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sched_ext: Rename pnt_seq to kick_sync

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The pnt_seq field and related infrastructure were originally named for
"pick next task sequence", reflecting their original implementation in
scx_next_task_picked(). However, the sequence counter is now incremented in
both put_prev_task_scx() and pick_task_scx() and its purpose is to
synchronize kick operations via SCX_KICK_WAIT, not specifically to track
pick_next_task events.

Rename to better reflect the actual semantics:
- pnt_seq -> kick_sync
- scx_kick_pseqs -> scx_kick_syncs
- pseqs variables -> ksyncs
- Update comments to refer to "kick_sync sequence" instead of "pick_task
  sequence"

This is a pure renaming with no functional changes.

Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2025-10-22 10:56:29 -10:00
parent a379fa1e2c
commit 987e00035c
2 changed files with 41 additions and 41 deletions
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80
kernel/sched/ext.c
View File

@ -68,18 +68,18 @@ static unsigned long scx_watchdog_timestamp = INITIAL_JIFFIES;
static struct delayed_work scx_watchdog_work; static struct delayed_work scx_watchdog_work;
/* /*
* For %SCX_KICK_WAIT: Each CPU has a pointer to an array of pick_task sequence * For %SCX_KICK_WAIT: Each CPU has a pointer to an array of kick_sync sequence
* numbers. The arrays are allocated with kvzalloc() as size can exceed percpu * numbers. The arrays are allocated with kvzalloc() as size can exceed percpu
* allocator limits on large machines. O(nr_cpu_ids^2) allocation, allocated * allocator limits on large machines. O(nr_cpu_ids^2) allocation, allocated
* lazily when enabling and freed when disabling to avoid waste when sched_ext * lazily when enabling and freed when disabling to avoid waste when sched_ext
* isn't active. * isn't active.
*/ */
struct scx_kick_pseqs { struct scx_kick_syncs {
struct rcu_head rcu; struct rcu_head rcu;
unsigned long seqs[]; unsigned long syncs[];
}; };
static DEFINE_PER_CPU(struct scx_kick_pseqs __rcu *, scx_kick_pseqs); static DEFINE_PER_CPU(struct scx_kick_syncs __rcu *, scx_kick_syncs);
/* /*
* Direct dispatch marker. * Direct dispatch marker.
@ -2301,7 +2301,7 @@ static void put_prev_task_scx(struct rq *rq, struct task_struct *p,
struct scx_sched *sch = scx_root; struct scx_sched *sch = scx_root;
/* see kick_cpus_irq_workfn() */ /* see kick_cpus_irq_workfn() */
smp_store_release(&rq->scx.pnt_seq, rq->scx.pnt_seq + 1); smp_store_release(&rq->scx.kick_sync, rq->scx.kick_sync + 1);
update_curr_scx(rq); update_curr_scx(rq);
@ -2357,7 +2357,7 @@ do_pick_task_scx(struct rq *rq, struct rq_flags *rf, bool force_scx)
struct task_struct *p; struct task_struct *p;
/* see kick_cpus_irq_workfn() */ /* see kick_cpus_irq_workfn() */
smp_store_release(&rq->scx.pnt_seq, rq->scx.pnt_seq + 1); smp_store_release(&rq->scx.kick_sync, rq->scx.kick_sync + 1);
rq_modified_clear(rq); rq_modified_clear(rq);
@ -3883,24 +3883,24 @@ static const char *scx_exit_reason(enum scx_exit_kind kind)
} }
} }
static void free_kick_pseqs_rcu(struct rcu_head *rcu) static void free_kick_syncs_rcu(struct rcu_head *rcu)
{ {
struct scx_kick_pseqs *pseqs = container_of(rcu, struct scx_kick_pseqs, rcu); struct scx_kick_syncs *ksyncs = container_of(rcu, struct scx_kick_syncs, rcu);
kvfree(pseqs); kvfree(ksyncs);
} }
static void free_kick_pseqs(void) static void free_kick_syncs(void)
{ {
int cpu; int cpu;
for_each_possible_cpu(cpu) { for_each_possible_cpu(cpu) {
