[newlib-cygwin] Cygwin: select: Speed up select() call for pty, pipe and fifo.

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=a1c7e920845ab21185f18950be3d84f4312222de

commit a1c7e920845ab21185f18950be3d84f4312222de
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date:   Mon Jan 6 23:38:34 2020 +0900

    Cygwin: select: Speed up select() call for pty, pipe and fifo.
    
    - The slowing down issue of X11 forwarding using ssh -Y, reported
      in https://www.cygwin.com/ml/cygwin/2019-12/msg00295.html,
      is due to the change of select() code for pty in the commit
      915fcd0ae8d83546ce135131cd25bf6795d97966. cygthread::detach()
      takes at most about 10msec because Sleep() is used in the thread.
      For this issue, this patch uses cygwait() instead of Sleep() and
      introduces an event to abort the wait. For not only pty, but pipe
      and fifo also have the same problem potentially, so this patch
      applies same strategy to them as well.

Diff:
---
 winsup/cygwin/select.cc | 15 ++++++++++++---
 winsup/cygwin/select.h  |  1 +
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
index e701442..b3aedf2 100644
--- a/winsup/cygwin/select.cc
+++ b/winsup/cygwin/select.cc
@@ -744,7 +744,7 @@ thread_pipe (void *arg)
 	  }
       if (!looping)
 	break;
-      Sleep (sleep_time >> 3);
+      cygwait (pi->bye, sleep_time >> 3);
       if (sleep_time < 80)
 	++sleep_time;
       if (pi->stop_thread)
@@ -763,6 +763,7 @@ start_thread_pipe (select_record *me, select_stuff *stuff)
     {
       pi->start = &stuff->start;
       pi->stop_thread = false;
+      pi->bye = CreateEvent (&sec_none_nih, TRUE, FALSE, NULL);
       pi->thread = new cygthread (thread_pipe, pi, "pipesel");
       me->h = *pi->thread;
       if (!me->h)
@@ -780,8 +781,10 @@ pipe_cleanup (select_record *, select_stuff *stuff)
   if (pi->thread)
     {
       pi->stop_thread = true;
+      SetEvent (pi->bye);
       pi->thread->detach ();
     }
+  CloseHandle (pi->bye);
   delete pi;
   stuff->device_specific_pipe = NULL;
 }
@@ -924,7 +927,7 @@ thread_fifo (void *arg)
 	  }
       if (!looping)
 	break;
-      Sleep (sleep_time >> 3);
+      cygwait (pi->bye, sleep_time >> 3);
       if (sleep_time < 80)
 	++sleep_time;
       if (pi->stop_thread)
@@ -943,6 +946,7 @@ start_thread_fifo (select_record *me, select_stuff *stuff)
     {
       pi->start = &stuff->start;
       pi->stop_thread = false;
+      pi->bye = CreateEvent (&sec_none_nih, TRUE, FALSE, NULL);
       pi->thread = new cygthread (thread_fifo, pi, "fifosel");
       me->h = *pi->thread;
       if (!me->h)
@@ -960,8 +964,10 @@ fifo_cleanup (select_record *, select_stuff *stuff)
   if (pi->thread)
     {
       pi->stop_thread = true;
+      SetEvent (pi->bye);
       pi->thread->detach ();
     }
+  CloseHandle (pi->bye);
   delete pi;
   stuff->device_specific_fifo = NULL;
 }
@@ -1279,7 +1285,7 @@ thread_pty_slave (void *arg)
 	  }
       if (!looping)
 	break;
-      Sleep (sleep_time >> 3);
+      cygwait (pi->bye, sleep_time >> 3);
       if (sleep_time < 80)
 	++sleep_time;
       if (pi->stop_thread)
@@ -1303,6 +1309,7 @@ pty_slave_startup (select_record *me, select_stuff *stuff)
     {
       pi->start = &stuff->start;
       pi->stop_thread = false;
+      pi->bye = CreateEvent (&sec_none_nih, TRUE, FALSE, NULL);
       pi->thread = new cygthread (thread_pty_slave, pi, "ptyssel");
       me->h = *pi->thread;
       if (!me->h)
@@ -1325,8 +1332,10 @@ pty_slave_cleanup (select_record *me, select_stuff *stuff)
   if (pi->thread)
     {
       pi->stop_thread = true;
+      SetEvent (pi->bye);
       pi->thread->detach ();
     }
+  CloseHandle (pi->bye);
   delete pi;
   stuff->device_specific_ptys = NULL;
 }
diff --git a/winsup/cygwin/select.h b/winsup/cygwin/select.h
index ae98c65..98fde3a 100644
--- a/winsup/cygwin/select.h
+++ b/winsup/cygwin/select.h
@@ -44,6 +44,7 @@ struct select_info
 {
   cygthread *thread;
   bool stop_thread;
+  HANDLE bye;
   select_record *start;
   select_info (): thread (NULL), stop_thread (0), start (NULL) {}
 };