[PATCH v2 07/12] sched: Replace rq->curr access w/ rq_curr(rq)

From: John Stultz
Date: Mon Mar 20 2023 - 19:38:15 EST

In preparing for proxy-execution changes add a bit of
indirection for reading and writing rq->curr.

Cc: Joel Fernandes <joelaf@xxxxxxxxxx>
Cc: Qais Yousef <qyousef@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Zimuzo Ezeozue <zezeozue@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: "Paul E . McKenney" <paulmck@xxxxxxxxxx>
Cc: kernel-team@xxxxxxxxxxx
Signed-off-by: John Stultz <jstultz@xxxxxxxxxx>
---
kernel/sched/core.c | 56 ++++++++++++++++++++-------------------
kernel/sched/core_sched.c | 2 +-
kernel/sched/deadline.c | 50 +++++++++++++++++-----------------
kernel/sched/debug.c | 2 +-
kernel/sched/fair.c | 25 ++++++++---------
kernel/sched/membarrier.c | 8 +++---
kernel/sched/pelt.h | 2 +-
kernel/sched/rt.c | 44 +++++++++++++++---------------
kernel/sched/sched.h | 42 ++++++++++++++++++++++++-----
9 files changed, 132 insertions(+), 99 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 488655f2319f..faaad249f8f7 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -257,7 +257,7 @@ void sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags)
* and re-examine whether the core is still in forced idle state.
*/
if (!(flags & DEQUEUE_SAVE) && rq->nr_running == 1 &&
- rq->core->core_forceidle_count && rq->curr == rq->idle)
+ rq->core->core_forceidle_count && rq_curr(rq) == rq->idle)
resched_curr(rq);
}

@@ -703,7 +703,7 @@ static void update_rq_clock_task(struct rq *rq, s64 delta)

rq->prev_irq_time += irq_delta;
delta -= irq_delta;
- psi_account_irqtime(rq->curr, irq_delta);
+ psi_account_irqtime(rq_curr(rq), irq_delta);
#endif
#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
if (static_key_false((&paravirt_steal_rq_enabled))) {
@@ -773,7 +773,7 @@ static enum hrtimer_restart hrtick(struct hrtimer *timer)

rq_lock(rq, &rf);
update_rq_clock(rq);
- rq->curr->sched_class->task_tick(rq, rq->curr, 1);
+ rq_curr(rq)->sched_class->task_tick(rq, rq_curr(rq), 1);
rq_unlock(rq, &rf);

return HRTIMER_NORESTART;
@@ -1020,7 +1020,7 @@ void wake_up_q(struct wake_q_head *head)
*/
void resched_curr(struct rq *rq)
{
- struct task_struct *curr = rq->curr;
+ struct task_struct *curr = rq_curr(rq);
int cpu;

lockdep_assert_rq_held(rq);
@@ -2175,16 +2175,18 @@ static inline void check_class_changed(struct rq *rq, struct task_struct *p,

void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
{
- if (p->sched_class == rq->curr->sched_class)
- rq->curr->sched_class->check_preempt_curr(rq, p, flags);
- else if (sched_class_above(p->sched_class, rq->curr->sched_class))
+ struct task_struct *curr = rq_curr(rq);
+
+ if (p->sched_class == curr->sched_class)
+ curr->sched_class->check_preempt_curr(rq, p, flags);
+ else if (sched_class_above(p->sched_class, curr->sched_class))
resched_curr(rq);

/*
* 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 (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
+ if (task_on_rq_queued(curr) && test_tsk_need_resched(curr))
rq_clock_skip_update(rq);
}

@@ -3859,11 +3861,11 @@ void wake_up_if_idle(int cpu)

rcu_read_lock();

