linux-kernel - Re: [patch 3/4] taskstats: Introduce cdata_acct for complete cumulative accounting

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Date:	Thu, 25 Nov 2010 18:45:58 +0100
From:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.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 3/4] taskstats: Introduce cdata_acct for complete
 cumulative accounting

On Thu, 2010-11-25 at 14:21 +0100, Oleg Nesterov wrote:
> On 11/25, Michael Holzheu wrote:
> But in fact this reminds we should cleanup this code somehow.
> By the time we call thread_group_times() there are no other
> threads.

Couldn't we just replace thread_group_times() with the following:

--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -101,12 +101,13 @@ static void __account_cdata(struct task_
         * group, which consolidates times for all threads in the
         * group including the group leader.
         */
-       thread_group_times(p, &tgutime, &tgstime);
        pcd = &p->real_parent->signal->cdata_wait;
        tcd = &p->signal->cdata_threads;
        cd = &p->signal->cdata_wait;

        spin_lock_irqsave(&p->real_parent->sighand->siglock, flags);
+       tgutime = cputime_add(tcd->utime, p->utime);
+       tgstime = cputime_add(tcd->stime, p->stime);
        pcd->utime =
                cputime_add(pcd->utime,
                cputime_add(tgutime,

Then we can move the __account_cdata() invocation down to the second
group_dead check.

Michael

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