#include <string.h>
#include <errno.h>
#include <poll.h>
+#include <sys/time.h>
+#include <syscall.h>
+#include <unistd.h>
#include "urcu-defer-static.h"
/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
#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);
extern void synchronize_rcu(void);
static pthread_mutex_t urcu_defer_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t defer_thread_mutex = PTHREAD_MUTEX_INITIALIZER;
+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 int num_deferers, alloc_deferers;
static pthread_t tid_defer;
-static int exit_defer;
static void internal_urcu_lock(pthread_mutex_t *mutex)
{
perror("Error in pthread mutex lock");
exit(-1);
}
+ pthread_testcancel();
poll(NULL,0,10);
}
#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
}
}
+/*
+ * 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.
*/
internal_urcu_unlock(&urcu_defer_mutex);
}
+/*
+ * _rcu_defer_queue - Queue a RCU callback.
+ */
+void _rcu_defer_queue(void (*fct)(void *p), void *p)
+{
+ unsigned long head, tail;
+
+ /*
+ * Head is only modified by ourself. Tail can be modified by reclamation
+ * thread.
+ */
+ head = defer_queue.head;
+ tail = LOAD_SHARED(defer_queue.tail);
+
+ /*
+ * If queue is full, empty it ourself.
+ * Worse-case: must allow 2 supplementary entries for fct pointer.
+ */
+ if (unlikely(head - tail >= DEFER_QUEUE_SIZE - 2)) {
+ assert(head - tail <= DEFER_QUEUE_SIZE);
+ rcu_defer_barrier_thread();
+ assert(head - LOAD_SHARED(defer_queue.tail) == 0);
+ }
+
+ if (unlikely(defer_queue.last_fct_in != fct)) {
+ defer_queue.last_fct_in = fct;
+ if (unlikely(DQ_IS_FCT_BIT(fct) || fct == DQ_FCT_MARK)) {
+ /*
+ * If the function to encode is not aligned or the
+ * marker, write DQ_FCT_MARK followed by the function
+ * pointer.
+ */
+ _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
+ DQ_FCT_MARK);
+ _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
+ fct);
+ } else {
+ DQ_SET_FCT_BIT(fct);
+ _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
+ fct);
+ }
+ } else {
+ if (unlikely(DQ_IS_FCT_BIT(p) || p == DQ_FCT_MARK)) {
+ /*
+ * If the data to encode is not aligned or the marker,
+ * write DQ_FCT_MARK followed by the function pointer.
+ */
+ _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
+ DQ_FCT_MARK);
+ _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK],
+ fct);
+ }
+ }
+ _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK], p);
+ 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.
+ */
+ wake_up_defer();
+}
+
void *thr_defer(void *args)
{
for (;;) {
- if (LOAD_SHARED(exit_defer))
- break;
+ pthread_testcancel();
+ /*
+ * "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.
+ */
+ wait_defer();
+ /* Sleeping after wait_defer to let many callbacks enqueue */
poll(NULL,0,100); /* wait for 100ms */
rcu_defer_barrier();
}
int ret;
void *tret;
- STORE_SHARED(exit_defer, 1);
+ pthread_cancel(tid_defer);
+ wake_up_defer();
ret = pthread_join(tid_defer, &tret);
assert(!ret);
}