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Cygwin: pty: Fix a race issue in startup of pseudo console.

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- 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.
This commit is contained in:
Takashi Yano via Cygwin-patches 2021-03-04 17:56:34 +09:00 committed by Corinna Vinschen
parent 182ba1f022
commit 919dea66d3
1 changed files with 12 additions and 4 deletions
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16
winsup/cygwin/fhandler_tty.cc
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@ -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) if (isHybrid)
return; 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 ()->pcon_pid = 0;
get_ttyp ()->switch_to_pcon_in = false; get_ttyp ()->switch_to_pcon_in = false;
get_ttyp ()->pcon_activated = false; get_ttyp ()->pcon_activated = false;
ReleaseMutex (pcon_mutex);
} }
ssize_t __stdcall ssize_t __stdcall
@ -3538,6 +3543,7 @@ fhandler_pty_slave::term_has_pcon_cap (const WCHAR *env)
goto maybe_dumb; goto maybe_dumb;
/* Check if terminal has CSI6n */ /* Check if terminal has CSI6n */
WaitForSingleObject (pcon_mutex, INFINITE);
WaitForSingleObject (input_mutex, INFINITE); WaitForSingleObject (input_mutex, INFINITE);
/* Set pcon_activated and pcon_start so that the response /* Set pcon_activated and pcon_start so that the response
will sent to io_handle rather than io_handle_cyg. */ 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); while (len);
get_ttyp ()->pcon_activated = false; get_ttyp ()->pcon_activated = false;
get_ttyp ()->pcon_pid = 0; get_ttyp ()->pcon_pid = 0;
ReleaseMutex (pcon_mutex);
if (len == 0) if (len == 0)
goto not_has_csi6n; goto not_has_csi6n;
@ -3588,6 +3595,7 @@ not_has_csi6n:
get_ttyp ()->pcon_start = false; get_ttyp ()->pcon_start = false;
get_ttyp ()->pcon_activated = false; get_ttyp ()->pcon_activated = false;
ReleaseMutex (input_mutex); ReleaseMutex (input_mutex);
ReleaseMutex (pcon_mutex);
maybe_dumb: maybe_dumb:
get_ttyp ()->pcon_cap_checked = true; get_ttyp ()->pcon_cap_checked = true;
return false; return false;