[RFC PATCH 38/86] sched: *_tsk_need_resched() now takes resched_t

From: Ankur Arora
Date: Tue Nov 07 2023 - 17:04:05 EST

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*_tsk_need_resched() need to test for the specific need-resched
flag.

The only users are RCU and the scheduler. For RCU we always want
to schedule at the earliest opportunity and that is always
RESCHED_eager.

For the scheduler, keep everything as RESCHED_eager for now.

Originally-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
---
include/linux/sched.h | 17 ++++++++++++-----
kernel/rcu/tree.c | 4 ++--
kernel/rcu/tree_exp.h | 4 ++--
kernel/rcu/tree_plugin.h | 4 ++--
kernel/rcu/tree_stall.h | 2 +-
kernel/sched/core.c | 9 +++++----
kernel/sched/deadline.c | 4 ++--
kernel/sched/fair.c | 2 +-
kernel/sched/idle.c | 2 +-
kernel/sched/rt.c | 4 ++--
10 files changed, 30 insertions(+), 22 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 12d0626601a0..6dd206b2ef50 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2060,19 +2060,26 @@ static inline bool test_tsk_thread_flag(struct task_struct *tsk, int flag)
return test_ti_thread_flag(task_thread_info(tsk), flag);
}

-static inline void set_tsk_need_resched(struct task_struct *tsk)
+static inline void set_tsk_need_resched(struct task_struct *tsk, resched_t lazy)
{
- set_tsk_thread_flag(tsk,TIF_NEED_RESCHED);
+ set_tsk_thread_flag(tsk, tif_resched(lazy));
}

static inline void clear_tsk_need_resched(struct task_struct *tsk)
{
- clear_tsk_thread_flag(tsk,TIF_NEED_RESCHED);
+ clear_tsk_thread_flag(tsk, tif_resched(RESCHED_eager));
+ clear_tsk_thread_flag(tsk, tif_resched(RESCHED_lazy));
}

-static inline bool test_tsk_need_resched(struct task_struct *tsk)
+static inline bool test_tsk_need_resched(struct task_struct *tsk, resched_t lazy)
{
- return unlikely(test_tsk_thread_flag(tsk,TIF_NEED_RESCHED));
+ return unlikely(test_tsk_thread_flag(tsk, tif_resched(lazy)));
+}
+
+static inline bool test_tsk_need_resched_any(struct task_struct *tsk)
+{
+ return test_tsk_need_resched(tsk, RESCHED_eager) ||
+ test_tsk_need_resched(tsk, RESCHED_lazy);
}

/*
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index cb1caefa8bd0..a7776ae78900 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2231,7 +2231,7 @@ void rcu_sched_clock_irq(int user)
if (smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) {
/* Idle and userspace execution already are quiescent states. */
if (!rcu_is_cpu_rrupt_from_idle() && !user) {
- set_tsk_need_resched(current);
+ set_tsk_need_resched(current, RESCHED_eager);
set_preempt_need_resched();
}
__this_cpu_write(rcu_data.rcu_urgent_qs, false);
@@ -2379,7 +2379,7 @@ static __latent_entropy void rcu_core(void)
if (IS_ENABLED(CONFIG_PREEMPT_COUNT) && (!(preempt_count() & PREEMPT_MASK))) {
rcu_preempt_deferred_qs(current);
} else if (rcu_preempt_need_deferred_qs(current)) {
- set_tsk_need_resched(current);
+ set_tsk_need_resched(current, RESCHED_eager);
set_preempt_need_resched();
}

diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 8239b39d945b..a4a23ac1115b 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -755,7 +755,7 @@ static void rcu_exp_handler(void *unused)
rcu_report_exp_rdp(rdp);
} else {
WRITE_ONCE(rdp->cpu_no_qs.b.exp, true);
- set_tsk_need_resched(t);
+ set_tsk_need_resched(t, RESCHED_eager);
set_preempt_need_resched();
}
return;
@@ -856,7 +856,7 @@ static void rcu_exp_need_qs(void)
__this_cpu_write(rcu_data.cpu_no_qs.b.exp, true);
/* Store .exp before .rcu_urgent_qs. */
smp_store_release(this_cpu_ptr(&rcu_data.rcu_urgent_qs), true);
- set_tsk_need_resched(current);
+ set_tsk_need_resched(current, RESCHED_eager);
set_preempt_need_resched();
}

