[Pkg-gnupg-maint] Bug#694635: gnupg: gpg froze with a zombie after a Ctrl-C (intr character)

[Vincent Lefevre]

On 2012-12-07 17:09:31 +0100, Werner Koch wrote:
> On Fri,  7 Dec 2012 16:31, vincent at vinc17.net said:
> > When it receives a SIGINT, gpg should quit immediately (possibly
> > after some clean-up). The problem is that gpg was still running.
> 
> Like Mutt, gpg has its own sigint handler.  It does some important
> cleanups.

But after the cleanups, it should quit. This is not always the case
(there is no CPU activity from gpg, so that I assume that the cleanups
are terminated).

> > The fact that gpg has a zombie child means at least a problem with gpg.
> 
> A zombie is not per se a problem.  It just means that gpg has not yet
> called the waitpid.  This may happen if a SIGINT was received while
> reading from the keyserver helper.

This is probably what happened. But the keyserver helper terminated
(either due to the SIGINT or because it has finished normally), so
that waiting for reading from the keyserver helper no longer makes
sense. Moreover a process shouldn't have a zombie child forever.

> Gpg is still a child of Mutt (I assume 5216 is the Mutt process) and
> thus Mutt might still be reading from gpg. You should include
> information about Mutt and best an lsof of those processes.

Concerning Mutt, the filter (pipe + fork + execl) is created by
a mutt_create_filter_fd function which
1. creates a pipe;
2. blocks the signals (ignore SIGINT and SIGQUIT; block SIGCHLD);
3. does a fork;
4a. in the child process: unblocks the signals, closes some fd's,
    and executes the command with execl;
4b. in the parent process: closes some fd's and returns.

So, when I type Ctrl-C, Mutt won't get the SIGINT because SIGINT
is ignored (Mutt does the right thing, following the specification
of system() in POSIX). This is normal because if the child process
uses SIGINT for its own use, this mustn't have any effect on Mutt.
So, Mutt keeps reading from gpg until gpg terminates in one way or
another. But the real problem is that gpg doesn't terminate.

-- 
Vincent Lefèvre <vincent at vinc17.net> - Web: <http://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)