[PATCH v3 21/57] sched: Misc cleanups

From: Peter Zijlstra
Date: Mon Jun 12 2023 - 05:59:31 EST

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Random remaining guard use...

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
kernel/sched/core.c | 163 ++++++++++++++++++++--------------------------------
1 file changed, 63 insertions(+), 100 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1454,16 +1454,12 @@ static void __uclamp_update_util_min_rt_

static void uclamp_update_util_min_rt_default(struct task_struct *p)
{
- struct rq_flags rf;
- struct rq *rq;
-
if (!rt_task(p))
return;

/* Protect updates to p->uclamp_* */
- rq = task_rq_lock(p, &rf);
+ guard(task_rq_lock)(p);
__uclamp_update_util_min_rt_default(p);
- task_rq_unlock(rq, p, &rf);
}

static inline struct uclamp_se
@@ -1759,9 +1755,8 @@ static void uclamp_update_root_tg(void)
uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX],
sysctl_sched_uclamp_util_max, false);

- rcu_read_lock();
+ guard(rcu)();
cpu_util_update_eff(&root_task_group.css);
- rcu_read_unlock();
}
#else
static void uclamp_update_root_tg(void) { }
@@ -1788,10 +1783,9 @@ static void uclamp_sync_util_min_rt_defa
smp_mb__after_spinlock();
read_unlock(&tasklist_lock);

- rcu_read_lock();
+ guard(rcu)();
for_each_process_thread(g, p)
uclamp_update_util_min_rt_default(p);
- rcu_read_unlock();
}

static int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
@@ -2243,10 +2237,9 @@ void migrate_disable(void)
return;
}

- preempt_disable();
+ guard(preempt)();
this_rq()->nr_pinned++;
p->migration_disabled = 1;
- preempt_enable();
}
EXPORT_SYMBOL_GPL(migrate_disable);

@@ -2270,7 +2263,7 @@ void migrate_enable(void)
* Ensure stop_task runs either before or after this, and that
* __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule().
*/
- preempt_disable();
+ guard(preempt)();
if (p->cpus_ptr != &p->cpus_mask)
__set_cpus_allowed_ptr(p, &ac);
/*
@@ -2281,7 +2274,6 @@ void migrate_enable(void)
barrier();
p->migration_disabled = 0;
this_rq()->nr_pinned--;
- preempt_enable();
}
EXPORT_SYMBOL_GPL(migrate_enable);

@@ -3449,13 +3441,11 @@ unsigned long wait_task_inactive(struct
*/
void kick_process(struct task_struct *p)
{
- int cpu;
+ guard(preempt)();
+ int cpu = task_cpu(p);

- preempt_disable();
- cpu = task_cpu(p);
if ((cpu != smp_processor_id()) && task_curr(p))
smp_send_reschedule(cpu);
- preempt_enable();
}
EXPORT_SYMBOL_GPL(kick_process);

@@ -6300,8 +6290,9 @@ static void sched_core_balance(struct rq
struct sched_domain *sd;
int cpu = cpu_of(rq);

- preempt_disable();
- rcu_read_lock();
+ guard(preempt)();
+ guard(rcu)();
+
raw_spin_rq_unlock_irq(rq);
for_each_domain(cpu, sd) {
if (need_resched())
@@ -6311,8 +6302,6 @@ static void sched_core_balance(struct rq
break;
}
raw_spin_rq_lock_irq(rq);
- rcu_read_unlock();
- preempt_enable();
}

static DEFINE_PER_CPU(struct balance_callback, core_balance_head);
@@ -8169,8 +8158,6 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pi
#ifdef CONFIG_SMP
int dl_task_check_affinity(struct task_struct *p, const struct cpumask *mask)
{
- int ret = 0;
-
/*
* If the task isn't a deadline task or admission control is
* disabled then we don't care about affinity changes.
@@ -8184,11 +8171,11 @@ int dl_task_check_affinity(struct task_s
* tasks allowed to run on all the CPUs in the task's
* root_domain.
*/
- rcu_read_lock();
+ guard(rcu)();
if (!cpumask_subset(task_rq(p)->rd->span, mask))
- ret = -EBUSY;
- rcu_read_unlock();
- return ret;
+ return -EBUSY;
+
+ return 0;
}
#endif

@@ -9197,10 +9184,8 @@ int task_can_attach(struct task_struct *
* success of set_cpus_allowed_ptr() on all attached tasks
* before cpus_mask may be changed.
*/
- if (p->flags & PF_NO_SETAFFINITY) {
- ret = -EINVAL;
- goto out;
- }
+ if (p->flags & PF_NO_SETAFFINITY)
+ return -EINVAL;

if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
cs_effective_cpus)) {
@@ -9211,7 +9196,6 @@ int task_can_attach(struct task_struct *
ret = dl_cpu_busy(cpu, p);
}

