[Intel-xe] [PATCH] drm/xe: Introduce xe_ASSERT macros

[Lucas De Marchi]

On Tue, Aug 08, 2023 at 06:04:20PM +0300, Jani Nikula wrote:
>On Tue, 08 Aug 2023, Lucas De Marchi <lucas.demarchi at intel.com> wrote:
>> On Mon, Aug 07, 2023 at 07:34:46PM +0200, Michal Wajdeczko wrote:
>>>As we are moving away from the controversial XE_BUG_ON macro,
>>>relying just on WARN_ON or drm_err does not cover the cases
>>>where we want to annotate functions with additional detailed
>>>debug checks to assert that all prerequisites are satisfied,
>>>without paying footprint or performance penalty on non-debug
>>>builds, where all misuses introduced during code integration
>>>were already fixed.
>>>
>>>Introduce family of xe_ASSERT macros that try to follow classic
>>>assert() utility and can be compiled out on non-debug builds.
>>>
>>>Macros are based on drm_WARN, but unlikely to origin, disallow
>>>use in expressions since we will compile that code out.
>>>
>>>As we are operating on the xe pointers, we can print additional
>>>information about the device, like tile or GT identifier, that
>>>is not available from generic WARN report:
>>>
>>>[ ] xe 0000:00:02.0: [drm] Assertion `true == false` failed!
>>>    platform: 1 subplatform: 1
>>>    graphics: Xe_LP 12.0 step B0
>>>    media: Xe_M 12.0 step B0
>>>    display: enabled step D0
>>>    tile: 0 VRAM 0 B
>>>    GT: 0 type 1
>>>
>>>[ ] xe 0000:b3:00.0: [drm] Assertion `true == false` failed!
>>>    platform: 7 subplatform: 3
>>>    graphics: Xe_HPG 12.55 step A1
>>>    media: Xe_HPM 12.55 step A1
>>>    display: disabled step **
>>>    tile: 0 VRAM 14.0 GiB
>>>    GT: 0 type 1
>>>
>>>[ ] WARNING: CPU: 0 PID: 2687 at drivers/gpu/drm/xe/xe_device.c:281 xe_device_probe+0x374/0x520 [xe]
>>>[ ] RIP: 0010:xe_device_probe+0x374/0x520 [xe]
>>>[ ] Call Trace:
>>>[ ]  ? __warn+0x7b/0x160
>>>[ ]  ? xe_device_probe+0x374/0x520 [xe]
>>>[ ]  ? report_bug+0x1c3/0x1d0
>>>[ ]  ? handle_bug+0x42/0x70
>>>[ ]  ? exc_invalid_op+0x14/0x70
>>>[ ]  ? asm_exc_invalid_op+0x16/0x20
>>>[ ]  ? xe_device_probe+0x374/0x520 [xe]
>>>[ ]  ? xe_device_probe+0x374/0x520 [xe]
>>>[ ]  xe_pci_probe+0x6e3/0x950 [xe]
>>>[ ]  ? lockdep_hardirqs_on+0xc7/0x140
>>>[ ]  pci_device_probe+0x9e/0x160
>>>[ ]  really_probe+0x19d/0x400
>>>
>>>Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
>>>Cc: Oded Gabbay <ogabbay at kernel.org>
>>>Cc: Jani Nikula <jani.nikula at intel.com>
>>>Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
>>>Cc: Matthew Brost <matthew.brost at intel.com>
>>>---
>>> drivers/gpu/drm/xe/xe_assert.h | 160 +++++++++++++++++++++++++++++++++
>>> 1 file changed, 160 insertions(+)
>>> create mode 100644 drivers/gpu/drm/xe/xe_assert.h
>>>
>>>diff --git a/drivers/gpu/drm/xe/xe_assert.h b/drivers/gpu/drm/xe/xe_assert.h
>>>new file mode 100644
>>>index 000000000000..7ea295b7091c
>>>--- /dev/null
>>>+++ b/drivers/gpu/drm/xe/xe_assert.h
>>>@@ -0,0 +1,160 @@
>>>+/* SPDX-License-Identifier: MIT */
>>>+/*
>>>+ * Copyright © 2023 Intel Corporation
>>>+ */
>>>+
>>>+#ifndef __XE_ASSERT_H__
>>>+#define __XE_ASSERT_H__
>>>+
>>>+#include <linux/string_helpers.h>
>>>+#include <drm/drm_print.h>
>>>+#include "xe_device_types.h"
>>>+#include "xe_step.h"
>>>+
>>>+/**
>>>+ * DOC: Xe ASSERTs
>>>+ *
>>>+ * While Xe driver aims to be simpler than legacy i915 driver it is still
>>>+ * complex enough that some changes introduced while adding new functionality
>>>+ * could break the existing code.
>>>+ *
>>>+ * Adding &drm_WARN or &drm_err to catch unwanted programming usage could lead
>>>+ * to undesired increased driver footprint and may impact production driver
>>>+ * performance as this additional code will be always present.
>>>+ *
>>>+ * To allow annotate functions with additional detailed debug checks to assert
>>>+ * that all prerequisites are satisfied, without worrying about footprint or
>>>+ * performance penalty on production builds where all potential misuses
>>>+ * introduced during code integration were already fixed, we introduce family
>>>+ * of ASSERT macros that try to follow classic assert() utility and can be
>>>+ * compiled out on non-debug builds:
>>>+ *
>>>+ *  * &xe_ASSERT
>>
>> pass by comment, not really checking anything else here... Why are we
>> mixing upper/lower case? It's perfectly fine to use XE_ as the namespace
>> like is done for other macros.
>
>I think it comes from drm_WARN, but yeah, could be XE_ASSERT.

yeah... I think copying that would be like perpetuating a mistake.

Lucas De Marchi

>
>>
>> Lucas De Marchi
>
>-- 
>Jani Nikula, Intel Open Source Graphics Center