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-rw-r--r--kernel/rcutiny_plugin.h77
1 files changed, 60 insertions, 17 deletions
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index 9cb1ae4aabd..22ecea0dfb6 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -132,6 +132,7 @@ static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = {
RCU_TRACE(.rcb.name = "rcu_preempt")
};
+static void rcu_read_unlock_special(struct task_struct *t);
static int rcu_preempted_readers_exp(void);
static void rcu_report_exp_done(void);
@@ -146,6 +147,16 @@ static int rcu_cpu_blocking_cur_gp(void)
/*
* Check for a running RCU reader. Because there is only one CPU,
* there can be but one running RCU reader at a time. ;-)
+ *
+ * Returns zero if there are no running readers. Returns a positive
+ * number if there is at least one reader within its RCU read-side
+ * critical section. Returns a negative number if an outermost reader
+ * is in the midst of exiting from its RCU read-side critical section
+ *
+ * Returns zero if there are no running readers. Returns a positive
+ * number if there is at least one reader within its RCU read-side
+ * critical section. Returns a negative number if an outermost reader
+ * is in the midst of exiting from its RCU read-side critical section.
*/
static int rcu_preempt_running_reader(void)
{
@@ -307,7 +318,6 @@ static int rcu_boost(void)
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;
raw_local_irq_restore(flags);
rt_mutex_lock(&mtx);
rt_mutex_unlock(&mtx); /* Keep lockdep happy. */
@@ -475,7 +485,7 @@ void rcu_preempt_note_context_switch(void)
unsigned long flags;
local_irq_save(flags); /* must exclude scheduler_tick(). */
- if (rcu_preempt_running_reader() &&
+ if (rcu_preempt_running_reader() > 0 &&
(t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
/* Possibly blocking in an RCU read-side critical section. */
@@ -494,6 +504,13 @@ void rcu_preempt_note_context_switch(void)
list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks);
if (rcu_cpu_blocking_cur_gp())
rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry;
+ } else if (rcu_preempt_running_reader() < 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);
}
/*
@@ -526,12 +543,15 @@ EXPORT_SYMBOL_GPL(__rcu_read_lock);
* 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;
unsigned long flags;
struct list_head *np;
+#ifdef CONFIG_RCU_BOOST
+ struct rt_mutex *rbmp = NULL;
+#endif /* #ifdef CONFIG_RCU_BOOST */
int special;
/*
@@ -552,7 +572,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
rcu_preempt_cpu_qs();
/* Hardware IRQ handlers cannot block. */
- if (in_irq()) {
+ if (in_irq() || in_serving_softirq()) {
local_irq_restore(flags);
return;
}
@@ -597,10 +617,10 @@ static void rcu_read_unlock_special(struct task_struct *t)
}
#ifdef CONFIG_RCU_BOOST
/* Unboost self if was boosted. */
- if (special & RCU_READ_UNLOCK_BOOSTED) {
- t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BOOSTED;
- rt_mutex_unlock(t->rcu_boost_mutex);
+ if (t->rcu_boost_mutex != NULL) {
+ rbmp = t->rcu_boost_mutex;
t->rcu_boost_mutex = NULL;
+ rt_mutex_unlock(rbmp);
}
#endif /* #ifdef CONFIG_RCU_BOOST */
local_irq_restore(flags);
@@ -618,13 +638,22 @@ void __rcu_read_unlock(void)
struct task_struct *t = current;
barrier(); /* needed if we ever invoke rcu_read_unlock in rcutiny.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(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);
@@ -649,7 +678,7 @@ static void rcu_preempt_check_callbacks(void)
invoke_rcu_callbacks();
if (rcu_preempt_gp_in_progress() &&
rcu_cpu_blocking_cur_gp() &&
- rcu_preempt_running_reader())
+ rcu_preempt_running_reader() > 0)
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
}
@@ -706,6 +735,11 @@ EXPORT_SYMBOL_GPL(call_rcu);
*/
void synchronize_rcu(void)
{
+ rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+ !lock_is_held(&rcu_lock_map) &&
+ !lock_is_held(&rcu_sched_lock_map),
+ "Illegal synchronize_rcu() in RCU read-side critical section");
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
if (!rcu_scheduler_active)
return;
@@ -882,7 +916,8 @@ static void rcu_preempt_process_callbacks(void)
static void invoke_rcu_callbacks(void)
{
have_rcu_kthread_work = 1;
- wake_up(&rcu_kthread_wq);
+ if (rcu_kthread_task != NULL)
+ wake_up(&rcu_kthread_wq);
}
#ifdef CONFIG_RCU_TRACE
@@ -943,12 +978,16 @@ early_initcall(rcu_spawn_kthreads);
#else /* #ifdef CONFIG_RCU_BOOST */
+/* Hold off callback invocation until early_initcall() time. */
+static int rcu_scheduler_fully_active __read_mostly;
+
/*
* Start up softirq processing of callbacks.
*/
void invoke_rcu_callbacks(void)
{
- raise_softirq(RCU_SOFTIRQ);
+ if (rcu_scheduler_fully_active)
+ raise_softirq(RCU_SOFTIRQ);
}
#ifdef CONFIG_RCU_TRACE
@@ -963,10 +1002,14 @@ static bool rcu_is_callbacks_kthread(void)
#endif /* #ifdef CONFIG_RCU_TRACE */
-void rcu_init(void)
+static int __init rcu_scheduler_really_started(void)
{
+ rcu_scheduler_fully_active = 1;
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+ raise_softirq(RCU_SOFTIRQ); /* Invoke any callbacks from early boot. */
+ return 0;
}
+early_initcall(rcu_scheduler_really_started);
#endif /* #else #ifdef CONFIG_RCU_BOOST */
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2024-11-16 17:40:24 +0000