Re: [Intel-gfx] [PATCH i-g-t] i915/gem_exec_balancer: Throw a few hangs into the virtual pipelines

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 15/11/2019 13:09, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2019-11-15 13:02:24)
>>
>> On 14/11/2019 19:15, Chris Wilson wrote:
>>> Although a virtual engine itself has no hang detection; that is on the
>>> underlying physical engines, it does provide a unique means for clients
>>> to try and break the system. Try and break it before they do.
>>>
>>> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>>> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>> ---
>>>    tests/i915/gem_exec_balancer.c | 105 +++++++++++++++++++++++++++++++++
>>>    1 file changed, 105 insertions(+)
>>>
>>> diff --git a/tests/i915/gem_exec_balancer.c b/tests/i915/gem_exec_balancer.c
>>> index 70c4529b4..86028cfdd 100644
>>> --- a/tests/i915/gem_exec_balancer.c
>>> +++ b/tests/i915/gem_exec_balancer.c
>>> @@ -24,6 +24,7 @@
>>>    #include <sched.h>
>>>    
>>>    #include "igt.h"
>>> +#include "igt_gt.h"
>>>    #include "igt_perf.h"
>>>    #include "i915/gem_ring.h"
>>>    #include "sw_sync.h"
>>> @@ -1314,6 +1315,102 @@ static void semaphore(int i915)
>>>        gem_quiescent_gpu(i915);
>>>    }
>>>    
>>> +static void set_unbannable(int i915, uint32_t ctx)
>>> +{
>>> +     struct drm_i915_gem_context_param p = {
>>> +             .ctx_id = ctx,
>>> +             .param = I915_CONTEXT_PARAM_BANNABLE,
>>> +     };
>>> +
>>> +     igt_assert_eq(__gem_context_set_param(i915, &p), 0);
>>> +}
>>> +
>>> +static void hangme(int i915)
>>> +{
>>> +     struct drm_i915_gem_exec_object2 batch = {
>>> +             .handle = batch_create(i915),
>>> +     };
>>> +
>>> +     /*
>>> +      * Fill the available engines with hanging virtual engines and verify
>>> +      * that execution continues onto the second batch.
>>> +      */
>>> +
>>> +     for (int class = 1; class < 32; class++) {
>>> +             struct i915_engine_class_instance *ci;
>>> +             struct client {
>>> +                     igt_spin_t *spin[2];
>>> +             } *client;
>>> +             unsigned int count;
>>> +             uint32_t bg;
>>> +
>>> +             ci = list_engines(i915, 1u << class, &count);
>>> +             if (!ci)
>>> +                     continue;
>>> +
>>> +             if (count < 2) {
>>> +                     free(ci);
>>> +                     continue;
>>> +             }
>>> +
>>> +             client = malloc(sizeof(*client) * count);
>>> +             igt_assert(client);
>>> +
>>> +             for (int i = 0; i < count; i++) {
>>> +                     uint32_t ctx = gem_context_create(i915);
>>> +                     struct client *c = &client[i];
>>> +                     unsigned int flags;
>>> +
>>> +                     set_unbannable(i915, ctx);
>>> +                     set_load_balancer(i915, ctx, ci, count, NULL);
>>> +
>>> +                     flags = IGT_SPIN_FENCE_OUT | IGT_SPIN_NO_PREEMPTION;
>>> +                     for (int j = 0; j < ARRAY_SIZE(c->spin); j++)  {
>>> +                             c->spin[j] = igt_spin_new(i915, ctx,
>>> +                                                       .flags = flags);
>>> +                             flags = IGT_SPIN_FENCE_OUT;
>>> +                     }
>>> +
>>> +                     gem_context_destroy(i915, ctx);
>>> +             }
>>> +
>>> +             /* Apply some background context to speed up hang detection */
>>> +             bg = gem_context_create(i915);
>>> +             set_engines(i915, bg, ci, count);
>>> +             for (int i = 0; i < count; i++) {
>>> +                     struct drm_i915_gem_execbuffer2 execbuf = {
>>> +                             .buffers_ptr = to_user_pointer(&batch),
>>> +                             .buffer_count = 1,
>>> +                             .flags = i,
>>> +                             .rsvd1 = bg,
>>> +                     };
>>> +                     gem_execbuf(i915, &execbuf);
>>> +             }
>>> +             gem_context_destroy(i915, bg);
>>> +
>>> +             for (int i = 0; i < count; i++) {
>>> +                     struct client *c = &client[i];
>>> +
>>> +                     igt_debug("Waiting for client[%d].spin[%d]\n", i, 0);
>>> +                     gem_sync(i915, c->spin[0]->handle);
>>> +                     igt_assert_eq(sync_fence_status(c->spin[0]->out_fence),
>>> +                                   -EIO);
>>> +
>>> +                     igt_debug("Waiting for client[%d].spin[%d]\n", i, 1);
>>> +                     gem_sync(i915, c->spin[1]->handle);
>>> +                     igt_assert_eq(sync_fence_status(c->spin[1]->out_fence),
>>> +                                   -EIO);
>>> +
>>> +                     igt_spin_free(i915, c->spin[0]);
>>> +                     igt_spin_free(i915, c->spin[1]);
>>> +             }
>>> +             free(client);
>>> +     }
>>> +
>>> +     gem_close(i915, batch.handle);
>>> +     gem_quiescent_gpu(i915);
>>> +}
>>> +
>>>    static void smoketest(int i915, int timeout)
>>>    {
>>>        struct drm_i915_gem_exec_object2 batch[2] = {
>>> @@ -1486,4 +1583,12 @@ igt_main
>>>        igt_fixture {
>>>                igt_stop_hang_detector();
>>>        }
>>> +
>>> +     igt_subtest("hang") {
>>> +             igt_hang_t hang = igt_allow_hang(i915, 0, 0);
>>> +
>>> +             hangme(i915);
>>> +
>>> +             igt_disallow_hang(i915, hang);
>>> +     }
>>>    }
>>>
>>
>> Looks good. But do we need some core helpers to figure out when preempt
>> timeout is compiled out?
> 
> It should still work the same, but slower; 10s hang detection rather
> than ~200ms.

You are talking about old hangcheck? I was thinking about all new 
Kconfig's compiled out. No heartbeats, no preemption timeout. Still works?

Regards,

Tvrtko

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