Re: [PATCH 0/10] Make bsd process accounting work in pid namespaces

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 15 May 2008 14:52:46 +0400 Pavel Emelyanov <xemul@openvz.org> wrote:

> fter I fixed access to task->tgid in kernel/acct.c, Oleg 
> pointed out some bad side effects with this accounting vs pid 
> namespaces interaction. I.e. when some task in pid namespace 
> sets this accounting up, this blocks all the others from doing 
> the same. Restricting this to init namespace only could help, 
> but didn't look as a grace solution.
> 
> So here is the approach to make this accounting work with pid
> namespaces properly.

We still have this silliness in acct_file_reopen():

		spin_unlock(&acct_lock);
		do_acct_process(acct, old_ns, old_acct);
		filp_close(old_acct, NULL);
		spin_lock(&acct_lock);

Was this lock-dropping safe before?

Is it safe now?

To work this out, we'd need to know what acct_lock protects.  What does
acct_lock protect?