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From: Takashi Yano <>
Subject: [newlib-cygwin] Cygwin: pty: Prevent deadlock on echo output.
Date: Sun, 13 Feb 2022 15:18:39 +0000 (GMT)	[thread overview]
Message-ID: <> (raw);h=bddd9c1c417e97791c44241cf94753e90464501c

commit bddd9c1c417e97791c44241cf94753e90464501c
Author: Takashi Yano <>
Date:   Thu Feb 10 17:22:11 2022 +0900

    Cygwin: pty: Prevent deadlock on echo output.
    - If the slave process writes a lot of text output, doecho() can
      cause deadlock. This is because output_mutex is held in slave::
      write() and if WriteFile() is blocked due to pipe full, doecho()
      tries to acquire output_mutex and gets into deadlock. With this
      patch, the deadlock is prevented on the sacrifice of atomicity
      of doecho().

 winsup/cygwin/ | 2 --
 1 file changed, 2 deletions(-)

diff --git a/winsup/cygwin/ b/winsup/cygwin/
index 7bef6958c..7e065c46a 100644
--- a/winsup/cygwin/
+++ b/winsup/cygwin/
@@ -496,11 +496,9 @@ void
 fhandler_pty_master::doecho (const void *str, DWORD len)
   ssize_t towrite = len;
-  acquire_output_mutex (mutex_timeout);
   if (!process_opost_output (echo_w, str, towrite, true,
 			     get_ttyp (), is_nonblocking ()))
     termios_printf ("Write to echo pipe failed, %E");
-  release_output_mutex ();

                 reply	other threads:[~2022-02-13 15:18 UTC|newest]

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