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

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Message-Id: <9AEF5153-4234-4C30-984A-8A3D51D04623@goldelico.com>
Date:   Thu, 14 Jun 2018 12:39:19 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Chanwoo Choi <cw00.choi@...sung.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>
Subject: Re: [PATCH] extcon: Release locking when sending the notification of connector state

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.

So you can add my

Reported-by: H. Nikolaus Schaller <hns@...delico.com>
Tested-by: H. Nikolaus Schaller <hns@...delico.com>

BR and thank you for the quick fix,
Nikolaus