linux-kernel - Re: [PATCH] x86/hpet: Cure interface abuse in the resume path

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Date:   Tue, 1 Aug 2017 09:43:27 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tomi Sarvela <tomi.p.sarvela@...el.com>
cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Martin Peres <martin.peres@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Marc Zyngier <marc.zyngier@....com>, jeffy.chen@...k-chips.com
Subject: Re: [PATCH] x86/hpet: Cure interface abuse in the resume path

On Tue, 1 Aug 2017, Tomi Sarvela wrote:
> On 31/07/17 23:07, Thomas Gleixner wrote:
> > The HPET resume path abuses irq_domain_[de]activate_irq() to restore the
> > MSI message in the HPET chip for the boot CPU on resume and it relies on an
> > implementation detail of the interrupt core code, which magically makes the
> > HPET unmask call invoked via a irq_disable/enable pair. This worked as long
> > as the irq code did unconditionally invoke the unmask() callback. With the
> > recent changes which keep track of the masked state to avoid expensive
> > hardware access, this does not longer work. As a consequence the HPET timer
> > interrupts are not unmasked which breaks resume as the boot CPU waits
> > forever that a timer interrupt arrives.
> > 
> > Make the restore of the MSI message explicit and invoke the unmask()
> > function directly. While at it get rid of the pointless affinity setting as
> > nothing can change the affinity of the interrupt and the vector across
> > suspend/resume. The restore of the MSI message reestablishes the previous
> > affinity setting which is the correct one.
> > 
> > Fixes: bf22ff45bed6 ("genirq: Avoid unnecessary low level irq function
> > calls")
> > Reported-by: Martin Peres <martin.peres@...ux.intel.com>
> > Reported-by: Tomi Sarvela <tomi.p.sarvela@...el.com>
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > Cc: jeffy.chen@...k-chips.com
> > Cc: Marc Zyngier <marc.zyngier@....com>
> > Cc: Peter Ziljstra <peterz@...radead.org>
> > Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
> 
> Tested-by: Tomi Sarvela <tomi.p.sarvela@...el.com>
> 
> Tested only on the regressed Eagle Lake testhost. This patch fixes the
> suspend/resume issue.

Tomi, can you please do me a favor?

Use plain 4.13-rc3 (without that patch) and add the following on the kernel
command line: 'nohpet'. Boot the machine and capture and provide the output
of

# dmesg
# cat /proc/interrupts
# cat /proc/timer_list

Then try the suspend cycle again.

Thanks,

	tglx