linux-kernel - Re: [PATCH] bus: mhi: core: Remove double locking from mhi_driver

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Date:   Thu, 5 Nov 2020 19:40:46 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Bhaumik Bhatt <bbhatt@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, hemantk@...eaurora.org,
        jhugo@...eaurora.org, linux-kernel@...r.kernel.org,
        skhan@...uxfoundation.org
Subject: Re: [PATCH] bus: mhi: core: Remove double locking from
 mhi_driver_remove()

On Thu, Oct 15, 2020 at 11:47:51AM -0700, Bhaumik Bhatt wrote:
> There is double acquisition of the pm_lock from mhi_driver_remove()
> function. Remove the read_lock_bh/read_unlock_bh calls for pm_lock
> taken during a call to mhi_device_put() as the lock is acquired
> within the function already. This will help avoid a potential
> kernel panic.
> 
> Fixes: 189ff97cca53 ("bus: mhi: core: Add support for data transfer")
> Reported-by: Shuah Khan <skhan@...uxfoundation.org>
> Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

Thanks,
Mani

> ---
>  drivers/bus/mhi/core/init.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
> index 0ffdebd..0a09f82 100644
> --- a/drivers/bus/mhi/core/init.c
> +++ b/drivers/bus/mhi/core/init.c
> @@ -1276,10 +1276,8 @@ static int mhi_driver_remove(struct device *dev)
>  		mutex_unlock(&mhi_chan->mutex);
>  	}
>  
> -	read_lock_bh(&mhi_cntrl->pm_lock);
>  	while (mhi_dev->dev_wake)
>  		mhi_device_put(mhi_dev);
> -	read_unlock_bh(&mhi_cntrl->pm_lock);
>  
>  	return 0;
>  }
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>