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[PATCH] sched: arch preempt notifier mechanism

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This adds a general mechanism whereby a task can request the scheduler to
notify it whenever it is preempted or scheduled back in.  This allows the
task to swap any special-purpose registers like the fpu or Intel's VT
registers.

Signed-off-by: Avi Kivity <avi@qumranet.com>
[ mingo@elte.hu: fixes, cleanups ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Avi Kivity
2007-07-26 13:40:43 +02:00
committed by Ingo Molnar
parent b47e8608a0
commit e107be36ef
4 changed files with 123 additions and 2 deletions
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3
kernel/Kconfig.preempt
View File

@@ -63,3 +63,6 @@ config PREEMPT_BKL
Say Y here if you are building a kernel for a desktop system.
Say N if you are unsure.
config PREEMPT_NOTIFIERS
bool

73
kernel/sched.c
View File

@@ -1592,6 +1592,10 @@ static void __sched_fork(struct task_struct *p)
INIT_LIST_HEAD(&p->run_list);
p->se.on_rq = 0;
#ifdef CONFIG_PREEMPT_NOTIFIERS
INIT_HLIST_HEAD(&p->preempt_notifiers);
#endif
/*
* We mark the process as running here, but have not actually
* inserted it onto the runqueue yet. This guarantees that
@@ -1673,6 +1677,63 @@ void fastcall wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
task_rq_unlock(rq, &flags);
}
#ifdef CONFIG_PREEMPT_NOTIFIERS
/**
* preempt_notifier_register - tell me when current is being being preempted
* and rescheduled
*/
void preempt_notifier_register(struct preempt_notifier *notifier)
{
hlist_add_head(&notifier->link, &current->preempt_notifiers);
}
EXPORT_SYMBOL_GPL(preempt_notifier_register);
/**
* preempt_notifier_unregister - no longer interested in preemption notifications
*
* This is safe to call from within a preemption notifier.
*/
void preempt_notifier_unregister(struct preempt_notifier *notifier)
{
hlist_del(&notifier->link);
}
EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
{
struct preempt_notifier *notifier;
struct hlist_node *node;
hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
notifier->ops->sched_in(notifier, raw_smp_processor_id());
}
static void
fire_sched_out_preempt_notifiers(struct task_struct *curr,
struct task_struct *next)
{
struct preempt_notifier *notifier;
struct hlist_node *node;
hlist_for_each_entry(notifier, node, &curr->preempt_notifiers, link)
notifier->ops->sched_out(notifier, next);
}
#else
static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
{
}
static void
fire_sched_out_preempt_notifiers(struct task_struct *curr,
struct task_struct *next)
{
}
#endif
/**
* prepare_task_switch - prepare to switch tasks
* @rq: the runqueue preparing to switch
@@ -1685,8 +1746,11 @@ void fastcall wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
* prepare_task_switch sets up locking and calls architecture specific
* hooks.
*/
static inline void prepare_task_switch(struct rq *rq, struct task_struct *next)
static inline void
prepare_task_switch(struct rq *rq, struct task_struct *prev,
struct task_struct *next)
{
fire_sched_out_preempt_notifiers(prev, next);
prepare_lock_switch(rq, next);
prepare_arch_switch(next);
}
@@ -1728,6 +1792,7 @@ static inline void finish_task_switch(struct rq *rq, struct task_struct *prev)
prev_state = prev->state;
finish_arch_switch(prev);
finish_lock_switch(rq, prev);
fire_sched_in_preempt_notifiers(current);
if (mm)
mmdrop(mm);
if (unlikely(prev_state == TASK_DEAD)) {
@@ -1768,7 +1833,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
{
struct mm_struct *mm, *oldmm;
prepare_task_switch(rq, next);
prepare_task_switch(rq, prev, next);
mm = next->mm;
oldmm = prev->active_mm;
/*
@@ -6335,6 +6400,10 @@ void __init sched_init(void)
set_load_weight(&init_task);
#ifdef CONFIG_PREEMPT_NOTIFIERS
INIT_HLIST_HEAD(&init_task.preempt_notifiers);
#endif
#ifdef CONFIG_SMP
nr_cpu_ids = highest_cpu + 1;
open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL);