Subject: Re: [PATCH v2] remoteproc: sysfs/debugfs: fix race while updating
 recovery flag
To:     Mukesh Ojha <quic_mojha@quicinc.com>, <andersson@kernel.org>,
        <mathieu.poirier@linaro.org>
CC:     <linux-remoteproc@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-arm-msm@vger.kernel.org>
References: <20230201054609.14575-1-quic_satyap@quicinc.com>
 <22bcf613-5c0f-3043-f8ad-41bf45c5dc07@quicinc.com>
From:   Satya Durga Srinivasu Prabhala <quic_satyap@quicinc.com>
Message-ID: <94e7154d-8c87-47e3-1f57-b84eb7522db6@quicinc.com>
Date:   Mon, 6 Feb 2023 18:12:02 -0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <22bcf613-5c0f-3043-f8ad-41bf45c5dc07@quicinc.com>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Precedence: bulk


On 2/1/23 4:05 AM, Mukesh Ojha wrote:
>
>
> On 2/1/2023 11:16 AM, Satya Durga Srinivasu Prabhala wrote:
>> When multiple clients try to update the recovery flag, it is
>> possible that, race condition would lead to undesired results
>> as updates to recovery flag isn't protected by any mechanism
>> today. To avoid such issues, take remoteproc mutex lock before
>> updating recovery flag and release the lock once done.
>>
>> Signed-off-by: Satya Durga Srinivasu Prabhala <quic_satyap@quicinc.com>
>
> LGTM.
>
> Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>

Thanks Mukesh.

Hi Bjorn,

Can you help cross check?

Best,
Satya

>
> -Mukesh
>> ---
>> v1 -> v2:
>> - addressed comments from Mukesh Ojha
>>    1. take & release lock only while updating recovery flag
>>    2. update debugfs
>>
>>   drivers/remoteproc/remoteproc_debugfs.c | 4 ++++
>>   drivers/remoteproc/remoteproc_sysfs.c   | 4 ++++
>>   2 files changed, 8 insertions(+)
>>
>> diff --git a/drivers/remoteproc/remoteproc_debugfs.c 
>> b/drivers/remoteproc/remoteproc_debugfs.c
>> index b86c1d09c70c..2c44d375024e 100644
>> --- a/drivers/remoteproc/remoteproc_debugfs.c
>> +++ b/drivers/remoteproc/remoteproc_debugfs.c
>> @@ -226,10 +226,14 @@ rproc_recovery_write(struct file *filp, const 
>> char __user *user_buf,
>>
>>       if (!strncmp(buf, "enabled", count)) {
>>           /* change the flag and begin the recovery process if needed */
>> +        mutex_lock(&rproc->lock);
>>           rproc->recovery_disabled = false;
>> +        mutex_unlock(&rproc->lock);
>>           rproc_trigger_recovery(rproc);
>>       } else if (!strncmp(buf, "disabled", count)) {
>> +        mutex_lock(&rproc->lock);
>>           rproc->recovery_disabled = true;
>> +        mutex_unlock(&rproc->lock);
>>       } else if (!strncmp(buf, "recover", count)) {
>>           /* begin the recovery process without changing the flag */
>>           rproc_trigger_recovery(rproc);
>> diff --git a/drivers/remoteproc/remoteproc_sysfs.c 
>> b/drivers/remoteproc/remoteproc_sysfs.c
>> index 8c7ea8922638..628e0de9a132 100644
>> --- a/drivers/remoteproc/remoteproc_sysfs.c
>> +++ b/drivers/remoteproc/remoteproc_sysfs.c
>> @@ -50,10 +50,14 @@ static ssize_t recovery_store(struct device *dev,
>>
>>       if (sysfs_streq(buf, "enabled")) {
>>           /* change the flag and begin the recovery process if needed */
>> +        mutex_lock(&rproc->lock);
>>           rproc->recovery_disabled = false;
>> +        mutex_unlock(&rproc->lock);
>>           rproc_trigger_recovery(rproc);
>>       } else if (sysfs_streq(buf, "disabled")) {
>> +        mutex_lock(&rproc->lock);
>>           rproc->recovery_disabled = true;
>> +        mutex_unlock(&rproc->lock);
>>       } else if (sysfs_streq(buf, "recover")) {
>>           /* begin the recovery process without changing the flag */
>>           rproc_trigger_recovery(rproc);