[newlib-cygwin] Cygwin: pty: Fix a possible race issue in initialization of pcon.

Takashi Yano tyan0@sourceware.org
Fri Mar 4 13:37:43 GMT 2022


https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=51095fe2ba9d109e34251d7221fe0bf768ec749b

commit 51095fe2ba9d109e34251d7221fe0bf768ec749b
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date:   Fri Mar 4 22:02:35 2022 +0900

    Cygwin: pty: Fix a possible race issue in initialization of pcon.
    
    - Currently, tty::pcon_start flag is cleared before transfer_input()
      in master::write(), however, the code in setup_pseudoconsole()
      waits for transfer_input() using tty::pcon_start. This possibly
      causes the race issue. The patch fixes this potential issue.

Diff:
---
 winsup/cygwin/fhandler_tty.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index cba25ee84..3ed84709e 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -3215,7 +3215,8 @@ fhandler_pty_slave::setup_pseudoconsole ()
 	  get_ttyp ()->pcon_start_pid = myself->pid;
 	  WriteFile (get_output_handle (), "\033[6n", 4, &n, NULL);
 	  ReleaseMutex (input_mutex);
-	  while (get_ttyp ()->pcon_start)
+	  while (get_ttyp ()->pcon_start_pid)
+	    /* wait for completion of transfer_input() in master::write(). */
 	    Sleep (1);
 	}
       /* Attach to the pseudo console which already exits. */


More information about the Cygwin-cvs mailing list