[lttng-dev] [RFC PATCH v2] wfstack: return whether pop is popping the last element
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Sun Jan 20 18:08:58 EST 2013
Newly introduced "with_state" pop API members return stack state
atomically sampled with the pop operation.
Allow testing behavior of pop with respect to number of push-to-empty
and pop-all-from-non-empty.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
---
diff --git a/tests/test_urcu_wfs.c b/tests/test_urcu_wfs.c
index 259ca24..9892354 100644
--- a/tests/test_urcu_wfs.c
+++ b/tests/test_urcu_wfs.c
@@ -171,6 +171,7 @@ static DEFINE_URCU_TLS(unsigned long long, nr_successful_dequeues);
static DEFINE_URCU_TLS(unsigned long long, nr_successful_enqueues);
static DEFINE_URCU_TLS(unsigned long long, nr_empty_dest_enqueues);
static DEFINE_URCU_TLS(unsigned long long, nr_pop_all);
+static DEFINE_URCU_TLS(unsigned long long, nr_pop_last);
static unsigned int nr_enqueuers;
static unsigned int nr_dequeuers;
@@ -230,14 +231,17 @@ fail:
static void do_test_pop(enum test_sync sync)
{
struct cds_wfs_node *node;
+ int state;
if (sync == TEST_SYNC_MUTEX)
cds_wfs_pop_lock(&s);
- node = __cds_wfs_pop_blocking(&s);
+ node = __cds_wfs_pop_with_state_blocking(&s, &state);
if (sync == TEST_SYNC_MUTEX)
cds_wfs_pop_unlock(&s);
if (node) {
+ if (state & CDS_WFS_STATE_LAST)
+ URCU_TLS(nr_pop_last)++;
free(node);
URCU_TLS(nr_successful_dequeues)++;
}
@@ -260,6 +264,7 @@ static void do_test_pop_all(enum test_sync sync)
return;
URCU_TLS(nr_pop_all)++;
+ URCU_TLS(nr_pop_last)++;
cds_wfs_for_each_blocking_safe(head, node, n) {
free(node);
@@ -308,24 +313,30 @@ static void *thr_dequeuer(void *_count)
printf_verbose("dequeuer thread_end, thread id : %lx, tid %lu, "
"dequeues %llu, successful_dequeues %llu "
- "pop_all %llu\n",
+ "pop_all %llu pop_last %llu\n",
pthread_self(),
(unsigned long) gettid(),
URCU_TLS(nr_dequeues), URCU_TLS(nr_successful_dequeues),
- URCU_TLS(nr_pop_all));
+ URCU_TLS(nr_pop_all),
+ URCU_TLS(nr_pop_last));
count[0] = URCU_TLS(nr_dequeues);
count[1] = URCU_TLS(nr_successful_dequeues);
count[2] = URCU_TLS(nr_pop_all);
+ count[3] = URCU_TLS(nr_pop_last);
return ((void*)2);
}
-static void test_end(struct cds_wfs_stack *s, unsigned long long *nr_dequeues)
+static void test_end(struct cds_wfs_stack *s, unsigned long long *nr_dequeues,
+ unsigned long long *nr_pop_last)
{
struct cds_wfs_node *node;
+ int state;
do {
- node = cds_wfs_pop_blocking(s);
+ node = cds_wfs_pop_with_state_blocking(s, &state);
if (node) {
+ if (state & CDS_WFS_STATE_LAST)
+ (*nr_pop_last)++;
free(node);
(*nr_dequeues)++;
}
@@ -358,7 +369,7 @@ int main(int argc, char **argv)
unsigned long long tot_successful_enqueues = 0,
tot_successful_dequeues = 0,
tot_empty_dest_enqueues = 0,
- tot_pop_all = 0;
