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

[H. Nikolaus Schaller]

Hi Roger and Chanwoo,

> Am 14.06.2018 um 12:18 schrieb Chanwoo Choi <cw00.choi@xxxxxxxxxxx>:
> 
> + H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
> 
> On 2018ë 06ì 14ì 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@xxxxxxxxxxxxxxx
>> Cc: Roger Quadros <rogerq@xxxxxx>
>> Cc: Kishon Vijay Abraham I <kishon@xxxxxx>
>> Signed-off-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
>> ---
>> 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@xxxxxxxxxxxxx>
Tested-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>

BR and thank you for the quick fix,
Nikolaus