Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  signal: align __lock_task_sighand() irq disabling and RCU
  softirq,rcu: Inform RCU of irq_exit() activity
  sched: Add irq_{enter,exit}() to scheduler_ipi()
  rcu: protect __rcu_read_unlock() against scheduler-using irq handlers
  rcu: Streamline code produced by __rcu_read_unlock()
  rcu: Fix RCU_BOOST race handling current->rcu_read_unlock_special
  rcu: decrease rcu_report_exp_rnp coupling with scheduler
This commit is contained in:
Linus Torvalds 2011-07-20 15:56:25 -07:00
commit cf6ace16a3
5 changed files with 103 additions and 28 deletions

View File

@ -1260,6 +1260,9 @@ struct task_struct {
#ifdef CONFIG_PREEMPT_RCU
int rcu_read_lock_nesting;
char rcu_read_unlock_special;
#if defined(CONFIG_RCU_BOOST) && defined(CONFIG_TREE_PREEMPT_RCU)
int rcu_boosted;
#endif /* #if defined(CONFIG_RCU_BOOST) && defined(CONFIG_TREE_PREEMPT_RCU) */
struct list_head rcu_node_entry;
#endif /* #ifdef CONFIG_PREEMPT_RCU */
#ifdef CONFIG_TREE_PREEMPT_RCU

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@ -68,6 +68,7 @@ struct rcu_state rcu_preempt_state = RCU_STATE_INITIALIZER(rcu_preempt_state);
DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data);
static struct rcu_state *rcu_state = &rcu_preempt_state;
static void rcu_read_unlock_special(struct task_struct *t);
static int rcu_preempted_readers_exp(struct rcu_node *rnp);
/*
@ -147,7 +148,7 @@ static void rcu_preempt_note_context_switch(int cpu)
struct rcu_data *rdp;
struct rcu_node *rnp;
if (t->rcu_read_lock_nesting &&
if (t->rcu_read_lock_nesting > 0 &&
(t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
/* Possibly blocking in an RCU read-side critical section. */
@ -190,6 +191,14 @@ static void rcu_preempt_note_context_switch(int cpu)
rnp->gp_tasks = &t->rcu_node_entry;
}
raw_spin_unlock_irqrestore(&rnp->lock, flags);
} else if (t->rcu_read_lock_nesting < 0 &&
t->rcu_read_unlock_special) {
/*
* Complete exit from RCU read-side critical section on
* behalf of preempted instance of __rcu_read_unlock().
*/
rcu_read_unlock_special(t);
}
/*
@ -284,7 +293,7 @@ static struct list_head *rcu_next_node_entry(struct task_struct *t,
* notify RCU core processing or task having blocked during the RCU
* read-side critical section.
*/
static void rcu_read_unlock_special(struct task_struct *t)
static noinline void rcu_read_unlock_special(struct task_struct *t)
{
int empty;
int empty_exp;
@ -309,7 +318,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
}
/* Hardware IRQ handlers cannot block. */
if (in_irq()) {
if (in_irq() || in_serving_softirq()) {
local_irq_restore(flags);
return;
}
@ -342,6 +351,11 @@ static void rcu_read_unlock_special(struct task_struct *t)
#ifdef CONFIG_RCU_BOOST
if (&t->rcu_node_entry == rnp->boost_tasks)
rnp->boost_tasks = np;
/* Snapshot and clear ->rcu_boosted with rcu_node lock held. */
if (t->rcu_boosted) {
special |= RCU_READ_UNLOCK_BOOSTED;
t->rcu_boosted = 0;
}
#endif /* #ifdef CONFIG_RCU_BOOST */
t->rcu_blocked_node = NULL;
@ -358,7 +372,6 @@ static void rcu_read_unlock_special(struct task_struct *t)
#ifdef CONFIG_RCU_BOOST
/* Unboost if we were boosted. */
if (special & RCU_READ_UNLOCK_BOOSTED) {
t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BOOSTED;
rt_mutex_unlock(t->rcu_boost_mutex);
t->rcu_boost_mutex = NULL;
}
@ -387,13 +400,22 @@ void __rcu_read_unlock(void)
struct task_struct *t = current;
barrier(); /* needed if we ever invoke rcu_read_unlock in rcutree.c */
--t->rcu_read_lock_nesting;
barrier(); /* decrement before load of ->rcu_read_unlock_special */
if (t->rcu_read_lock_nesting == 0 &&
unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
rcu_read_unlock_special(t);
if (t->rcu_read_lock_nesting != 1)
--t->rcu_read_lock_nesting;
else {
t->rcu_read_lock_nesting = INT_MIN;
barrier(); /* assign before ->rcu_read_unlock_special load */
if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
rcu_read_unlock_special(t);
barrier(); /* ->rcu_read_unlock_special load before assign */
t->rcu_read_lock_nesting = 0;
}
#ifdef CONFIG_PROVE_LOCKING
WARN_ON_ONCE(ACCESS_ONCE(t->rcu_read_lock_nesting) < 0);
{
int rrln = ACCESS_ONCE(t->rcu_read_lock_nesting);
WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
}
#endif /* #ifdef CONFIG_PROVE_LOCKING */
}
EXPORT_SYMBOL_GPL(__rcu_read_unlock);
@ -589,7 +611,8 @@ static void rcu_preempt_check_callbacks(int cpu)
rcu_preempt_qs(cpu);
return;
}
if (per_cpu(rcu_preempt_data, cpu).qs_pending)
if (t->rcu_read_lock_nesting > 0 &&
per_cpu(rcu_preempt_data, cpu).qs_pending)
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
}
@ -695,9 +718,12 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp)
raw_spin_lock_irqsave(&rnp->lock, flags);
for (;;) {
if (!sync_rcu_preempt_exp_done(rnp))
if (!sync_rcu_preempt_exp_done(rnp)) {
raw_spin_unlock_irqrestore(&rnp->lock, flags);
break;
}
if (rnp->parent == NULL) {
raw_spin_unlock_irqrestore(&rnp->lock, flags);
wake_up(&sync_rcu_preempt_exp_wq);
break;
}
@ -707,7 +733,6 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp)
raw_spin_lock(&rnp->lock); /* irqs already disabled */
rnp->expmask &= ~mask;
}
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
/*
@ -1174,7 +1199,7 @@ static int rcu_boost(struct rcu_node *rnp)
t = container_of(tb, struct task_struct, rcu_node_entry);
rt_mutex_init_proxy_locked(&mtx, t);
t->rcu_boost_mutex = &mtx;
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BOOSTED;
t->rcu_boosted = 1;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */
rt_mutex_unlock(&mtx); /* Keep lockdep happy. */

