bug#28192: TRAMP: Sometimes hangs, sometimes not

[Michael Albinus <michael.albinus@gmx.de>]

Alexander Shukaev <emacs@Alexander.Shukaev.name> writes:

> Hi everyone and Michael,

Hi Alexander,

> I observe weird behavior with TRAMP.  Sometimes it hangs, and
> sometimes performing the same action, it does not.  Let me expand with
> the example.  First see the attached backtrace of a hang ('hang.bt')
> and then see the attached debug of a hang ('hang.debug').  Notice how
> I waited for almost 3 minutes until eventually pressing <C-g> to
> generate the backtrace and as soon as I exited the backtrace buffer,
> the last line
>
> 00:36:39.418776 tramp-maybe-open-connection (3) # Opening connection
> for root@g75vw using sudo...failed
>
> got printed in the debug buffer.
>
> What looks peculiar is this bit:
>
> 00:32:56.556463 tramp-send-command (6) # test -d /usr/bin 2>/dev/null;
> echo tramp_exit_status $?
> 00:32:57.493123 tramp-send-command (6) # test -e /\*scratch\*
> 2>/dev/null; echo tramp_exit_status $?
> 00:32:57.567582 tramp-wait-for-regexp (6) #
> tramp_exit_status 1
> ///deee5cb9d3522d2a1faeef9e0327d4f1#$
> 00:33:57.490307 tramp-send-command (6) # test -e /\*scratch\*
> 2>/dev/null; echo tramp_exit_status $?
> 00:33:57.491565 tramp-wait-for-regexp (6) #
> tramp_exit_status 1
> ///deee5cb9d3522d2a1faeef9e0327d4f1#$
>
> That is where did the status of '/usr/bin' test go?  And why on earth
> would '*scratch*' be tested?  I verified and files like with
> '*scratch*' names of course do not exist.  It looks like TRAMP hangs
> after these tests.

There are even more dubious tests. See for example

> 00:21:44.114726 tramp-send-command (6) # test -e /\>copy-region-as-kill 2>/dev/null; echo tramp_exit_status $?

I doubt, that you have a file "/>copy-region-as-kill".

> Phew...  Any ideas where to start looking?

Does the same problem happen if you start

# emacs -Q --eval '(setq tramp-verbose 6)'

> Regards,
> Alexander

Best regards, Michael.