,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
void set_user_nice(struct task_struct *p, long nice)
{
- int old_prio, delta, on_rq;
+ int old_prio, delta, queued;
unsigned long flags;
struct rq *rq;
@@ -3062,8 +3062,8 @@ void set_user_nice(struct task_struct *p, long nice)
p->static_prio = NICE_TO_PRIO(nice);
goto out_unlock;
}
- on_rq = p->on_rq;
- if (on_rq)
+ queued = task_queued(p);
+ if (queued)
dequeue_task(rq, p, 0);
p->static_prio = NICE_TO_PRIO(nice);
@@ -3072,7 +3072,7 @@ void set_user_nice(struct task_struct *p, long nice)
p->prio = effective_prio(p);
delta = p->prio - old_prio;
- if (on_rq) {
+ if (queued) {
enqueue_task(rq, p, 0);
/*
* If the task increased its priority or is running and
@@ -3344,7 +3344,7 @@ static int __sched_setscheduler(struct task_struct *p,
{
int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 :
MAX_RT_PRIO - 1 - attr->sched_priority;
- int retval, oldprio, oldpolicy = -1, on_rq, running;
+ int retval, oldprio, oldpolicy = -1, queued, running;
int policy = attr->sched_policy;
unsigned long flags;
const struct sched_class *prev_class;
@@ -3541,9 +3541,9 @@ static int __sched_setscheduler(struct task_struct *p,
return 0;
}
- on_rq = p->on_rq;
+ queued = task_queued(p);
running = task_current(rq, p);
- if (on_rq)
+ if (queued)
dequeue_task(rq, p, 0);
if (running)
p->sched_class->put_prev_task(rq, p);
@@ -3553,7 +3553,7 @@ static int __sched_setscheduler(struct task_struct *p,
if (running)
p->sched_class->set_curr_task(rq);
- if (on_rq) {
+ if (queued) {
/*
* We enqueue to tail when the priority of a task is
* increased (user space view).
@@ -4568,7 +4568,7 @@ void init_idle(struct task_struct *idle, int cpu)
rcu_read_unlock();
rq->curr = rq->idle = idle;
- idle->on_rq = 1;
+ idle->on_rq = ONRQ_QUEUED;
#if defined(CONFIG_SMP)
idle->on_cpu = 1;
#endif
@@ -4645,7 +4645,7 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
goto out;
dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);
- if (p->on_rq) {
+ if (task_queued(p)) {
struct migration_arg arg = { p, dest_cpu };
/* Need help from migration thread: drop lock and wait. */
task_rq_unlock(rq, p, &flags);
@@ -4695,7 +4695,7 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
* If we're not on a rq, the next wake-up will ensure we're
* placed properly.
*/
- if (p->on_rq) {
+ if (task_queued(p)) {
dequeue_task(rq_src, p, 0);
set_task_cpu(p, dest_cpu);
enqueue_task(rq_dest, p, 0);
@@ -4736,13 +4736,13 @@ void sched_setnuma(struct task_struct *p, int nid)
{
struct rq *rq;
unsigned long flags;
- bool on_rq, running;
+ bool queued, running;
rq = task_rq_lock(p, &flags);
- on_rq = p->on_rq;
+ queued = task_queued(p);
running = task_current(rq, p);
- if (on_rq)
+ if (queued)
dequeue_task(rq, p, 0);
if (running)
p->sched_class->put_prev_task(rq, p);
@@ -4751,7 +4751,7 @@ void sched_setnuma(struct task_struct *p, int nid)
if (running)
p->sched_class->set_curr_task(rq);
- if (on_rq)
+ if (queued)
enqueue_task(rq, p, 0);
task_rq_unlock(rq, p, &flags);
}
@@ -7117,13 +7117,13 @@ static void normalize_task(struct rq *rq, struct task_struct *p)
.sched_policy = SCHED_NORMAL,
};
int old_prio = p->prio;
- int on_rq;
+ int queued;
- on_rq = p->on_rq;
- if (on_rq)
+ queued = task_queued(p);
+ if (queued)
dequeue_task(rq, p, 0);
__setscheduler(rq, p, &attr);
- if (on_rq) {
+ if (queued) {
enqueue_task(rq, p, 0);
resched_curr(rq);
}
@@ -7311,16 +7311,16 @@ void sched_offline_group(struct task_group *tg)
void sched_move_task(struct task_struct *tsk)
{
struct task_group *tg;
- int on_rq, running;
+ int queued, running;
unsigned long flags;