- if (!is_idle_task(rcu_dereference(rq->curr)))
+ if (!is_idle_task(rq_curr_unlocked(rq)))
goto out;

rq_lock_irqsave(rq, &rf);
- if (is_idle_task(rq->curr))
+ if (is_idle_task(rq_curr(rq)))
resched_curr(rq);
/* Else CPU is not idle, do nothing here: */
rq_unlock_irqrestore(rq, &rf);
@@ -4388,7 +4390,7 @@ struct task_struct *cpu_curr_snapshot(int cpu)
struct task_struct *t;

smp_mb(); /* Pairing determined by caller's synchronization design. */
- t = rcu_dereference(cpu_curr(cpu));
+ t = cpu_curr_unlocked(cpu);
smp_mb(); /* Pairing determined by caller's synchronization design. */
return t;
}
@@ -5197,7 +5199,7 @@ static struct rq *finish_task_switch(struct task_struct *prev)
* kernel thread and not issued an IPI. It is therefore possible to
* schedule between user->kernel->user threads without passing though
* switch_mm(). Membarrier requires a barrier after storing to
- * rq->curr, before returning to userspace, so provide them here:
+ * rq_curr(rq), before returning to userspace, so provide them here:
*
* - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
* provided by mmdrop(),
@@ -5280,7 +5282,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
membarrier_switch_mm(rq, prev->active_mm, next->mm);
/*
* sys_membarrier() requires an smp_mb() between setting
- * rq->curr / membarrier_switch_mm() and returning to userspace.
+ * rq_curr(rq) / membarrier_switch_mm() and returning to userspace.
*
* The below provides this either through switch_mm(), or in
* case 'prev->active_mm == next->mm' through
@@ -5564,7 +5566,7 @@ void scheduler_tick(void)
{
int cpu = smp_processor_id();
struct rq *rq = cpu_rq(cpu);
- struct task_struct *curr = rq->curr;
+ struct task_struct *curr = rq_curr(rq);
struct rq_flags rf;
unsigned long thermal_pressure;
u64 resched_latency;
@@ -5657,7 +5659,7 @@ static void sched_tick_remote(struct work_struct *work)
goto out_requeue;

rq_lock_irq(rq, &rf);
- curr = rq->curr;
+ curr = rq_curr(rq);
if (cpu_is_offline(cpu))
goto out_unlock;

@@ -6201,7 +6203,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
/* Did we break L1TF mitigation requirements? */
WARN_ON_ONCE(!cookie_match(next, rq_i->core_pick));

- if (rq_i->curr == rq_i->core_pick) {
+ if (rq_curr(rq_i) == rq_i->core_pick) {
rq_i->core_pick = NULL;
continue;
}
@@ -6232,7 +6234,7 @@ static bool try_steal_cookie(int this, int that)
if (!cookie)
goto unlock;

- if (dst->curr != dst->idle)
+ if (rq_curr(dst) != dst->idle)
goto unlock;

p = sched_core_find(src, cookie);
@@ -6240,7 +6242,7 @@ static bool try_steal_cookie(int this, int that)
goto unlock;

do {
- if (p == src->core_pick || p == src->curr)
+ if (p == src->core_pick || p == rq_curr(src))
goto next;

if (!is_cpu_allowed(p, this))
@@ -6511,7 +6513,7 @@ static void __sched notrace __schedule(unsigned int sched_mode)

cpu = smp_processor_id();
rq = cpu_rq(cpu);
- prev = rq->curr;
+ prev = rq_curr(rq);

schedule_debug(prev, !!sched_mode);

@@ -6534,7 +6536,7 @@ static void __sched notrace __schedule(unsigned int sched_mode)
* if (signal_pending_state()) if (p->state & @state)
*
* Also, the membarrier system call requires a full memory barrier
- * after coming from user-space, before storing to rq->curr.
+ * after coming from user-space, before storing to rq_curr().
*/
rq_lock(rq, &rf);
smp_mb__after_spinlock();
@@ -6593,14 +6595,14 @@ static void __sched notrace __schedule(unsigned int sched_mode)
if (likely(prev != next)) {
rq->nr_switches++;
/*
- * RCU users of rcu_dereference(rq->curr) may not see
+ * RCU users of rcu_dereference(rq_curr(rq)) may not see
* changes to task_struct made by pick_next_task().
*/
- RCU_INIT_POINTER(rq->curr, next);
+ rq_set_curr_rcu_init(rq, next);
/*
* The membarrier system call requires each architecture
* to have a full memory barrier after updating
- * rq->curr, before returning to user-space.
+ * rq_curr(rq), before returning to user-space.
*
* Here are the schemes providing that barrier on the
* various architectures:
@@ -7037,7 +7039,7 @@ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
* real need to boost.
*/
if (unlikely(p == rq->idle)) {
- WARN_ON(p != rq->curr);
+ WARN_ON(p != rq_curr(rq));
WARN_ON(p->pi_blocked_on);
goto out_unlock;
}
@@ -7253,7 +7255,7 @@ int idle_cpu(int cpu)
{
struct rq *rq = cpu_rq(cpu);

