eventfd - allow atomic read and waitqueue remove
KVM needs a wait to atomically remove themselves from the eventfd ->poll()
wait queue head, in order to handle correctly their IRQfd deassign
operation.
This patch introduces such API, plus a way to read an eventfd from its
context.
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h
index 94dd103..91bb4f2 100644
--- a/include/linux/eventfd.h
+++ b/include/linux/eventfd.h
@@ -10,6 +10,7 @@
#include <linux/fcntl.h>
#include <linux/file.h>
+#include <linux/wait.h>
/*
* CAREFUL: Check include/asm-generic/fcntl.h when defining
@@ -34,6 +35,9 @@
struct eventfd_ctx *eventfd_ctx_fdget(int fd);
struct eventfd_ctx *eventfd_ctx_fileget(struct file *file);
int eventfd_signal(struct eventfd_ctx *ctx, int n);
+ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait, __u64 *cnt);
+int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_t *wait,
+ __u64 *cnt);
#else /* CONFIG_EVENTFD */
@@ -61,6 +65,18 @@
}
+static inline ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait,
+ __u64 *cnt)
+{
+ return -ENOSYS;
+}
+
+static inline int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx,
+ wait_queue_t *wait, __u64 *cnt)
+{
+ return -ENOSYS;
+}
+
#endif
#endif /* _LINUX_EVENTFD_H */