console: fix deadlock in pcon teardown#134
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When a process inside a pseudo console (pcon) exits, the sequence was:
exit()
-> atexit handlers (including pcon_hand_over_proc)
pcon_hand_over_proc closes parent_pty_input_mutex
-- handle slot now free to be recycled --
-> _exit() -> do_exit() -> close_all_files() -> fhandler_console::close()
set_input_mode() waits on input_mutex <-- hangs
The fix, suggested by Takashi Yano: remove the atexit registration
entirely and instead call pcon_hand_over_proc() directly from
fhandler_console::close(), after both input_mutex and output_mutex
have been closed. By that point close() has already waited for
cons_master_thread to exit, so parent_pty_input_mutex is no longer
accessed by any other thread and can be safely closed.
Fixes: msys2/msys2-runtime#338
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Let's synchronize Git for Windows' fork of the MSYS2 runtime with the MSYS2 upstream, to benefit from the pcon teardown fix. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
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/open pr The workflow run was started |
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When a process inside a pseudo console (pcon) exits, the sequence was:
exit()
-> atexit handlers (including pcon_hand_over_proc)
pcon_hand_over_proc closes parent_pty_input_mutex
-- handle slot now free to be recycled --
-> _exit() -> do_exit() -> close_all_files() -> fhandler_console::close()
set_input_mode() waits on input_mutex <-- hangs
The fix, suggested by Takashi Yano: remove the atexit registration entirely and instead call pcon_hand_over_proc() directly from fhandler_console::close(), after both input_mutex and output_mutex have been closed. By that point close() has already waited for cons_master_thread to exit, so parent_pty_input_mutex is no longer accessed by any other thread and can be safely closed.
This closes git-for-windows/git#6257