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- Add PREEMPT_RT maintainers

Browse Source 
- Fix another aspect of delayed dequeued tasks wrt determining their state,
   i.e., whether they're runnable or blocked
 
 - Handle delayed dequeued tasks and their migration wrt PSI properly
 
 - Fix the situation where a delayed dequeue task gets enqueued into a new
   class, which should not happen
 
 - Fix a case where memory allocation would happen while the runqueue lock is
   held, which is a no-no
 
 - Do not over-schedule when tasks with shorter slices preempt the currently
   running task
 
 - Make sure delayed to deque entities are properly handled before unthrottling
 
 - Other smaller cleanups and improvements
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Merge tag 'sched_urgent_for_v6.12_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduling fixes from Borislav Petkov:

 - Add PREEMPT_RT maintainers

 - Fix another aspect of delayed dequeued tasks wrt determining their
   state, i.e., whether they're runnable or blocked

 - Handle delayed dequeued tasks and their migration wrt PSI properly

 - Fix the situation where a delayed dequeue task gets enqueued into a
   new class, which should not happen

 - Fix a case where memory allocation would happen while the runqueue
   lock is held, which is a no-no

 - Do not over-schedule when tasks with shorter slices preempt the
   currently running task

 - Make sure delayed to deque entities are properly handled before
   unthrottling

 - Other smaller cleanups and improvements

* tag 'sched_urgent_for_v6.12_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  MAINTAINERS: Add an entry for PREEMPT_RT.
  sched/fair: Fix external p->on_rq users
  sched/psi: Fix mistaken CPU pressure indication after corrupted task state bug
  sched/core: Dequeue PSI signals for blocked tasks that are delayed
  sched: Fix delayed_dequeue vs switched_from_fair()
  sched/core: Disable page allocation in task_tick_mm_cid()
  sched/deadline: Use hrtick_enabled_dl() before start_hrtick_dl()
  sched/eevdf: Fix wakeup-preempt by checking cfs_rq->nr_running
  sched: Fix sched_delayed vs cfs_bandwidth
This commit is contained in:
Linus Torvalds 2024-10-20 11:30:56 -07:00
commit 2b4d25010d
17 changed files with 148 additions and 74 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
MAINTAINERS
View File

@ -19527,6 +19527,14 @@ S: Maintained
F: Documentation/tools/rtla/
F: tools/tracing/rtla/
Real-time Linux (PREEMPT_RT)
M: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
M: Clark Williams <clrkwllms@kernel.org>
M: Steven Rostedt <rostedt@goodmis.org>
L: linux-rt-devel@lists.linux.dev
S: Supported
K: PREEMPT_RT
REALTEK AUDIO CODECS
M: Oder Chiou <oder_chiou@realtek.com>
S: Maintained

5
include/linux/sched.h
View File

@ -2133,6 +2133,11 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
#endif /* CONFIG_SMP */
static inline bool task_is_runnable(struct task_struct *p)
{
return p->on_rq && !p->se.sched_delayed;
}
extern bool sched_task_on_rq(struct task_struct *p);
extern unsigned long get_wchan(struct task_struct *p);
extern struct task_struct *cpu_curr_snapshot(int cpu);

5
include/linux/task_work.h
View File

@ -14,11 +14,14 @@ init_task_work(struct callback_head *twork, task_work_func_t func)
}
enum task_work_notify_mode {
TWA_NONE,
TWA_NONE = 0,
TWA_RESUME,
TWA_SIGNAL,
TWA_SIGNAL_NO_IPI,
TWA_NMI_CURRENT,
TWA_FLAGS = 0xff00,
TWAF_NO_ALLOC = 0x0100,
};
static inline bool task_work_pending(struct task_struct *task)

2
kernel/events/core.c
View File

@ -9251,7 +9251,7 @@ static void perf_event_switch(struct task_struct *task,
},
};
if (!sched_in && task->on_rq) {
if (!sched_in && task_is_runnable(task)) {
switch_event.event_id.header.misc |=
PERF_RECORD_MISC_SWITCH_OUT_PREEMPT;
}