- if (rq->curr != rq->idle)
+ if (rq_curr(rq) != rq->idle)
return 0;

if (rq->nr_running)
@@ -9154,7 +9156,7 @@ void __init init_idle(struct task_struct *idle, int cpu)
rcu_read_unlock();

rq->idle = idle;
- rcu_assign_pointer(rq->curr, idle);
+ rq_set_curr(rq, idle);
idle->on_rq = TASK_ON_RQ_QUEUED;
#ifdef CONFIG_SMP
idle->on_cpu = 1;
@@ -9328,7 +9330,7 @@ static DEFINE_PER_CPU(struct cpu_stop_work, push_work);
*/
static void balance_push(struct rq *rq)
{
- struct task_struct *push_task = rq->curr;
+ struct task_struct *push_task = rq_curr(rq);

lockdep_assert_rq_held(rq);

diff --git a/kernel/sched/core_sched.c b/kernel/sched/core_sched.c
index a57fd8f27498..ece2157a265d 100644
--- a/kernel/sched/core_sched.c
+++ b/kernel/sched/core_sched.c
@@ -273,7 +273,7 @@ void __sched_core_account_forceidle(struct rq *rq)

for_each_cpu(i, smt_mask) {
rq_i = cpu_rq(i);
- p = rq_i->core_pick ?: rq_i->curr;
+ p = rq_i->core_pick ?: rq_curr(rq_i);

if (p == rq_i->idle)
continue;
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 5a7c4edd5b13..4e3acc76708f 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1179,7 +1179,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
#endif

enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
- if (dl_task(rq->curr))
+ if (dl_task(rq_curr(rq)))
check_preempt_curr_dl(rq, p, 0);
else
resched_curr(rq);
@@ -1306,7 +1306,7 @@ static u64 grub_reclaim(u64 delta, struct rq *rq, struct sched_dl_entity *dl_se)
*/
static void update_curr_dl(struct rq *rq)
{
- struct task_struct *curr = rq->curr;
+ struct task_struct *curr = rq_curr(rq);
struct sched_dl_entity *dl_se = &curr->dl;
s64 delta_exec, scaled_delta_exec;
int cpu = cpu_of(rq);
@@ -1792,7 +1792,7 @@ static void yield_task_dl(struct rq *rq)
* it and the bandwidth timer will wake it up and will give it
* new scheduling parameters (thanks to dl_yielded=1).
*/
- rq->curr->dl.dl_yielded = 1;
+ rq_curr(rq)->dl.dl_yielded = 1;

update_rq_clock(rq);
update_curr_dl(rq);
@@ -1829,7 +1829,7 @@ select_task_rq_dl(struct task_struct *p, int cpu, int flags)
rq = cpu_rq(cpu);

rcu_read_lock();
- curr = READ_ONCE(rq->curr); /* unlocked access */
+ curr = rq_curr_unlocked(rq); /* XXX jstultz: using rcu_dereference intead of READ_ONCE */

/*
* If we are dealing with a -deadline task, we must
@@ -1904,8 +1904,8 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
* Current can't be migrated, useless to reschedule,
* let's hope p can move out.
*/
- if (rq->curr->nr_cpus_allowed == 1 ||
- !cpudl_find(&rq->rd->cpudl, rq->curr, NULL))
+ if (rq_curr(rq)->nr_cpus_allowed == 1 ||
+ !cpudl_find(&rq->rd->cpudl, rq_curr(rq), NULL))
return;

