linux-kernel - Re: [PATCH 4/4] drm/vc4: tests: Retry pv-muxing tests when EDEADLK

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Message-ID: <e3517bd6-a9c2-4193-92d8-b6510b967d0a@igalia.com>
Date: Sun, 23 Mar 2025 15:07:59 -0300
From: Maíra Canal <mcanal@...lia.com>
To: Maxime Ripard <mripard@...nel.org>,
 Dave Stevenson <dave.stevenson@...pberrypi.com>,
 Raspberry Pi Kernel Maintenance <kernel-list@...pberrypi.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] drm/vc4: tests: Retry pv-muxing tests when EDEADLK

Hi Maxime,

On 18/03/25 11:17, Maxime Ripard wrote:
> Some functions used by the HVS->PV muxing tests can return with EDEADLK,
> meaning the entire sequence should be restarted. It's not a fatal error
> and we should treat it as a recoverable error, and recover, instead of
> failing the test like we currently do.
> 
> Fixes: 76ec18dc5afa ("drm/vc4: tests: Add unit test suite for the PV muxing")
> Signed-off-by: Maxime Ripard <mripard@...nel.org>
> ---
>   drivers/gpu/drm/vc4/tests/vc4_test_pv_muxing.c | 44 ++++++++++++++++++++++++++
>   1 file changed, 44 insertions(+)
> 
> diff --git a/drivers/gpu/drm/vc4/tests/vc4_test_pv_muxing.c b/drivers/gpu/drm/vc4/tests/vc4_test_pv_muxing.c
> index 52c04ef33206bf4f9e21e3c8b7cea932824a67fa..94e05bddb630a79aab189d9bc16f09a9d84ce396 100644
> --- a/drivers/gpu/drm/vc4/tests/vc4_test_pv_muxing.c
> +++ b/drivers/gpu/drm/vc4/tests/vc4_test_pv_muxing.c
> @@ -685,20 +685,26 @@ static void drm_vc4_test_pv_muxing(struct kunit *test)
>   
>   	drm_modeset_acquire_init(&ctx, 0);
>   
>   	vc4 = priv->vc4;
>   	drm = &vc4->base;
> +
> +retry:
>   	state = drm_kunit_helper_atomic_state_alloc(test, drm, &ctx);
>   	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, state);
>   	for (i = 0; i < params->nencoders; i++) {
>   		enum vc4_encoder_type enc_type = params->encoders[i];
>   
>   		ret = vc4_mock_atomic_add_output(test, state, enc_type);
> +		if (ret == -EDEADLK)
> +			goto retry;
>   		KUNIT_ASSERT_EQ(test, ret, 0);
>   	}
>   
>   	ret = drm_atomic_check_only(state);
> +	if (ret == -EDEADLK)
> +		goto retry;

Shouldn't we call `drm_modeset_backoff()` before retrying (maybe
`drm_atomic_state_clear()` as well)?

Best Regards,
- Maíra

>   	KUNIT_EXPECT_EQ(test, ret, 0);
>   
>   	KUNIT_EXPECT_TRUE(test,
>   			  check_fifo_conflict(test, state));
>