[igt-dev] [PATCH v3 i-g-t 09/15] tests/i915/i915_hangman: Remove reliance on context persistance

[John Harrison]

On 1/13/2022 12:30, Matthew Brost wrote:
> On Thu, Jan 13, 2022 at 11:59:41AM -0800, John.C.Harrison at Intel.com wrote:
>> From: John Harrison <John.C.Harrison at Intel.com>
>>
>> The hang test was relying on context persitence for no particular
>> reason. That is, it would set a bunch of background spinners running
>> then immediately destroy the active contexts but expect the spinners
>> to keep spinning. With the current implementation of context
>> persistence in i915, that means that super high priority pings are
>> sent to each engine at the start of the test. Depending upon the
>> timing and platform, one of those unexpected pings could cause test
>> failures.
>>
>> There is no need to require context persitence in this test. So change
>> to managing the contexts cleanly and only destroying them when they
>> are no longer in use.
>>
>> Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
>> ---
>>   tests/i915/i915_hangman.c | 15 ++++++++++-----
>>   1 file changed, 10 insertions(+), 5 deletions(-)
>>
>> diff --git a/tests/i915/i915_hangman.c b/tests/i915/i915_hangman.c
>> index 918418760..6601db5f6 100644
>> --- a/tests/i915/i915_hangman.c
>> +++ b/tests/i915/i915_hangman.c
>> @@ -289,27 +289,29 @@ test_engine_hang(const intel_ctx_t *ctx,
>>   		 const struct intel_execution_engine2 *e, unsigned int flags)
>>   {
>>   	const struct intel_execution_engine2 *other;
>> -	const intel_ctx_t *tmp_ctx;
>> +	const intel_ctx_t *local_ctx[GEM_MAX_ENGINES];
> This is fine for now as GEM_MAX_ENGINES is relatively small but what if
> we change this to large value, let's say 4k? I think the stack could
> overflow then. Maybe not a concern, maybe it is? I'll leave this up to
> if this should be kmalloc'd or not in the next rev.
Seems unlikely we are going that big any time soon. And such stack 
reduction can always be done as part of any huge engine count update. 
Although, this is userland not kernel - you can slap gigabytes on the 
stack and it won't blow up ;).

John.

> Everything else looks good.
>
> With that:
> Reviewed-by: Matthew Brost <matthew.brost at intel.com>
>
>>   	igt_spin_t *spin, *next;
>>   	IGT_LIST_HEAD(list);
>>   	uint64_t ahnd = get_reloc_ahnd(device, ctx->id), ahndN;
>> +	int num_ctx;
>>   
>>   	igt_skip_on(flags & IGT_SPIN_INVALID_CS &&
>>   		    gem_engine_has_cmdparser(device, &ctx->cfg, e->flags));
>>   
>>   	/* Fill all the other engines with background load */
>> +	num_ctx = 0;
>>   	for_each_ctx_engine(device, ctx, other) {
>>   		if (other->flags == e->flags)
>>   			continue;
>>   
>> -		tmp_ctx = intel_ctx_create(device, &ctx->cfg);
>> -		ahndN = get_reloc_ahnd(device, tmp_ctx->id);
>> +		local_ctx[num_ctx] = intel_ctx_create(device, &ctx->cfg);
>> +		ahndN = get_reloc_ahnd(device, local_ctx[num_ctx]->id);
>>   		spin = __igt_spin_new(device,
>>   				      .ahnd = ahndN,
>> -				      .ctx = tmp_ctx,
>> +				      .ctx = local_ctx[num_ctx],
>>   				      .engine = other->flags,
>>   				      .flags = IGT_SPIN_FENCE_OUT);
>> -		intel_ctx_destroy(device, tmp_ctx);
>> +		num_ctx++;
>>   
>>   		igt_list_move(&spin->link, &list);
>>   	}
>> @@ -339,7 +341,10 @@ test_engine_hang(const intel_ctx_t *ctx,
>>   		igt_spin_free(device, spin);
>>   		put_ahnd(ahndN);
>>   	}
>> +
>>   	put_ahnd(ahnd);
>> +	while (num_ctx)
>> +		intel_ctx_destroy(device, local_ctx[--num_ctx]);
>>   
>>   	check_alive();
>>   }
>> -- 
>> 2.25.1
>>