Re: Killing a hung ssh process in a TRAMP session

[Michael Albinus]

Suvayu Ali <fatkasuvayu+linux@gmail.com> writes:

> Hi Michael,

Hi,

> These are the steps I took to generate the backtrace, after setting
> the variables as you requested.
>
> * Opened a remote file and edited it.
> * Disconnected my network connection.
> * Tried to save the file with `C-x C-s'
> * After emacs hung, I took a screenshot
> * Killed emacs with `kill -FPE <emacs_pid>'
> * Copied the backtrace to a buffer, saved it as raw-text.
> * Executed the kill command again (as emacs was still unresponsive)
>
> I have attached the screenshot and the text file with the backtrace.
>
> Hope this will help. And as always, thanks for the help.

I could reproduce it. Unfortunately, there is no simple way to solve it
inside Tramp (but I will continue to investigate). Therefore, I have
added the following item to Tramp's Frequently Asked Questions, HTH:

   * TRAMP does not recognize hung `ssh' sessions

     When your network connection is down, `ssh' sessions might hang.
     TRAMP cannot detect it safely, because it still sees a running
     `ssh' process.  Timeouts cannot be used as well, because it
     cannot be predicted, how long a remote command will last, for
     example when copying very large files.

     Therefore, you must configure the `ssh' process to die in such a
     case.  The following entry in `~/.ssh/config' would do the job:

          Host *
               ServerAliveInterval 5

Best regards, Michael.