-out:
return ret;
}

@@ -10433,11 +10417,9 @@ static int cpu_cgroup_css_online(struct

#ifdef CONFIG_UCLAMP_TASK_GROUP
/* Propagate the effective uclamp value for the new group */
- mutex_lock(&uclamp_mutex);
- rcu_read_lock();
+ guard(mutex)(&uclamp_mutex);
+ guard(rcu)();
cpu_util_update_eff(css);
- rcu_read_unlock();
- mutex_unlock(&uclamp_mutex);
#endif

return 0;
@@ -10588,8 +10570,8 @@ static ssize_t cpu_uclamp_write(struct k

static_branch_enable(&sched_uclamp_used);

- mutex_lock(&uclamp_mutex);
- rcu_read_lock();
+ guard(mutex)(&uclamp_mutex);
+ guard(rcu)();

tg = css_tg(of_css(of));
if (tg->uclamp_req[clamp_id].value != req.util)
@@ -10604,9 +10586,6 @@ static ssize_t cpu_uclamp_write(struct k
/* Update effective clamps to track the most restrictive value */
cpu_util_update_eff(of_css(of));

- rcu_read_unlock();
- mutex_unlock(&uclamp_mutex);
-
return nbytes;
}

@@ -10632,10 +10611,10 @@ static inline void cpu_uclamp_print(stru
u64 percent;
u32 rem;

- rcu_read_lock();
- tg = css_tg(seq_css(sf));
- util_clamp = tg->uclamp_req[clamp_id].value;
- rcu_read_unlock();
+ scoped_guard (rcu) {
+ tg = css_tg(seq_css(sf));
+ util_clamp = tg->uclamp_req[clamp_id].value;
+ }

if (util_clamp == SCHED_CAPACITY_SCALE) {
seq_puts(sf, "max\n");
@@ -10952,7 +10931,6 @@ static int tg_cfs_schedulable_down(struc

static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
{
- int ret;
struct cfs_schedulable_data data = {
.tg = tg,
.period = period,
@@ -10964,11 +10942,8 @@ static int __cfs_schedulable(struct task
do_div(data.quota, NSEC_PER_USEC);
}

- rcu_read_lock();
- ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
- rcu_read_unlock();
-
- return ret;
+ guard(rcu)();
+ return walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
}

static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
@@ -11529,14 +11504,12 @@ int __sched_mm_cid_migrate_from_fetch_ci
* are not the last task to be migrated from this cpu for this mm, so
* there is no need to move src_cid to the destination cpu.
*/
- rcu_read_lock();
+ guard(rcu)();
src_task = rcu_dereference(src_rq->curr);
if (READ_ONCE(src_task->mm_cid_active) && src_task->mm == mm) {
- rcu_read_unlock();
t->last_mm_cid = -1;
return -1;
}
- rcu_read_unlock();

return src_cid;
}
@@ -11580,18 +11553,17 @@ int __sched_mm_cid_migrate_from_try_stea
* the lazy-put flag, this task will be responsible for transitioning
* from lazy-put flag set to MM_CID_UNSET.
*/
- rcu_read_lock();
- src_task = rcu_dereference(src_rq->curr);
- if (READ_ONCE(src_task->mm_cid_active) && src_task->mm == mm) {
- rcu_read_unlock();
- /*
- * We observed an active task for this mm, there is therefore
- * no point in moving this cid to the destination cpu.
- */
- t->last_mm_cid = -1;
- return -1;
+ scoped_guard (rcu) {
+ src_task = rcu_dereference(src_rq->curr);
+ if (READ_ONCE(src_task->mm_cid_active) && src_task->mm == mm) {
+ /*
+ * We observed an active task for this mm, there is therefore
+ * no point in moving this cid to the destination cpu.
+ */
+ t->last_mm_cid = -1;
+ return -1;
+ }
}
- rcu_read_unlock();

/*
* The src_cid is unused, so it can be unset.
@@ -11664,7 +11636,6 @@ static void sched_mm_cid_remote_clear(st
{
struct rq *rq = cpu_rq(cpu);
struct task_struct *t;
- unsigned long flags;
int cid, lazy_cid;

cid = READ_ONCE(pcpu_cid->cid);
@@ -11699,23 +11670,21 @@ static void sched_mm_cid_remote_clear(st
* the lazy-put flag, that task will be responsible for transitioning
* from lazy-put flag set to MM_CID_UNSET.
*/
- rcu_read_lock();
- t = rcu_dereference(rq->curr);
- if (READ_ONCE(t->mm_cid_active) && t->mm == mm) {
- rcu_read_unlock();
- return;
+ scoped_guard (rcu) {
+ t = rcu_dereference(rq->curr);
+ if (READ_ONCE(t->mm_cid_active) && t->mm == mm)
+ return;
}
- rcu_read_unlock();

