[tip: sched/core] sched: Introduce affinity_context

From: tip-bot2 for Waiman Long
Date: Fri Oct 28 2022 - 02:43:49 EST

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The following commit has been merged into the sched/core branch of tip:

Commit-ID: 713a2e21a5137e96d2594f53d19784ffde3ddbd0
Gitweb: https://git.kernel.org/tip/713a2e21a5137e96d2594f53d19784ffde3ddbd0
Author: Waiman Long <longman@xxxxxxxxxx>
AuthorDate: Thu, 22 Sep 2022 14:00:40 -04:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Thu, 27 Oct 2022 11:01:21 +02:00

sched: Introduce affinity_context

In order to prepare for passing through additional data through the
affinity call-chains, convert the mask and flags argument into a
structure.

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20220922180041.1768141-5-longman@xxxxxxxxxx
---
kernel/sched/core.c | 114 +++++++++++++++++++++++++--------------
kernel/sched/deadline.c | 7 +--
kernel/sched/sched.h | 11 ++--
3 files changed, 85 insertions(+), 47 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f6f2807..5ad4e2e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2189,14 +2189,18 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
#ifdef CONFIG_SMP

static void
-__do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32 flags);
+__do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx);

static int __set_cpus_allowed_ptr(struct task_struct *p,
- const struct cpumask *new_mask,
- u32 flags);
+ struct affinity_context *ctx);

static void migrate_disable_switch(struct rq *rq, struct task_struct *p)
{
+ struct affinity_context ac = {
+ .new_mask = cpumask_of(rq->cpu),
+ .flags = SCA_MIGRATE_DISABLE,
+ };
+
if (likely(!p->migration_disabled))
return;

@@ -2206,7 +2210,7 @@ static void migrate_disable_switch(struct rq *rq, struct task_struct *p)
/*
* Violates locking rules! see comment in __do_set_cpus_allowed().
*/
- __do_set_cpus_allowed(p, cpumask_of(rq->cpu), SCA_MIGRATE_DISABLE);
+ __do_set_cpus_allowed(p, &ac);
}

void migrate_disable(void)
@@ -2228,6 +2232,10 @@ EXPORT_SYMBOL_GPL(migrate_disable);
void migrate_enable(void)
{
struct task_struct *p = current;
+ struct affinity_context ac = {
+ .new_mask = &p->cpus_mask,
+ .flags = SCA_MIGRATE_ENABLE,
+ };

if (p->migration_disabled > 1) {
p->migration_disabled--;
@@ -2243,7 +2251,7 @@ void migrate_enable(void)
*/
preempt_disable();
if (p->cpus_ptr != &p->cpus_mask)
- __set_cpus_allowed_ptr(p, &p->cpus_mask, SCA_MIGRATE_ENABLE);
+ __set_cpus_allowed_ptr(p, &ac);
/*
* Mustn't clear migration_disabled() until cpus_ptr points back at the
* regular cpus_mask, otherwise things that race (eg.
@@ -2523,19 +2531,19 @@ out_unlock:
* sched_class::set_cpus_allowed must do the below, but is not required to
* actually call this function.
*/
-void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask, u32 flags)
+void set_cpus_allowed_common(struct task_struct *p, struct affinity_context *ctx)
{
- if (flags & (SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) {
- p->cpus_ptr = new_mask;
+ if (ctx->flags & (SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) {
+ p->cpus_ptr = ctx->new_mask;
return;
}

- cpumask_copy(&p->cpus_mask, new_mask);
- p->nr_cpus_allowed = cpumask_weight(new_mask);
+ cpumask_copy(&p->cpus_mask, ctx->new_mask);
+ p->nr_cpus_allowed = cpumask_weight(ctx->new_mask);
}

static void
-__do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32 flags)
+__do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx)
{
struct rq *rq = task_rq(p);
bool queued, running;
@@ -2552,7 +2560,7 @@ __do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32
*
* XXX do further audits, this smells like something putrid.
*/
- if (flags & SCA_MIGRATE_DISABLE)
+ if (ctx->flags & SCA_MIGRATE_DISABLE)
SCHED_WARN_ON(!p->on_cpu);
else
lockdep_assert_held(&p->pi_lock);
@@ -2571,7 +2579,7 @@ __do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32
if (running)
put_prev_task(rq, p);

- p->sched_class->set_cpus_allowed(p, new_mask, flags);
+ p->sched_class->set_cpus_allowed(p, ctx);

if (queued)
enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
@@ -2581,7 +2589,12 @@ __do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32

void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
{
- __do_set_cpus_allowed(p, new_mask, 0);
+ struct affinity_context ac = {
+ .new_mask = new_mask,
+ .flags = 0,
+ };
+
+ __do_set_cpus_allowed(p, &ac);
}

int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src,
@@ -2834,8 +2847,7 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag
* Called with both p->pi_lock and rq->lock held; drops both before returning.
*/
static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
- const struct cpumask *new_mask,
- u32 flags,
+ struct affinity_context *ctx,
struct rq *rq,
struct rq_flags *rf)
__releases(rq->lock)
@@ -2864,7 +2876,7 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
cpu_valid_mask = cpu_online_mask;
}

