https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=20ddde2f552afedf7ef662bb21fec7a56f50040f

commit 20ddde2f552afedf7ef662bb21fec7a56f50040f
Author: Corinna Vinschen <cori...@vinschen.de>
Date:   Mon Jan 11 10:36:33 2016 +0100

    select(2): Drop checking descriptors in case of immediate timeout.
    
        * select.cc (select): Call sel.poll only if sel.wait returned
        select_ok.
    
    Signed-off-by: Corinna Vinschen <cori...@vinschen.de>

Diff:
---
 winsup/cygwin/select.cc | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
index b4c3778..fa6859c 100644
--- a/winsup/cygwin/select.cc
+++ b/winsup/cygwin/select.cc
@@ -189,12 +189,17 @@ select (int maxfds, fd_set *readfds, fd_set *writefds, 
fd_set *exceptfds,
          UNIX_FD_ZERO (readfds, maxfds);
          UNIX_FD_ZERO (writefds, maxfds);
          UNIX_FD_ZERO (exceptfds, maxfds);
-         /* Set bit mask from sel records even in case of a timeout so we
-            don't miss one.  This also sets ret to the right value >= 0,
-            matching the number of bits set in the fds records. */
-         ret = sel.poll (readfds, writefds, exceptfds);
-         if (!ret && res != select_stuff::select_set_zero)
-           res = select_stuff::select_loop;
+         if (res == select_stuff::select_set_zero)
+           ret = 0;
+         else
+           {
+             /* Set bit mask from sel records.  This also sets ret to the
+                right value >= 0, matching the number of bits set in the
+                fds records.  if ret is 0, continue to loop. */
+             ret = sel.poll (readfds, writefds, exceptfds);
+             if (!ret)
+               res = select_stuff::select_loop;
+           }
        }
       /* Always clean up everything here.  If we're looping then build it
         all up again.  */

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