On Tue, Sep 11, 2007 at 12:59:59AM +0100, Daniel P. Berrange wrote:
> I noticed that when using the SSH tunnel for the remote driver I ended up
> with alot of zombie SSH processes. We simply forgot to waitpid() on the
> child when a connection attempt failed, or when shutting down an open remote
> connection. Attached is a possible patch
Looks fine, like Rich maybe a bit of refactoring might be good. The
only worries I have is the following scenario:
- the ssh process dies
- libvirt based application takes some time to notice it
- the OS span a new process with the same PID after a PID rollabck
(not completely unlikely since the ssh may have been started a long
time ago)
- we end-up killing a random process in the system
I think this is mostly avoidable by resetting priv->pid to -1 or 0 on
any child communication error, and before doing the kill in the patch.
Even better would be to be able to check that the process corresponding
to priv->pid is still a child of the current process, I wonder if this
can be achieved without blocking with an initial waitpid()
Maybe I'm too cautious, I'm fine with the principle of the patch though
> @@ -646,6 +648,19 @@ doRemoteOpen (virConnectPtr conn, struct
> gnutls_bye (priv->session, GNUTLS_SHUT_RDWR);
> close (priv->sock);
> }
> + if (priv->pid > 0) {
> + pid_t reap;
> + int status, n = 0;
> + kill(priv->pid, SIGTERM);
> + do {
> + if (n)
> + usleep(n*1000);
> + if (n > 3)
> + kill(priv->pid, SIGKILL);
> + reap = waitpid(priv->pid, &status, WNOHANG);
> + n++;
> + } while (reap != -1 && reap != priv->pid);
> + }
>
> /* Free up the URL and strings. */
> xmlFreeURI (uri);
Daniel
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