#include <string.h>
#include <errno.h>
#include <poll.h>
-#include <linux/futex.h>
#include <sys/time.h>
#include <syscall.h>
#include <unistd.h>
#include "urcu-defer.h"
#define futex(...) syscall(__NR_futex, __VA_ARGS__)
+#define FUTEX_WAIT 0
+#define FUTEX_WAKE 1
void __attribute__((destructor)) urcu_defer_exit(void);
static pthread_mutex_t urcu_defer_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t defer_thread_mutex = PTHREAD_MUTEX_INITIALIZER;
-int defer_thread_futex;
+static int defer_thread_futex;
/*
* Written to only by each individual deferer. Read by both the deferer and
* the reclamation tread.
*/
-struct defer_queue __thread defer_queue;
+static struct defer_queue __thread defer_queue;
/* Thread IDs of registered deferers */
#define INIT_NUM_THREADS 4
static pthread_t tid_defer;
-/*
- * Wake-up any waiting defer thread. Called from many concurrent threads.
- */
-static void wake_up_defer(void)
-{
- if (unlikely(atomic_read(&defer_thread_futex) == -1))
- atomic_set(&defer_thread_futex, 0);
- futex(&defer_thread_futex, FUTEX_WAKE,
- 0, NULL, NULL, 0);
-}
-
-/*
- * Defer thread waiting. Single thread.
- */
-static void wait_defer(void)
-{
- atomic_dec(&defer_thread_futex);
- if (atomic_read(&defer_thread_futex) == -1)
- futex(&defer_thread_futex, FUTEX_WAIT, -1,
- NULL, NULL, 0);
-}
-
static void internal_urcu_lock(pthread_mutex_t *mutex)
{
int ret;
}
}
+/*
+ * Wake-up any waiting defer thread. Called from many concurrent threads.
+ */
+static void wake_up_defer(void)
+{
+ if (unlikely(atomic_read(&defer_thread_futex) == -1)) {
+ atomic_set(&defer_thread_futex, 0);
+ futex(&defer_thread_futex, FUTEX_WAKE, 1,
+ NULL, NULL, 0);
+ }
+}
+
+static unsigned long rcu_defer_num_callbacks(void)
+{
+ unsigned long num_items = 0, head;
+ struct deferer_registry *index;
+
+ internal_urcu_lock(&urcu_defer_mutex);
+ for (index = registry; index < registry + num_deferers; index++) {
+ head = LOAD_SHARED(index->defer_queue->head);
+ num_items += head - index->defer_queue->tail;
+ }
+ internal_urcu_unlock(&urcu_defer_mutex);
+ return num_items;
+}
+
+/*
+ * Defer thread waiting. Single thread.
+ */
+static void wait_defer(void)
+{
+ atomic_dec(&defer_thread_futex);
+ smp_mb(); /* Write futex before read queue */
+ if (rcu_defer_num_callbacks()) {
+ smp_mb(); /* Read queue before write futex */
+ /* Callbacks are queued, don't wait. */
+ atomic_set(&defer_thread_futex, 0);
+ } else {
+ smp_rmb(); /* Read queue before read futex */
+ if (atomic_read(&defer_thread_futex) == -1)
+ futex(&defer_thread_futex, FUTEX_WAIT, -1,
+ NULL, NULL, 0);
+ }
+}
+
/*
* Must be called after Q.S. is reached.
*/
smp_wmb(); /* Publish new pointer before head */
/* Write q[] before head. */
STORE_SHARED(defer_queue.head, head);
+ smp_mb(); /* Write queue head before read futex */
/*
* Wake-up any waiting defer thread.
*/
{
for (;;) {
pthread_testcancel();
- printf("a\n");
/*
* "Be green". Don't wake up the CPU if there is no RCU work
* to perform whatsoever. Aims at saving laptop battery life by
* leaving the processor in sleep state when idle.
*/
- printf("b\n");
wait_defer();
- printf("e\n");
/* Sleeping after wait_defer to let many callbacks enqueue */
- //TEST poll(NULL,0,100); /* wait for 100ms */
- printf("f\n");
+ poll(NULL,0,100); /* wait for 100ms */
rcu_defer_barrier();
- printf("perform deferred call_rcu() from worker thread %lu.\n",
- time(NULL));
}
return NULL;