#include <poll.h>
#include "urcu/wfcqueue.h"
-#include "urcu/wfstack.h"
#include "urcu/map/urcu-qsbr.h"
#define BUILD_QSBR_LIB
#include "urcu/static/urcu-qsbr.h"
static CDS_LIST_HEAD(registry);
-struct gp_waiters_thread {
- struct cds_wfs_node node;
- struct urcu_wait wait;
-};
-
/*
- * Stack keeping threads awaiting to wait for a grace period. Contains
+ * Queue keeping threads awaiting to wait for a grace period. Contains
* struct gp_waiters_thread objects.
*/
-static struct cds_wfs_stack gp_waiters = {
- .head = CDS_WFS_END,
- .lock = PTHREAD_MUTEX_INITIALIZER,
-};
+static DEFINE_URCU_WAIT_QUEUE(gp_waiters);
static void mutex_lock(pthread_mutex_t *mutex)
{
CDS_LIST_HEAD(cur_snap_readers);
CDS_LIST_HEAD(qsreaders);
unsigned long was_online;
- struct gp_waiters_thread gp_waiters_thread;
- struct cds_wfs_head *gp_waiters_head;
- struct cds_wfs_node *waiters_iter, *waiters_iter_n;
+ DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING);
+ struct urcu_waiters waiters;
was_online = URCU_TLS(rcu_reader).ctr;
cmm_smp_mb();
/*
- * Add ourself to gp_waiters stack of threads awaiting to wait
+ * Add ourself to gp_waiters queue of threads awaiting to wait
* for a grace period. Proceed to perform the grace period only
- * if we are the first thread added into the stack.
+ * if we are the first thread added into the queue.
*/
- cds_wfs_node_init(&gp_waiters_thread.node);
- urcu_wait_init(&gp_waiters_thread.wait);
- if (cds_wfs_push(&gp_waiters, &gp_waiters_node) != 0) {
- /* Not first in stack: will be awakened by another thread. */
- urcu_adaptative_busy_wait(&gp_waiters_thread.wait);
+ if (urcu_wait_add(&gp_waiters, &wait) != 0) {
+ /* Not first in queue: will be awakened by another thread. */
+ urcu_adaptative_busy_wait(&wait);
goto gp_end;
}
+ /* We won't need to wake ourself up */
+ urcu_wait_set_state(&wait, URCU_WAIT_RUNNING);
mutex_lock(&rcu_gp_lock);
/*
- * Pop all waiters into our local stack head.
+ * Move all waiters into our local queue.
*/
- gp_waiters_head = __cds_wfs_pop_all(&gp_waiters);
+ urcu_move_waiters(&waiters, &gp_waiters);
if (cds_list_empty(®istry))
goto out;
cds_list_splice(&qsreaders, ®istry);
out:
mutex_unlock(&rcu_gp_lock);
-
- /* Wake all waiters in our stack head, excluding ourself. */
- cds_wfs_for_each_blocking_safe(gp_waiters_head, waiters_iter,
- waiters_iter_n) {
- struct gp_waiters_thread *wt;
-
- wt = caa_container_of(waiters_iter,
- struct gp_waiters_thread, node);
- if (wt == &gp_waiters_thread)
- continue;
- urcu_adaptative_wake_up(&wt->wait);
- }
-
+ urcu_wake_all_waiters(&waiters);
gp_end:
/*
* Finish waiting for reader threads before letting the old ptr being
{
CDS_LIST_HEAD(qsreaders);
unsigned long was_online;
- struct gp_waiters_thread gp_waiters_thread;
- struct cds_wfs_head *gp_waiters_head;
- struct cds_wfs_node *waiters_iter, *waiters_iter_n;
+ DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING);
+ struct urcu_waiters waiters;
was_online = URCU_TLS(rcu_reader).ctr;
cmm_smp_mb();
/*
- * Add ourself to gp_waiters stack of threads awaiting to wait
+ * Add ourself to gp_waiters queue of threads awaiting to wait
* for a grace period. Proceed to perform the grace period only
- * if we are the first thread added into the stack.
+ * if we are the first thread added into the queue.
