Wait queues, allowing conditional sleep in hypervisor context.

Signed-off-by: Keir Fraser <keir@xen.org>

1 files changed, 54 insertions, 0 deletions

diff --git a/xen/include/xen/wait.h b/xen/include/xen/wait.h
new file mode 100644
index 0000000000..c1793fd304
--- /dev/null
+++ b/xen/include/xen/wait.h
@@ -0,0 +1,54 @@
+/******************************************************************************
+ * wait.h
+ * 
+ * Sleep in hypervisor context for some event to occur.
+ */
+
+#ifndef __XEN_WAIT_H__
+#define __XEN_WAIT_H__
+
+#include <xen/types.h>
+#include <xen/list.h>
+#include <xen/spinlock.h>
+
+struct waitqueue_head {
+    spinlock_t lock;
+    struct list_head list;
+};
+
+/* Statically define and initialise a waitqueue. */
+#define DEFINE_WAITQUEUE_HEAD(name)             \
+    struct waitqueue_head name = {              \
+        .lock = SPIN_LOCK_UNLOCKED,             \
+        .list = LIST_HEAD_INIT((name).list)     \
+    }
+
+/* Dynamically initialise a waitqueue. */
+void init_waitqueue_head(struct waitqueue_head *wq);
+
+/* Wake all VCPUs waiting on specified waitqueue. */
+void wake_up(struct waitqueue_head *wq);
+
+/* Wait on specified waitqueue until @condition is true. */
+#define wait_event(wq, condition)               \
+do {                                            \
+    if ( condition )                            \
+        break;                                  \
+    for ( ; ; ) {                               \
+        prepare_to_wait(&wq);                   \
+        if ( condition )                        \
+            break;                              \
+        wait();                                 \
+    }                                           \
+    finish_wait(&wq);                           \
+} while (0)
+
+/* Private functions. */
+int init_waitqueue_vcpu(struct vcpu *v);
+void destroy_waitqueue_vcpu(struct vcpu *v);
+void prepare_to_wait(struct waitqueue_head *wq);
+void wait(void);
+void finish_wait(struct waitqueue_head *wq);
+void check_wakeup_from_wait(void);
+
+#endif /* __XEN_WAIT_H__ */