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

[Viresh Kumar]

Hi Qian,

First of all thanks for testing this, I need more of your help to test
this out :)

FWIW, I did test this on my Hikey board today, with some hacks, and
tried multiple insmod/rmmod operations for the driver, and I wasn't
able to reproduce the issue you reported. I did enable the list-debug
config option.

On 14-06-21, 09:48, Qian Cai wrote:
> 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

This is a strange place to get the issue from. And this is a new
issue.

> [  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 ]---

Can you give details on what exactly did you try to do, to get this ?
Normal boot or something more ?

I have made some changes to the way calls were happening, may get this
thing sorted. Can you please try this branch ?

https://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm.git/log/?h=cpufreq/cppc

I can see one place where race can happen, i.e. between
topology_clear_scale_freq_source() and topology_scale_freq_tick(). It
is possible that sfd->set_freq_scale() may get called for a previously
set handler as there is no protection there.

I will see how to fix that. But I am not sure if the issue reported
above comes from there.

Anyway, please give my branch a try, lets see.

-- 
viresh