From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Americo Wang <xiyou.wangcong@gmail.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>,
Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
Roland McGrath <roland@redhat.com>,
Spencer Candland <spencer@bluehost.com>,
Stanislaw Gruszka <sgruszka@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC,PATCH 1/2] cputimers/proc: do_task_stat()->task_times() can race with getrusage()
Date: Fri, 26 Mar 2010 09:23:44 +0530 [thread overview]
Message-ID: <20100326035344.GQ3308@balbir.in.ibm.com> (raw)
In-Reply-To: <20100324204550.GA31777@redhat.com>
* Oleg Nesterov <oleg@redhat.com> [2010-03-24 21:45:50]:
> do_task_stat()->task_times() can race with getrusage(), they both can
> try to update task->prev_Xtime at the same time.
>
> Remove this bit of d180c5bc "sched: Introduce task_times() to replace
> task_{u,s}time()".
One of the reasons for adding this accuracy was to avoid sampling
based noise and errors that occur with utime and stime.
As long as there is no preemption during the assignment, I think we
should be OK.
I see two options
1. Disable preemption around assignment
2. Remove task_times() from getrusage()
--
Three Cheers,
Balbir
next prev parent reply other threads:[~2010-03-26 3:53 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-24 20:45 Oleg Nesterov
2010-03-26 3:53 ` Balbir Singh [this message]
2010-03-26 7:37 ` Stanislaw Gruszka
2010-03-26 16:12 ` Stanislaw Gruszka
2010-03-26 21:49 ` Oleg Nesterov
2010-03-29 11:17 ` Stanislaw Gruszka
2010-03-29 12:54 ` Oleg Nesterov
2010-03-29 18:12 ` [PATCH -mm 0/4] cputimers/proc: do_task_stat: don't walk through the thread list under ->siglock Oleg Nesterov
2010-03-29 18:12 ` [PATCH -mm 1/4] cputimers: thread_group_cputime: cleanup rcu/signal stuff Oleg Nesterov
2010-03-29 18:13 ` [PATCH -mm 2/4] cputimers: make sure thread_group_cputime() can't count the same thread twice lockless Oleg Nesterov
2010-03-30 11:01 ` Stanislaw Gruszka
2010-03-30 13:43 ` Oleg Nesterov
2010-03-29 18:13 ` [PATCH -mm 3/4] cputimers: thread_group_times: make it rcu-safe Oleg Nesterov
2010-03-29 18:14 ` [PATCH -mm 1/4] cputimers: do_task_stat: avoid ->siglock for while_each_thread() Oleg Nesterov
2010-03-29 18:16 ` Oleg Nesterov
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