Re: [PATCH 0/5] cpufreq: cppc: Fix suspend/resume specific races with FIE code

[Qian Cai <quic_qiancai@quicinc.com>]

On 6/10/2021 4:23 AM, Viresh Kumar wrote:
> Hi Qian,
> 
> It would be helpful if you can test this patchset and confirm if the races you
> mentioned went away or not and that the FIE code works as we wanted it to.
> 
> I don't have a real setup and so it won't be easy for me to test this out.
> 
> I have already sent a temporary fix for 5.13 and this patchset is targeted for
> 5.14 and is based over that.

Unfortunately, this series looks like needing more works.

[  487.773586][    T0] CPU17: Booted secondary processor 0x0000000801 [0x503f0002]
[  487.976495][  T670] list_del corruption. next->prev should be ffff009b66e9ec70, but was ffff009b66dfec70
[  487.987037][  T670] ------------[ cut here ]------------
[  487.992351][  T670] kernel BUG at lib/list_debug.c:54!
[  487.997810][  T670] Internal error: Oops - BUG: 0 [#1] SMP
[  488.003295][  T670] Modules linked in: cpufreq_userspace xfs loop cppc_cpufreq processor efivarfs ip_tables x_tables ext4 mbcache jbd2 dm_mod igb i2c_algo_bit nvme mlx5_core i2c_core nvme_core firmware_class
[  488.021759][  T670] CPU: 1 PID: 670 Comm: cppc_fie Not tainted 5.13.0-rc5-next-20210611+ #46
[  488.030190][  T670] Hardware name: MiTAC RAPTOR EV-883832-X3-0001/RAPTOR, BIOS 1.6 06/28/2020
[  488.038705][  T670] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO BTYPE=--)
[  488.045398][  T670] pc : __list_del_entry_valid+0x154/0x158
[  488.050969][  T670] lr : __list_del_entry_valid+0x154/0x158
[  488.056534][  T670] sp : ffff8000229afd70
[  488.060534][  T670] x29: ffff8000229afd70 x28: ffff0008c8f4f340 x27: dfff800000000000
[  488.068361][  T670] x26: ffff009b66e9ec70 x25: ffff800011c8b4d0 x24: ffff0008d4bfe488
[  488.076188][  T670] x23: ffff0008c8f4f340 x22: ffff0008c8f4f340 x21: ffff009b6789ec70
[  488.084015][  T670] x20: ffff0008d4bfe4c8 x19: ffff009b66e9ec70 x18: ffff0008c8f4fd70
[  488.091842][  T670] x17: 20747562202c3037 x16: 6365396536366239 x15: 0000000000000028
[  488.099669][  T670] x14: 0000000000000000 x13: 0000000000000001 x12: ffff60136cdd3447
[  488.107495][  T670] x11: 1fffe0136cdd3446 x10: ffff60136cdd3446 x9 : ffff8000103ee444
[  488.115322][  T670] x8 : ffff009b66e9a237 x7 : 0000000000000001 x6 : ffff009b66e9a230
[  488.123149][  T670] x5 : 00009fec9322cbba x4 : ffff60136cdd3447 x3 : 1fffe001191e9e69
[  488.130975][  T670] x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000054
[  488.138803][  T670] Call trace:
[  488.141935][  T670]  __list_del_entry_valid+0x154/0x158
[  488.147153][  T670]  kthread_worker_fn+0x15c/0xda0
[  488.151939][  T670]  kthread+0x3ac/0x460
[  488.155854][  T670]  ret_from_fork+0x10/0x18
[  488.160120][  T670] Code: 911e8000 aa1303e1 910a0000 941b595b (d4210000)
[  488.166901][  T670] ---[ end trace e637e2d38b2cc087 ]---
[  488.172206][  T670] Kernel panic - not syncing: Oops - BUG: Fatal exception
[  488.179182][  T670] SMP: stopping secondary CPUs
[  489.209347][  T670] SMP: failed to stop secondary CPUs 0-1,10-11,16-17,31
[  489.216128][  T][  T670] Memoryn ]---

> 
> -------------------------8<-------------------------
> 
> The CPPC driver currently stops the frequency invariance related
> kthread_work and irq_work from cppc_freq_invariance_exit() which is only
> called during driver's removal.
> 
> This is not sufficient as the CPUs can get hot-plugged out while the
> driver is in use, the same also happens during system suspend/resume.
> 
> In such a cases we can reach a state where the CPU is removed by the
> kernel but its kthread_work or irq_work aren't stopped.
> 
> Fix this by implementing the start_cpu() and stop_cpu() callbacks in the
> cpufreq core, which will be called for each CPU's addition/removal.
> 
> A similar call was already available in the cpufreq core, which isn't required
> anymore and so its users are migrated to use exit() callback instead.
> 
> This is targeted for v5.14-rc1.
> 
> --
> Viresh
> 
> Viresh Kumar (5):
>   cpufreq: cppc: Migrate to ->exit() callback instead of ->stop_cpu()
>   cpufreq: intel_pstate: Migrate to ->exit() callback instead of
>     ->stop_cpu()
>   cpufreq: powerenv: Migrate to ->exit() callback instead of
>     ->stop_cpu()
>   cpufreq: Add start_cpu() and stop_cpu() callbacks
>   cpufreq: cppc: Fix suspend/resume specific races with the FIE code
> 
>  Documentation/cpu-freq/cpu-drivers.rst |   7 +-
>  drivers/cpufreq/Kconfig.arm            |   1 -
>  drivers/cpufreq/cppc_cpufreq.c         | 163 ++++++++++++++-----------
>  drivers/cpufreq/cpufreq.c              |  11 +-
>  drivers/cpufreq/intel_pstate.c         |   9 +-
>  drivers/cpufreq/powernv-cpufreq.c      |  23 ++--
>  include/linux/cpufreq.h                |   5 +-
>  7 files changed, 119 insertions(+), 100 deletions(-)
>