*/
- cds_wfs_node_init(&gp_waiters_thread.node);
- urcu_wait_init(&gp_waiters_thread.wait);
- if (cds_wfs_push(&gp_waiters, &gp_waiters_thread.node) != 0) {
- /* Not first in stack: will be awakened by another thread. */
- urcu_adaptative_busy_wait(&gp_waiters_thread.wait);
+ if (urcu_wait_add(&gp_waiters, &wait) != 0) {
+ /* Not first in queue: will be awakened by another thread. */
+ urcu_adaptative_busy_wait(&wait);
goto gp_end;
}
+ /* We won't need to wake ourself up */
+ urcu_wait_set_state(&wait, URCU_WAIT_RUNNING);
mutex_lock(&rcu_gp_lock);
/*
- * Pop all waiters into our local stack head.
+ * Move all waiters into our local queue.
*/
- gp_waiters_head = __cds_wfs_pop_all(&gp_waiters);
+ urcu_move_waiters(&waiters, &gp_waiters);
if (cds_list_empty(®istry))
goto out;
cds_list_splice(&qsreaders, ®istry);
out:
mutex_unlock(&rcu_gp_lock);
-
- /* Wake all waiters in our stack head, excluding ourself. */
- cds_wfs_for_each_blocking_safe(gp_waiters_head, waiters_iter,
- waiters_iter_n) {
- struct gp_waiters_thread *wt;
-
- wt = caa_container_of(waiters_iter,
- struct gp_waiters_thread, node);
- if (wt == &gp_waiters_thread)
- continue;
- urcu_adaptative_wake_up(&wt->wait);
- }
-
+ urcu_wake_all_waiters(&waiters);
gp_end:
if (was_online)
rcu_thread_online();
*/
#include <urcu/uatomic.h>
+#include <urcu/wfstack.h>
/*
* Number of busy-loop attempts before waiting on futex for grace period
URCU_WAIT_WAITING = 0,
/* non-zero are used as masks. */
URCU_WAIT_WAKEUP = (1 << 0),
- URCU_WAIT_AWAKENED = (1 << 1),
+ URCU_WAIT_RUNNING = (1 << 1),
URCU_WAIT_TEARDOWN = (1 << 2),
};
-struct urcu_wait {
- int32_t futex;
+struct urcu_wait_node {
+ struct cds_wfs_node node;
+ int32_t state; /* enum urcu_wait_state */
};
+#define URCU_WAIT_NODE_INIT(name, _state) \
+ { .state = _state }
+
+#define DEFINE_URCU_WAIT_NODE(name, state) \
+ struct urcu_wait_node name = URCU_WAIT_NODE_INIT(name, state)
+
+#define DECLARE_URCU_WAIT_NODE(name) \
+ struct urcu_wait_node name
+
+struct urcu_wait_queue {
+ struct cds_wfs_stack stack;
+};
+
+#define URCU_WAIT_QUEUE_HEAD_INIT(name) \
+ { .stack.head = CDS_WFS_END, .stack.lock = PTHREAD_MUTEX_INITIALIZER }
+
+#define DECLARE_URCU_WAIT_QUEUE(name) \
+ struct urcu_wait_queue name
+
+#define DEFINE_URCU_WAIT_QUEUE(name) \
+ struct urcu_wait_queue name = URCU_WAIT_QUEUE_HEAD_INIT(name)
+
+struct urcu_waiters {
+ struct cds_wfs_head *head;
+};
+
+/*
+ * Add ourself atomically to a wait queue. Return 0 if queue was
+ * previously empty, else return 1.
+ * A full memory barrier is issued before being added to the wait queue.
+ */
+static inline
+bool urcu_wait_add(struct urcu_wait_queue *queue,
+ struct urcu_wait_node *node)
+{
+ return cds_wfs_push(&queue->stack, &node->node);
+}
+
+/*
+ * Atomically move all waiters from wait queue into our local struct
+ * urcu_waiters.
