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    SubjectRe: [Regression 3.4] tick_broadcast_mask is not restored after a CPU has been offline/onlined
    On Tue, Jul 31, 2012 at 11:18:32AM +0800, Feng Tang wrote:
    > Hi Paul,
    >
    > On Mon, 30 Jul 2012 10:42:18 -0700
    > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
    >
    > > On Mon, Jul 30, 2012 at 10:08:47AM -0700, Paul E. McKenney wrote:
    > > > 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@linux.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.
    > >
    > > But should papering be appropriate, here is the patch.
    > >
    > > Thanx, Paul
    >
    > Just found and have a patch to fix a typo in acpi processor_driver.c, which
    > could also fix this tick_broadcast_mask issue.
    >
    > Patch is in https://lkml.org/lkml/2012/7/30/483
    >
    > So I think we don't need this "papering over" patch :)

    Very good, I have dropped it.

    Thanx, Paul

    > Thanks,
    > Feng
    >
    > >
    > > ------------------------------------------------------------------------
    > >
    > > ACPI: Repair fix to unprotected smp_processor_id()
    > >
    > > Commit 9505626d (ACPI: Fix unprotected smp_processor_id() in
    > > acpi_processor_cst_has_changed()) introduced a suspend/resume bug.
    > > This commit therefore introduces a bug-for-bug compatible fix for the
    > > original problem.
    > >
    > > Reported-by: Feng Tang <feng.tang@intel.com>
    > > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
    > >
    > > diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
    > > index 47a8caa..19c151a 100644
    > > --- a/drivers/acpi/processor_idle.c
    > > +++ b/drivers/acpi/processor_idle.c
    > > @@ -1218,7 +1218,8 @@ int acpi_processor_cst_has_changed(struct
    > > acpi_processor *pr)
    > > * to make the code that updates C-States be called once.
    > > */
    > >
    > > - if (pr->id == 0 && cpuidle_get_driver() == &acpi_idle_driver) {
    > > + if (raw_smp_processor_id() == 0 &&
    > > + cpuidle_get_driver() == &acpi_idle_driver) {
    > >
    > > cpuidle_pause_and_lock();
    > > /* Protect against cpu-hotplug */
    > >
    >



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