hrtime.h: add documentation

I updated the patch with documentation but forgot about it,
earlier :x

[ruby-core:88616] [Misc #15014]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64535 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 0 deletions

diff --git a/thread.c b/thread.c
index 79112b4968..a1d5ddee73 100644
--- a/thread.c
+++ b/thread.c
@@ -1155,6 +1155,11 @@ getclockofday(struct timespec *ts)
     rb_timespec_now(ts);
 }
 
+/*
+ * Don't inline this, since library call is already time consuming
+ * and we don't want "struct timespec" on stack too long for GC
+ */
+NOINLINE(rb_hrtime_t rb_hrtime_now(void));
 rb_hrtime_t
 rb_hrtime_now(void)
 {