/*
@@ -1944,7 +1944,7 @@ static int balance_dl(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
int flags)
{
- if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {
+ if (dl_entity_preempt(&p->dl, &rq_curr(rq)->dl)) {
resched_curr(rq);
return;
}
@@ -1954,8 +1954,8 @@ static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
* In the unlikely case current and p have the same deadline
* let us try to decide what's the best thing to do...
*/
- if ((p->dl.deadline == rq->curr->dl.deadline) &&
- !test_tsk_need_resched(rq->curr))
+ if ((p->dl.deadline == rq_curr(rq)->dl.deadline) &&
+ !test_tsk_need_resched(rq_curr(rq)))
check_preempt_equal_dl(rq, p);
#endif /* CONFIG_SMP */
}
@@ -1989,7 +1989,7 @@ static void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first)
if (hrtick_enabled_dl(rq))
start_hrtick_dl(rq, p);

- if (rq->curr->sched_class != &dl_sched_class)
+ if (rq_curr(rq)->sched_class != &dl_sched_class)
update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);

deadline_queue_push_tasks(rq);
@@ -2301,13 +2301,13 @@ static int push_dl_task(struct rq *rq)

retry:
/*
- * If next_task preempts rq->curr, and rq->curr
+ * If next_task preempts rq_curr(rq), and rq_curr(rq)
* can move away, it makes sense to just reschedule
* without going further in pushing next_task.
*/
- if (dl_task(rq->curr) &&
- dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
- rq->curr->nr_cpus_allowed > 1) {
+ if (dl_task(rq_curr(rq)) &&
+ dl_time_before(next_task->dl.deadline, rq_curr(rq)->dl.deadline) &&
+ rq_curr(rq)->nr_cpus_allowed > 1) {
resched_curr(rq);
return 0;
}
@@ -2315,7 +2315,7 @@ static int push_dl_task(struct rq *rq)
if (is_migration_disabled(next_task))
return 0;

- if (WARN_ON(next_task == rq->curr))
+ if (WARN_ON(next_task == rq_curr(rq)))
return 0;

/* We might release rq lock */
@@ -2423,7 +2423,7 @@ static void pull_dl_task(struct rq *this_rq)
*/
if (p && dl_time_before(p->dl.deadline, dmin) &&
dl_task_is_earliest_deadline(p, this_rq)) {
- WARN_ON(p == src_rq->curr);
+ WARN_ON(p == rq_curr(src_rq));
WARN_ON(!task_on_rq_queued(p));

/*
@@ -2431,7 +2431,7 @@ static void pull_dl_task(struct rq *this_rq)
* deadline than the current task of its runqueue.
*/
if (dl_time_before(p->dl.deadline,
- src_rq->curr->dl.deadline))
+ rq_curr(src_rq)->dl.deadline))
goto skip;

if (is_migration_disabled(p)) {
@@ -2468,11 +2468,11 @@ static void pull_dl_task(struct rq *this_rq)
static void task_woken_dl(struct rq *rq, struct task_struct *p)
{
if (!task_on_cpu(rq, p) &&
- !test_tsk_need_resched(rq->curr) &&
+ !test_tsk_need_resched(rq_curr(rq)) &&
p->nr_cpus_allowed > 1 &&
- dl_task(rq->curr) &&
- (rq->curr->nr_cpus_allowed < 2 ||
- !dl_entity_preempt(&p->dl, &rq->curr->dl))) {
+ dl_task(rq_curr(rq)) &&
+ (rq_curr(rq)->nr_cpus_allowed < 2 ||
+ !dl_entity_preempt(&p->dl, &rq_curr(rq)->dl))) {
push_dl_tasks(rq);
}
}
@@ -2635,12 +2635,12 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
return;
}

