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Subject: Re: [PATCH] interconnect: Check for valid path in icc_set_bw()
To:     Bjorn Andersson <bjorn.andersson@linaro.org>
Cc:     linux-pm@vger.kernel.org, evgreen@chromium.org,
        daidavid1@codeaurora.org, okukatla@codeaurora.org,
        jcrouse@codeaurora.org, linux-kernel@vger.kernel.org
References: <20191220171310.24169-1-georgi.djakov@linaro.org>
 <20191220190426.GE549437@yoga>
From:   Georgi Djakov <georgi.djakov@linaro.org>
Message-ID: <6a9d1b18-b34a-6ecb-0fe6-66dd7ee8cb52@linaro.org>
Date:   Sat, 21 Dec 2019 04:43:04 +0200
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In-Reply-To: <20191220190426.GE549437@yoga>
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Hi Bjorn,

Thanks for the comments!

On 20.12.19 21:04, Bjorn Andersson wrote:
> On Fri 20 Dec 09:13 PST 2019, Georgi Djakov wrote:
> 
>> Use IS_ERR() to ensure that the path passed to icc_set_bw() is valid.
>>
>> Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
>> ---
>>  drivers/interconnect/core.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
>> index 63c164264b73..14a6f7ade44a 100644
>> --- a/drivers/interconnect/core.c
>> +++ b/drivers/interconnect/core.c
>> @@ -498,6 +498,11 @@ int icc_set_bw(struct icc_path *path, u32 avg_bw, u32 peak_bw)
>>  	if (!path || !path->num_nodes)
>>  		return 0;
>>  
>> +	if (IS_ERR(path)) {
> 
> This is a sign of a logical error, and the print is likely to be
> ignored/lost in the noise. So I think the response should aid to help
> the developer hitting this to resolve the issue.
> 
> So I think this is more visible and more useful as:
> 
> 	if (WARN_ON(IS_ERR(path)))
> 		return -EINVAL;

That's actually what i had in mind initially, but then started
wondering whether this isn't a bit too noisy. But oh well, let's
scream loud if something is done incorrectly.

> 
> PS. Doesn't path->num_nodes == 0 fall in this category as well? When
> would you have a path object with no nodes passed to this function?

Yes, will make the warning cover this case too.

Thanks,
Georgi

> 
> Regards,
> Bjorn
> 
>> +		pr_err("%s: invalid path=%ld\n", __func__, PTR_ERR(path));
>> +		return -EINVAL;
>> +	}
>> +
>>  	mutex_lock(&icc_lock);
>>  
>>  	old_avg = path->reqs[0].avg_bw;