Re: mutex warning in cpufreq + RFC patch

[Viresh Kumar]

On 31 August 2013 06:06, Stephen Boyd <sboyd@xxxxxxxxxxxxxx> wrote:
> Yes that patch may reduce the chance of the race condition but I
> don't believe it removes it entirely. I believe this bug still
> exists in linux-next. Consider the scenario where CPU1 is going
> down.
>
> __cpufreq_remove_dev()
>  ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
>   __cpufreq_governor()
>    policy->governor->governor(policy, CPUFREQ_GOV_STOP);
>     cpufreq_governor_dbs()
>      case CPUFREQ_GOV_STOP:
>       mutex_destroy(&cpu_cdbs->timer_mutex)
>       cpu_cdbs->cur_policy = NULL;
>   <PREEMPT>
> store()
>  __cpufreq_set_policy()
>   ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
>    __cpufreq_governor()
>     policy->governor->governor(policy, CPUFREQ_GOV_LIMITS);
>      case CPUFREQ_GOV_LIMITS:
>       mutex_lock(&cpu_cdbs->timer_mutex); <-- Warning (destroyed mutex)
>        if (policy->max < cpu_cdbs->cur_policy->cur) <- cur_policy == NULL

Some of the crashes you reported would be fixed by the patches I sent
today morning.

Let me know if anything else is left for latest linux-next...

Btw, I am facing another crash which I am not sure how to fix.. It
came with your script:

[  190.850481] ------------[ cut here ]------------
[  190.850489] WARNING: CPU: 3 PID: 14140 at
/home/arm/work/kernel/mywork/linux.git/include/linux/kref.h:47
kobject_get+0x42/0x50()
[  190.850490] Modules linked in: nfsd nfs fscache lockd arc4 iwldvm
mac80211 i915 iwlwifi drm_kms_helper nfs_acl auth_rpcgss cfg80211
sunrpc drm joyd
ev thinkpad_acpi snd_hda_codec_hdmi snd_seq_midi
snd_hda_codec_conexant oid_registry btusb snd_rawmidi snd_hda_intel
snd_hda_codec i2c_algo_bit rfcomm
 snd_seq_midi_event bnep psmouse snd_seq snd_hwdep snd_pcm bluetooth
snd_timer snd_seq_device parport_pc snd_page_alloc ppdev tpm_tis snd
soundcore lp
c_ich lp parport video serio_raw mac_hid wmi nvram binfmt_misc btrfs
raid6_pq e1000e ptp pps_core xor sdhci_pci sdhci zlib_deflate
libcrc32c
[  190.850563] CPU: 3 PID: 14140 Comm: sh Not tainted 3.11.0-rc7-custom #39
[  190.850567] Hardware name: LENOVO 4236G50/4236G50, BIOS 83ET70WW
(1.40 ) 06/12/2012
[  190.850571]  000000000000002f ffff8800c8bdfc38 ffffffff816746c3
0000000000000007
[  190.850580]  0000000000000000 ffff8800c8bdfc78 ffffffff8104cf8c
ffff88011e5f9b18
[  190.850587]  ffff880118eaf000 0000000000000001 0000000000000202
0000000000000008
[  190.850593] Call Trace:
[  190.850607]  [<ffffffff816746c3>] dump_stack+0x46/0x58
[  190.850615]  [<ffffffff8104cf8c>] warn_slowpath_common+0x8c/0xc0
[  190.850622]  [<ffffffff8104cfda>] warn_slowpath_null+0x1a/0x20
[  190.850629]  [<ffffffff81324e02>] kobject_get+0x42/0x50
[  190.850638]  [<ffffffff81533ab0>] cpufreq_cpu_get+0x80/0xc0
[  190.850647]  [<ffffffff81533c11>] cpufreq_get_policy+0x21/0x120
[  190.850655]  [<ffffffff81533fdf>] store_scaling_min_freq+0x3f/0xa0
[  190.850666]  [<ffffffff816785b6>] ? down_write+0x16/0x40
[  190.850674]  [<ffffffff81533000>] store+0x70/0xb0
[  190.850683]  [<ffffffff811f2582>] sysfs_write_file+0xe2/0x170
[  190.850693]  [<ffffffff81181e8e>] vfs_write+0xce/0x200
[  190.850700]  [<ffffffff81182392>] SyS_write+0x52/0xa0
[  190.850707]  [<ffffffff81683882>] system_call_fastpath+0x16/0x1b
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