struct rq *rq;
rq = task_rq_lock(tsk, &flags);
running = task_current(rq, tsk);
- on_rq = tsk->on_rq;
+ queued = task_queued(tsk);
- if (on_rq)
+ if (queued)
dequeue_task(rq, tsk, 0);
if (unlikely(running))
tsk->sched_class->put_prev_task(rq, tsk);
@@ -7333,14 +7333,14 @@ void sched_move_task(struct task_struct *tsk)
#ifdef CONFIG_FAIR_GROUP_SCHED
if (tsk->sched_class->task_move_group)
- tsk->sched_class->task_move_group(tsk, on_rq);
+ tsk->sched_class->task_move_group(tsk, queued);
else
#endif
set_task_rq(tsk, task_cpu(tsk));
if (unlikely(running))
tsk->sched_class->set_curr_task(rq);
- if (on_rq)
+ if (queued)
enqueue_task(rq, tsk, 0);
task_rq_unlock(rq, tsk, &flags);
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 255ce13..4cc3b14 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -530,7 +530,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
update_rq_clock(rq);
dl_se->dl_throttled = 0;
dl_se->dl_yielded = 0;
- if (p->on_rq) {
+ if (task_queued(p)) {
enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
if (task_has_dl_policy(rq->curr))
check_preempt_curr_dl(rq, p, 0);
@@ -1030,7 +1030,7 @@ struct task_struct *pick_next_task_dl(struct rq *rq, struct task_struct *prev)
* means a stop task can slip in, in which case we need to
* re-start task selection.
*/
- if (rq->stop && rq->stop->on_rq)
+ if (rq->stop && task_queued(rq->stop))
return RETRY_TASK;
}
@@ -1257,7 +1257,7 @@ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
if (unlikely(task_rq(task) != rq ||
!cpumask_test_cpu(later_rq->cpu,
&task->cpus_allowed) ||
- task_running(rq, task) || !task->on_rq)) {
+ task_running(rq, task) || !task_queued(task))) {
double_unlock_balance(rq, later_rq);
later_rq = NULL;
break;
@@ -1296,7 +1296,7 @@ static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
BUG_ON(task_current(rq, p));
BUG_ON(p->nr_cpus_allowed <= 1);
- BUG_ON(!p->on_rq);
+ BUG_ON(!task_queued(p));
BUG_ON(!dl_task(p));
return p;
@@ -1443,7 +1443,7 @@ static int pull_dl_task(struct rq *this_rq)
dl_time_before(p->dl.deadline,
this_rq->dl.earliest_dl.curr))) {
WARN_ON(p == src_rq->curr);
- WARN_ON(!p->on_rq);
+ WARN_ON(!task_queued(p));
/*
* Then we pull iff p has actually an earlier
@@ -1596,7 +1596,7 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
if (unlikely(p->dl.dl_throttled))
return;
- if (p->on_rq && rq->curr != p) {
+ if (task_queued(p) && rq->curr != p) {
#ifdef CONFIG_SMP
if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
/* Only reschedule if pushing failed */
@@ -1614,7 +1614,7 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
static void prio_changed_dl(struct rq *rq, struct task_struct *p,
int oldprio)
{
- if (p->on_rq || rq->curr == p) {
+ if (task_queued(p) || rq->curr == p) {
#ifdef CONFIG_SMP
/*
* This might be too much, but unfortunately
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bfa3c86..48420ae 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7465,7 +7465,7 @@ static void task_fork_fair(struct task_struct *p)
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
{
- if (!p->se.on_rq)
+ if (!task_queued(p))
return;
/*
@@ -7490,11 +7490,11 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p)
* switched back to the fair class the enqueue_entity(.flags=0) will
* do the right thing.
*
- * If it's on_rq, then the dequeue_entity(.flags=0) will already
- * have normalized the vruntime, if it's !on_rq, then only when
+ * If it's queued, then the dequeue_entity(.flags=0) will already
+ * have normalized the vruntime, if it's !queued, then only when
* the task is sleeping will it still have non-normalized vruntime.
