Message-ID: <1365513508.30071.4.camel@laptop>
Subject: Re: [PATCH 3/7] sched: Update rq clock on tickless CPUs before
 calling check_preempt_curr()
From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Alessio Igor Bogani <abogani@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Chris Metcalf <cmetcalf@tilera.com>, Christoph Lameter <cl@linux.com>,
        Geoff Levand <geoff@infradead.org>,
        Gilad Ben Yossef <gilad@benyossef.com>,
        Hakan Akkan <hakanakkan@gmail.com>,
        Li Zhong <zhong@linux.vnet.ibm.com>,
        Namhyung Kim <namhyung.kim@lge.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Paul Gortmaker <paul.gortmaker@windriver.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>, Paul Turner <pjt@google.com>,
        Mike Galbraith <efault@gmx.de>
Date: Tue, 09 Apr 2013 15:18:28 +0200
In-Reply-To: <1365266760-24725-4-git-send-email-fweisbec@gmail.com>
References: <1365266760-24725-1-git-send-email-fweisbec@gmail.com>
	 <1365266760-24725-4-git-send-email-fweisbec@gmail.com>
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On Sat, 2013-04-06 at 18:45 +0200, Frederic Weisbecker wrote:
> check_preempt_wakeup() of fair class needs an uptodate sched clock
> value to update runtime stats of the current task.
> 
> When a task is woken up, activate_task() is usually called right
> before
> ttwu_do_wakeup() unless the task is still in the runqueue. In this
> case we need to update the rq clock manually in case the CPU runs
> tickless because ttwu_do_wakeup() calls check_preempt_wakeup().

again, same story.. I think the entire nohz specific clock update stuff
is completely broken and you're finding sites that are simply missing
clock updates.

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