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 41021080ad25..f87191e008ff 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -658,7 +658,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
// Also if no expediting and no possible deboosting,
// slow is OK. Plus nohz_full CPUs eventually get
// tick enabled.
- set_tsk_need_resched(current);
+ set_tsk_need_resched(current, RESCHED_eager);
set_preempt_need_resched();
if (IS_ENABLED(CONFIG_IRQ_WORK) && irqs_were_disabled &&
expboost && !rdp->defer_qs_iw_pending && cpu_online(rdp->cpu)) {
@@ -725,7 +725,7 @@ static void rcu_flavor_sched_clock_irq(int user)
(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK))) {
/* No QS, force context switch if deferred. */
if (rcu_preempt_need_deferred_qs(t)) {
- set_tsk_need_resched(t);
+ set_tsk_need_resched(t, RESCHED_eager);
set_preempt_need_resched();
}
} else if (rcu_preempt_need_deferred_qs(t)) {
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 6f06dc12904a..b74b7b04cf35 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -705,7 +705,7 @@ static void print_cpu_stall(unsigned long gps)
* progress and it could be we're stuck in kernel space without context
* switches for an entirely unreasonable amount of time.
*/
- set_tsk_need_resched(current);
+ set_tsk_need_resched(current, RESCHED_eager);
set_preempt_need_resched();
}

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e30007c11722..e2215c417323 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -927,7 +927,7 @@ static bool set_nr_if_polling(struct task_struct *p)
#else
static inline bool set_nr_and_not_polling(struct task_struct *p)
{
- set_tsk_need_resched(p);
+ set_tsk_need_resched(p, RESCHED_eager);
return true;
}

@@ -1039,13 +1039,13 @@ void resched_curr(struct rq *rq)

lockdep_assert_rq_held(rq);

- if (test_tsk_need_resched(curr))
+ if (test_tsk_need_resched(curr, RESCHED_eager))
return;

cpu = cpu_of(rq);

if (cpu == smp_processor_id()) {
- set_tsk_need_resched(curr);
+ set_tsk_need_resched(curr, RESCHED_eager);
set_preempt_need_resched();
return;
}
@@ -2223,7 +2223,8 @@ 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 (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
+ if (task_on_rq_queued(rq->curr) &&
+ test_tsk_need_resched(rq->curr, RESCHED_eager))
rq_clock_skip_update(rq);
}

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 58b542bf2893..e6815c3bd2f0 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1953,7 +1953,7 @@ static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
* 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))
+ !test_tsk_need_resched(rq->curr, RESCHED_eager))
check_preempt_equal_dl(rq, p);
#endif /* CONFIG_SMP */
}
@@ -2467,7 +2467,7 @@ 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, RESCHED_eager) &&
p->nr_cpus_allowed > 1 &&
dl_task(rq->curr) &&
(rq->curr->nr_cpus_allowed < 2 ||
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index df348aa55d3c..4d86c618ffa2 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8087,7 +8087,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
* prevents us from potentially nominating it as a false LAST_BUDDY
* below.
*/
- if (test_tsk_need_resched(curr))
+ if (test_tsk_need_resched(curr, RESCHED_eager))
return;

/* Idle tasks are by definition preempted by non-idle tasks. */
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index d4a55448e459..eacd204e2879 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -329,7 +329,7 @@ static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer)
struct idle_timer *it = container_of(timer, struct idle_timer, timer);

WRITE_ONCE(it->done, 1);
- set_tsk_need_resched(current);
+ set_tsk_need_resched(current, RESCHED_eager);

return HRTIMER_NORESTART;
}
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 0597ba0f85ff..a79ce6746dd0 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1735,7 +1735,7 @@ 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->prio && !test_tsk_need_resched(rq->curr, RESCHED_eager))
check_preempt_equal_prio(rq, p);
#endif
}
@@ -2466,7 +2466,7 @@ 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, RESCHED_eager) &&
p->nr_cpus_allowed > 1 &&
(dl_task(rq->curr) || rt_task(rq->curr)) &&
(rq->curr->nr_cpus_allowed < 2 ||
--
2.31.1

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