- if (rq->curr != p) {
+ if (rq_curr(rq) != p) {
#ifdef CONFIG_SMP
if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
deadline_queue_push_tasks(rq);
#endif
- if (dl_task(rq->curr))
+ if (dl_task(rq_curr(rq)))
check_preempt_curr_dl(rq, p, 0);
else
resched_curr(rq);
@@ -2684,8 +2684,8 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
*
* Otherwise, if p was given an earlier deadline, reschedule.
*/
- if (!dl_task(rq->curr) ||
- dl_time_before(p->dl.deadline, rq->curr->dl.deadline))
+ if (!dl_task(rq_curr(rq)) ||
+ dl_time_before(p->dl.deadline, rq_curr(rq)->dl.deadline))
resched_curr(rq);
}
#else
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 1637b65ba07a..55f57156502d 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -743,7 +743,7 @@ do { \
P(nr_switches);
P(nr_uninterruptible);
PN(next_balance);
- SEQ_printf(m, " .%-30s: %ld\n", "curr->pid", (long)(task_pid_nr(rq->curr)));
+ SEQ_printf(m, " .%-30s: %ld\n", "curr->pid", (long)(task_pid_nr(rq_curr(rq))));
PN(clock);
PN(clock_task);
#undef P
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 03e61be5c94f..8b35dfc0c442 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -919,7 +919,7 @@ static s64 update_curr_se(struct rq *rq, struct sched_entity *curr)
*/
s64 update_curr_common(struct rq *rq)
{
- struct task_struct *curr = rq->curr;
+ struct task_struct *curr = rq_curr(rq);
s64 delta_exec;

delta_exec = update_curr_se(rq, &curr->se);
@@ -964,7 +964,7 @@ static void update_curr(struct cfs_rq *cfs_rq)

static void update_curr_fair(struct rq *rq)
{
- update_curr(cfs_rq_of(&rq->curr->se));
+ update_curr(cfs_rq_of(&rq_curr(rq)->se));
}

static inline void
@@ -1958,7 +1958,7 @@ static bool task_numa_compare(struct task_numa_env *env,
return false;

rcu_read_lock();
- cur = rcu_dereference(dst_rq->curr);
+ cur = rcu_dereference(rq_curr(dst_rq));
if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
cur = NULL;

@@ -2747,7 +2747,7 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,
}

rcu_read_lock();
- tsk = READ_ONCE(cpu_rq(cpu)->curr);
+ tsk = READ_ONCE(cpu_curr(cpu));

if (!cpupid_match_pid(tsk, cpupid))
goto no_join;
@@ -3969,7 +3969,7 @@ static inline void migrate_se_pelt_lag(struct sched_entity *se)
rq = rq_of(cfs_rq);

rcu_read_lock();
- is_idle = is_idle_task(rcu_dereference(rq->curr));
+ is_idle = is_idle_task(rq_curr_unlocked(rq));
rcu_read_unlock();

/*
@@ -5498,7 +5498,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
assert_list_leaf_cfs_rq(rq);

/* Determine whether we need to wake up potentially idle CPU: */
- if (rq->curr == rq->idle && rq->cfs.nr_running)
+ if (rq_curr(rq) == rq->idle && rq->cfs.nr_running)
resched_curr(rq);
}

@@ -6148,7 +6148,7 @@ static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
*/
static void hrtick_update(struct rq *rq)
{
- struct task_struct *curr = rq->curr;
+ struct task_struct *curr = rq_curr(rq);

if (!hrtick_enabled_fair(rq) || curr->sched_class != &fair_sched_class)
return;
@@ -7788,7 +7788,7 @@ static void set_skip_buddy(struct sched_entity *se)
*/
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
{
- struct task_struct *curr = rq->curr;
+ struct task_struct *curr = rq_curr(rq);
struct sched_entity *se = &curr->se, *pse = &p->se;
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
int scale = cfs_rq->nr_running >= sched_nr_latency;
@@ -8086,7 +8086,7 @@ static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
*/
static void yield_task_fair(struct rq *rq)
{
- struct task_struct *curr = rq->curr;
+ struct task_struct *curr = rq_curr(rq);
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
struct sched_entity *se = &curr->se;

@@ -8821,7 +8821,7 @@ static bool __update_blocked_others(struct rq *rq, bool *done)
* update_load_avg() can call cpufreq_update_util(). Make sure that RT,
* DL and IRQ signals have been updated before updating CFS.
*/
- curr_class = rq->curr->sched_class;
+ curr_class = rq_curr(rq)->sched_class;

thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));

@@ -9640,8 +9640,9 @@ static unsigned int task_running_on_cpu(int cpu, struct task_struct *p)
static int idle_cpu_without(int cpu, struct task_struct *p)
{
struct rq *rq = cpu_rq(cpu);
+ struct task_struct *curr = rq_curr(rq);