View File

@ -2544,13 +2544,9 @@ static int ttwu_remote(struct task_struct *p, int wake_flags)
}
#ifdef CONFIG_SMP
static void sched_ttwu_pending(void)
static void sched_ttwu_do_pending(struct task_struct *list)
{
struct rq *rq = this_rq();
struct task_struct *list = xchg(&rq->wake_list, NULL);
if (!list)
return;
raw_spin_lock(&rq->lock);
@ -2563,9 +2559,45 @@ static void sched_ttwu_pending(void)
raw_spin_unlock(&rq->lock);
}
#ifdef CONFIG_HOTPLUG_CPU
static void sched_ttwu_pending(void)
{
struct rq *rq = this_rq();
struct task_struct *list = xchg(&rq->wake_list, NULL);
if (!list)
return;
sched_ttwu_do_pending(list);
}
#endif /* CONFIG_HOTPLUG_CPU */
void scheduler_ipi(void)
{
sched_ttwu_pending();
struct rq *rq = this_rq();
struct task_struct *list = xchg(&rq->wake_list, NULL);
if (!list)
return;
/*
* Not all reschedule IPI handlers call irq_enter/irq_exit, since
* traditionally all their work was done from the interrupt return
* path. Now that we actually do some work, we need to make sure
* we do call them.
*
* Some archs already do call them, luckily irq_enter/exit nest
* properly.
*
* Arguably we should visit all archs and update all handlers,
* however a fair share of IPIs are still resched only so this would
* somewhat pessimize the simple resched case.
*/
irq_enter();
sched_ttwu_do_pending(list);
irq_exit();
}
static void ttwu_queue_remote(struct task_struct *p, int cpu)

View File

@ -1178,18 +1178,25 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
{
struct sighand_struct *sighand;
rcu_read_lock();
for (;;) {
local_irq_save(*flags);
rcu_read_lock();
sighand = rcu_dereference(tsk->sighand);
if (unlikely(sighand == NULL))
if (unlikely(sighand == NULL)) {
rcu_read_unlock();
local_irq_restore(*flags);
break;
}
spin_lock_irqsave(&sighand->siglock, *flags);
if (likely(sighand == tsk->sighand))
spin_lock(&sighand->siglock);
if (likely(sighand == tsk->sighand)) {
rcu_read_unlock();
break;
spin_unlock_irqrestore(&sighand->siglock, *flags);
}
spin_unlock(&sighand->siglock);
rcu_read_unlock();
local_irq_restore(*flags);
}
rcu_read_unlock();
return sighand;
}

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@ -315,16 +315,24 @@ static inline void invoke_softirq(void)
{
if (!force_irqthreads)
__do_softirq();
else
else {
__local_bh_disable((unsigned long)__builtin_return_address(0),
SOFTIRQ_OFFSET);
wakeup_softirqd();
__local_bh_enable(SOFTIRQ_OFFSET);
}
}
#else
static inline void invoke_softirq(void)
{
if (!force_irqthreads)
do_softirq();
else
else {
__local_bh_disable((unsigned long)__builtin_return_address(0),
SOFTIRQ_OFFSET);
wakeup_softirqd();
__local_bh_enable(SOFTIRQ_OFFSET);
}
}
#endif