*/
- if (!p->on_rq && p->state != TASK_RUNNING) {
+ if (!task_queued(p) && p->state != TASK_RUNNING) {
/*
* Fix up our vruntime so that the current sleep doesn't
* cause 'unlimited' sleep bonus.
@@ -7529,7 +7529,7 @@ static void switched_to_fair(struct rq *rq, struct task_struct *p)
*/
se->depth = se->parent ? se->parent->depth + 1 : 0;
#endif
- if (!se->on_rq)
+ if (!task_queued(p))
return;
/*
@@ -7575,7 +7575,7 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
}
#ifdef CONFIG_FAIR_GROUP_SCHED
-static void task_move_group_fair(struct task_struct *p, int on_rq)
+static void task_move_group_fair(struct task_struct *p, int queued)
{
struct sched_entity *se = &p->se;
struct cfs_rq *cfs_rq;
@@ -7594,7 +7594,7 @@ static void task_move_group_fair(struct task_struct *p, int on_rq)
* fair sleeper stuff for the first placement, but who cares.
*/
/*
- * When !on_rq, vruntime of the task has usually NOT been normalized.
+ * When !queued, vruntime of the task has usually NOT been normalized.
* But there are some cases where it has already been normalized:
*
* - Moving a forked child which is waiting for being woken up by
@@ -7605,14 +7605,14 @@ static void task_move_group_fair(struct task_struct *p, int on_rq)
* To prevent boost or penalty in the new cfs_rq caused by delta
* min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
*/
- if (!on_rq && (!se->sum_exec_runtime || p->state == TASK_WAKING))
- on_rq = 1;
+ if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
+ queued = 1;
- if (!on_rq)
+ if (!queued)
se->vruntime -= cfs_rq_of(se)->min_vruntime;
set_task_rq(p, task_cpu(p));
se->depth = se->parent ? se->parent->depth + 1 : 0;
- if (!on_rq) {
+ if (!queued) {
cfs_rq = cfs_rq_of(se);
se->vruntime += cfs_rq->min_vruntime;
#ifdef CONFIG_SMP
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 5f6edca..9395320 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1448,7 +1448,7 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev)
* means a dl or stop task can slip in, in which case we need
* to re-start task selection.
*/
- if (unlikely((rq->stop && rq->stop->on_rq) ||
+ if (unlikely((rq->stop && task_queued(rq->stop)) ||
rq->dl.dl_nr_running))
return RETRY_TASK;
}
@@ -1624,7 +1624,7 @@ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
!cpumask_test_cpu(lowest_rq->cpu,
tsk_cpus_allowed(task)) ||
task_running(rq, task) ||
- !task->on_rq)) {
+ !task_queued(task))) {
double_unlock_balance(rq, lowest_rq);
lowest_rq = NULL;
@@ -1658,7 +1658,7 @@ static struct task_struct *pick_next_pushable_task(struct rq *rq)
BUG_ON(task_current(rq, p));
BUG_ON(p->nr_cpus_allowed <= 1);
- BUG_ON(!p->on_rq);
+ BUG_ON(!task_queued(p));
BUG_ON(!rt_task(p));
return p;
@@ -1809,7 +1809,7 @@ static int pull_rt_task(struct rq *this_rq)
*/
if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
WARN_ON(p == src_rq->curr);
- WARN_ON(!p->on_rq);
+ WARN_ON(!task_queued(p));
/*
* There's a chance that p is higher in priority
@@ -1870,7 +1870,7 @@ static void set_cpus_allowed_rt(struct task_struct *p,
BUG_ON(!rt_task(p));
- if (!p->on_rq)
+ if (!task_queued(p))
return;
weight = cpumask_weight(new_mask);
@@ -1936,7 +1936,7 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
* we may need to handle the pulling of RT tasks
* now.
*/
- if (!p->on_rq || rq->rt.rt_nr_running)
+ if (!task_queued(p) || rq->rt.rt_nr_running)
return;
if (pull_rt_task(rq))
@@ -1970,7 +1970,7 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p)
* If that current running task is also an RT task
* then see if we can move to another run queue.
