Re: multi-threaded serial I/O patch

[Christopher Faylor <cgf at redhat dot com>]

If I understand what you're doing, it seems like you've goten rid of the
need for detecting 'overlapped_armed'.  This was supposed to signify that
overlapped I/O was present with the standard "io_status" structure.

Since you're (correctly) not using this anymore, I think I will apply your
patch and get rid of the overlapped_armed assumptions.

Thanks for the patch!

cgf

On Mon, Jan 29, 2001 at 05:28:20PM -0800, Bill Hegardt wrote:
>
>Attached is a patch and ChangeLog entry for the multi-threaded serial
>I/O problem I fixed.
>
>Mon Jan 29 17:15:22 2001  Bill Hegardt <bill@troyxcd.com>
>
>        * fhandler_serial.cc (raw_write): Use local copy of OVERLAPPED
>structure instead of io_status which was shared
>		with the raw_read routine resulting in a race condition.
>--- fhandler_serial.original	Fri Jan 19 16:22:00 2001
>+++ fhandler_serial.cc	Mon Jan 29 16:47:32 2001
>@@ -161,15 +161,19 @@ int
> fhandler_serial::raw_write (const void *ptr, size_t len)
> {
>   DWORD bytes_written;
>+  OVERLAPPED osWrite;
>+
>+  memset (&osWrite, 0, sizeof (osWrite));
>+  osWrite.hEvent = CreateEvent (&sec_none_nih, TRUE, FALSE, NULL);
>+  ProtectHandle (osWrite.hEvent);
> 
>   if (overlapped_armed)
>     PurgeComm (get_handle (), PURGE_TXABORT | PURGE_RXABORT);
>-  ResetEvent (io_status.hEvent);
> 
>   for (;;)
>     {
>       overlapped_armed = TRUE;
>-      if (WriteFile (get_handle(), ptr, len, &bytes_written, &io_status))
>+      if (WriteFile (get_handle(), ptr, len, &bytes_written, &osWrite))
> 	break;
> 
>       switch (GetLastError ())
>@@ -182,16 +186,19 @@ fhandler_serial::raw_write (const void *
> 	    goto err;
> 	}
> 
>-      if (!GetOverlappedResult (get_handle (), &io_status, &bytes_written, TRUE))
>+      if (!GetOverlappedResult (get_handle (), &osWrite, &bytes_written, TRUE))
> 	goto err;
> 
>       break;
>     }
> 
>+  CloseHandle(osWrite.hEvent);
>+ 
>   overlapped_armed = FALSE;
>   return bytes_written;
> 
> err:
>+  CloseHandle(osWrite.hEvent);
>   __seterrno ();
>   return -1;
> }


-- 
cgf@cygnus.com                        Red Hat, Inc.
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