7
kernel/freezer.c
View File

@ -109,7 +109,12 @@ static int __set_task_frozen(struct task_struct *p, void *arg)
{
unsigned int state = READ_ONCE(p->__state);
if (p->on_rq)
/*
* Allow freezing the sched_delayed tasks; they will not execute until
* ttwu() fixes them up, so it is safe to swap their state now, instead
* of waiting for them to get fully dequeued.
*/
if (task_is_runnable(p))
return 0;
if (p != current && task_curr(p))

9
kernel/rcu/tasks.h
View File

@ -985,6 +985,15 @@ static bool rcu_tasks_is_holdout(struct task_struct *t)
if (!READ_ONCE(t->on_rq))
return false;
/*
* t->on_rq && !t->se.sched_delayed *could* be considered sleeping but
* since it is a spurious state (it will transition into the
* traditional blocked state or get woken up without outside
* dependencies), not considering it such should only affect timing.
*
* Be conservative for now and not include it.
*/
/*
* Idle tasks (or idle injection) within the idle loop are RCU-tasks
* quiescent states. But CPU boot code performed by the idle task

65
kernel/sched/core.c
View File

@ -548,6 +548,11 @@ sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { }
* ON_RQ_MIGRATING state is used for migration without holding both
* rq->locks. It indicates task_cpu() is not stable, see task_rq_lock().
*
* Additionally it is possible to be ->on_rq but still be considered not
* runnable when p->se.sched_delayed is true. These tasks are on the runqueue
* but will be dequeued as soon as they get picked again. See the
* task_is_runnable() helper.
*
* p->on_cpu <- { 0, 1 }:
*
* is set by prepare_task() and cleared by finish_task() such that it will be
@ -2012,11 +2017,6 @@ void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
if (!(flags & ENQUEUE_NOCLOCK))
update_rq_clock(rq);
if (!(flags & ENQUEUE_RESTORE)) {
sched_info_enqueue(rq, p);
psi_enqueue(p, (flags & ENQUEUE_WAKEUP) && !(flags & ENQUEUE_MIGRATED));
}
p->sched_class->enqueue_task(rq, p, flags);
/*
* Must be after ->enqueue_task() because ENQUEUE_DELAYED can clear
@ -2024,6 +2024,11 @@ void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
*/
uclamp_rq_inc(rq, p);
if (!(flags & ENQUEUE_RESTORE)) {
sched_info_enqueue(rq, p);
psi_enqueue(p, flags & ENQUEUE_MIGRATED);
}
if (sched_core_enabled(rq))
sched_core_enqueue(rq, p);
}
@ -2041,7 +2046,7 @@ inline bool dequeue_task(struct rq *rq, struct task_struct *p, int flags)
if (!(flags & DEQUEUE_SAVE)) {
sched_info_dequeue(rq, p);
psi_dequeue(p, flags & DEQUEUE_SLEEP);
psi_dequeue(p, !(flags & DEQUEUE_SLEEP));
}
/*
@ -4323,9 +4328,10 @@ static bool __task_needs_rq_lock(struct task_struct *p)
* @arg: Argument to function.
*
* Fix the task in it's current state by avoiding wakeups and or rq operations
* and call @func(@arg) on it. This function can use ->on_rq and task_curr()
* to work out what the state is, if required. Given that @func can be invoked
* with a runqueue lock held, it had better be quite lightweight.
* and call @func(@arg) on it. This function can use task_is_runnable() and
* task_curr() to work out what the state is, if required. Given that @func
* can be invoked with a runqueue lock held, it had better be quite
* lightweight.
*
* Returns:
* Whatever @func returns
@ -6544,6 +6550,7 @@ static void __sched notrace __schedule(int sched_mode)
* as a preemption by schedule_debug() and RCU.
*/
bool preempt = sched_mode > SM_NONE;
bool block = false;
unsigned long *switch_count;
unsigned long prev_state;
struct rq_flags rf;
@ -6629,6 +6636,7 @@ static void __sched notrace __schedule(int sched_mode)
* After this, schedule() must not care about p->state any more.
*/
block_task(rq, prev, flags);
block = true;
}
switch_count = &prev->nvcsw;
}
@ -6674,7 +6682,7 @@ picked:
migrate_disable_switch(rq, prev);
psi_account_irqtime(rq, prev, next);
psi_sched_switch(prev, next, !task_on_rq_queued(prev));
psi_sched_switch(prev, next, block);
trace_sched_switch(preempt, prev, next, prev_state);
@ -7017,20 +7025,20 @@ int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flag
}
EXPORT_SYMBOL(default_wake_function);
void __setscheduler_prio(struct task_struct *p, int prio)
const struct sched_class *__setscheduler_class(struct task_struct *p, int prio)
{
if (dl_prio(prio))
p->sched_class = &dl_sched_class;
else if (rt_prio(prio))
p->sched_class = &rt_sched_class;
#ifdef CONFIG_SCHED_CLASS_EXT
else if (task_should_scx(p))
p->sched_class = &ext_sched_class;
#endif
else
p->sched_class = &fair_sched_class;
return &dl_sched_class;
p->prio = prio;
if (rt_prio(prio))
return &rt_sched_class;
#ifdef CONFIG_SCHED_CLASS_EXT
if (task_should_scx(p))
return &ext_sched_class;
#endif
return &fair_sched_class;
}
#ifdef CONFIG_RT_MUTEXES
@ -7076,7 +7084,7 @@ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
{
int prio, oldprio, queued, running, queue_flag =
DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
const struct sched_class *prev_class;
const struct sched_class *prev_class, *next_class;
struct rq_flags rf;
struct rq *rq;
@ -7134,6 +7142,11 @@ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
queue_flag &= ~DEQUEUE_MOVE;
prev_class = p->sched_class;
next_class = __setscheduler_class(p, prio);
if (prev_class != next_class && p->se.sched_delayed)
dequeue_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_DELAYED | DEQUEUE_NOCLOCK);
queued = task_on_rq_queued(p);
running = task_current(rq, p);
if (queued)
@ -7171,7 +7184,9 @@ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
p->rt.timeout = 0;
}
__setscheduler_prio(p, prio);
p->sched_class = next_class;
p->prio = prio;
check_class_changing(rq, p, prev_class);
if (queued)
@ -10465,7 +10480,9 @@ void task_tick_mm_cid(struct rq *rq, struct task_struct *curr)
return;
if (time_before(now, READ_ONCE(curr->mm->mm_cid_next_scan)))
return;
task_work_add(curr, work, TWA_RESUME);
/* No page allocation under rq lock */
task_work_add(curr, work, TWA_RESUME | TWAF_NO_ALLOC);
}
void sched_mm_cid_exit_signals(struct task_struct *t)

