On Tue, 8 Mar 2022 at 01:14, Bjorn Andersson <bjorn.andersson@xxxxxxxxxx> wrote:
>
> On Mon 07 Mar 07:30 PST 2022, Dmitry Baryshkov wrote:
>
> > The qcom_lmh_dcvs_notify() will get the dev_pm_opp instance for
> > throttling, but will not put it, ending up with leaking a reference
> > count and the following backtrace when putting the CPU offline.
> >
>
> Good catch, and nice to see this kind of testing of the driver!
>
> > Correctly put the reference count of the returned opp instance.
> >
> > [ 84.418025] ------------[ cut here ]------------
> > [ 84.422770] WARNING: CPU: 7 PID: 43 at drivers/opp/core.c:1396 _opp_table_kref_release+0x188/0x190
> > [ 84.431966] Modules linked in:
> > [ 84.435106] CPU: 7 PID: 43 Comm: cpuhp/7 Tainted: G S 5.17.0-rc6-00388-g7cf3c0d89c44-dirty #721
> > [ 84.451631] pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
> > [ 84.458781] pc : _opp_table_kref_release+0x188/0x190
> > [ 84.463878] lr : _opp_table_kref_release+0x78/0x190
> > [ 84.468885] sp : ffff80000841bc70
> > [ 84.472294] x29: ffff80000841bc70 x28: ffff6664afe3d000 x27: ffff1db6729e5908
> > [ 84.479621] x26: 0000000000000000 x25: 0000000000000000 x24: ffff1db6729e58e0
> > [ 84.486946] x23: ffff8000080a5000 x22: ffff1db40aad80e0 x21: ffff1db4002fec80
> > [ 84.494277] x20: ffff1db40aad8000 x19: ffffb751c3186300 x18: ffffffffffffffff
> > [ 84.501603] x17: 5300326563697665 x16: 645f676e696c6f6f x15: 00001186c1df5448
> > [ 84.508928] x14: 00000000000002e9 x13: 0000000000000000 x12: 0000000000000000
> > [ 84.516256] x11: ffffb751c3186368 x10: ffffb751c39a2a70 x9 : 0000000000000000
> > [ 84.523585] x8 : ffff1db4008edf00 x7 : ffffb751c328c000 x6 : 0000000000000001
> > [ 84.530916] x5 : 0000000000040000 x4 : 0000000000000001 x3 : ffff1db4008edf00
> > [ 84.538247] x2 : 0000000000000000 x1 : ffff1db400aa6100 x0 : ffff1db40aad80d0
> > [ 84.545579] Call trace:
> > [ 84.548101] _opp_table_kref_release+0x188/0x190
> > [ 84.552842] dev_pm_opp_remove_all_dynamic+0x8c/0xc0
> > [ 84.557949] qcom_cpufreq_hw_cpu_exit+0x30/0xdc
> > [ 84.562608] cpufreq_offline.isra.0+0x1b4/0x1d8
> > [ 84.567270] cpuhp_cpufreq_offline+0x10/0x6c
> > [ 84.571663] cpuhp_invoke_callback+0x16c/0x2b0
> > [ 84.576231] cpuhp_thread_fun+0x190/0x250
> > [ 84.580353] smpboot_thread_fn+0x12c/0x230
> > [ 84.584568] kthread+0xfc/0x100
> > [ 84.587810] ret_from_fork+0x10/0x20
> > [ 84.591490] irq event stamp: 3482
> > [ 84.594901] hardirqs last enabled at (3481): [<ffffb751c13c3db0>] call_rcu+0x39c/0x50c
> > [ 84.603119] hardirqs last disabled at (3482): [<ffffb751c236b518>] el1_dbg+0x24/0x8c
> > [ 84.611074] softirqs last enabled at (310): [<ffffb751c1290410>] _stext+0x410/0x588
> > [ 84.619028] softirqs last disabled at (305): [<ffffb751c131bf68>] __irq_exit_rcu+0x158/0x174
> > [ 84.627691] ---[ end trace 0000000000000000 ]---
> >
> > Fixes: 275157b367f4 ("cpufreq: qcom-cpufreq-hw: Add dcvs interrupt support")
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > ---
> > drivers/cpufreq/qcom-cpufreq-hw.c | 12 ++++++++----
> > 1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
> > index 920c80d91c21..580520215ee7 100644
> > --- a/drivers/cpufreq/qcom-cpufreq-hw.c
> > +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
> > @@ -309,12 +309,16 @@ static void qcom_lmh_dcvs_notify(struct qcom_cpufreq_data *data)
> >
> > opp = dev_pm_opp_find_freq_floor(dev, &freq_hz);
> > if (IS_ERR(opp) && PTR_ERR(opp) == -ERANGE)
> > - dev_pm_opp_find_freq_ceil(dev, &freq_hz);
> > + opp = dev_pm_opp_find_freq_ceil(dev, &freq_hz);
> >
> > - throttled_freq = freq_hz / HZ_PER_KHZ;
>
> Maybe I'm missing something, but where did this division go after your
> change?
Oops. It got dropped when fixing the conflict. Let's get it back.
>
> > + if (IS_ERR(opp)) {
> > + dev_warn(dev, "Can't find the OPP for throttling: %pe!\n", opp);
>
> qcom_lmh_dcvs_notify() will be invoked repeatedly to poll the hardware
> for changing circumstances during thermal pressure. If for some reason
> dev_pm_opp_find_freq_ceil() is unable to find an opp it will probably
> continue to fail every 10ms.
I'll change it to dev_warn_ratelimited() instead. dev_warn_once() can
easily get lost.
>
> As such I think you should either omit the warning print, or possibly
> use dev_warn_once().
>
> Regards,
> Bjorn
>
> > + } else {
> > + /* Update thermal pressure (the boost frequencies are accepted) */
> > + arch_update_thermal_pressure(policy->related_cpus, throttled_freq);
> >
> > - /* Update thermal pressure (the boost frequencies are accepted) */
> > - arch_update_thermal_pressure(policy->related_cpus, throttled_freq);
> > + dev_pm_opp_put(opp);
> > + }
> >
> > /*
> > * In the unlikely case policy is unregistered do not enable
> > --
> > 2.34.1
> >
--
With best wishes
Dmitry
