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?
> + 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.
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
>