- if (rq->curr != rq->idle && rq->curr != p)
+ if (curr != rq->idle && curr != p)
return 0;

/*
@@ -10839,7 +10840,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
* if the curr task on busiest CPU can't be
* moved to this_cpu:
*/
- if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) {
+ if (!cpumask_test_cpu(this_cpu, rq_curr(busiest)->cpus_ptr)) {
raw_spin_rq_unlock_irqrestore(busiest, flags);
goto out_one_pinned;
}
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index 2ad881d07752..e55e39f74ea4 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -283,7 +283,7 @@ static int membarrier_global_expedited(void)
* Skip the CPU if it runs a kernel thread which is not using
* a task mm.
*/
- p = rcu_dereference(cpu_rq(cpu)->curr);
+ p = cpu_curr_unlocked(cpu);
if (!p->mm)
continue;

@@ -355,7 +355,7 @@ static int membarrier_private_expedited(int flags, int cpu_id)
if (cpu_id >= nr_cpu_ids || !cpu_online(cpu_id))
goto out;
rcu_read_lock();
- p = rcu_dereference(cpu_rq(cpu_id)->curr);
+ p = cpu_curr_unlocked(cpu_id);
if (!p || p->mm != mm) {
rcu_read_unlock();
goto out;
@@ -368,7 +368,7 @@ static int membarrier_private_expedited(int flags, int cpu_id)
for_each_online_cpu(cpu) {
struct task_struct *p;

- p = rcu_dereference(cpu_rq(cpu)->curr);
+ p = cpu_curr_unlocked(cpu);
if (p && p->mm == mm)
__cpumask_set_cpu(cpu, tmpmask);
}
@@ -466,7 +466,7 @@ static int sync_runqueues_membarrier_state(struct mm_struct *mm)
struct rq *rq = cpu_rq(cpu);
struct task_struct *p;

- p = rcu_dereference(rq->curr);
+ p = rq_curr_unlocked(rq);
if (p && p->mm == mm)
__cpumask_set_cpu(cpu, tmpmask);
}
diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h
index 3a0e0dc28721..bf3276f8df78 100644
--- a/kernel/sched/pelt.h
+++ b/kernel/sched/pelt.h
@@ -94,7 +94,7 @@ static inline void _update_idle_rq_clock_pelt(struct rq *rq)
*/
static inline void update_rq_clock_pelt(struct rq *rq, s64 delta)
{
- if (unlikely(is_idle_task(rq->curr))) {
+ if (unlikely(is_idle_task(rq_curr(rq)))) {
_update_idle_rq_clock_pelt(rq);
return;
}
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 18eb6ce60c5c..91c992230aba 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -574,7 +574,7 @@ static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)

static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
{
- struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
+ struct task_struct *curr = rq_curr(rq_of_rt_rq(rt_rq));
struct rq *rq = rq_of_rt_rq(rt_rq);
struct sched_rt_entity *rt_se;

@@ -958,7 +958,7 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
* and this unthrottle will get accounted as
* 'runtime'.
*/
- if (rt_rq->rt_nr_running && rq->curr == rq->idle)
+ if (rt_rq->rt_nr_running && rq_curr(rq) == rq->idle)
rq_clock_cancel_skipupdate(rq);
}
if (rt_rq->rt_time || rt_rq->rt_nr_running)
@@ -1044,7 +1044,7 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
*/
static void update_curr_rt(struct rq *rq)
{
- struct task_struct *curr = rq->curr;
+ struct task_struct *curr = rq_curr(rq);
struct sched_rt_entity *rt_se = &curr->rt;
s64 delta_exec;

@@ -1582,7 +1582,7 @@ static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)

static void yield_task_rt(struct rq *rq)
{
- requeue_task_rt(rq, rq->curr, 0);
+ requeue_task_rt(rq, rq_curr(rq), 0);
}

#ifdef CONFIG_SMP
@@ -1602,7 +1602,7 @@ select_task_rq_rt(struct task_struct *p, int cpu, int flags)
rq = cpu_rq(cpu);

rcu_read_lock();
- curr = READ_ONCE(rq->curr); /* unlocked access */
+ curr = rq_curr_unlocked(rq); /* XXX jstultz: using rcu_dereference intead of READ_ONCE */

