linux-kernel - Re: [PATCH] extcon: Release locking when sending the notification of connector state

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Date:   Fri, 15 Jun 2018 09:52:16 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     "H. Nikolaus Schaller" <hns@...delico.com>,
        Roger Quadros <rogerq@...com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        chanwoo@...nel.org, myungjoo.ham@...sung.com,
        stable <stable@...r.kernel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Tony Giaccone <tony@...ccone.org>
Subject: Re: [PATCH] extcon: Release locking when sending the notification
 of connector state

Hi Roger,

If possible, Could you please review this patch? 

Regards,
Chanwoo Choi

On 2018년 06월 14일 20:33, H. Nikolaus Schaller wrote:
> 
>> Am 14.06.2018 um 12:39 schrieb H. Nikolaus Schaller <hns@...delico.com>:
>>
>> Hi Roger and Chanwoo,
>>
>>> Am 14.06.2018 um 12:18 schrieb Chanwoo Choi <cw00.choi@...sung.com>:
>>>
>>> + H. Nikolaus Schaller <hns@...delico.com>
>>>
>>> On 2018년 06월 14일 13:14, Chanwoo Choi wrote:
>>>> Previously, extcon used the spinlock before calling the notifier_call_chain
>>>> to prevent the scheduled out of task and to prevent the notification delay.
>>>> When spinlock is locked for sending the notification, deadlock issue
>>>> occured on the side of extcon consumer device. To fix this issue,
>>>> extcon consumer device should always use the work. it is always not
>>>> reasonable to use work.
>>>>
>>>> To fix this issue on extcon consumer device, release locking when sending
>>>> the notification of connector state.
>>>>
>>>> Fixes: ab11af049f88 ("extcon: Add the synchronization extcon APIs to support the notification")
>>>> Cc: stable@...r.kernel.org
>>>> Cc: Roger Quadros <rogerq@...com>
>>>> Cc: Kishon Vijay Abraham I <kishon@...com>
>>>> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
>>>> ---
>>>> drivers/extcon/extcon.c | 3 ++-
>>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c
>>>> index 8bff5fd18185..f75b08a45d4e 100644
>>>> --- a/drivers/extcon/extcon.c
>>>> +++ b/drivers/extcon/extcon.c
>>>> @@ -433,8 +433,8 @@ int extcon_sync(struct extcon_dev *edev, unsigned int id)
>>>> 		return index;
>>>>
>>>> 	spin_lock_irqsave(&edev->lock, flags);
>>>> -
>>>> 	state = !!(edev->state & BIT(index));
>>>> +	spin_unlock_irqrestore(&edev->lock, flags);
>>>>
>>>> 	/*
>>>> 	 * Call functions in a raw notifier chain for the specific one
>>>> @@ -448,6 +448,7 @@ int extcon_sync(struct extcon_dev *edev, unsigned int id)
>>>> 	 */
>>>> 	raw_notifier_call_chain(&edev->nh_all, state, edev);
>>>>
>>>> +	spin_lock_irqsave(&edev->lock, flags);
>>>> 	/* This could be in interrupt handler */
>>>> 	prop_buf = (char *)get_zeroed_page(GFP_ATOMIC);
>>>> 	if (!prop_buf) {
>>>>
>>
>> I have tested on the Pyra handheld prototype and now it works. Plugging in an OTG cable
>> enables/disables OTG power as expected and there are no kernel oops any more.
> 
> I did take some minutes to check and it now also works again on the OMAP5EVM.
> 
> BR,
> Nikolaus
> 
>