2
kernel/sched/deadline.c
View File

@ -2385,7 +2385,7 @@ static void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first)
deadline_queue_push_tasks(rq);
if (hrtick_enabled(rq))
if (hrtick_enabled_dl(rq))
start_hrtick_dl(rq, &p->dl);
}

4
kernel/sched/ext.c
View File

@ -4493,7 +4493,7 @@ static void scx_ops_disable_workfn(struct kthread_work *work)
sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx);
__setscheduler_prio(p, p->prio);
p->sched_class = __setscheduler_class(p, p->prio);
check_class_changing(task_rq(p), p, old_class);
sched_enq_and_set_task(&ctx);
@ -5204,7 +5204,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx);
p->scx.slice = SCX_SLICE_DFL;
__setscheduler_prio(p, p->prio);
p->sched_class = __setscheduler_class(p, p->prio);
check_class_changing(task_rq(p), p, old_class);
sched_enq_and_set_task(&ctx);

27
kernel/sched/fair.c
View File

@ -1247,7 +1247,7 @@ static void update_curr(struct cfs_rq *cfs_rq)
account_cfs_rq_runtime(cfs_rq, delta_exec);
if (rq->nr_running == 1)
if (cfs_rq->nr_running == 1)
return;
if (resched || did_preempt_short(cfs_rq, curr)) {
@ -6058,10 +6058,13 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
for_each_sched_entity(se) {
struct cfs_rq *qcfs_rq = cfs_rq_of(se);
if (se->on_rq) {
SCHED_WARN_ON(se->sched_delayed);
/* Handle any unfinished DELAY_DEQUEUE business first. */
if (se->sched_delayed) {
int flags = DEQUEUE_SLEEP | DEQUEUE_DELAYED;
dequeue_entity(qcfs_rq, se, flags);
} else if (se->on_rq)
break;
}
enqueue_entity(qcfs_rq, se, ENQUEUE_WAKEUP);
if (cfs_rq_is_idle(group_cfs_rq(se)))
@ -13174,22 +13177,6 @@ static void attach_task_cfs_rq(struct task_struct *p)
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
detach_task_cfs_rq(p);
/*
* Since this is called after changing class, this is a little weird
* and we cannot use DEQUEUE_DELAYED.
*/
if (p->se.sched_delayed) {
/* First, dequeue it from its new class' structures */
dequeue_task(rq, p, DEQUEUE_NOCLOCK | DEQUEUE_SLEEP);
/*
* Now, clean up the fair_sched_class side of things
* related to sched_delayed being true and that wasn't done
* due to the generic dequeue not using DEQUEUE_DELAYED.
*/
finish_delayed_dequeue_entity(&p->se);
p->se.rel_deadline = 0;
__block_task(rq, p);
}
}
static void switched_to_fair(struct rq *rq, struct task_struct *p)

2
kernel/sched/sched.h
View File

@ -3800,7 +3800,7 @@ static inline int rt_effective_prio(struct task_struct *p, int prio)
extern int __sched_setscheduler(struct task_struct *p, const struct sched_attr *attr, bool user, bool pi);
extern int __sched_setaffinity(struct task_struct *p, struct affinity_context *ctx);
extern void __setscheduler_prio(struct task_struct *p, int prio);
extern const struct sched_class *__setscheduler_class(struct task_struct *p, int prio);
extern void set_load_weight(struct task_struct *p, bool update_load);
extern void enqueue_task(struct rq *rq, struct task_struct *p, int flags);
