linux-kernel - Re: [Regression 3.4] tick_broadcast_mask is not restored after a CPU has been offline/onlined

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Message-ID: <20120730170847.GE2391@linux.vnet.ibm.com>
Date:	Mon, 30 Jul 2012 10:08:47 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Feng Tang <feng.tang@...el.com>
Cc:	"Paul E. McKenney" <paul.mckenney@...aro.org>,
	Len Brown <len.brown@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mail List <linux-kernel@...r.kernel.org>
Subject: Re: [Regression 3.4] tick_broadcast_mask is not restored after a CPU
 has been offline/onlined

On Mon, Jul 30, 2012 at 11:07:47PM +0800, Feng Tang wrote:
> Hi Paul,
> 
> On Mon, 30 Jul 2012 06:39:13 -0700
> "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:
> 
> > On Mon, Jul 30, 2012 at 03:15:59PM +0800, Feng Tang wrote:
> > > Hi All,
> > > 
> > > When I debugged a suspend/resume bug, I found that tick_broadcast_mask is
> > > not restored for a CPU after it is offline/onlined since kernel 3.4, while
> > > it's fine for 3.3.
> > 
> > Could you please try 3.5?
> 
> Yes, it's the same for 3.5

Thank you for checking, Feng.

Len, the comment above the change says:

	/*
	 * FIXME:  Design the ACPI notification to make it once per
	 * system instead of once per-cpu.  This condition is a hack
	 * to make the code that updates C-States be called once.
	 */

Is it time for this design-level change?  Or is there something obvious
that I missed when fixing the smp_processor_id() splat?

I could revert back, but use raw_smp_processor_id() rather than
smp_processor_id(), but that feels like papering over a problem rather
than fixing it.

Thoughts?

							Thanx, Paul

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