[PATCH 3/7] dma-buf: add dma_fence_chain_alloc/free self tests

[Christian König]

Am 11.06.21 um 09:58 schrieb Daniel Vetter:
> On Thu, Jun 10, 2021 at 11:17:56AM +0200, Christian König wrote:
>> Exercise the newly added functions.
>>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
> I have honestly no idea what this checks. Spawning a few threads to
> validate kmalloc/kfree feels a bit silly. Now testing whether we correctly
> rcu-delay the freeing here would make some sense, but even that feels a
> bit silly.
>
> I guess if you want this explain with comments what it does and why?

This was soley to figure out if the garbage collection is working 
properly and how much overhead it generates.

No actual need to commit it.

Christian.

> -Daniel
>
>
>> ---
>>   drivers/dma-buf/st-dma-fence-chain.c | 48 ++++++++++++++++++++++++++++
>>   1 file changed, 48 insertions(+)
>>
>> diff --git a/drivers/dma-buf/st-dma-fence-chain.c b/drivers/dma-buf/st-dma-fence-chain.c
>> index 8ce1ea59d31b..855c129c6093 100644
>> --- a/drivers/dma-buf/st-dma-fence-chain.c
>> +++ b/drivers/dma-buf/st-dma-fence-chain.c
>> @@ -95,6 +95,53 @@ static int sanitycheck(void *arg)
>>   	return err;
>>   }
>>   
>> +static int __alloc_free(void *arg)
>> +{
>> +	atomic_t *counter = arg;
>> +	int i, j;
>> +
>> +	for (i = 0; i < 1024; ++i) {
>> +		struct dma_fence_chain *chains[64];
>> +
>> +		for (j = 0; j < ARRAY_SIZE(chains); ++j)
>> +			chains[j] = dma_fence_chain_alloc();
>> +
>> +		for (j = 0; j < ARRAY_SIZE(chains); ++j)
>> +			dma_fence_chain_free(chains[j]);
>> +
>> +		atomic_add(ARRAY_SIZE(chains), counter);
>> +	}
>> +	return 0;
>> +}
>> +
>> +static int alloc_free(void *arg)
>> +{
>> +	struct task_struct *threads[8];
>> +	atomic_t counter = ATOMIC_INIT(0);
>> +	int i, err = 0;
>> +
>> +	for (i = 0; i < ARRAY_SIZE(threads); i++) {
>> +		threads[i] = kthread_run(__alloc_free, &counter, "dmabuf/%d",
>> +					 i);
>> +		if (IS_ERR(threads[i])) {
>> +			err = PTR_ERR(threads[i]);
>> +			break;
>> +		}
>> +	}
>> +
>> +	while (i--) {
>> +		int ret;
>> +
>> +		ret = kthread_stop(threads[i]);
>> +		if (ret && !err)
>> +			err = ret;
>> +	}
>> +
>> +	pr_info("Completed %u cycles\n", atomic_read(&counter));
>> +
>> +	return err;
>> +}
>> +
>>   struct fence_chains {
>>   	unsigned int chain_length;
>>   	struct dma_fence **fences;
>> @@ -677,6 +724,7 @@ int dma_fence_chain(void)
>>   {
>>   	static const struct subtest tests[] = {
>>   		SUBTEST(sanitycheck),
>> +		SUBTEST(alloc_free),
>>   		SUBTEST(find_seqno),
>>   		SUBTEST(find_signaled),
>>   		SUBTEST(find_out_of_order),
>> -- 
>> 2.25.1
>>