extern bool dequeue_task(struct rq *rq, struct task_struct *p, int flags);

48
kernel/sched/stats.h
View File

@ -119,45 +119,63 @@ static inline void psi_account_irqtime(struct rq *rq, struct task_struct *curr,
/*
* PSI tracks state that persists across sleeps, such as iowaits and
* memory stalls. As a result, it has to distinguish between sleeps,
* where a task's runnable state changes, and requeues, where a task
* and its state are being moved between CPUs and runqueues.
* where a task's runnable state changes, and migrations, where a task
* and its runnable state are being moved between CPUs and runqueues.
*
* A notable case is a task whose dequeue is delayed. PSI considers
* those sleeping, but because they are still on the runqueue they can
* go through migration requeues. In this case, *sleeping* states need
* to be transferred.
*/
static inline void psi_enqueue(struct task_struct *p, bool wakeup)
static inline void psi_enqueue(struct task_struct *p, bool migrate)
{
int clear = 0, set = TSK_RUNNING;
int clear = 0, set = 0;
if (static_branch_likely(&psi_disabled))
return;
if (p->in_memstall)
set |= TSK_MEMSTALL_RUNNING;
if (!wakeup) {
if (p->se.sched_delayed) {
/* CPU migration of "sleeping" task */
SCHED_WARN_ON(!migrate);
if (p->in_memstall)
set |= TSK_MEMSTALL;
if (p->in_iowait)
set |= TSK_IOWAIT;
} else if (migrate) {
/* CPU migration of runnable task */
set = TSK_RUNNING;
if (p->in_memstall)
set |= TSK_MEMSTALL | TSK_MEMSTALL_RUNNING;
} else {
/* Wakeup of new or sleeping task */
if (p->in_iowait)
clear |= TSK_IOWAIT;
set = TSK_RUNNING;
if (p->in_memstall)
set |= TSK_MEMSTALL_RUNNING;
}
psi_task_change(p, clear, set);
}
static inline void psi_dequeue(struct task_struct *p, bool sleep)
static inline void psi_dequeue(struct task_struct *p, bool migrate)
{
if (static_branch_likely(&psi_disabled))
return;
/*
* When migrating a task to another CPU, clear all psi
* state. The enqueue callback above will work it out.
*/
if (migrate)
psi_task_change(p, p->psi_flags, 0);
/*
* A voluntary sleep is a dequeue followed by a task switch. To
* avoid walking all ancestors twice, psi_task_switch() handles
* TSK_RUNNING and TSK_IOWAIT for us when it moves TSK_ONCPU.
* Do nothing here.
*/
if (sleep)
return;
psi_task_change(p, p->psi_flags, 0);
}
static inline void psi_ttwu_dequeue(struct task_struct *p)
@ -190,8 +208,8 @@ static inline void psi_sched_switch(struct task_struct *prev,
}
#else /* CONFIG_PSI */
static inline void psi_enqueue(struct task_struct *p, bool wakeup) {}
static inline void psi_dequeue(struct task_struct *p, bool sleep) {}
static inline void psi_enqueue(struct task_struct *p, bool migrate) {}
static inline void psi_dequeue(struct task_struct *p, bool migrate) {}
static inline void psi_ttwu_dequeue(struct task_struct *p) {}
static inline void psi_sched_switch(struct task_struct *prev,
struct task_struct *next,

