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    SubjectRe: [PATCH 04/36] cpuidle,intel_idle: Fix CPUIDLE_FLAG_IRQ_ENABLE
    Hi Peter,

    On Mon, 13 Jun 2022 10:44:22 +0200, Peter Zijlstra <peterz@infradead.org>
    wrote:

    > On Thu, Jun 09, 2022 at 04:49:21PM -0700, Jacob Pan wrote:
    > > Hi Peter,
    > >
    > > On Wed, 08 Jun 2022 16:27:27 +0200, Peter Zijlstra
    > > <peterz@infradead.org> wrote:
    > >
    > > > Commit c227233ad64c ("intel_idle: enable interrupts before C1 on
    > > > Xeons") wrecked intel_idle in two ways:
    > > >
    > > > - must not have tracing in idle functions
    > > > - must return with IRQs disabled
    > > >
    > > > Additionally, it added a branch for no good reason.
    > > >
    > > > Fixes: c227233ad64c ("intel_idle: enable interrupts before C1 on
    > > > Xeons") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    > > > ---
    > > > drivers/idle/intel_idle.c | 48
    > > > +++++++++++++++++++++++++++++++++++----------- 1 file changed, 37
    > > > insertions(+), 11 deletions(-)
    > > >
    > > > --- a/drivers/idle/intel_idle.c
    > > > +++ b/drivers/idle/intel_idle.c
    > > > @@ -129,21 +137,37 @@ static unsigned int mwait_substates __in
    > > > *
    > > > * Must be called under local_irq_disable().
    > > > */
    > > nit: this comment is no long true, right?
    >
    > It still is, all the idle routines are called with interrupts disabled,
    > but must also exit with interrupts disabled.
    >
    > If the idle method requires interrupts to be enabled, it must be sure to
    > disable them again before returning. Given all the RCU/tracing concerns
    > it must use raw_local_irq_*() for this though.
    Makes sense, it is just little confusing when the immediate caller does
    raw_local_irq_enable() which does not cancel out local_irq_disable().

    Thanks,

    Jacob

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