From f2ed2d7b32a2b1e1cf5e5e0e2bd92f3d66c3d264 Mon Sep 17 00:00:00 2001
From: Andy Wingo <wingo@pobox.com>
Date: Wed, 15 Feb 2017 21:11:52 +0100
Subject: Add epoll-add*!

* fibers/epoll.scm (epoll-add*!): New function, tries an epoll-modify!
  then falls back to epoll-add!.
---
 fibers/epoll.scm | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fibers/epoll.scm b/fibers/epoll.scm
index 20d92ae..d4674a7 100644
--- a/fibers/epoll.scm
+++ b/fibers/epoll.scm
@@ -31,6 +31,7 @@
             epoll?
             epoll-add!
             epoll-modify!
+            epoll-add*!
             epoll-remove!
             epoll-wake!
             epoll
@@ -111,9 +112,15 @@
 (define (epoll-add! epoll fd events)
   (primitive-epoll-ctl (epoll-fd epoll) EPOLL_CTL_ADD fd events))
 
-(define* (epoll-modify! epoll fd events)
+(define (epoll-modify! epoll fd events)
   (primitive-epoll-ctl (epoll-fd epoll) EPOLL_CTL_MOD fd events))
 
+(define (epoll-add*! epoll fd events)
+  (catch 'system-error
+    (lambda () (epoll-modify! epoll fd events))
+    (lambda _
+      (epoll-add! epoll fd events))))
+
 (define (epoll-remove! epoll fd)
   (primitive-epoll-ctl (epoll-fd epoll) EPOLL_CTL_DEL fd))
 
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