- if (!kthread && !cpumask_subset(new_mask, cpu_allowed_mask)) {
+ if (!kthread && !cpumask_subset(ctx->new_mask, cpu_allowed_mask)) {
ret = -EINVAL;
goto out;
}
@@ -2873,18 +2885,18 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
* Must re-check here, to close a race against __kthread_bind(),
* sched_setaffinity() is not guaranteed to observe the flag.
*/
- if ((flags & SCA_CHECK) && (p->flags & PF_NO_SETAFFINITY)) {
+ if ((ctx->flags & SCA_CHECK) && (p->flags & PF_NO_SETAFFINITY)) {
ret = -EINVAL;
goto out;
}

- if (!(flags & SCA_MIGRATE_ENABLE)) {
- if (cpumask_equal(&p->cpus_mask, new_mask))
+ if (!(ctx->flags & SCA_MIGRATE_ENABLE)) {
+ if (cpumask_equal(&p->cpus_mask, ctx->new_mask))
goto out;

if (WARN_ON_ONCE(p == current &&
is_migration_disabled(p) &&
- !cpumask_test_cpu(task_cpu(p), new_mask))) {
+ !cpumask_test_cpu(task_cpu(p), ctx->new_mask))) {
ret = -EBUSY;
goto out;
}
@@ -2895,18 +2907,18 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
* for groups of tasks (ie. cpuset), so that load balancing is not
* immediately required to distribute the tasks within their new mask.
*/
- dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, new_mask);
+ dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, ctx->new_mask);
if (dest_cpu >= nr_cpu_ids) {
ret = -EINVAL;
goto out;
}

- __do_set_cpus_allowed(p, new_mask, flags);
+ __do_set_cpus_allowed(p, ctx);

- if (flags & SCA_USER)
+ if (ctx->flags & SCA_USER)
user_mask = clear_user_cpus_ptr(p);

- ret = affine_move_task(rq, p, rf, dest_cpu, flags);
+ ret = affine_move_task(rq, p, rf, dest_cpu, ctx->flags);

kfree(user_mask);

@@ -2928,18 +2940,23 @@ out:
* call is not atomic; no spinlocks may be held.
*/
static int __set_cpus_allowed_ptr(struct task_struct *p,
- const struct cpumask *new_mask, u32 flags)
+ struct affinity_context *ctx)
{
struct rq_flags rf;
struct rq *rq;

rq = task_rq_lock(p, &rf);
- return __set_cpus_allowed_ptr_locked(p, new_mask, flags, rq, &rf);
+ return __set_cpus_allowed_ptr_locked(p, ctx, rq, &rf);
}

int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
{
- return __set_cpus_allowed_ptr(p, new_mask, 0);
+ struct affinity_context ac = {
+ .new_mask = new_mask,
+ .flags = 0,
+ };
+
+ return __set_cpus_allowed_ptr(p, &ac);
}
EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);

@@ -2955,6 +2972,7 @@ static int restrict_cpus_allowed_ptr(struct task_struct *p,
const struct cpumask *subset_mask)
{
struct cpumask *user_mask = NULL;
+ struct affinity_context ac;
struct rq_flags rf;
struct rq *rq;
int err;
@@ -2991,7 +3009,11 @@ static int restrict_cpus_allowed_ptr(struct task_struct *p,
p->user_cpus_ptr = user_mask;
}

- return __set_cpus_allowed_ptr_locked(p, new_mask, 0, rq, &rf);
+ ac = (struct affinity_context){
+ .new_mask = new_mask,
+ };
+
+ return __set_cpus_allowed_ptr_locked(p, &ac, rq, &rf);

err_unlock:
task_rq_unlock(rq, p, &rf);
@@ -3045,7 +3067,7 @@ out_free_mask:
}

static int
-__sched_setaffinity(struct task_struct *p, const struct cpumask *mask);
+__sched_setaffinity(struct task_struct *p, struct affinity_context *ctx);

/*
* Restore the affinity of a task @p which was previously restricted by a
@@ -3058,6 +3080,9 @@ __sched_setaffinity(struct task_struct *p, const struct cpumask *mask);
void relax_compatible_cpus_allowed_ptr(struct task_struct *p)
{
struct cpumask *user_mask = p->user_cpus_ptr;
+ struct affinity_context ac = {
+ .new_mask = user_mask,
+ };
unsigned long flags;