+ tot_pop_all = 0, tot_pop_last = 0;
unsigned long long end_dequeues = 0;
int i, a, retval = 0;
@@ -471,7 +482,7 @@ int main(int argc, char **argv)
tid_enqueuer = malloc(sizeof(*tid_enqueuer) * nr_enqueuers);
tid_dequeuer = malloc(sizeof(*tid_dequeuer) * nr_dequeuers);
count_enqueuer = malloc(3 * sizeof(*count_enqueuer) * nr_enqueuers);
- count_dequeuer = malloc(3 * sizeof(*count_dequeuer) * nr_dequeuers);
+ count_dequeuer = malloc(4 * sizeof(*count_dequeuer) * nr_dequeuers);
cds_wfs_init(&s);
next_aff = 0;
@@ -484,7 +495,7 @@ int main(int argc, char **argv)
}
for (i = 0; i < nr_dequeuers; i++) {
err = pthread_create(&tid_dequeuer[i], NULL, thr_dequeuer,
- &count_dequeuer[3 * i]);
+ &count_dequeuer[4 * i]);
if (err != 0)
exit(1);
}
@@ -524,34 +535,36 @@ int main(int argc, char **argv)
err = pthread_join(tid_dequeuer[i], &tret);
if (err != 0)
exit(1);
- tot_dequeues += count_dequeuer[3 * i];
- tot_successful_dequeues += count_dequeuer[3 * i + 1];
- tot_pop_all += count_dequeuer[3 * i + 2];
+ tot_dequeues += count_dequeuer[4 * i];
+ tot_successful_dequeues += count_dequeuer[4 * i + 1];
+ tot_pop_all += count_dequeuer[4 * i + 2];
+ tot_pop_last += count_dequeuer[4 * i + 3];
}
- test_end(&s, &end_dequeues);
+ test_end(&s, &end_dequeues, &tot_pop_last);
printf_verbose("total number of enqueues : %llu, dequeues %llu\n",
tot_enqueues, tot_dequeues);
printf_verbose("total number of successful enqueues : %llu, "
"enqueues to empty dest : %llu, "
"successful dequeues %llu, "
- "pop_all : %llu\n",
+ "pop_all : %llu, pop_last : %llu\n",
tot_successful_enqueues,
tot_empty_dest_enqueues,
tot_successful_dequeues,
- tot_pop_all);
+ tot_pop_all, tot_pop_last);
printf("SUMMARY %-25s testdur %4lu nr_enqueuers %3u wdelay %6lu "
"nr_dequeuers %3u "
"rdur %6lu nr_enqueues %12llu nr_dequeues %12llu "
"successful enqueues %12llu enqueues to empty dest %12llu "
"successful dequeues %12llu pop_all %12llu "
- "end_dequeues %llu nr_ops %12llu\n",
+ "pop_last %llu end_dequeues %llu nr_ops %12llu\n",
argv[0], duration, nr_enqueuers, wdelay,
nr_dequeuers, rduration, tot_enqueues, tot_dequeues,
tot_successful_enqueues,
tot_empty_dest_enqueues,
- tot_successful_dequeues, tot_pop_all, end_dequeues,
+ tot_successful_dequeues, tot_pop_all, tot_pop_last,
+ end_dequeues,
tot_enqueues + tot_dequeues);
if (tot_successful_enqueues != tot_successful_dequeues + end_dequeues) {
printf("WARNING! Discrepancy between nr succ. enqueues %llu vs "
@@ -561,16 +574,14 @@ int main(int argc, char **argv)
retval = 1;
}
/*
- * If only using pop_all to dequeue, the enqueuer should see
- * exactly as many empty queues than the number of non-empty
- * stacks dequeued.
+ * The enqueuer should see exactly as many empty queues than the
+ * number of non-empty stacks dequeued.
