[openib-general][PATCH][kdapl]: inc/dec module ref count

[Guy German]

Hi Muli,

Muli Ben-Yehuda <mailto:mulix at mulix.org> wrote:
> On Thu, Jul 28, 2005 at 10:14:15AM +0300, Guy German wrote:
> 
>> [kdapl]: increments the module ref count on ia_open, thus making
>> sure the kdapl_ib module would not be rmmod-ed while in use
>> 
>> Signed-off-by: Guy German <guyg at voltaire.com>
>> 
>> Index: infiniband/ulp/kdapl/ib/dapl_ia.c
>> ===================================================================
>> --- infiniband/ulp/kdapl/ib/dapl_ia.c	(revision 2914)
>> +++ infiniband/ulp/kdapl/ib/dapl_ia.c	(working copy)
>> @@ -649,6 +649,7 @@ int dapl_ia_open(const char *name, int a 
>> status = 0; 
>>  	*ia_ptr = (struct dat_ia *)ia;
>>  	*async_evd = (struct dat_evd *)evd;
>> +	try_module_get(THIS_MODULE);
> 
> This does not look right. First, try_module_get() may fail. Second,
> you're calling it in the context of your module - what happens if
> someone tried to remove it while dapl_ia_open() is running and before
> the call? 

Wouldn't it be solved by moving the try_module_get call to the 
beginning of the dapl_ia_open function ? 

You are right - try_module_get() can fail when the module is not ready 
to be entered. should be something like: 
+ if (!try_module_get(THIS_MODULE))
+	return -EBUSY;

Guy.

> 
> The right place to do module refcounting is in the caller, not in the
> callee. In this case - whereever dapl_ia_open() can be called from.
> 
>>  bail:
>>  	if (status != 0)
>> @@ -679,6 +680,7 @@ int dapl_ia_close(struct dat_ia *ia_ptr,  	else
>>  		status = -EINVAL;
>> 
>> +	module_put(THIS_MODULE);
> 
> Likewise.
> 
> Cheers,
> Muli