linux-kernel - Re: [patch 4/4] taskstats: Export "cdata

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20101129164329.GA16648@redhat.com>
Date:	Mon, 29 Nov 2010 17:43:29 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
Cc:	Shailabh Nagar <nagar1234@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	John stultz <johnstul@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [patch 4/4] taskstats: Export "cdata_acct" with taskstats

On 11/25, Michael Holzheu wrote:
>
> Hello Oleg,
>
> On Thu, 2010-11-25 at 14:26 +0100, Oleg Nesterov wrote:
> > On 11/19, Michael Holzheu wrote:
> > >
> > > From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
> > >
> > > With this patch the (full) cumulative CPU time is added to "struct taskstats".
> > > The CPU time is only returned for the thread group leader.
> > >
> > > ...
> > >
> > > +	if (tsk->tgid == tsk->pid
> >
> > thread_group_leader() ?
>
> Yes, that's better.
>
> > > && lock_task_sighand(tsk, &flags)) {
> >
> > Do you really need ->siglock? Starting from 2.6.35 it is always
> > safe to access ->signal.
>
> Hmmm, if you say that...
>
> I just did it like it is done in e.g. fs/proc/base.c (proc_pid_limits).
> Can we remove the locking there, too?

We can certainly remove more siglock's which were previously
needed to access ->signal.

This particular one is just wrong. We need task_lock(group_leader)
to read signal->rlim atomically. However, it is not trivial to do
this correctly. Probably we should ignore this minor problem.

In any case, this ->siglock buys nothing today.

Oleg.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/