linux-kernel - Re: [PATCH] s390: correct misuses of module_put in appldata_generic

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Message-ID: <CAABZP2zrLqTRu4sTbYSQ58G1SHGR_YhdGC7365aVmyq6q1n_dg@mail.gmail.com>
Date:	Tue, 18 Mar 2014 09:24:55 +0800
From:	Zhouyi Zhou <zhouzhouyi@...il.com>
To:	Gerald Schaefer <gerald.schaefer@...ibm.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-s390@...r.kernel.org, joe@...ches.com, gang.chen@...anux.com,
	linux390@...ibm.com, heiko.carstens@...ibm.com,
	schwidefsky@...ibm.com, Zhouyi Zhou <yizhouzhou@....ac.cn>
Subject: Re: [PATCH] s390: correct misuses of module_put in appldata_generic_handler.

Thanks Gerald for reviewing and sorry for not elaborated it in the e-mail.

Firstly, I think you can't call module_put after fail try_module_get

Secondly, there exists duplicate module_put on the program path (the last
one is before return 0)

On Mon, Mar 17, 2014 at 9:28 PM, Gerald Schaefer
<gerald.schaefer@...ibm.com> wrote:
> On Sat, 15 Mar 2014 21:35:40 +0800
> Zhouyi Zhou <zhouzhouyi@...il.com> wrote:
>
>> correct misuses of module_put in  appldata_generic_handler
>
> Sorry, I don't see any misuse, could you elaborate?
>
>>
>> Signed-off-by: Zhouyi Zhou <yizhouzhou@....ac.cn>
>> ---
>>  arch/s390/appldata/appldata_base.c | 3 ---
>>  1 file changed, 3 deletions(-)
>>
>> diff --git a/arch/s390/appldata/appldata_base.c b/arch/s390/appldata/appldata_base.c
>> index 47c8630..683e0282 100644
>> --- a/arch/s390/appldata/appldata_base.c
>> +++ b/arch/s390/appldata/appldata_base.c
>> @@ -343,7 +343,6 @@ appldata_generic_handler(struct ctl_table *ctl, int write,
>>               // protect work queue callback
>>               if (!try_module_get(ops->owner)) {
>>                       mutex_unlock(&appldata_ops_mutex);
>> -                     module_put(ops->owner);
>>                       return -ENODEV;
>>               }
>>               ops->callback(ops->data);       // init record
>> @@ -354,7 +353,6 @@ appldata_generic_handler(struct ctl_table *ctl, int write,
>>               if (rc != 0) {
>>                       pr_err("Starting the data collection for %s "
>>                              "failed with rc=%d\n", ops->name, rc);
>> -                     module_put(ops->owner);
>>               } else
>>                       ops->active = 1;
>>       } else if ((buf[0] == '0') && (ops->active == 1)) {
>> @@ -365,7 +363,6 @@ appldata_generic_handler(struct ctl_table *ctl, int write,
>>               if (rc != 0)
>>                       pr_err("Stopping the data collection for %s "
>>                              "failed with rc=%d\n", ops->name, rc);
>> -             module_put(ops->owner);
>>       }
>>       mutex_unlock(&appldata_ops_mutex);
>>  out:
>
--
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