linux-kernel - Re: [PATCH 2/2] extcon: Fix extcon_cable_get_state() from getting old state after notification

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Date:	Fri, 31 Jul 2015 15:38:08 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	Roger Quadros <rogerq@...com>
Cc:	linux-omap@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] extcon: Fix extcon_cable_get_state() from getting old
 state after notification

Hi Roger,

On 07/06/2015 11:46 PM, Roger Quadros wrote:
> Currently the extcon code notifiers the interested listeners
> before it updates the extcon state with the new state.
> This will cause the listeners that use extcon_cable_get_state()
> to get the stale state and loose the new state.
> 
> Fix this by first changing the extcon state variable and then
> notifying listeners.
> 
> Signed-off-by: Roger Quadros <rogerq@...com>
> ---
>  drivers/extcon/extcon.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)

Applied it.

Thanks,
Chanwoo Choi

> 
> diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c
> index 868c6e2..26d1e1e 100644
> --- a/drivers/extcon/extcon.c
> +++ b/drivers/extcon/extcon.c
> @@ -275,19 +275,25 @@ int extcon_update_state(struct extcon_dev *edev, u32 mask, u32 state)
>  	spin_lock_irqsave(&edev->lock, flags);
>  
>  	if (edev->state != ((edev->state & ~mask) | (state & mask))) {
> +		u32 old_state;
> +
>  		if (check_mutually_exclusive(edev, (edev->state & ~mask) |
>  						   (state & mask))) {
>  			spin_unlock_irqrestore(&edev->lock, flags);
>  			return -EPERM;
>  		}
>  
> +		old_state = edev->state;
> +		edev->state &= ~mask;
> +		edev->state |= state & mask;
> +
>  		for (index = 0; index < edev->max_supported; index++) {
> -			if (is_extcon_changed(edev->state, state, index, &attached))
> -				raw_notifier_call_chain(&edev->nh[index], attached, edev);
> +			if (is_extcon_changed(old_state, edev->state, index,
> +					      &attached))
> +				raw_notifier_call_chain(&edev->nh[index],
> +							attached, edev);
>  		}
>  
> -		edev->state &= ~mask;
> -		edev->state |= state & mask;
>  
>  		/* This could be in interrupt handler */
>  		prop_buf = (char *)get_zeroed_page(GFP_ATOMIC);
> 

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