ssh-add -l hangs under cygwin test 3.6.0-0.139.g...

[Takashi Yano]

On Sun, 30 Jun 2024 20:33:19 +0900
jojelino wrote:
> On 6/29/2024 2:39 PM, Brian Inglis via Cygwin wrote:
> > Reran cygport --debug upload and command hanging was ssh-add -l!
> > 
>    296   72109 [main] ssh-add 63275 win32env_to_cygenv: 0xA000232E0: 
> TERM_PROGRAM=mintty
>    189   72298 [main] ssh-add 63275 win32env_to_cygenv: 0xA00023300: 
> TERM_PROGRAM_VERSION=3.7.1
> 
> I was able to reproduce this problem by entering below command with 
> ffmpeg from https://www.gyan.dev/ffmpeg/builds/ , this ffmpeg build 
> spams putc. So, without piping its output to `tee', It would not 
> possible track down any cause among lengthy trace output.
> 
> strace mintty -e /bin/timeout 10 sh -c './ffmpeg -h full|& tee'
> 
> In summary, When `timeout' expires, `timeout' signals SIGHUP to pgrp of 
> itself, btw some member of the pgrp may have acquired any of 
> synchronization object of some part of cygwin internal when a member 
> process of the pgrp did encounter the signal interrupt from `timeout'. 
> In my case it was output_mutex of pty.
> 
>   1565 10693297 [main] timeout 745 kill_pgrp: pid 0, signal 15
>   2701 15224348 [main] mintty 744 
> fhandler_pty_master::process_slave_output: bytes read 256
>   1736 9525442 [sig] sh 746 proc_subproc: args: 4, 1
>   3137 6700294 [main] tee 748 fhandler_pty_slave::write: pty5, 
> write(0x7FFFFC780, 1024)
>   1347 9526789 [sig] sh 746 proc_subproc: clear waiting threads
>   2084 15226432 [main] mintty 744 
> fhandler_pty_master::process_slave_output: returning 256
>   1110 6701404 [main] tee 748 fhandler_pty_slave::write: (1267): pty 
> output_mutex (0x4C0): waiti
> -1 ms
>    732 9527521 [sig] sh 746 checkstate: child_procs count 2
>   3648 10696945 [main] timeout 745 open_shared: name cygpid.724, shared 
> 0x1A0050000 (wanted 0x1A
> 0000), h 0x16C, m 6, created 0
>   1055 6702459 [main] tee 748 fhandler_pty_slave::write: (1267): pty 
> output_mutex: acquired
> 
>   2092 15753306 [main] mintty 744 fhandler_pty_master::close: (2095): 
> pty output_mutex (0x4AC):
> ting -1 ms
> 
> And below is a location where `tee' did hang.
> 
> #3  0x00007ffd0e408fdf in fhandler_pty_slave::write (this=0x800009a10,
>      ptr=0x7ffffc780, len=<optimized out>)
>      at ../../.././winsup/cygwin/fhandler/pty.cc:1268
> 1268      if (!process_opost_output (get_output_handle (), ptr, towrite, 
> false,
> (gdb)  li
> 1263      termios_printf ("pty%d, write(%p, %lu)", get_minor (), ptr, len);
> 1264
> 1265      push_process_state process_state (PID_TTYOU);
> 1266
> 1267      acquire_output_mutex (mutex_timeout);
> 1268      if (!process_opost_output (get_output_handle (), ptr, towrite, 
> false,
> 1269                                 get_ttyp (), is_nonblocking ()))
> 
> 
> I ended up prepending two CancelIo call just above of 
> acquire_output_mutex located in fhandler_pty_master::close of pty.cc.
> 
>  >	  CancelIo(get_ttyp()->to_master());
>  >	  CancelIo(get_ttyp()->to_master_nat());
> 	  acquire_output_mutex (mutex_timeout);
> 
> Hope it helps

I cannot reproduce the issue.

1) Which cygwin version do you use?
2) Is this really the same problem with the problem original post reported?
   (i.e. reproducible with 3.6.0-0.139 and not reproduced with 3.5.3)

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>