linux-kernel - Re: [PATCH] cpufreq: ti-cpufreq: Fix couple of minor issues in probe()

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Date:   Mon, 2 Apr 2018 10:45:07 -0500
From:   Suman Anna <s-anna@...com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
CC:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Dave Gerlach <d-gerlach@...com>, Tero Kristo <t-kristo@...com>,
        <linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Zumeng Chen <zumeng.chen@...il.com>
Subject: Re: [PATCH] cpufreq: ti-cpufreq: Fix couple of minor issues in
 probe()

Hi Viresh,

On 04/02/2018 01:32 AM, Viresh Kumar wrote:
> On 26-03-18, 16:52, Suman Anna wrote:
>> Commit 05829d9431df ("cpufreq: ti-cpufreq: kfree opp_data when
>> failure") has fixed a memory leak in the failure path, however
>> kmemleak still keeps reporting a leak even on successful probes.
>> This is a false-positive and is mostly a result of the opp_data
> 
> I don't agree to this reasoning for this particular patch. The code is just fine
> and kmemleak is something that requires a fix.
> 
>> variable not being stored anywhere in the probe function. The
>> patch also returned a positive value on the get_cpu_device()
>> failure instead of a negative value.
> 
> Maybe that could have been fixed in a separate patch, cc'ing stable kernels as
> well.
> 
>> unreferenced object 0xecae4d80 (size 64):
>>   comm "swapper/0", pid 1, jiffies 4294937673 (age 154.420s)
>>   hex dump (first 32 bytes):
>>     10 40 d9 ee 74 b7 db ee 00 24 ac ec 20 a3 ea c0  .@.......$.. ...
>>     00 26 ac ec 00 00 00 00 00 00 00 00 00 00 00 00  .&..............
>>   backtrace:
>>     [<ec080d62>] platform_drv_probe+0x50/0xac
>>     [<cbde8566>] driver_probe_device+0x24c/0x330
>>     [<a5818eb4>] bus_for_each_drv+0x54/0xb8
>>     [<2c6f7021>] __device_attach+0xcc/0x13c
>>     [<a04478a2>] bus_probe_device+0x88/0x90
>>     [<b322c963>] device_add+0x38c/0x5b4
>>     [<6f1af99b>] platform_device_add+0x100/0x220
>>     [<cef42bca>] platform_device_register_full+0xf0/0x104
>>     [<4d492439>] ti_cpufreq_init+0x44/0x6c
>>     [<81222e89>] do_one_initcall+0x48/0x190
>>     [<3bebf42a>] kernel_init_freeable+0x1f4/0x2b8
>>     [<230ad7df>] kernel_init+0x8/0x110
>>     [<43a165c3>] ret_from_fork+0x14/0x20
>>     [<  (null)>]   (null)
>>     [<87288797>] 0xffffffff
>>
>> Fix both issues by replacing the previous logic by using the devres
>> managed API for allocating the opp_data variable, and simplifying
>> the get_cpu_device() failure return path.
>>
>> Fixes: 05829d9431df ("cpufreq: ti-cpufreq: kfree opp_data when failure")
>> Cc: Zumeng Chen <zumeng.chen@...il.com>
>> Signed-off-by: Suman Anna <s-anna@...com>
>> ---
>>  drivers/cpufreq/ti-cpufreq.c | 7 ++-----
>>  1 file changed, 2 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/cpufreq/ti-cpufreq.c b/drivers/cpufreq/ti-cpufreq.c
>> index a099b7bf74cd..7d353a21935b 100644
>> --- a/drivers/cpufreq/ti-cpufreq.c
>> +++ b/drivers/cpufreq/ti-cpufreq.c
>> @@ -217,7 +217,7 @@ static int ti_cpufreq_probe(struct platform_device *pdev)
>>  	if (!match)
>>  		return -ENODEV;
>>  
>> -	opp_data = kzalloc(sizeof(*opp_data), GFP_KERNEL);
>> +	opp_data = devm_kzalloc(&pdev->dev, sizeof(*opp_data), GFP_KERNEL);
>>  	if (!opp_data)
>>  		return -ENOMEM;
>>  
>> @@ -226,8 +226,7 @@ static int ti_cpufreq_probe(struct platform_device *pdev)
>>  	opp_data->cpu_dev = get_cpu_device(0);
>>  	if (!opp_data->cpu_dev) {
>>  		pr_err("%s: Failed to get device for CPU0\n", __func__);
>> -		ret = ENODEV;
>> -		goto free_opp_data;
>> +		return -ENODEV;
>>  	}
>>  
>>  	opp_data->opp_node = dev_pm_opp_of_get_opp_desc_node(opp_data->cpu_dev);
>> @@ -285,8 +284,6 @@ static int ti_cpufreq_probe(struct platform_device *pdev)
>>  
>>  fail_put_node:
>>  	of_node_put(opp_data->opp_node);
>> -free_opp_data:
>> -	kfree(opp_data);
>>  
>>  	return ret;
>>  }
> 
> I am fine with the diff though, as that makes sense. So maybe do this ?
> 
> - send separate patch for ENODEV thing
> - and another patch to move to devres with a different reason than fixing false
>   positive

OK, thanks for your comments. Will split this patch and post the new
patches.

regards
Suman