13
kernel/sched/syscalls.c
View File

@ -529,7 +529,7 @@ int __sched_setscheduler(struct task_struct *p,
{
int oldpolicy = -1, policy = attr->sched_policy;
int retval, oldprio, newprio, queued, running;
const struct sched_class *prev_class;
const struct sched_class *prev_class, *next_class;
struct balance_callback *head;
struct rq_flags rf;
int reset_on_fork;
@ -706,6 +706,12 @@ change:
queue_flags &= ~DEQUEUE_MOVE;
}
prev_class = p->sched_class;
next_class = __setscheduler_class(p, newprio);
if (prev_class != next_class && p->se.sched_delayed)
dequeue_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_DELAYED | DEQUEUE_NOCLOCK);
queued = task_on_rq_queued(p);
running = task_current(rq, p);
if (queued)
@ -713,11 +719,10 @@ change:
if (running)
put_prev_task(rq, p);
prev_class = p->sched_class;
if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) {
__setscheduler_params(p, attr);
__setscheduler_prio(p, newprio);
p->sched_class = next_class;
p->prio = newprio;
}
__setscheduler_uclamp(p, attr);
check_class_changing(rq, p, prev_class);

15
kernel/task_work.c
View File

@ -55,15 +55,26 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
enum task_work_notify_mode notify)
{
struct callback_head *head;
int flags = notify & TWA_FLAGS;
notify &= ~TWA_FLAGS;
if (notify == TWA_NMI_CURRENT) {
if (WARN_ON_ONCE(task != current))
return -EINVAL;
if (!IS_ENABLED(CONFIG_IRQ_WORK))
return -EINVAL;
} else {
/* record the work call stack in order to print it in KASAN reports */
kasan_record_aux_stack(work);
/*
* Record the work call stack in order to print it in KASAN
* reports.
*
* Note that stack allocation can fail if TWAF_NO_ALLOC flag
* is set and new page is needed to expand the stack buffer.
*/
if (flags & TWAF_NO_ALLOC)
kasan_record_aux_stack_noalloc(work);
else
kasan_record_aux_stack(work);
}
head = READ_ONCE(task->task_works);

6
kernel/time/tick-sched.c
View File

@ -434,6 +434,12 @@ static void tick_nohz_kick_task(struct task_struct *tsk)
* smp_mb__after_spin_lock()
* tick_nohz_task_switch()
* LOAD p->tick_dep_mask
*
* XXX given a task picks up the dependency on schedule(), should we
* only care about tasks that are currently on the CPU instead of all
* that are on the runqueue?
*
* That is, does this want to be: task_on_cpu() / task_curr()?
*/
if (!sched_task_on_rq(tsk))
return;

2
kernel/trace/trace_selftest.c
View File

@ -1485,7 +1485,7 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
/* reset the max latency */
tr->max_latency = 0;
while (p->on_rq) {
while (task_is_runnable(p)) {
/*
* Sleep to make sure the -deadline thread is asleep too.
* On virtual machines we can't rely on timings,

2
virt/kvm/kvm_main.c
View File

@ -6387,7 +6387,7 @@ static void kvm_sched_out(struct preempt_notifier *pn,
WRITE_ONCE(vcpu->scheduled_out, true);
if (current->on_rq && vcpu->wants_to_run) {
if (task_is_runnable(current) && vcpu->wants_to_run) {
WRITE_ONCE(vcpu->preempted, true);
WRITE_ONCE(vcpu->ready, true);
}