[newlib-cygwin] Cygwin: FIFO: fix the use of the read_ready event

Corinna Vinschen corinna@sourceware.org
Tue Apr 16 11:16:00 GMT 2019


https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=6b20be09442d09e745d60e76dc680b8fd45d36ea

commit 6b20be09442d09e745d60e76dc680b8fd45d36ea
Author: Ken Brown <kbrown@cornell.edu>
Date:   Sun Apr 14 19:16:01 2019 +0000

    Cygwin: FIFO: fix the use of the read_ready event
    
    Make read_ready a manual reset event.  It should always be set shortly
    after startup of the listen_client thread and remain set until the
    thread terminates.  (We don't want writers to connect without being
    recorded in the client handler list.)
    
    Remove the unnecessary code that checks for read_ready when a reader
    is opening.

Diff:
---
 winsup/cygwin/fhandler_fifo.cc | 51 +++++++++++++-----------------------------
 1 file changed, 16 insertions(+), 35 deletions(-)

diff --git a/winsup/cygwin/fhandler_fifo.cc b/winsup/cygwin/fhandler_fifo.cc
index f9796f3..479021e 100644
--- a/winsup/cygwin/fhandler_fifo.cc
+++ b/winsup/cygwin/fhandler_fifo.cc
@@ -344,6 +344,8 @@ fhandler_fifo::listen_client ()
 DWORD
 fhandler_fifo::listen_client_thread ()
 {
+  DWORD ret = -1;
+
   while (1)
     {
       bool found;
@@ -360,7 +362,7 @@ fhandler_fifo::listen_client_thread ()
 	    if (disconnect_and_reconnect (i) < 0)
 	      {
 		fifo_client_unlock ();
-		goto errout;
+		goto out;
 	      }
 	    else
 	      /* Recheck fc_handler[i].state. */
@@ -383,23 +385,27 @@ fhandler_fifo::listen_client_thread ()
 	res = add_client_handler ();
       fifo_client_unlock ();
       if (res < 0)
-	goto errout;
+	goto out;
       else if (!found)
 	continue;
 
+      /* Allow a writer to open. */
       if (!arm (read_ready))
 	{
 	  __seterrno ();
-	  goto errout;
+	  goto out;
 	}
 
       /* Wait for a client to connect. */
       wait_ret = WaitForMultipleObjects (nhandlers + 1, w, false, INFINITE);
       i = wait_ret - WAIT_OBJECT_0;
       if (i < 0 || i > nhandlers)
-	goto errout;
-      else if (i == nhandlers)	/* Reader is closing. */
-	return 0;
+	goto out;
+      else if (i == nhandlers)	/* Thread termination requested. */
+	{
+	  ret = 0;
+	  goto out;
+	}
       else
 	{
 	  fifo_client_lock ();
@@ -410,9 +416,9 @@ fhandler_fifo::listen_client_thread ()
 	  yield ();
 	}
     }
-errout:
+out:
   ResetEvent (read_ready);
-  return -1;
+  return ret;
 }
 
 int
@@ -457,7 +463,7 @@ fhandler_fifo::open (int flags, mode_t)
 
   char npbuf[MAX_PATH];
   __small_sprintf (npbuf, "r-event.%08x.%016X", get_dev (), get_ino ());
-  if (!(read_ready = CreateEvent (sa_buf, duplexer, false, npbuf)))
+  if (!(read_ready = CreateEvent (sa_buf, true, false, npbuf)))
     {
       debug_printf ("CreateEvent for %s failed, %E", npbuf);
       res = error_set_errno;
@@ -523,32 +529,7 @@ fhandler_fifo::open (int flags, mode_t)
 	  res = error_errno_set;
 	  goto out;
 	}
-      /* Wait for the listen_client thread to signal read_ready.  This
-	 should be quick.  */
-      HANDLE w[2] = { listen_client_thr, read_ready };
-      switch (WaitForMultipleObjects (2, w, FALSE, INFINITE))
-	{
-	case WAIT_OBJECT_0:
-	  debug_printf ("listen_client_thread exited unexpectedly");
-	  DWORD err;
-	  GetExitCodeThread (listen_client_thr, &err);
-	  __seterrno_from_win_error (err);
-	  res = error_errno_set;
-	  goto out;
-	  break;
-	case WAIT_OBJECT_0 + 1:
-	  if (!arm (read_ready))
-	    {
-	      res = error_set_errno;
-	      goto out;
-	    }
-	  break;
-	default:
-	  res = error_set_errno;
-	  goto out;
-	  break;
-	}
-      if (!duplexer && !wait (write_ready))
+      else if (!duplexer && !wait (write_ready))
 	{
 	  res = error_errno_set;
 	  goto out;



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