[PATCH v3] ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512

[Catalin Marinas]

On Fri, Mar 08, 2024 at 03:01:28PM +0100, Marek Szyprowski wrote:
> This patch landed in today's linux-next as commit 0499a78369ad ("ARM64: 
> Dynamically allocate cpumasks and increase supported CPUs to 512"). 
> Unfortunately it triggers the following warning during boot on most of 
> my ARM64-based test boards. Here is an example from Odroid-N2 board:
> 
>   ------------[ cut here ]------------
>   WARNING: CPU: 4 PID: 63 at drivers/opp/core.c:2554 
> dev_pm_opp_set_config+0x390/0x710
>   Modules linked in: dw_hdmi_i2s_audio meson_gxl smsc onboard_usb_hub(+) 
> rtc_pcf8563 panfrost snd_soc_meson_axg_sound_card drm_shmem_helper 
> crct10dif_ce dwmac_generic snd_soc_meson_card_utils gpu_sched 
> snd_soc_meson_g12a_toacodec snd_soc_meson_g12a_tohdmitx rc_odroid 
> snd_soc_meson_codec_glue pwm_meson ao_cec_g12a meson_gxbb_wdt meson_ir 
> snd_soc_meson_axg_frddr snd_soc_meson_axg_toddr snd_soc_meson_axg_tdmin 
> meson_vdec(C) v4l2_mem2mem videobuf2_dma_contig snd_soc_meson_axg_tdmout 
> videobuf2_memops axg_audio videobuf2_v4l2 sclk_div videodev 
> reset_meson_audio_arb snd_soc_meson_axg_fifo clk_phase dwmac_meson8b 
> stmmac_platform videobuf2_common mdio_mux_meson_g12a meson_drm 
> meson_dw_hdmi rtc_meson_vrtc stmmac meson_ddr_pmu_g12 mc dw_hdmi 
> drm_display_helper pcs_xpcs snd_soc_meson_t9015 meson_canvas gpio_fan 
> display_connector snd_soc_meson_axg_tdm_interface 
> snd_soc_simple_amplifier snd_soc_meson_axg_tdm_formatter nvmem_meson_efuse
>   hub 1-1:1.0: USB hub found
>   CPU: 4 PID: 63 Comm: kworker/u12:5 Tainted: G         C 6.8.0-rc3+ #14677
>   Hardware name: Hardkernel ODROID-N2 (DT)
>   Workqueue: events_unbound deferred_probe_work_func
>   pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>   pc : dev_pm_opp_set_config+0x390/0x710
>   lr : dev_pm_opp_set_config+0x5c/0x710
>   ...
>   Call trace:
>    dev_pm_opp_set_config+0x390/0x710
>    dt_cpufreq_probe+0x268/0x480
>    platform_probe+0x68/0xd8
>    really_probe+0x148/0x2b4
>    __driver_probe_device+0x78/0x12c
>    driver_probe_device+0xdc/0x164
>    __device_attach_driver+0xb8/0x138
>    bus_for_each_drv+0x84/0xe0
>    __device_attach+0xa8/0x1b0
>    device_initial_probe+0x14/0x20
>    bus_probe_device+0xb0/0xb4
>    deferred_probe_work_func+0x8c/0xc8
>    process_one_work+0x1ec/0x53c
>    worker_thread+0x298/0x408
>    kthread+0x124/0x128
>    ret_from_fork+0x10/0x20
>   irq event stamp: 317178
>   hardirqs last  enabled at (317177): [<ffff8000801788d4>] 
> ktime_get_coarse_real_ts64+0x10c/0x110
>   hardirqs last disabled at (317178): [<ffff800081222030>] el1_dbg+0x24/0x8c
>   softirqs last  enabled at (315802): [<ffff800080010a60>] 
> __do_softirq+0x4a0/0x4e8
>   softirqs last disabled at (315793): [<ffff8000800169b0>] 
> ____do_softirq+0x10/0x1c
>   ---[ end trace 0000000000000000 ]---
>   cpu cpu2: error -EBUSY: failed to set regulators
>   cpufreq-dt: probe of cpufreq-dt failed with error -16
> 
> It looks that cpufreq-dt and/or opp drivers needs some adjustments 
> related with this change.

That's strange. Is this with defconfig? I wonder whether NR_CPUS being
larger caused the issue with this specific code. Otherwise
CPUMASK_OFFSTACK may not work that well on arm64.

> 
> 
> > ---
> >
> >
> > Original post: https://www.spinics.net/lists/linux-mm/msg369701.html
> > V2: https://lkml.org/lkml/2024/2/7/505
> >
> >
> > V1->V2
> >
> > - Keep quotation marks
> > - Remove whiltespace damage
> > - Add tested by
> >
> > V2->V3:
> > - Add test results
> > - Rework descriptions
> >
> >
> >  arch/arm64/Kconfig | 16 +++++++++++++++-
> >  1 file changed, 15 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index aa7c1d435139..4e767dede47d 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -1427,7 +1427,21 @@ config SCHED_SMT
> >  config NR_CPUS
> >      int "Maximum number of CPUs (2-4096)"
> >      range 2 4096
> > -    default "256"
> > +    default "512"
> > +
> > +#
> > +# Determines the placement of cpumasks.
> > +#
> > +# With CPUMASK_OFFSTACK the cpumasks are dynamically allocated.
> > +# Useful for machines with lots of core because it avoids increasing
> > +# the size of many of the data structures in the kernel.
> > +#
> > +# If this is off then the cpumasks have a static sizes and are
> > +# embedded within data structures.
> > +#
> > +    config CPUMASK_OFFSTACK
> > +    def_bool y
> > +    depends on NR_CPUS > 256
> >
> >  config HOTPLUG_CPU
> >      bool "Support for hot-pluggable CPUs"
> 
> Best regards
> -- 
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
> 

-- 
Catalin