*/
- if (test_wait_empty && test_pop_all && !test_pop
- && tot_empty_dest_enqueues != tot_pop_all) {
+ if (tot_empty_dest_enqueues != tot_pop_last) {
printf("WARNING! Discrepancy between empty enqueue (%llu) and "
- "number of non-empty pop_all (%llu)\n",
+ "number of pop last (%llu)\n",
tot_empty_dest_enqueues,
- tot_pop_all);
+ tot_pop_last);
retval = 1;
}
free(count_enqueuer);
diff --git a/urcu/static/wfstack.h b/urcu/static/wfstack.h
index 9bc9519..db0d5b8 100644
--- a/urcu/static/wfstack.h
+++ b/urcu/static/wfstack.h
@@ -161,29 +161,37 @@ ___cds_wfs_node_sync_next(struct cds_wfs_node *node, int blocking)
static inline
struct cds_wfs_node *
-___cds_wfs_pop(struct cds_wfs_stack *s, int blocking)
+___cds_wfs_pop(struct cds_wfs_stack *s, int *state, int blocking)
{
struct cds_wfs_head *head, *new_head;
struct cds_wfs_node *next;
+ if (state)
+ *state = 0;
for (;;) {
head = CMM_LOAD_SHARED(s->head);
- if (___cds_wfs_end(head))
+ if (___cds_wfs_end(head)) {
return NULL;
+ }
next = ___cds_wfs_node_sync_next(&head->node, blocking);
- if (!blocking && next == CDS_WFS_WOULDBLOCK)
+ if (!blocking && next == CDS_WFS_WOULDBLOCK) {
return CDS_WFS_WOULDBLOCK;
+ }
new_head = caa_container_of(next, struct cds_wfs_head, node);
- if (uatomic_cmpxchg(&s->head, head, new_head) == head)
+ if (uatomic_cmpxchg(&s->head, head, new_head) == head) {
+ if (state && ___cds_wfs_end(new_head))
+ *state |= CDS_WFS_STATE_LAST;
return &head->node;
- if (!blocking)
+ }
+ if (!blocking) {
return CDS_WFS_WOULDBLOCK;
+ }
/* busy-loop if head changed under us */
}
}
/*
- * __cds_wfs_pop_blocking: pop a node from the stack.
+ * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
*
* Returns NULL if stack is empty.
*
@@ -197,12 +205,36 @@ ___cds_wfs_pop(struct cds_wfs_stack *s, int blocking)
* __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
* 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
* and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
+ *
+ * "state" saves state flags atomically sampled with pop operation.
*/
static inline
struct cds_wfs_node *
+___cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state)
+{
+ return ___cds_wfs_pop(s, state, 1);
+}
+
+static inline
+struct cds_wfs_node *
___cds_wfs_pop_blocking(struct cds_wfs_stack *s)
{
- return ___cds_wfs_pop(s, 1);
+ return ___cds_wfs_pop_with_state_blocking(s, NULL);
+}
+
+/*
+ * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack.
+ *
+ * Same as __cds_wfs_pop_with_state_blocking, but returns
+ * CDS_WFS_WOULDBLOCK if it needs to block.
+ *
+ * "state" saves state flags atomically sampled with pop operation.
+ */
+static inline
+struct cds_wfs_node *
+___cds_wfs_pop_with_state_nonblocking(struct cds_wfs_stack *s, int *state)
+{
+ return ___cds_wfs_pop(s, state, 0);
}
/*
@@ -215,7 +247,7 @@ static inline
struct cds_wfs_node *
___cds_wfs_pop_nonblocking(struct cds_wfs_stack *s)
{
- return ___cds_wfs_pop(s, 0);
+ return ___cds_wfs_pop_with_state_nonblocking(s, NULL);
}
/*
@@ -280,21 +312,31 @@ static inline void _cds_wfs_pop_unlock(struct cds_wfs_stack *s)
}
/*
- * Call __cds_wfs_pop_blocking with an internal pop mutex held.
+ * Call __cds_wfs_pop_with_state_blocking with an internal pop mutex held.
*/
static inline
struct cds_wfs_node *
-_cds_wfs_pop_blocking(struct cds_wfs_stack *s)
+_cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state)
{
struct cds_wfs_node *retnode;
_cds_wfs_pop_lock(s);
- retnode = ___cds_wfs_pop_blocking(s);
+ retnode = ___cds_wfs_pop_with_state_blocking(s, state);
_cds_wfs_pop_unlock(s);
return retnode;
}
/*
+ * Call _cds_wfs_pop_with_state_blocking without saving any state.
+ */
+static inline
+struct cds_wfs_node *
+_cds_wfs_pop_blocking(struct cds_wfs_stack *s)
+{
+ return _cds_wfs_pop_with_state_blocking(s, NULL);
+}
+
+/*
* Call __cds_wfs_pop_all with an internal pop mutex held.
