[RFC PATCH] use snprintf instead of sprintf in rcu_torture_printk

[Pranith Kumar]

(dropping some CCs)

On 06/19/2014 05:00 PM, Paul E. McKenney wrote:
> On Wed, Jun 18, 2014 at 12:49:42PM -0700, Joe Perches wrote:
>>
>> I believe the function doesn't work well.
>>
>> static void
>> rcu_torture_stats_print(void)
>> {
>> 	int size = nr_cpu_ids * 200 + 8192;
>> 	char *buf;
>>
>> 	buf = kmalloc(size, GFP_KERNEL);
>> 	if (!buf) {
>> 		pr_err("rcu-torture: Out of memory, need: %d\n", size);
>> 		return;
>> 	}
>> 	rcu_torture_printk(buf);
>> 	pr_alert("%s", buf);
>> 	kfree(buf);
>> }
>>
>> rcu_torture_printk simply fills buf
>>
>> btw: I believe the arguments should pass size and
>>      rcu_torture_printk should use snprintf/size
>>
>> but all printks are limited to a maximum of 1024
>> bytes so the large allocation is senseless and
>> would even if it worked, would likely need to be
>> vmalloc/vfree
> 
> Fair point!
> 
> Pranith, Romanov, if you would like part of RCU that is less touchy
> about random hacking, this would be a good place to start.  Scripts in
> tools/testing/selftests/rcutorture/bin do care about some of the format,
> but the variable-length portion generated by cur_ops->stats() is as far
> as I know only parsed by human eyes.
> 

Here is a first run of the change. Please let me know if I am totally off. RFC. :)

Three things on Todo list:

* We need to check that we are using less than the allocated size of the buffer (used > size). (we are allocating a big buffer, so not sure if necessary)
* Need to check with the scripts if they are working.
* I used a loop for pr_alert(). I am not sure this is right, there should be a better way for printing large buffers

If the overall structure is ok I will go ahead and check how the scripts are handling these changes.