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    SubjectRe: 2.6.21-rc6-mm1
    On Tue, Apr 10, 2007 at 07:59:29PM -0400, Adam Belay wrote:
    > On Tue, 2007-04-10 at 15:20 -0700, Venki Pallipadi wrote:
    > > On Mon, Apr 09, 2007 at 07:40:52PM +0200, Rafael J. Wysocki wrote:
    > > > On Monday, 9 April 2007 18:14, Pallipadi, Venkatesh wrote:
    > > > >
    > > > > >-----Original Message-----
    > > > > >From: Rafael J. Wysocki [mailto:rjw@sisk.pl]
    > > > > >Sent: Monday, April 09, 2007 9:08 AM
    > > > > >To: Andrew Morton
    > > > > >Cc: linux-kernel@vger.kernel.org; randy.dunlap@oracle.com;
    > > > > >lenb@kernel.org; Pallipadi, Venkatesh
    > > > > >Subject: Re: 2.6.21-rc6-mm1
    > > > > >
    > > > > >On Sunday, 8 April 2007 23:35, Andrew Morton wrote:
    > > > > >>
    > > > > >>
    > > > > >ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2
    > > > > >.6.21-rc6/2.6.21-rc6-mm1/
    > > > > >>
    > > > > >>
    > > > > >> - Lots of x86 updates
    > > > > >>
    > > > > >> - This is a 25MB diff against mainline, which is rather large.
    > > > > >
    > > > > >The cpuidle thing tends to hang my x86-64 machines on boot.
    > > > > >
    > > > >
    > > > > Hi Rafael,
    > > > >
    > > > > At what point during boot does it hang?
    > > >
    > > > When mounting the root filesystem. It hangs completely, even the magic SysRq
    > > > doesn't work
    > > >
    > >
    > > Rafael: Below patch should fix the hang.
    > > Len: Please include this patch in acpi-test.
    > >
    > > Thanks,
    > > Venki
    > >
    > > Prevent hang on x86-64, when ACPI processor driver is added as a module on
    > > a system that does not support C-states.
    > >
    > > x86-64 expects all idle handlers to enable interrupts before returning from
    > > idle handler. This is due to enter_idle(), exit_idle() races. Make
    > > cpuidle_idle_call() confirm to this when there is no pm_idle_old.
    > >
    > > Also, cpuidle look at the return values of attch_driver() and set
    > > current_driver to NULL if attach fails on all CPUs.
    >
    > My vote would be to instead remove enter_idle() and exit_idle() from
    > x86-64, just as was done with i386. Performance monitoring
    > infrastructure shouldn't be interfering with the idle interrupt
    > delivery, as that could only hurt performance... Besides, there's
    > probably a better way of doing this than an idle notifier anyway.
    >

    Agreed. I did not like local_irq_enable() in cpuidle either, but added it
    anyway as it was a corner case when cpuidle is active and no driver is
    active and not a common case. I thought we will have it as a bandaid solution
    until enter_idle, exit_idle is around.

    Andi/Stephane: What are the plans around enter_idle exit_idle in x86-64.
    Is it still being used by perfmon for x86-64 arch?

    Thanks,
    Venki
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