/*
* The cid is unused, so it can be unset.
* Disable interrupts to keep the window of cid ownership without rq
* lock small.
*/
- local_irq_save(flags);
- if (try_cmpxchg(&pcpu_cid->cid, &lazy_cid, MM_CID_UNSET))
- __mm_cid_put(mm, cid);
- local_irq_restore(flags);
+ scoped_guard (irqsave) {
+ if (try_cmpxchg(&pcpu_cid->cid, &lazy_cid, MM_CID_UNSET))
+ __mm_cid_put(mm, cid);
+ }
}

static void sched_mm_cid_remote_clear_old(struct mm_struct *mm, int cpu)
@@ -11737,14 +11706,13 @@ static void sched_mm_cid_remote_clear_ol
* snapshot associated with this cid if an active task using the mm is
* observed on this rq.
*/
- rcu_read_lock();
- curr = rcu_dereference(rq->curr);
- if (READ_ONCE(curr->mm_cid_active) && curr->mm == mm) {
- WRITE_ONCE(pcpu_cid->time, rq_clock);
- rcu_read_unlock();
- return;
+ scoped_guard (rcu) {
+ curr = rcu_dereference(rq->curr);
+ if (READ_ONCE(curr->mm_cid_active) && curr->mm == mm) {
+ WRITE_ONCE(pcpu_cid->time, rq_clock);
+ return;
+ }
}
- rcu_read_unlock();

if (rq_clock < pcpu_cid->time + SCHED_MM_CID_PERIOD_NS)
return;
@@ -11838,7 +11806,6 @@ void task_tick_mm_cid(struct rq *rq, str
void sched_mm_cid_exit_signals(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
- struct rq_flags rf;
struct rq *rq;

if (!mm)
@@ -11846,7 +11813,7 @@ void sched_mm_cid_exit_signals(struct ta

preempt_disable();
rq = this_rq();
- rq_lock_irqsave(rq, &rf);
+ guard(rq_lock_irqsave)(rq);
preempt_enable_no_resched(); /* holding spinlock */
WRITE_ONCE(t->mm_cid_active, 0);
/*
@@ -11856,13 +11823,11 @@ void sched_mm_cid_exit_signals(struct ta
smp_mb();
mm_cid_put(mm);
t->last_mm_cid = t->mm_cid = -1;
- rq_unlock_irqrestore(rq, &rf);
}

void sched_mm_cid_before_execve(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
- struct rq_flags rf;
struct rq *rq;

if (!mm)
@@ -11870,7 +11835,7 @@ void sched_mm_cid_before_execve(struct t

preempt_disable();
rq = this_rq();
- rq_lock_irqsave(rq, &rf);
+ guard(rq_lock_irqsave)(rq);
preempt_enable_no_resched(); /* holding spinlock */
WRITE_ONCE(t->mm_cid_active, 0);
/*
@@ -11880,13 +11845,11 @@ void sched_mm_cid_before_execve(struct t
smp_mb();
mm_cid_put(mm);
t->last_mm_cid = t->mm_cid = -1;
- rq_unlock_irqrestore(rq, &rf);
}

void sched_mm_cid_after_execve(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
- struct rq_flags rf;
struct rq *rq;

if (!mm)
@@ -11894,16 +11857,16 @@ void sched_mm_cid_after_execve(struct ta

preempt_disable();
rq = this_rq();
- rq_lock_irqsave(rq, &rf);
- preempt_enable_no_resched(); /* holding spinlock */
- WRITE_ONCE(t->mm_cid_active, 1);
- /*
- * Store t->mm_cid_active before loading per-mm/cpu cid.
- * Matches barrier in sched_mm_cid_remote_clear_old().
- */
- smp_mb();
- t->last_mm_cid = t->mm_cid = mm_cid_get(rq, mm);
- rq_unlock_irqrestore(rq, &rf);
+ scoped_guard (rq_lock_irqsave, rq) {
+ preempt_enable_no_resched(); /* holding spinlock */
+ WRITE_ONCE(t->mm_cid_active, 1);
+ /*
+ * Store t->mm_cid_active before loading per-mm/cpu cid.
+ * Matches barrier in sched_mm_cid_remote_clear_old().
+ */
+ smp_mb();
+ t->last_mm_cid = t->mm_cid = mm_cid_get(rq, mm);
+ }
rseq_set_notify_resume(t);
}

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