/*
@@ -3065,7 +3090,7 @@ void relax_compatible_cpus_allowed_ptr(struct task_struct *p)
* we free the mask explicitly to avoid it being inherited across
* a subsequent fork().
*/
- if (!user_mask || !__sched_setaffinity(p, user_mask))
+ if (!user_mask || !__sched_setaffinity(p, &ac))
return;

raw_spin_lock_irqsave(&p->pi_lock, flags);
@@ -3550,10 +3575,9 @@ void sched_set_stop_task(int cpu, struct task_struct *stop)
#else /* CONFIG_SMP */

static inline int __set_cpus_allowed_ptr(struct task_struct *p,
- const struct cpumask *new_mask,
- u32 flags)
+ struct affinity_context *ctx)
{
- return set_cpus_allowed_ptr(p, new_mask);
+ return set_cpus_allowed_ptr(p, ctx->new_mask);
}

static inline void migrate_disable_switch(struct rq *rq, struct task_struct *p) { }
@@ -8090,7 +8114,7 @@ int dl_task_check_affinity(struct task_struct *p, const struct cpumask *mask)
#endif

static int
-__sched_setaffinity(struct task_struct *p, const struct cpumask *mask)
+__sched_setaffinity(struct task_struct *p, struct affinity_context *ctx)
{
int retval;
cpumask_var_t cpus_allowed, new_mask;
@@ -8104,13 +8128,16 @@ __sched_setaffinity(struct task_struct *p, const struct cpumask *mask)
}

cpuset_cpus_allowed(p, cpus_allowed);
- cpumask_and(new_mask, mask, cpus_allowed);
+ cpumask_and(new_mask, ctx->new_mask, cpus_allowed);
+
+ ctx->new_mask = new_mask;
+ ctx->flags |= SCA_CHECK;

retval = dl_task_check_affinity(p, new_mask);
if (retval)
goto out_free_new_mask;
again:
- retval = __set_cpus_allowed_ptr(p, new_mask, SCA_CHECK | SCA_USER);
+ retval = __set_cpus_allowed_ptr(p, ctx);
if (retval)
goto out_free_new_mask;

@@ -8133,6 +8160,9 @@ out_free_cpus_allowed:

long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
{
+ struct affinity_context ac = {
+ .new_mask = in_mask,
+ };
struct task_struct *p;
int retval;

@@ -8167,7 +8197,7 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
if (retval)
goto out_put_task;

- retval = __sched_setaffinity(p, in_mask);
+ retval = __sched_setaffinity(p, &ac);
out_put_task:
put_task_struct(p);
return retval;
@@ -8948,6 +8978,12 @@ void show_state_filter(unsigned int state_filter)
*/
void __init init_idle(struct task_struct *idle, int cpu)
{
+#ifdef CONFIG_SMP
+ struct affinity_context ac = (struct affinity_context) {
+ .new_mask = cpumask_of(cpu),
+ .flags = 0,
+ };
+#endif
struct rq *rq = cpu_rq(cpu);
unsigned long flags;

@@ -8972,7 +9008,7 @@ void __init init_idle(struct task_struct *idle, int cpu)
*
* And since this is boot we can forgo the serialization.
*/
- set_cpus_allowed_common(idle, cpumask_of(cpu), 0);
+ set_cpus_allowed_common(idle, &ac);
#endif
/*
* We're having a chicken and egg problem, even though we are
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 9ae8f41..0d97d54 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2485,8 +2485,7 @@ static void task_woken_dl(struct rq *rq, struct task_struct *p)
}

static void set_cpus_allowed_dl(struct task_struct *p,
- const struct cpumask *new_mask,
- u32 flags)
+ struct affinity_context *ctx)
{
struct root_domain *src_rd;
struct rq *rq;
@@ -2501,7 +2500,7 @@ static void set_cpus_allowed_dl(struct task_struct *p,
* update. We already made space for us in the destination
* domain (see cpuset_can_attach()).
*/
- if (!cpumask_intersects(src_rd->span, new_mask)) {
+ if (!cpumask_intersects(src_rd->span, ctx->new_mask)) {
struct dl_bw *src_dl_b;

src_dl_b = dl_bw_of(cpu_of(rq));
@@ -2515,7 +2514,7 @@ static void set_cpus_allowed_dl(struct task_struct *p,
raw_spin_unlock(&src_dl_b->lock);
}

- set_cpus_allowed_common(p, new_mask, flags);
+ set_cpus_allowed_common(p, ctx);
}

/* Assumes rq->lock is held */
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 5f18460..6c91fb7 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2145,6 +2145,11 @@ extern const u32 sched_prio_to_wmult[40];

#define RETRY_TASK ((void *)-1UL)

+struct affinity_context {
+ const struct cpumask *new_mask;
+ unsigned int flags;
+};
+
struct sched_class {

#ifdef CONFIG_UCLAMP_TASK
@@ -2173,9 +2178,7 @@ struct sched_class {

void (*task_woken)(struct rq *this_rq, struct task_struct *task);

- void (*set_cpus_allowed)(struct task_struct *p,
- const struct cpumask *newmask,
- u32 flags);
+ void (*set_cpus_allowed)(struct task_struct *p, struct affinity_context *ctx);

void (*rq_online)(struct rq *rq);
void (*rq_offline)(struct rq *rq);
@@ -2286,7 +2289,7 @@ extern void update_group_capacity(struct sched_domain *sd, int cpu);

extern void trigger_load_balance(struct rq *rq);

-extern void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask, u32 flags);
+extern void set_cpus_allowed_common(struct task_struct *p, struct affinity_context *ctx);

static inline struct task_struct *get_push_task(struct rq *rq)
{

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