[newlib-cygwin] Cygwin: pty: Fix a race issue in startup of pseudo console.
Corinna Vinschen
corinna@sourceware.org
Fri Mar 5 15:12:02 GMT 2021
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=919dea66d3ca17eac4aa08d4156516feb165ec82
commit 919dea66d3ca17eac4aa08d4156516feb165ec82
Author: Takashi Yano via Cygwin-patches <cygwin-patches@cygwin.com>
Date: Thu Mar 4 17:56:34 2021 +0900
Cygwin: pty: Fix a race issue in startup of pseudo console.
- If two non-cygwin apps are started simultaneously and this is the
first execution of non-cygwin apps in the pty, these occasionally
hang up. The cause is the race issue between term_has_pcon_cap(),
reset_switch_to_pcon() and setup_pseudoconsole(). This patch fixes
the issue.
Diff:
---
winsup/cygwin/fhandler_tty.cc | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index 3fcaa8277..930501d01 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -1118,15 +1118,20 @@ fhandler_pty_slave::reset_switch_to_pcon (void)
}
}
}
- if (get_ttyp ()->pcon_pid && get_ttyp ()->pcon_pid != myself->pid
- && !!pinfo (get_ttyp ()->pcon_pid))
- /* There is a process which is grabbing pseudo console. */
- return;
if (isHybrid)
return;
+ WaitForSingleObject (pcon_mutex, INFINITE);
+ if (get_ttyp ()->pcon_pid && get_ttyp ()->pcon_pid != myself->pid
+ && !!pinfo (get_ttyp ()->pcon_pid))
+ {
+ /* There is a process which is grabbing pseudo console. */
+ ReleaseMutex (pcon_mutex);
+ return;
+ }
get_ttyp ()->pcon_pid = 0;
get_ttyp ()->switch_to_pcon_in = false;
get_ttyp ()->pcon_activated = false;
+ ReleaseMutex (pcon_mutex);
}
ssize_t __stdcall
@@ -3538,6 +3543,7 @@ fhandler_pty_slave::term_has_pcon_cap (const WCHAR *env)
goto maybe_dumb;
/* Check if terminal has CSI6n */
+ WaitForSingleObject (pcon_mutex, INFINITE);
WaitForSingleObject (input_mutex, INFINITE);
/* Set pcon_activated and pcon_start so that the response
will sent to io_handle rather than io_handle_cyg. */
@@ -3573,6 +3579,7 @@ fhandler_pty_slave::term_has_pcon_cap (const WCHAR *env)
while (len);
get_ttyp ()->pcon_activated = false;
get_ttyp ()->pcon_pid = 0;
+ ReleaseMutex (pcon_mutex);
if (len == 0)
goto not_has_csi6n;
@@ -3588,6 +3595,7 @@ not_has_csi6n:
get_ttyp ()->pcon_start = false;
get_ttyp ()->pcon_activated = false;
ReleaseMutex (input_mutex);
+ ReleaseMutex (pcon_mutex);
maybe_dumb:
get_ttyp ()->pcon_cap_checked = true;
return false;
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