@@ -187,6 +187,11 @@ Marking quiescent states is done with the following three APIs:
thread.
+rcu_thread_offline() and rcu_thread_online() can be nested. The end of
+the extended quiescent state will coincide with the outermost call to
+rcu_thread_online().
+
+
The following APIs can be used to use RCU in a thread that is not
created with qemu_thread_create():
@@ -77,6 +77,9 @@ struct rcu_reader_data {
unsigned long ctr;
bool waiting;
+ /* Data used by reader only */
+ unsigned offline;
+
/* Data used for registry, protected by rcu_gp_lock */
QLIST_ENTRY(rcu_reader_data) node;
};
@@ -127,9 +130,14 @@ static inline void rcu_read_unlock(void)
static inline void rcu_quiescent_state(void)
{
struct rcu_reader_data *p_rcu_reader = get_rcu_reader();
+ unsigned ctr;
+
+ if (p_rcu_reader->offline > 0) {
+ return;
+ }
/* Reuses smp_rmb() in the last rcu_read_unlock(). */
- unsigned ctr = atomic_read(&rcu_gp_ctr);
+ ctr = atomic_read(&rcu_gp_ctr);
atomic_xchg(&p_rcu_reader->ctr, ctr);
if (atomic_read(&p_rcu_reader->waiting)) {
atomic_set(&p_rcu_reader->waiting, false);
@@ -141,6 +149,10 @@ static inline void rcu_thread_offline(void)
{
struct rcu_reader_data *p_rcu_reader = get_rcu_reader();
+ if (p_rcu_reader->offline++ > 0) {
+ return;
+ }
+
atomic_xchg(&p_rcu_reader->ctr, 0);
if (atomic_read(&p_rcu_reader->waiting)) {
atomic_set(&p_rcu_reader->waiting, false);
@@ -150,7 +162,12 @@ static inline void rcu_thread_offline(void)
static inline void rcu_thread_online(void)
{
- rcu_quiescent_state();
+ struct rcu_reader_data *p_rcu_reader = get_rcu_reader();
+
+ assert(p_rcu_reader->offline != 0);
+ if (--p_rcu_reader->offline == 0) {
+ rcu_quiescent_state();
+ }
}
extern void synchronize_rcu(void);