module_param(rcu_expedited, int, 0);
+#if defined(CONFIG_DEBUG_LOCK_ALLOC) && defined(CONFIG_PREEMPT_COUNT)
+/**
+ * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?
+ *
+ * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an
+ * RCU-sched read-side critical section. In absence of
+ * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
+ * critical section unless it can prove otherwise. Note that disabling
+ * of preemption (including disabling irqs) counts as an RCU-sched
+ * read-side critical section. This is useful for debug checks in functions
+ * that required that they be called within an RCU-sched read-side
+ * critical section.
+ *
+ * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
+ * and while lockdep is disabled.
+ *
+ * Note that if the CPU is in the idle loop from an RCU point of
+ * view (ie: that we are in the section between rcu_idle_enter() and
+ * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU
+ * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs
+ * that are in such a section, considering these as in extended quiescent
+ * state, so such a CPU is effectively never in an RCU read-side critical
+ * section regardless of what RCU primitives it invokes. This state of
+ * affairs is required --- we need to keep an RCU-free window in idle
+ * where the CPU may possibly enter into low power mode. This way we can
+ * notice an extended quiescent state to other CPUs that started a grace
+ * period. Otherwise we would delay any grace period as long as we run in
+ * the idle task.
+ *
+ * Similarly, we avoid claiming an SRCU read lock held if the current
+ * CPU is offline.
+ */
+int rcu_read_lock_sched_held(void)
+{
+ int lockdep_opinion = 0;
+
+ if (!debug_lockdep_rcu_enabled())
+ return 1;
+ if (!rcu_is_watching())
+ return 0;
+ if (!rcu_lockdep_current_cpu_online())
+ return 0;
+ if (debug_locks)
+ lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
+ return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
+}
+EXPORT_SYMBOL(rcu_read_lock_sched_held);
+#endif
+
#ifndef CONFIG_TINY_RCU
static atomic_t rcu_expedited_nesting =
barrier(); /* critical section before exit code. */
t->rcu_read_lock_nesting = INT_MIN;
barrier(); /* assign before ->rcu_read_unlock_special load */
- if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special.s)))
+ if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))
rcu_read_unlock_special(t);
barrier(); /* ->rcu_read_unlock_special load before assign */
t->rcu_read_lock_nesting = 0;
}
#ifdef CONFIG_PROVE_LOCKING
{
- int rrln = ACCESS_ONCE(t->rcu_read_lock_nesting);
+ int rrln = READ_ONCE(t->rcu_read_lock_nesting);
WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
}
rcu = container_of(head, struct rcu_synchronize, head);
complete(&rcu->completion);
}
+EXPORT_SYMBOL_GPL(wakeme_after_rcu);
-void wait_rcu_gp(call_rcu_func_t crf)
+void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
+ struct rcu_synchronize *rs_array)
{
- struct rcu_synchronize rcu;
+ int i;
- init_rcu_head_on_stack(&rcu.head);
- init_completion(&rcu.completion);
- /* Will wake me after RCU finished. */
- crf(&rcu.head, wakeme_after_rcu);
- /* Wait for it. */
- wait_for_completion(&rcu.completion);
- destroy_rcu_head_on_stack(&rcu.head);
+ /* Initialize and register callbacks for each flavor specified. */
+ for (i = 0; i < n; i++) {
+ if (checktiny &&
+ (crcu_array[i] == call_rcu ||
+ crcu_array[i] == call_rcu_bh)) {
+ might_sleep();
+ continue;
+ }
+ init_rcu_head_on_stack(&rs_array[i].head);
+ init_completion(&rs_array[i].completion);
+ (crcu_array[i])(&rs_array[i].head, wakeme_after_rcu);
+ }
+
+ /* Wait for all callbacks to be invoked. */
+ for (i = 0; i < n; i++) {
+ if (checktiny &&
+ (crcu_array[i] == call_rcu ||
+ crcu_array[i] == call_rcu_bh))
+ continue;
+ wait_for_completion(&rs_array[i].completion);
+ destroy_rcu_head_on_stack(&rs_array[i].head);
+ }
}
-EXPORT_SYMBOL_GPL(wait_rcu_gp);
+EXPORT_SYMBOL_GPL(__wait_rcu_gp);
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
void init_rcu_head(struct rcu_head *head)
int rcu_jiffies_till_stall_check(void)
{
- int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
+ int till_stall_check = READ_ONCE(rcu_cpu_stall_timeout);
/*
* Limit check must be consistent with the Kconfig limits
* for CONFIG_RCU_CPU_STALL_TIMEOUT.