struct scx_kick_pseqs **pseqs = per_cpu_ptr(&scx_kick_pseqs, cpu); struct scx_kick_syncs **ksyncs = per_cpu_ptr(&scx_kick_syncs, cpu);
struct scx_kick_pseqs *to_free; struct scx_kick_syncs *to_free;
to_free = rcu_replace_pointer(*pseqs, NULL, true); to_free = rcu_replace_pointer(*ksyncs, NULL, true);
if (to_free) if (to_free)
call_rcu(&to_free->rcu, free_kick_pseqs_rcu); call_rcu(&to_free->rcu, free_kick_syncs_rcu);
} }
} }
@ -4038,7 +4038,7 @@ static void scx_disable_workfn(struct kthread_work *work)
free_percpu(scx_dsp_ctx); free_percpu(scx_dsp_ctx);
scx_dsp_ctx = NULL; scx_dsp_ctx = NULL;
scx_dsp_max_batch = 0; scx_dsp_max_batch = 0;
free_kick_pseqs(); free_kick_syncs();
mutex_unlock(&scx_enable_mutex); mutex_unlock(&scx_enable_mutex);
@ -4287,10 +4287,10 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
seq_buf_init(&ns, buf, avail); seq_buf_init(&ns, buf, avail);
dump_newline(&ns); dump_newline(&ns);
dump_line(&ns, "CPU %-4d: nr_run=%u flags=0x%x cpu_rel=%d ops_qseq=%lu pnt_seq=%lu", dump_line(&ns, "CPU %-4d: nr_run=%u flags=0x%x cpu_rel=%d ops_qseq=%lu ksync=%lu",
cpu, rq->scx.nr_running, rq->scx.flags, cpu, rq->scx.nr_running, rq->scx.flags,
rq->scx.cpu_released, rq->scx.ops_qseq, rq->scx.cpu_released, rq->scx.ops_qseq,
rq->scx.pnt_seq); rq->scx.kick_sync);
dump_line(&ns, " curr=%s[%d] class=%ps", dump_line(&ns, " curr=%s[%d] class=%ps",
rq->curr->comm, rq->curr->pid, rq->curr->comm, rq->curr->pid,
rq->curr->sched_class); rq->curr->sched_class);
@ -4401,7 +4401,7 @@ static void scx_vexit(struct scx_sched *sch,
irq_work_queue(&sch->error_irq_work); irq_work_queue(&sch->error_irq_work);
} }
static int alloc_kick_pseqs(void) static int alloc_kick_syncs(void)
{ {
int cpu; int cpu;
@ -4410,19 +4410,19 @@ static int alloc_kick_pseqs(void)
* can exceed percpu allocator limits on large machines. * can exceed percpu allocator limits on large machines.
*/ */
for_each_possible_cpu(cpu) { for_each_possible_cpu(cpu) {
struct scx_kick_pseqs **pseqs = per_cpu_ptr(&scx_kick_pseqs, cpu); struct scx_kick_syncs **ksyncs = per_cpu_ptr(&scx_kick_syncs, cpu);
struct scx_kick_pseqs *new_pseqs; struct scx_kick_syncs *new_ksyncs;
WARN_ON_ONCE(rcu_access_pointer(*pseqs)); WARN_ON_ONCE(rcu_access_pointer(*ksyncs));
new_pseqs = kvzalloc_node(struct_size(new_pseqs, seqs, nr_cpu_ids), new_ksyncs = kvzalloc_node(struct_size(new_ksyncs, syncs, nr_cpu_ids),
GFP_KERNEL, cpu_to_node(cpu)); GFP_KERNEL, cpu_to_node(cpu));
if (!new_pseqs) { if (!new_ksyncs) {
free_kick_pseqs(); free_kick_syncs();
return -ENOMEM; return -ENOMEM;
} }
rcu_assign_pointer(*pseqs, new_pseqs); rcu_assign_pointer(*ksyncs, new_ksyncs);
} }
return 0; return 0;
@ -4578,14 +4578,14 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
goto err_unlock; goto err_unlock;
} }
ret = alloc_kick_pseqs(); ret = alloc_kick_syncs();
if (ret) if (ret)
goto err_unlock; goto err_unlock;
sch = scx_alloc_and_add_sched(ops); sch = scx_alloc_and_add_sched(ops);
if (IS_ERR(sch)) { if (IS_ERR(sch)) {
ret = PTR_ERR(sch); ret = PTR_ERR(sch);
goto err_free_pseqs; goto err_free_ksyncs;
} }
/* /*
@ -4788,8 +4788,8 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
return 0; return 0;
err_free_pseqs: err_free_ksyncs:
free_kick_pseqs(); free_kick_syncs();
err_unlock: err_unlock:
mutex_unlock(&scx_enable_mutex); mutex_unlock(&scx_enable_mutex);
return ret; return ret;
@ -5119,7 +5119,7 @@ static bool can_skip_idle_kick(struct rq *rq)
return !is_idle_task(rq->curr) && !(rq->scx.flags & SCX_RQ_IN_BALANCE); return !is_idle_task(rq->curr) && !(rq->scx.flags & SCX_RQ_IN_BALANCE);
