linux-kernel - Re: [PATCH v3 4/4] bus: mhi: host: Take irqsave lock after TRE is generated

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Message-ID: <28bae567-23ae-4b06-b77b-946cf46aa74e@quicinc.com>
Date:   Fri, 10 Nov 2023 11:42:52 +0800
From:   Qiang Yu <quic_qianyu@...cinc.com>
To:     Manivannan Sadhasivam <mani@...nel.org>
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 v3 4/4] bus: mhi: host: Take irqsave lock after TRE is
 generated


On 11/10/2023 12:29 AM, Manivannan Sadhasivam wrote:
> On Tue, Nov 07, 2023 at 03:16:05PM +0800, Qiang Yu wrote:
>> From: Hemant Kumar <quic_hemantk@...cinc.com>
>>
>> Take irqsave lock after TRE is generated to avoid deadlock due to core
>> getting interrupts enabled as local_bh_enable must not be called with
>> irqs disabled based on upstream patch.
>>
> You still didn't address any of the comments provided by Jeff in v2.
>
> - Mani

Hi Mani, thanks for review. Sorry, missing this part. Will change to 
following commit message.

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

>> 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 b137d54..93b5110 100644
>> --- a/drivers/bus/mhi/host/main.c
>> +++ b/drivers/bus/mhi/host/main.c
>> @@ -1129,17 +1129,15 @@ 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
>> @@ -1159,7 +1157,6 @@ 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
>>
>>