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From: Takashi Yano <takashi.yano@nifty.ne.jp>
To: cygwin-patches@cygwin.com
Subject: [PATCH 3/8] Cygwin: pty: Prevent deadlock on echo output.
Date: Sun, 13 Feb 2022 23:39:05 +0900	[thread overview]
Message-ID: <20220213143910.1947-4-takashi.yano@nifty.ne.jp> (raw)
In-Reply-To: <20220213143910.1947-1-takashi.yano@nifty.ne.jp>

- 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/fhandler_tty.cc | 2 --
 1 file changed, 2 deletions(-)

diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index 7bef6958c..7e065c46a 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -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 ();
 }
 
 int
-- 
2.35.1


  parent reply	other threads:[~2022-02-13 14:40 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-13 14:39 [PATCH 0/8] Several modifications for pty and console code Takashi Yano
2022-02-13 14:39 ` [PATCH 1/8] Cygwin: pty, console: Fix Ctrl-C handling for non-cygwin apps Takashi Yano
2022-02-13 14:39 ` [PATCH 2/8] Cygwin: pty: Pass Ctrl-Z (EOF) to non-cygwin apps with disable_pcon Takashi Yano
2022-02-13 14:39 ` Takashi Yano [this message]
2022-02-13 14:39 ` [PATCH 4/8] Cygwin: pty: Revise the code to wait for completion of forwarding Takashi Yano
2022-02-13 14:39 ` [PATCH 5/8] Cygwin: pty: Discard input in from_master_nat pipe on signal as well Takashi Yano
2022-02-13 14:39 ` [PATCH 6/8] Cygwin: pty: Fix a bug in tty_min::segpgid() Takashi Yano
2022-02-13 14:39 ` [PATCH 7/8] Cygwin: console: Fix console mode for non-cygwin inferior of GDB Takashi Yano
2022-02-13 14:39 ` [PATCH 8/8] Cygwin: console: Set console mode even if stdin/stdout is redirected Takashi Yano

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