} }
static bool kick_one_cpu(s32 cpu, struct rq *this_rq, unsigned long *pseqs) static bool kick_one_cpu(s32 cpu, struct rq *this_rq, unsigned long *ksyncs)
{ {
struct rq *rq = cpu_rq(cpu); struct rq *rq = cpu_rq(cpu);
struct scx_rq *this_scx = &this_rq->scx; struct scx_rq *this_scx = &this_rq->scx;
@ -5146,7 +5146,7 @@ static bool kick_one_cpu(s32 cpu, struct rq *this_rq, unsigned long *pseqs)
if (cpumask_test_cpu(cpu, this_scx->cpus_to_wait)) { if (cpumask_test_cpu(cpu, this_scx->cpus_to_wait)) {
if (cur_class == &ext_sched_class) { if (cur_class == &ext_sched_class) {
pseqs[cpu] = rq->scx.pnt_seq; ksyncs[cpu] = rq->scx.kick_sync;
should_wait = true; should_wait = true;
} else { } else {
cpumask_clear_cpu(cpu, this_scx->cpus_to_wait); cpumask_clear_cpu(cpu, this_scx->cpus_to_wait);
@ -5182,20 +5182,20 @@ static void kick_cpus_irq_workfn(struct irq_work *irq_work)
{ {
struct rq *this_rq = this_rq(); struct rq *this_rq = this_rq();
struct scx_rq *this_scx = &this_rq->scx; struct scx_rq *this_scx = &this_rq->scx;
struct scx_kick_pseqs __rcu *pseqs_pcpu = __this_cpu_read(scx_kick_pseqs); struct scx_kick_syncs __rcu *ksyncs_pcpu = __this_cpu_read(scx_kick_syncs);
bool should_wait = false; bool should_wait = false;
unsigned long *pseqs; unsigned long *ksyncs;
s32 cpu; s32 cpu;
if (unlikely(!pseqs_pcpu)) { if (unlikely(!ksyncs_pcpu)) {
pr_warn_once("kick_cpus_irq_workfn() called with NULL scx_kick_pseqs"); pr_warn_once("kick_cpus_irq_workfn() called with NULL scx_kick_syncs");
return; return;
} }
pseqs = rcu_dereference_bh(pseqs_pcpu)->seqs; ksyncs = rcu_dereference_bh(ksyncs_pcpu)->syncs;
for_each_cpu(cpu, this_scx->cpus_to_kick) { for_each_cpu(cpu, this_scx->cpus_to_kick) {
should_wait |= kick_one_cpu(cpu, this_rq, pseqs); should_wait |= kick_one_cpu(cpu, this_rq, ksyncs);
cpumask_clear_cpu(cpu, this_scx->cpus_to_kick); cpumask_clear_cpu(cpu, this_scx->cpus_to_kick);
cpumask_clear_cpu(cpu, this_scx->cpus_to_kick_if_idle); cpumask_clear_cpu(cpu, this_scx->cpus_to_kick_if_idle);
} }
@ -5209,7 +5209,7 @@ static void kick_cpus_irq_workfn(struct irq_work *irq_work)
return; return;
for_each_cpu(cpu, this_scx->cpus_to_wait) { for_each_cpu(cpu, this_scx->cpus_to_wait) {
unsigned long *wait_pnt_seq = &cpu_rq(cpu)->scx.pnt_seq; unsigned long *wait_kick_sync = &cpu_rq(cpu)->scx.kick_sync;
/* /*
* Busy-wait until the task running at the time of kicking is no * Busy-wait until the task running at the time of kicking is no
@ -5223,7 +5223,7 @@ static void kick_cpus_irq_workfn(struct irq_work *irq_work)
* the wait when $cpu is taken by a higher sched class. * the wait when $cpu is taken by a higher sched class.
*/ */
if (cpu != cpu_of(this_rq)) if (cpu != cpu_of(this_rq))
smp_cond_load_acquire(wait_pnt_seq, VAL != pseqs[cpu]); smp_cond_load_acquire(wait_kick_sync, VAL != ksyncs[cpu]);
cpumask_clear_cpu(cpu, this_scx->cpus_to_wait); cpumask_clear_cpu(cpu, this_scx->cpus_to_wait);
} }

2
kernel/sched/sched.h
View File

@ -803,7 +803,7 @@ struct scx_rq {
cpumask_var_t cpus_to_kick_if_idle; cpumask_var_t cpus_to_kick_if_idle;
cpumask_var_t cpus_to_preempt; cpumask_var_t cpus_to_preempt;
cpumask_var_t cpus_to_wait; cpumask_var_t cpus_to_wait;
unsigned long pnt_seq; unsigned long kick_sync;
struct balance_callback deferred_bal_cb; struct balance_callback deferred_bal_cb;
struct irq_work deferred_irq_work; struct irq_work deferred_irq_work;
struct irq_work kick_cpus_irq_work; struct irq_work kick_cpus_irq_work;