*/
static inline
diff --git a/urcu/wfstack.h b/urcu/wfstack.h
index 34ddb3f..fc0b44b 100644
--- a/urcu/wfstack.h
+++ b/urcu/wfstack.h
@@ -60,6 +60,10 @@ extern "C" {
#define CDS_WFS_WOULDBLOCK ((void *) -1UL)
+enum cds_wfs_state {
+ CDS_WFS_STATE_LAST = (1U << 0),
+};
+
/*
* struct cds_wfs_node is returned by __cds_wfs_pop, and also used as
* iterator on stack. It is not safe to dereference the node next
@@ -95,6 +99,7 @@ struct cds_wfs_stack {
/* Locking performed internally */
#define cds_wfs_pop_blocking _cds_wfs_pop_blocking
+#define cds_wfs_pop_with_state_blocking _cds_wfs_pop_with_state_blocking
#define cds_wfs_pop_all_blocking _cds_wfs_pop_all_blocking
/*
@@ -111,7 +116,11 @@ struct cds_wfs_stack {
/* Synchronization ensured by the caller. See synchronization table. */
#define __cds_wfs_pop_blocking ___cds_wfs_pop_blocking
+#define __cds_wfs_pop_with_state_blocking \
+ ___cds_wfs_pop_with_state_blocking
#define __cds_wfs_pop_nonblocking ___cds_wfs_pop_nonblocking
+#define __cds_wfs_pop_with_state_nonblocking \
+ ___cds_wfs_pop_with_state_nonblocking
#define __cds_wfs_pop_all ___cds_wfs_pop_all
#else /* !_LGPL_SOURCE */
@@ -152,6 +161,15 @@ extern int cds_wfs_push(struct cds_wfs_stack *s, struct cds_wfs_node *node);
extern struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s);
/*
+ * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
+ *
+ * Same as cds_wfs_pop_blocking, but stores whether the stack was
+ * empty into state (CDS_WFS_STATE_LAST).
+ */
+extern struct cds_wfs_node *
+ cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state);
+
+/*
* cds_wfs_pop_all_blocking: pop all nodes from a stack.
*
* Calls __cds_wfs_pop_all with an internal pop mutex held.
@@ -224,6 +242,15 @@ extern void cds_wfs_pop_unlock(struct cds_wfs_stack *s);
extern struct cds_wfs_node *__cds_wfs_pop_blocking(struct cds_wfs_stack *s);
/*
+ * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
+ *
+ * Same as __cds_wfs_pop_blocking, but stores whether the stack was
+ * empty into state (CDS_WFS_STATE_LAST).
+ */
+extern struct cds_wfs_node *
+ __cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state);
+
+/*
* __cds_wfs_pop_nonblocking: pop a node from the stack.
*
* Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
@@ -232,6 +259,16 @@ extern struct cds_wfs_node *__cds_wfs_pop_blocking(struct cds_wfs_stack *s);
extern struct cds_wfs_node *__cds_wfs_pop_nonblocking(struct cds_wfs_stack *s);
/*
+ * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
+ *
+ * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
+ * empty into state (CDS_WFS_STATE_LAST).
+ */
+extern struct cds_wfs_node *
+ __cds_wfs_pop_with_state_nonblocking(struct cds_wfs_stack *s,
+ int *state);
+
+/*
* __cds_wfs_pop_all: pop all nodes from a stack.
*
* __cds_wfs_pop_all does not require any synchronization with other
diff --git a/wfstack.c b/wfstack.c
index 4ccb6b9..c8bd7e6 100644
--- a/wfstack.c
+++ b/wfstack.c
@@ -53,6 +53,12 @@ struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s)
return _cds_wfs_pop_blocking(s);
}
+struct cds_wfs_node *
+ cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state)
+{
+ return _cds_wfs_pop_with_state_blocking(s, state);
+}
+
struct cds_wfs_head *cds_wfs_pop_all_blocking(struct cds_wfs_stack *s)
{
return _cds_wfs_pop_all_blocking(s);
@@ -88,11 +94,24 @@ struct cds_wfs_node *__cds_wfs_pop_blocking(struct cds_wfs_stack *s)
return ___cds_wfs_pop_blocking(s);
}
+struct cds_wfs_node *
+ __cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state)
+{
+ return ___cds_wfs_pop_with_state_blocking(s, state);
+}
+
struct cds_wfs_node *__cds_wfs_pop_nonblocking(struct cds_wfs_stack *s)
{
return ___cds_wfs_pop_nonblocking(s);
}
+struct cds_wfs_node *
+ __cds_wfs_pop_with_state_nonblocking(struct cds_wfs_stack *s,
+ int *state)
+{
+ return ___cds_wfs_pop_with_state_nonblocking(s, state);
+}
+
struct cds_wfs_head *__cds_wfs_pop_all(struct cds_wfs_stack *s)
{
return ___cds_wfs_pop_all(s);
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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