linux-kernel - RE: [BISECTION RESULT] sched: revert cpu_clock to pre-27ec4407790d075c325e1f4da0a19c56953cce23 state

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Message-ID: <57C9024A16AD2D4C97DC78E552063EA308329447@orsmsx505.amr.corp.intel.com>
Date:	Tue, 5 Aug 2008 07:59:48 -0700
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Nishanth Aravamudan <nacc@...ibm.com>
CC:	"mingo@...e.hu" <mingo@...e.hu>,
	"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Bill Gatliff <bgat@...lgatliff.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>
Subject: RE: [BISECTION RESULT] sched: revert cpu_clock to
	pre-27ec4407790d075c325e1f4da0a19c56953cce23 state

+u64 sched_clock_cpu(int cpu)
+{
+       if (unlikely(!sched_clock_running))
+               return 0;
+
+       return sched_clock();
+}

This looks like it will solve the issue on the boot cpu.  It
leaves a potential hole as we bring up other cpus if[1] there
are any printk() calls before they get to cpu_init() to
initialize ar.kr3.  This code path is all under arch/ia64
though ... so if we shoot ourselves in the foot, it will be
our own fault.

-Tony

[1] Currently there is just one Dprintk() call in this path
at the start of start_secondary() ... I could put it inside
#ifndef CONFIG_PRINTK_TIME so as not to surprise anyone that
enabled it.
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