linux-kernel - Re: [PATCH v4 4/4] bus: mhi: host: Take irqsave lock after TRE is generated

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Message-ID: <20231124100916.GB4536@thinkpad>
Date:   Fri, 24 Nov 2023 15:39:16 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Qiang Yu <quic_qianyu@...cinc.com>
Cc:     quic_jhugo@...cinc.com, mhi@...ts.linux.dev,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_cang@...cinc.com, quic_mrana@...cinc.com,
        Hemant Kumar <quic_hemantk@...cinc.com>,
        Lazarus Motha <quic_lmotha@...cinc.com>
Subject: Re: [PATCH v4 4/4] bus: mhi: host: Take irqsave lock after TRE is
 generated

On Tue, Nov 14, 2023 at 01:27:41PM +0800, Qiang Yu wrote:
> From: Hemant Kumar <quic_hemantk@...cinc.com>
> 
> If CONFIG_TRACE_IRQFLAGS is enabled, irq will be enabled once __local_bh_
> enable_ip is called as part of write_unlock_bh. Hence, let's take irqsave

"__local_bh_enable_ip" is a function name, so you should not break it.

> lock after TRE is generated to avoid running write_unlock_bh when irqsave
> lock is held.
> 

I still don't understand this commit message. Where is the write_unlock_bh()
being called?

- Mani

> Signed-off-by: Hemant Kumar <quic_hemantk@...cinc.com>
> Signed-off-by: Lazarus Motha <quic_lmotha@...cinc.com>
> Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>
> ---
>  drivers/bus/mhi/host/main.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
> index 33f27e2..d7abd0b 100644
> --- a/drivers/bus/mhi/host/main.c
> +++ b/drivers/bus/mhi/host/main.c
> @@ -1128,17 +1128,15 @@ static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
>  	if (unlikely(MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state)))
>  		return -EIO;
>  
> -	read_lock_irqsave(&mhi_cntrl->pm_lock, flags);
> -
>  	ret = mhi_is_ring_full(mhi_cntrl, tre_ring);
> -	if (unlikely(ret)) {
> -		ret = -EAGAIN;
> -		goto exit_unlock;
> -	}
> +	if (unlikely(ret))
> +		return -EAGAIN;
>  
>  	ret = mhi_gen_tre(mhi_cntrl, mhi_chan, buf_info, mflags);
>  	if (unlikely(ret))
> -		goto exit_unlock;
> +		return ret;
> +
> +	read_lock_irqsave(&mhi_cntrl->pm_lock, flags);
>  
>  	/* Packet is queued, take a usage ref to exit M3 if necessary
>  	 * for host->device buffer, balanced put is done on buffer completion
> @@ -1158,7 +1156,6 @@ static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
>  	if (dir == DMA_FROM_DEVICE)
>  		mhi_cntrl->runtime_put(mhi_cntrl);
>  
> -exit_unlock:
>  	read_unlock_irqrestore(&mhi_cntrl->pm_lock, flags);
>  
>  	return ret;
> -- 
> 2.7.4
> 
> 

-- 
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