(__select): Don't poll on the last call __io_select unless there's only a singl...

diff --git a/sysdeps/mach/hurd/select.c b/sysdeps/mach/hurd/select.c
index 188f65b3c090aef90820e205e32b1504055cdaa7..60bb489612b712ffd31146dfaf25eff9aff3b125 100644 (file)
--- a/sysdeps/mach/hurd/select.c
+++ b/sysdeps/mach/hurd/select.c
@@ -126,15 +126,22 @@ DEFUN(__select, (nfds, readfds, writefds, exceptfds, timeout),
        int type = d[i].type;
        d[i].reply_port = __mach_reply_port ();
        err = __io_select (d[i].io_port, d[i].reply_port,
-                          /* Poll for each but the last.  */
-                          (i == lastfd && got == 0) ? to : 0,
+                          /* Poll only when there's a single descriptor.  */
+                          (firstfd == lastfd) ? to : 0,
                           &type);
        switch (err)
          {
          case MACH_RCV_TIMED_OUT:
            /* No immediate response.  This is normal.  */
            err = 0;
-           if (got == 0)
+           if (firstfd == lastfd)
+             /* When there's a single descriptor, we don't need a portset,
+                so just pretend we have one, but really use the single reply
+                port.  */
+             portset = d[i].reply_port;
+           else if (got == 0)
+             /* We've got multiple reply ports, so we need a port set to
+                multiplex them.  */
              {
                /* We will wait again for a reply later.  */
                if (portset == MACH_PORT_NULL)
@@ -276,7 +283,10 @@ DEFUN(__select, (nfds, readfds, writefds, exceptfds, timeout),
   for (i = firstfd; i <= lastfd; ++i)
     if (d[i].type)
       __mach_port_destroy (__mach_task_self (), d[i].reply_port);
-  if (portset != MACH_PORT_NULL)
+  if (firstfd != lastfd && portset != MACH_PORT_NULL)
+    /* Destroy PORTSET, but only if it's not actually the reply port for a
+       single descriptor (in which case it's destroyed in the previous loop;
+       not doing it here is just a bit more efficient).  */
     __mach_port_destroy (__mach_task_self (), portset);
 
   if (err)