*/
if (till_stall_check < 3) {
- ACCESS_ONCE(rcu_cpu_stall_timeout) = 3;
+ WRITE_ONCE(rcu_cpu_stall_timeout, 3);
till_stall_check = 3;
} else if (till_stall_check > 300) {
- ACCESS_ONCE(rcu_cpu_stall_timeout) = 300;
+ WRITE_ONCE(rcu_cpu_stall_timeout, 300);
till_stall_check = 300;
}
return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
* Post an RCU-tasks callback. First call must be from process context
* after the scheduler if fully operational.
*/
-void call_rcu_tasks(struct rcu_head *rhp, void (*func)(struct rcu_head *rhp))
+void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func)
{
unsigned long flags;
bool needwake;
void synchronize_rcu_tasks(void)
{
/* Complain if the scheduler has not started. */
- rcu_lockdep_assert(!rcu_scheduler_active,
- "synchronize_rcu_tasks called too soon");
+ RCU_LOCKDEP_WARN(!rcu_scheduler_active,
+ "synchronize_rcu_tasks called too soon");
/* Wait for the grace period. */
wait_rcu_gp(call_rcu_tasks);
{
int cpu;
- if (!ACCESS_ONCE(t->rcu_tasks_holdout) ||
- t->rcu_tasks_nvcsw != ACCESS_ONCE(t->nvcsw) ||
- !ACCESS_ONCE(t->on_rq) ||
+ if (!READ_ONCE(t->rcu_tasks_holdout) ||
+ t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) ||
+ !READ_ONCE(t->on_rq) ||
(IS_ENABLED(CONFIG_NO_HZ_FULL) &&
!is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
- ACCESS_ONCE(t->rcu_tasks_holdout) = false;
+ WRITE_ONCE(t->rcu_tasks_holdout, false);
list_del_init(&t->rcu_tasks_holdout_list);
put_task_struct(t);
return;
*/
rcu_read_lock();
for_each_process_thread(g, t) {
- if (t != current && ACCESS_ONCE(t->on_rq) &&
+ if (t != current && READ_ONCE(t->on_rq) &&
!is_idle_task(t)) {
get_task_struct(t);
- t->rcu_tasks_nvcsw = ACCESS_ONCE(t->nvcsw);
- ACCESS_ONCE(t->rcu_tasks_holdout) = true;
+ t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
+ WRITE_ONCE(t->rcu_tasks_holdout, true);
list_add(&t->rcu_tasks_holdout_list,
&rcu_tasks_holdouts);
}
struct task_struct *t1;
schedule_timeout_interruptible(HZ);
- rtst = ACCESS_ONCE(rcu_task_stall_timeout);
+ rtst = READ_ONCE(rcu_task_stall_timeout);
needreport = rtst > 0 &&
time_after(jiffies, lastreport + rtst);
if (needreport)
static struct task_struct *rcu_tasks_kthread_ptr;
struct task_struct *t;
- if (ACCESS_ONCE(rcu_tasks_kthread_ptr)) {
+ if (READ_ONCE(rcu_tasks_kthread_ptr)) {
smp_mb(); /* Ensure caller sees full kthread. */
return;
}
t = kthread_run(rcu_tasks_kthread, NULL, "rcu_tasks_kthread");
BUG_ON(IS_ERR(t));
smp_mb(); /* Ensure others see full kthread. */
- ACCESS_ONCE(rcu_tasks_kthread_ptr) = t;
+ WRITE_ONCE(rcu_tasks_kthread_ptr, t);
mutex_unlock(&rcu_tasks_kthread_mutex);
}
Code Review / kvmfornfv.git / blobdiff