Re: [PATCH v2 03/38] drm/i915: Add some selftests for sg_table manipulation

[Chris Wilson <chris@chris-wilson.co.uk>]

On Thu, Feb 02, 2017 at 12:41:42PM +0000, Tvrtko Ursulin wrote:
> 
> On 01/02/2017 11:34, Chris Wilson wrote:
> >On Wed, Feb 01, 2017 at 11:17:39AM +0000, Tvrtko Ursulin wrote:
> 
> >>>+
> >>>+			for (npages = npages_funcs; *npages; npages++) {
> >>>+				prandom_seed_state(&prng,
> >>>+						   i915_selftest.random_seed);
> >>>+				if (!alloc_table(&pt, sz, sz, *npages, &prng))
> >>>+					return 0; /* out of memory, give up */
> >>
> >>You don't have skip status? Sounds not ideal to silently abort.
> >
> >It runs until we use all physical memory, if left to its own devices. It's
> >not a skip if we have already completed some tests. ENOMEM of the test
> >setup itself is not what I'm testing for here, the test is for the
> >iterators.
> 
> But suppose you mess up the test so the starting condition asks for
> impossible amount of memory but the test claims it passed. I don't
> think that is a good behaviour.

Returing ENOMEM when the failure is intentional is not an option either.

diff --git a/drivers/gpu/drm/i915/selftests/scatterlist.c b/drivers/gpu/drm/i915/selftests/scatterlist.c
index fa5bd09c863f..5eb732231749 100644
--- a/drivers/gpu/drm/i915/selftests/scatterlist.c
+++ b/drivers/gpu/drm/i915/selftests/scatterlist.c
@@ -245,6 +245,7 @@ static int igt_sg_alloc(void *ignored)
        const unsigned long max_order = 20; /* approximating a 4GiB object */
        struct rnd_state prng;
        unsigned long prime;
+       int alloc_error = -ENOMEM;
 
        for_each_prime_number(prime, max_order) {
                unsigned long size = BIT(prime);
@@ -260,7 +261,7 @@ static int igt_sg_alloc(void *ignored)
                                prandom_seed_state(&prng,
                                                   i915_selftest.random_seed);
                                if (!alloc_table(&pt, sz, sz, *npages, &prng))
-                                       return 0; /* out of memory, give up */
+                                       return alloc_error;
 
                                prandom_seed_state(&prng,
                                                   i915_selftest.random_seed);
@@ -270,6 +271,8 @@ static int igt_sg_alloc(void *ignored)
                                sg_free_table(&pt.st);
                                if (err)
                                        return err;
+
+                               alloc_error = 0;
                        }
                }
        }

-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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