Re: dialog --pause not timing out on serial console (dialog 1.2)

[Thomas Dickey]

On Thu, Jul 15, 2021 at 10:26:40AM +0300, Stefan Puiu wrote:
> Hi Thomas,
> 
> On Wed, Jul 14, 2021 at 11:37 PM Thomas Dickey <dickey@his.com> wrote:
> [...]
> > > Somebody managed to reproduce this again, and this time I debugged
> > > dialog a bit with gdb, and it seems to be stuck inside a tcsetattr
> > > call:
> > >
> > > (gdb) bt
> > > #0  0x0000003b96aeb5cc in __GI_tcsetattr (fd=1,
> > > optional_actions=optional_actions@entry=1,
> > >     termios_p=termios_p@entry=0x7fff17feba40) at
> > > ../sysdeps/unix/sysv/linux/tcsetattr.c:83
> > > #1  0x0000003b98e1677a in _nc_set_tty_mode
> > > (buf=buf@entry=0x7fff17feba40) at
> > > ../../ncurses/tinfo/lib_ttyflags.c:108
> > > #2  0x0000003b98e10d8c in cbreak () at ../../ncurses/tinfo/lib_raw.c:155
> > > #3  0x0000003b97214f33 in _nc_initscr () at 
> > > ../../ncurses/base/lib_newterm.c:79
> >
> > hmm - ncurses kind of expects the system to return an error :-)
> >
> > perhaps the serial I/O driver isn't that cooperative.
> >
> > If that happened often enough, I'd have some code to do a sanity check
> > on "tty" to make sure the initialization wouldn't hang.
> 
> This hang doesn't seem to reproduce consistently, unfortunately. As
> far as I can tell, most times dialog runs fine. Also, even when it
> hangs, hooking up the serial console through software unblocks it. Is
> there a way to find what is the serial driver used here? It would've
> been good to have tried to print hung tasks using the magic sysrq key,
> but it didn't occur to me to do that while the problem was reproduced.

It's probably done entirely in the kernel (debugging kernel modules takes
a lot of time).

-- 
Thomas E. Dickey <dickey@invisible-island.net>
https://invisible-island.net
ftp://ftp.invisible-island.net

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