linux-kernel - Re: [RFT][PATCH 0/3] cpufreq / PM: QoS: Introduce frequency QoS and use it in cpufreq

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Date:   Thu, 17 Oct 2019 18:14:32 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Dmitry Osipenko <digetx@...il.com>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [RFT][PATCH 0/3] cpufreq / PM: QoS: Introduce frequency QoS and
 use it in cpufreq

On Wed, Oct 16, 2019 at 03:23:43PM +0100, Sudeep Holla wrote:
> On Wed, Oct 16, 2019 at 12:37:58PM +0200, Rafael J. Wysocki wrote:
> > Hi All,
> >
> > The motivation for this series is to address the problem discussed here:
> >
> > https://lore.kernel.org/linux-pm/5ad2624194baa2f53acc1f1e627eb7684c577a19.1562210705.git.viresh.kumar@linaro.org/T/#md2d89e95906b8c91c15f582146173dce2e86e99f
> >
> > and also reported here:
> >
> > https://lore.kernel.org/linux-pm/20191015155735.GA29105@bogus/
> >
> > Plus, generally speaking, using the policy CPU as a proxy for the policy
> > with respect to PM QoS does not feel particularly straightforward to me
> > and adds extra complexity.
> >
> > Anyway, the first patch adds frequency QoS that is based on "raw" PM QoS (kind
> > of in analogy with device PM QoS) and is just about min and max frequency
> > requests (no direct relationship to devices).
> >
> > The second patch switches over cpufreq and its users to the new frequency QoS.
> > [The Fixes: tag has been tentatively added to it.]
> >
> > The third one removes frequency request types from device PM QoS.
> >
> > Unfortunately, the patches are rather big, but also they are quite
> > straightforward.
> >
> > I didn't have the time to test this series, so giving it a go would be much
> > appreciated.
>
> Thanks for the spinning these patches so quickly.
>
For the record, I thought of providing the crash that this series fixes.
After applying [1] which fixes the boot issue I was seeing on TC2, I started
seeing the below crash, which this series fixes.

FWIW,
Tested-by: Sudeep Holla <sudeep.holla@....com>

--

Unable to handle kernel paging request at virtual address 31b2c303
pgd = 772b96e1
[31b2c303] *pgd=a4050003, *pmd=00000000
Internal error: Oops: 206 [#1] SMP THUMB2
Modules linked in:
CPU: 1 PID: 518 Comm: bash Not tainted 5.4.0-rc3-00062-g6e3a7fd7a87e-dirty #123
Hardware name: ARM-Versatile Express
PC is at blocking_notifier_chain_unregister+0x2a/0x78
LR is at blocking_notifier_chain_unregister+0x1b/0x78
Flags: NzCv  IRQs on  FIQs off  Mode SVC_32  ISA Thumb  Segment user
Control: 70c5387d  Table: a57b08c0  DAC: 55555555
Process bash (pid: 518, stack limit = 0x018ebe57)
(blocking_notifier_chain_unregister) from (dev_pm_qos_remove_notifier+0x5d/0xb4)
(dev_pm_qos_remove_notifier) from (cpufreq_policy_free+0x77/0xc8)
(cpufreq_policy_free) from (subsys_interface_unregister+0x4f/0x80)
(subsys_interface_unregister) from (cpufreq_unregister_driver+0x29/0x6c)
(cpufreq_unregister_driver) from (bL_cpufreq_switcher_notifier+0x41/0x4c)
(bL_cpufreq_switcher_notifier) from (notifier_call_chain+0x3d/0x58)
(notifier_call_chain) from (blocking_notifier_call_chain+0x29/0x38)
(blocking_notifier_call_chain) from (bL_activation_notify+0x13/0x40)
(bL_activation_notify) from (bL_switcher_active_store+0x59/0x190)
(bL_switcher_active_store) from (kernfs_fop_write+0x85/0x12c)
(kernfs_fop_write) from (__vfs_write+0x21/0x130)
(__vfs_write) from (vfs_write+0x6b/0xfc)
(vfs_write) from (ksys_write+0x6d/0x90)
(ksys_write) from (ret_fast_syscall+0x1/0x5a)