/*
* If the current task on @p's runqueue is an RT task, then
@@ -1666,8 +1666,8 @@ static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
* Current can't be migrated, useless to reschedule,
* let's hope p can move out.
*/
- if (rq->curr->nr_cpus_allowed == 1 ||
- !cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
+ if (rq_curr(rq)->nr_cpus_allowed == 1 ||
+ !cpupri_find(&rq->rd->cpupri, rq_curr(rq), NULL))
return;

/*
@@ -1710,7 +1710,7 @@ static int balance_rt(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
*/
static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
{
- if (p->prio < rq->curr->prio) {
+ if (p->prio < rq_curr(rq)->prio) {
resched_curr(rq);
return;
}
@@ -1728,7 +1728,7 @@ static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flag
* to move current somewhere else, making room for our non-migratable
* task.
*/
- if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
+ if (p->prio == rq_curr(rq)->prio && !test_tsk_need_resched(rq_curr(rq)))
check_preempt_equal_prio(rq, p);
#endif
}
@@ -1753,7 +1753,7 @@ static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, bool f
* utilization. We only care of the case where we start to schedule a
* rt task
*/
- if (rq->curr->sched_class != &rt_sched_class)
+ if (rq_curr(rq)->sched_class != &rt_sched_class)
update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);

rt_queue_push_tasks(rq);
@@ -2062,7 +2062,7 @@ static int push_rt_task(struct rq *rq, bool pull)
* higher priority than current. If that's the case
* just reschedule current.
*/
- if (unlikely(next_task->prio < rq->curr->prio)) {
+ if (unlikely(next_task->prio < rq_curr(rq)->prio)) {
resched_curr(rq);
return 0;
}
@@ -2083,10 +2083,10 @@ static int push_rt_task(struct rq *rq, bool pull)
* Note that the stoppers are masqueraded as SCHED_FIFO
* (cf. sched_set_stop_task()), so we can't rely on rt_task().
*/
- if (rq->curr->sched_class != &rt_sched_class)
+ if (rq_curr(rq)->sched_class != &rt_sched_class)
return 0;

- cpu = find_lowest_rq(rq->curr);
+ cpu = find_lowest_rq(rq_curr(rq));
if (cpu == -1 || cpu == rq->cpu)
return 0;

@@ -2107,7 +2107,7 @@ static int push_rt_task(struct rq *rq, bool pull)
return 0;
}

- if (WARN_ON(next_task == rq->curr))
+ if (WARN_ON(next_task == rq_curr(rq)))
return 0;

/* We might release rq lock */
@@ -2404,7 +2404,7 @@ static void pull_rt_task(struct rq *this_rq)
* the to-be-scheduled task?
*/
if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
- WARN_ON(p == src_rq->curr);
+ WARN_ON(p == rq_curr(src_rq));
WARN_ON(!task_on_rq_queued(p));

/*
@@ -2415,7 +2415,7 @@ static void pull_rt_task(struct rq *this_rq)
* p if it is lower in priority than the
* current task on the run queue
*/
- if (p->prio < src_rq->curr->prio)
+ if (p->prio < rq_curr(src_rq)->prio)
goto skip;

if (is_migration_disabled(p)) {
@@ -2455,11 +2455,11 @@ static void pull_rt_task(struct rq *this_rq)
static void task_woken_rt(struct rq *rq, struct task_struct *p)
{
bool need_to_push = !task_on_cpu(rq, p) &&
- !test_tsk_need_resched(rq->curr) &&
+ !test_tsk_need_resched(rq_curr(rq)) &&
p->nr_cpus_allowed > 1 &&
- (dl_task(rq->curr) || rt_task(rq->curr)) &&
- (rq->curr->nr_cpus_allowed < 2 ||
- rq->curr->prio <= p->prio);
+ (dl_task(rq_curr(rq)) || rt_task(rq_curr(rq))) &&
+ (rq_curr(rq)->nr_cpus_allowed < 2 ||
+ rq_curr(rq)->prio <= p->prio);

