verify backend fudge factors by reading kernel sources

Changes

@@ -5,6 +5,9 @@ TODO: ev_loop_wakeup
 TODO: confusion about threads ongiong
 TODO: not_blocked flag.
 
+	- correct backend_fudge for most backends, and implement a windows
+          specific workaround to avoid looping because we call both
+          select and Sleep, both with different time resolutions.
 	- change the default periodic reschedule function to hopefully be more
           exact and correct even in corner cases or in the far future.
         - document reasonable ranges for interval and offset.

ev_epoll.c

@@ -234,7 +234,7 @@ epoll_init (EV_P_ int flags)
 
   fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
 
-  backend_fudge  = 0.; /* kernel sources seem to indicate this to be zero */
+  backend_fudge  = 1./1024.; /* epoll does sometimes return early, this is just to avoid the worst */
   backend_modify = epoll_modify;
   backend_poll   = epoll_poll;
 

ev_kqueue.c

@@ -161,7 +161,7 @@ kqueue_init (EV_P_ int flags)
 
   fcntl (backend_fd, F_SETFD, FD_CLOEXEC); /* not sure if necessary, hopefully doesn't hurt */
 
-  backend_fudge  = 0.;
+  backend_fudge  = 1e-9; /* apparently, they did the right thing in freebsd */
   backend_modify = kqueue_modify;
   backend_poll   = kqueue_poll;
 

ev_poll.c

@@ -129,7 +129,7 @@ poll_poll (EV_P_ ev_tstamp timeout)
 int inline_size
 poll_init (EV_P_ int flags)
 {
-  backend_fudge  = 0.; /* posix says this is zero */
+  backend_fudge  = 1e-3;
   backend_modify = poll_modify;
   backend_poll   = poll_poll;
 

ev_select.c

@@ -195,7 +195,12 @@ select_poll (EV_P_ ev_tstamp timeout)
        */
       if (errno == EINVAL)
         {
-          ev_sleep (timeout);
+          if (timeout)
+            {
+              unsigned long ms = timeout * 1e3;
+              Sleep (ms ? ms : 1);
+            }
+
           return;
         }
       #endif
@@ -269,7 +274,7 @@ select_poll (EV_P_ ev_tstamp timeout)
 int inline_size
 select_init (EV_P_ int flags)
 {
-  backend_fudge  = 0.; /* posix says this is zero */
+  backend_fudge  = 1e-6;
   backend_modify = select_modify;
   backend_poll   = select_poll;
 
@@ -307,4 +312,3 @@ select_destroy (EV_P)
   #endif
 }
 
-