X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu%2Fstatic%2Fwfstack.h;fp=urcu%2Fstatic%2Fwfstack.h;h=ff18c4a3f213214188ef6bfe6f6c98a795132bab;hp=0000000000000000000000000000000000000000;hb=af7c2dbeac32c663b64ad05e4eca70e18784463b;hpb=acfd099eae9026369f558e73b2a7e35860962d9d

diff --git a/urcu/static/wfstack.h b/urcu/static/wfstack.h
new file mode 100644
index 0000000..ff18c4a
--- /dev/null
+++ b/urcu/static/wfstack.h
@@ -0,0 +1,121 @@
+#ifndef _URCU_WFSTACK_STATIC_H
+#define _URCU_WFSTACK_STATIC_H
+
+/*
+ * wfstack-static.h
+ *
+ * Userspace RCU library - Stack with Wait-Free push, Blocking pop.
+ *
+ * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See wfstack.h for linking
+ * dynamically with the userspace rcu library.
+ *
+ * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <pthread.h>
+#include <assert.h>
+#include <poll.h>
+#include <urcu/compiler.h>
+#include <urcu/uatomic_arch.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define CDS_WF_STACK_END			((void *)0x1UL)
+#define CDS_WFS_ADAPT_ATTEMPTS		10	/* Retry if being set */
+#define CDS_WFS_WAIT			10	/* Wait 10 ms if being set */
+
+void _cds_wfs_node_init(struct cds_wfs_node *node)
+{
+	node->next = NULL;
+}
+
+void _cds_wfs_init(struct cds_wfs_stack *s)
+{
+	int ret;
+
+	s->head = CDS_WF_STACK_END;
+	ret = pthread_mutex_init(&s->lock, NULL);
+	assert(!ret);
+}
+
+void _cds_wfs_push(struct cds_wfs_stack *s, struct cds_wfs_node *node)
+{
+	struct cds_wfs_node *old_head;
+
+	assert(node->next == NULL);
+	/*
+	 * uatomic_xchg() implicit memory barrier orders earlier stores to node
+	 * (setting it to NULL) before publication.
+	 */
+	old_head = uatomic_xchg(&s->head, node);
+	/*
+	 * At this point, dequeuers see a NULL node->next, they should busy-wait
+	 * until node->next is set to old_head.
+	 */
+	CMM_STORE_SHARED(node->next, old_head);
+}
+
+/*
+ * Returns NULL if stack is empty.
+ */
+struct cds_wfs_node *
+___cds_wfs_pop_blocking(struct cds_wfs_stack *s)
+{
+	struct cds_wfs_node *head, *next;
+	int attempt = 0;
+
+retry:
+	head = CMM_LOAD_SHARED(s->head);
+	if (head == CDS_WF_STACK_END)
+		return NULL;
+	/*
+	 * Adaptative busy-looping waiting for push to complete.
+	 */
+	while ((next = CMM_LOAD_SHARED(head->next)) == NULL) {
+		if (++attempt >= CDS_WFS_ADAPT_ATTEMPTS) {
+			poll(NULL, 0, CDS_WFS_WAIT);	/* Wait for 10ms */
+			attempt = 0;
+		} else
+			caa_cpu_relax();
+	}
+	if (uatomic_cmpxchg(&s->head, head, next) == head)
+		return head;
+	else
+		goto retry;		/* Concurrent modification. Retry. */
+}
+
+struct cds_wfs_node *
+_cds_wfs_pop_blocking(struct cds_wfs_stack *s)
+{
+	struct cds_wfs_node *retnode;
+	int ret;
+
+	ret = pthread_mutex_lock(&s->lock);
+	assert(!ret);
+	retnode = ___cds_wfs_pop_blocking(s);
+	ret = pthread_mutex_unlock(&s->lock);
+	assert(!ret);
+	return retnode;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _URCU_WFSTACK_STATIC_H */