if (need_to_push)
push_rt_tasks(rq);
@@ -2543,7 +2543,7 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p)
if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)
rt_queue_push_tasks(rq);
#endif /* CONFIG_SMP */
- if (p->prio < rq->curr->prio && cpu_online(cpu_of(rq)))
+ if (p->prio < rq_curr(rq)->prio && cpu_online(cpu_of(rq)))
resched_curr(rq);
}
}
@@ -2584,7 +2584,7 @@ prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
* greater than the current running task
* then reschedule.
*/
- if (p->prio < rq->curr->prio)
+ if (p->prio < rq_curr(rq)->prio)
resched_curr(rq);
}
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index d18e3c3a3f40..00f73ca4c618 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1008,7 +1008,7 @@ struct rq {
*/
unsigned int nr_uninterruptible;

- struct task_struct __rcu *curr;
+ struct task_struct __rcu *curr_exec;
struct task_struct *idle;
struct task_struct *stop;
unsigned long next_balance;
@@ -1201,12 +1201,42 @@ static inline bool is_migration_disabled(struct task_struct *p)

DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);

+static inline struct task_struct *rq_curr(struct rq *rq)
+{
+ return rq->curr_exec;
+}
+
+/* XXX jstultz: Would rq_curr_rcu() be a better name? */
+static inline struct task_struct *rq_curr_unlocked(struct rq *rq)
+{
+ return rcu_dereference(rq->curr_exec);
+}
+
+static inline void rq_set_curr(struct rq *rq, struct task_struct *task)
+{
+ rcu_assign_pointer(rq->curr_exec, task);
+}
+
+/*
+ * XXX jstultz: seems like rcu_assign_pointer above would also
+ * work for this, but trying to match usage.
+ */
+static inline void rq_set_curr_rcu_init(struct rq *rq, struct task_struct *task)
+{
+ RCU_INIT_POINTER(rq->curr_exec, task);
+}
+
#define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
#define this_rq() this_cpu_ptr(&runqueues)
#define task_rq(p) cpu_rq(task_cpu(p))
-#define cpu_curr(cpu) (cpu_rq(cpu)->curr)
+#define cpu_curr(cpu) (rq_curr(cpu_rq(cpu)))
#define raw_rq() raw_cpu_ptr(&runqueues)

+static inline struct task_struct *cpu_curr_unlocked(int cpu)
+{
+ return rq_curr_unlocked(cpu_rq(cpu));
+}
+
struct sched_group;
#ifdef CONFIG_SCHED_CORE
static inline struct cpumask *sched_group_span(struct sched_group *sg);
@@ -2070,7 +2100,7 @@ static inline u64 global_rt_runtime(void)

static inline int task_current(struct rq *rq, struct task_struct *p)
{
- return rq->curr == p;
+ return rq_curr(rq) == p;
}

static inline int task_on_cpu(struct rq *rq, struct task_struct *p)
@@ -2230,7 +2260,7 @@ struct sched_class {

static inline void put_prev_task(struct rq *rq, struct task_struct *prev)
{
- WARN_ON_ONCE(rq->curr != prev);
+ WARN_ON_ONCE(rq_curr(rq) != prev);
prev->sched_class->put_prev_task(rq, prev);
}

@@ -2311,7 +2341,7 @@ extern void set_cpus_allowed_common(struct task_struct *p, struct affinity_conte

static inline struct task_struct *get_push_task(struct rq *rq)
{
- struct task_struct *p = rq->curr;
+ struct task_struct *p = rq_curr(rq);

lockdep_assert_rq_held(rq);

@@ -3193,7 +3223,7 @@ static inline bool sched_energy_enabled(void) { return false; }
* The scheduler provides memory barriers required by membarrier between:
* - prior user-space memory accesses and store to rq->membarrier_state,
* - store to rq->membarrier_state and following user-space memory accesses.
- * In the same way it provides those guarantees around store to rq->curr.
+ * In the same way it provides those guarantees around store to rq_curr(rq).
*/
static inline void membarrier_switch_mm(struct rq *rq,
struct mm_struct *prev_mm,
--
2.40.0.rc1.284.g88254d51c5-goog