lib9p_srv: Re-think flush semantics

1 files changed, 16 insertions, 0 deletions

diff --git a/libcr_ipc/include/libcr_ipc/chan.h b/libcr_ipc/include/libcr_ipc/chan.h
index 79be220..853b4ad 100644
--- a/libcr_ipc/include/libcr_ipc/chan.h
+++ b/libcr_ipc/include/libcr_ipc/chan.h
@@ -97,9 +97,25 @@
 	       (CH)->core.waiters.front->val.op == _CR_SELECT_OP_SEND); \
 })
 
+/**
+ * cr_chan_num_waiters(ch) returns the number of coroutines currently
+ * blocked on the channel.
+ *
+ * @runs_in coroutine
+ * @cr_pauses never
+ * @cr_yields never
+ *
+ * size_t cr_chan_num_waiters(NAME##_t *ch);
+ */
+#define cr_chan_num_waiters(CH) ({ \
+	cr_assert_in_coroutine();  \
+	((CH)->core.nwaiters);     \
+})
+
 DLIST_DECLARE(_cr_select_arg_list);
 struct _cr_chan {
 	struct _cr_select_arg_list   waiters;
+	size_t                       nwaiters;
 };
 
 /* cr_select arguments ********************************************************/