*/
- if (p->on_rq && rq->curr != p) {
+ if (task_queued(p) && rq->curr != p) {
#ifdef CONFIG_SMP
if (p->nr_cpus_allowed > 1 && rq->rt.overloaded &&
/* Don't resched if we changed runqueues */
@@ -1989,7 +1989,7 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p)
static void
prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
{
- if (!p->on_rq)
+ if (!task_queued(p))
return;
if (rq->curr == p) {
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 579712f..2c83b6e 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -15,6 +15,9 @@
struct rq;
+/* task_struct::on_rq states: */
+#define ONRQ_QUEUED 1
+
extern __read_mostly int scheduler_running;
extern unsigned long calc_load_update;
@@ -942,6 +945,10 @@ static inline int task_running(struct rq *rq, struct task_struct *p)
#endif
}
+static inline int task_queued(struct task_struct *p)
+{
+ return p->on_rq == ONRQ_QUEUED;
+}
#ifndef prepare_arch_switch
# define prepare_arch_switch(next) do { } while (0)
diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
index bfe0eda..1a4bb0f 100644
--- a/kernel/sched/stop_task.c
+++ b/kernel/sched/stop_task.c
@@ -28,7 +28,7 @@ pick_next_task_stop(struct rq *rq, struct task_struct *prev)
{
struct task_struct *stop = rq->stop;
- if (!stop || !stop->on_rq)
+ if (!stop || !task_queued(stop))
return NULL;
put_prev_task(rq, prev);
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v3 5/5] sched/fair: Remove double_lock_balance() from load_balance()
2014-07-30 21:42 [PATCH v3 0/5] sched: Add on_rq states and remove several double rq locks Kirill Tkhai
` (3 preceding siblings ...)
2014-07-30 21:43 ` [PATCH v3 4/5] sched/fair: Remove double_lock_balance() from active_load_balance_cpu_stop() Kirill Tkhai
@ 2014-07-30 21:43 ` Kirill Tkhai
4 siblings, 0 replies; 6+ messages in thread
From: Kirill Tkhai @ 2014-07-30 21:43 UTC (permalink / raw)
To: linux-kernel
Cc: nicolas.pitre, peterz, pjt, oleg, rostedt, umgwanakikbuti, ktkhai,
tim.c.chen, mingo
Keep on_rq = ONRQ_MIGRATING, while task is migrating, instead.
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
---
kernel/sched/fair.c | 99 ++++++++++++++++++++++++++++++++++++---------------
1 file changed, 70 insertions(+), 29 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8e2ee4b..475d05e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4706,7 +4706,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
return;
/*
- * This is possible from callers such as move_task(), in which we
+ * This is possible from callers such as attach_tasks(), in which we
* unconditionally check_prempt_curr() after an enqueue (which may have
* lead to a throttle). This both saves work and prevents false
* next-buddy nomination below.
@@ -5114,18 +5114,20 @@ struct lb_env {
unsigned int loop_max;
enum fbq_type fbq_type;
+ struct list_head tasks;
};
/*
- * move_task - move a task from one runqueue to another runqueue.
- * Both runqueues must be locked.
+ * detach_task - detach a task for migration specified in env
*/
-static void move_task(struct task_struct *p, struct lb_env *env)
+static void detach_task(struct task_struct *p, struct lb_env *env)
{
+ lockdep_assert_held(&env->src_rq->lock);
+
deactivate_task(env->src_rq, p, 0);
+ list_add(&p->se.group_node, &env->tasks);
+ p->on_rq = ONRQ_MIGRATING;
set_task_cpu(p, env->dst_cpu);
- activate_task(env->dst_rq, p, 0);
- check_preempt_curr(env->dst_rq, p, 0);
}
/*
@@ -5363,9 +5365,9 @@ static struct task_struct *detach_one_task(struct lb_env *env)
/*
* Right now, this is only the second place where
- * lb_gained[env->idle] is updated (other is move_tasks)
+ * lb_gained[env->idle] is updated (other is detach_tasks)
* so we can safely collect stats here rather than
- * inside move_tasks().
+ * inside detach_tasks().
*/
schedstat_inc(env->sd, lb_gained[env->idle]);
return p;
@@ -5376,18 +5378,18 @@ static struct task_struct *detach_one_task(struct lb_env *env)
static const unsigned int sched_nr_migrate_break = 32;
/*
- * move_tasks tries to move up to imbalance weighted load from busiest to
- * this_rq, as part of a balancing operation within domain "sd".
- * Returns 1 if successful and 0 otherwise.
- *
- * Called with both runqueues locked.
+ * detach_tasks tries to detach up to imbalance weighted load from busiest_rq,
+ * as part of a balancing operation within domain "sd".
