From e107be36efb2a233833e8c9899039a370e4b2318 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Thu, 26 Jul 2007 13:40:43 +0200 Subject: [PATCH] sched: arch preempt notifier mechanism 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 [ mingo@elte.hu: fixes, cleanups ] Signed-off-by: Ingo Molnar --- kernel/Kconfig.preempt | 3 +++ kernel/sched.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 74 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt index c64ce9c14207..6b066632e40c 100644 --- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -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 + diff --git a/kernel/sched.c b/kernel/sched.c index 93cf241cfbe9..e901aa59f206 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -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(¬ifier->link, ¤t->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(¬ifier->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); -- cgit v1.2.1