+ */
+static inline
+void urcu_move_waiters(struct urcu_waiters *waiters,
+ struct urcu_wait_queue *queue)
+{
+ waiters->head = __cds_wfs_pop_all(&queue->stack);
+}
+
+static inline
+void urcu_wait_set_state(struct urcu_wait_node *node,
+ enum urcu_wait_state state)
+{
+ node->state = state;
+}
+
static inline
-void urcu_wait_init(struct urcu_wait *wait)
+void urcu_wait_node_init(struct urcu_wait_node *node,
+ enum urcu_wait_state state)
{
- wait->futex = URCU_WAIT_WAITING;
+ urcu_wait_set_state(node, state);
+ cds_wfs_node_init(&node->node);
}
/*
* Note: urcu_adaptative_wake_up needs "value" to stay allocated
- * throughout its execution. In this scheme, the waiter owns the futex
+ * throughout its execution. In this scheme, the waiter owns the node
* memory, and we only allow it to free this memory when it receives the
* URCU_WAIT_TEARDOWN flag.
*/
static inline
-void urcu_adaptative_wake_up(struct urcu_wait *wait)
+void urcu_adaptative_wake_up(struct urcu_wait_node *wait)
{
cmm_smp_mb();
- assert(uatomic_read(&wait->futex) == URCU_WAIT_WAITING);
- uatomic_set(&wait->futex, URCU_WAIT_WAKEUP);
- if (!(uatomic_read(&wait->futex) & URCU_WAIT_AWAKENED))
- futex_noasync(&wait->futex, FUTEX_WAKE, 1, NULL, NULL, 0);
+ assert(uatomic_read(&wait->state) == URCU_WAIT_WAITING);
+ uatomic_set(&wait->state, URCU_WAIT_WAKEUP);
+ if (!(uatomic_read(&wait->state) & URCU_WAIT_RUNNING))
+ futex_noasync(&wait->state, FUTEX_WAKE, 1, NULL, NULL, 0);
/* Allow teardown of struct urcu_wait memory. */
- uatomic_or(&wait->futex, URCU_WAIT_TEARDOWN);
+ uatomic_or(&wait->state, URCU_WAIT_TEARDOWN);
}
/*
* Caller must initialize "value" to URCU_WAIT_WAITING before passing its
* memory to waker thread.
*/
-static void urcu_adaptative_busy_wait(struct urcu_wait *wait)
+static inline
+void urcu_adaptative_busy_wait(struct urcu_wait_node *wait)
{
unsigned int i;
- /* Load and test condition before read futex */
+ /* Load and test condition before read state */
cmm_smp_rmb();
for (i = 0; i < URCU_WAIT_ATTEMPTS; i++) {
- if (uatomic_read(&wait->futex) != URCU_WAIT_WAITING)
+ if (uatomic_read(&wait->state) != URCU_WAIT_WAITING)
goto skip_futex_wait;
caa_cpu_relax();
}
- futex_noasync(&wait->futex, FUTEX_WAIT,
+ futex_noasync(&wait->state, FUTEX_WAIT,
URCU_WAIT_WAITING, NULL, NULL, 0);
skip_futex_wait:
- /* Tell waker thread than we are awakened. */
- uatomic_or(&wait->futex, URCU_WAIT_AWAKENED);
+ /* Tell waker thread than we are runnning. */
+ uatomic_or(&wait->state, URCU_WAIT_RUNNING);
/*
* Wait until waker thread lets us know it's ok to tear down
* memory allocated for struct urcu_wait.
*/
for (i = 0; i < URCU_WAIT_ATTEMPTS; i++) {
- if (uatomic_read(&wait->futex) & URCU_WAIT_TEARDOWN)
+ if (uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN)
break;
caa_cpu_relax();
}
- while (!(uatomic_read(&wait->futex) & URCU_WAIT_TEARDOWN))
+ while (!(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN))
poll(NULL, 0, 10);
- assert(uatomic_read(&wait->futex) & URCU_WAIT_TEARDOWN);
+ assert(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN);
+}
+
+static inline
+void urcu_wake_all_waiters(struct urcu_waiters *waiters)
+{
+ struct cds_wfs_node *iter, *iter_n;
+
+ /* Wake all waiters in our stack head */
+ cds_wfs_for_each_blocking_safe(waiters->head, iter, iter_n) {
+ struct urcu_wait_node *wait_node =
+ caa_container_of(iter, struct urcu_wait_node, node);
+
+ /* Don't wake already running threads */
+ if (wait_node->state & URCU_WAIT_RUNNING)
+ continue;
+ urcu_adaptative_wake_up(wait_node);
+ }
}
#endif /* _URCU_WAIT_H */
projects / urcu.git / commitdiff
