Subject: [PATCH 0/7] PM / devfreq: Add NoCP devfreq-event and support busfreq on exyno5422-odroidxu3

From: [email-masked] (Chanwoo Choi)
Date: Mon, 11 Apr 2016 11:16:18 +0900

Hi Anand,

On 2016? 04? 09? 03:24, Chanwoo Choi wrote:
> Hi Anand,
> 
> On Sat, Apr 9, 2016 at 3:11 AM, Anand Moon <[email-masked]> wrote:
>> Hi Chanwoo,
>>

[snip]

>>>
>>
>> I am observing following deadlock. Both on Odroid U3 and Odroid XU4.
> 
> Thanks for your test. I'll test it again and fix it.

This possible recursive locking is fixed with following diff:

Thanks for your report. I'll fix it on next patchset[1] (v9).
[1] https://lkml.org/lkml/2016/4/8/14

diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
index 28a9ae32d330..a4b0b02ee797 100644
--- a/drivers/devfreq/governor_passive.c
+++ b/drivers/devfreq/governor_passive.c
@@ -102,7 +102,7 @@ static int update_devfreq_passive(struct devfreq *devfreq, unsigned long freq)
        if (!devfreq->governor)
                return -EINVAL;
 
-       mutex_lock(&devfreq->lock);
+       mutex_lock_nested(&devfreq->lock, SINGLE_DEPTH_NESTING);
 
        ret = devfreq->governor->get_target_freq(devfreq, &freq);
        if (ret < 0)

Best Regards,
Chanwoo Choi

> 
>>
>> [    7.718372] [ INFO: possible recursive locking detected ]
>> [    7.723747] 4.6.0-rc2-xu4ml #4 Not tainted
>> [    7.727817] ---------------------------------------------
>> [    7.733190] kworker/u16:1/136 is trying to acquire lock:
>> [    7.738476]  (&devfreq->lock){+.+.+.}, at: [<c05be41c>]
>> update_devfreq_passive+0x2c/0x88
>> [    7.746534]
>> [    7.746534] but task is already holding lock:
>> [    7.752339]  (&devfreq->lock){+.+.+.}, at: [<c05bd838>]
>> devfreq_monitor+0x1c/0x78
>> [    7.759791]
>> [    7.759791] other info that might help us debug this:
>> [    7.766291]  Possible unsafe locking scenario:
>> [    7.766291]
>> [    7.766307] usb 5-1: new high-speed USB device number 2 using xhci-hcd
>> [    7.778682]        CPU0
>> [    7.781107]        ----
>> [    7.783533]   lock(&devfreq->lock);
>> [    7.786999]   lock(&devfreq->lock);
>> [    7.790467]
>> [    7.790467]  *** DEADLOCK ***
>> [    7.790467]
>> [    7.796359]  May be due to missing lock nesting notation
>> [    7.796359]
>> [    7.803120] 4 locks held by kworker/u16:1/136:
>> [    7.807537]  #0:  ("%s"("devfreq_wq")){.+.+..}, at: [<c013b41c>]
>> process_one_work+0x13c/0x454
>> [    7.816029]  #1:  ((&(&devfreq->work)->work)){+.+...}, at:
>> [<c013b41c>] process_one_work+0x13c/0x454
>> [    7.825128]  #2:  (&devfreq->lock){+.+.+.}, at: [<c05bd838>]
>> devfreq_monitor+0x1c/0x78
>> [    7.833013]  #3:  (&nh->srcu){......}, at: [<c014309c>]
>> __srcu_notifier_call_chain+0x54/0xe0
>> [    7.841419]
>> [    7.841419] stack backtrace:
>> [    7.845758] CPU: 1 PID: 136 Comm: kworker/u16:1 Not tainted
>> 4.6.0-rc2-xu4ml #4
>> [    7.852946] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
>> [    7.859017] Workqueue: devfreq_wq devfreq_monitor
>> [    7.863717] [<c010eb48>] (unwind_backtrace) from [<c010b884>]
>> (show_stack+0x10/0x14)
>> [    7.871417] [<c010b884>] (show_stack) from [<c037715c>]
>> (dump_stack+0xa4/0xd0)
>> [    7.878613] [<c037715c>] (dump_stack) from [<c017112c>]
>> (__lock_acquire+0x1ce8/0x207c)
>> [    7.886492] [<c017112c>] (__lock_acquire) from [<c0172010>]
>> (lock_acquire+0x90/0xd4)
>> [    7.892726] usb 5-1: New USB device found, idVendor=0bda, idProduct=8153
>> [    7.892737] usb 5-1: New USB device strings: Mfr=1, Product=2, SerialNumber=6
>> [    7.892745] usb 5-1: Product: USB 10/100/1000 LAN
>> [    7.892753] usb 5-1: Manufacturer: Realtek
>> [    7.892761] usb 5-1: SerialNumber: 000001000000
>> [    7.921248] [<c0172010>] (lock_acquire) from [<c075d298>]
>> (mutex_lock_nested+0x78/0x4ec)
>> [    7.929301] [<c075d298>] (mutex_lock_nested) from [<c05be41c>]
>> (update_devfreq_passive+0x2c/0x88)
>> [    7.938138] [<c05be41c>] (update_devfreq_passive) from [<c05be4c0>]
>> (devfreq_passive_notifier_call+0x48/0x50)
>> [    7.948016] [<c05be4c0>] (devfreq_passive_notifier_call) from
>> [<c0142d84>] (notifier_call_chain+0x54/0xa4)
>> [    7.957633] [<c0142d84>] (notifier_call_chain) from [<c01430e0>]
>> (__srcu_notifier_call_chain+0x98/0xe0)
>> [    7.966991] [<c01430e0>] (__srcu_notifier_call_chain) from
>> [<c0143140>] (srcu_notifier_call_chain+0x18/0x20)
>> [    7.976783] [<c0143140>] (srcu_notifier_call_chain) from
>> [<c05bd774>] (update_devfreq+0xe4/0x18c)
>> [    7.985622] [<c05bd774>] (update_devfreq) from [<c05bd840>]
>> (devfreq_monitor+0x24/0x78)
>> [    7.993595] [<c05bd840>] (devfreq_monitor) from [<c013b48c>]
>> (process_one_work+0x1ac/0x454)
>> [    8.001913] [<c013b48c>] (process_one_work) from [<c013b784>]
>> (worker_thread+0x50/0x508)
>> [    8.009976] [<c013b784>] (worker_thread) from [<c0141cf4>]
>> (kthread+0xf8/0x110)
>> [    8.017254] [<c0141cf4>] (kthread) from [<c0107750>]
>> (ret_from_fork+0x14/0x24)
>>
>> Best Regards
>> -Anand Moon
>> --
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