+ * Returns number of detached tasks if successful and 0 otherwise.
*/
-static int move_tasks(struct lb_env *env)
+static int detach_tasks(struct lb_env *env)
{
struct list_head *tasks = &env->src_rq->cfs_tasks;
struct task_struct *p;
unsigned long load;
- int pulled = 0;
+ int detached = 0;
+
+ lockdep_assert_held(&env->src_rq->lock);
if (env->imbalance <= 0)
return 0;
@@ -5418,14 +5420,15 @@ static int move_tasks(struct lb_env *env)
if ((load / 2) > env->imbalance)
goto next;
- move_task(p, env);
- pulled++;
+ detach_task(p, env);
+
+ detached++;
env->imbalance -= load;
#ifdef CONFIG_PREEMPT
/*
* NEWIDLE balancing is a source of latency, so preemptible
- * kernels will stop after the first task is pulled to minimize
+ * kernels will stop after the first task is detached to minimize
* the critical section.
*/
if (env->idle == CPU_NEWLY_IDLE)
@@ -5445,13 +5448,31 @@ static int move_tasks(struct lb_env *env)
}
/*
- * Right now, this is one of only two places move_task() is called,
- * so we can safely collect move_task() stats here rather than
- * inside move_task().
+ * Right now, this is one of only two places we collect this stat
+ * so we can safely collect detach_one_task() stats here rather
+ * than inside detach_one_task().
*/
- schedstat_add(env->sd, lb_gained[env->idle], pulled);
+ schedstat_add(env->sd, lb_gained[env->idle], detached);
- return pulled;
+ return detached;
+}
+
+/* Attach tasks previously detached in detach_tasks() */
+static void attach_tasks(struct lb_env *env)
+{
+ struct list_head *tasks = &env->tasks;
+ struct task_struct *p;
+
+ lockdep_assert_held(&env->dst_rq->lock);
+
+ while (!list_empty(tasks)) {
+ p = list_first_entry(tasks, struct task_struct, se.group_node);
+ BUG_ON(task_rq(p) != env->dst_rq);
+ list_del_init(&p->se.group_node);
+ p->on_rq = ONRQ_QUEUED;
+ activate_task(env->dst_rq, p, 0);
+ check_preempt_curr(env->dst_rq, p, 0);
+ }
}
#ifdef CONFIG_FAIR_GROUP_SCHED
@@ -6561,6 +6582,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
.loop_break = sched_nr_migrate_break,
.cpus = cpus,
.fbq_type = all,
+ .tasks = LIST_HEAD_INIT(env.tasks),
};
/*
@@ -6610,16 +6632,35 @@ static int load_balance(int this_cpu, struct rq *this_rq,
env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
more_balance:
- local_irq_save(flags);
- double_rq_lock(env.dst_rq, busiest);
+ raw_spin_lock_irqsave(&busiest->lock, flags);
/*
* cur_ld_moved - load moved in current iteration
* ld_moved - cumulative load moved across iterations
*/
- cur_ld_moved = move_tasks(&env);
- ld_moved += cur_ld_moved;
- double_rq_unlock(env.dst_rq, busiest);
+ cur_ld_moved = detach_tasks(&env);
+
+ /*
+ * We've detached some tasks from busiest_rq. Every
+ * task is masked "ONRQ_MIGRATED", so we can safely
+ * unlock busiest->lock, and we are able to be sure
+ * that nobody can manipulate the tasks in parallel.
+ * See task_rq_lock() family for the details.
+ */
+
+ raw_spin_unlock(&busiest->lock);
+
+ if (cur_ld_moved) {
+ raw_spin_lock(&env.dst_rq->lock);
+ /*
+ * Attach the tasks to env->dst_rq
+ * and mask them "ONRQ_QUEUED".
+ */
+ attach_tasks(&env);
+ raw_spin_unlock(&env.dst_rq->lock);
+ ld_moved += cur_ld_moved;
+ }
+
local_irq_restore(flags);
/*
@@ -6755,7 +6796,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
* If we've begun active balancing, start to back off. This
* case may not be covered by the all_pinned logic if there
* is only 1 task on the busy runqueue (because we don't call
- * move_tasks).
+ * detach_tasks).
*/
if (sd->balance_interval < sd->max_interval)
sd->balance_interval *= 2;
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