linux-kernel - [PATCH v4 6/6] dma-buf: Check status of enable-signaling bit on debug

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Message-ID: <20220914164321.2156-7-Arvind.Yadav@amd.com>
Date:   Wed, 14 Sep 2022 22:13:21 +0530
From:   Arvind Yadav <Arvind.Yadav@....com>
To:     <Christian.Koenig@....com>, <andrey.grodzovsky@....com>,
        <shashank.sharma@....com>, <amaranath.somalapuram@....com>,
        <Arunpravin.PaneerSelvam@....com>, <sumit.semwal@...aro.org>,
        <gustavo@...ovan.org>, <airlied@...ux.ie>, <daniel@...ll.ch>,
        <linux-media@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linaro-mm-sig@...ts.linaro.org>, <linux-kernel@...r.kernel.org>
CC:     Arvind Yadav <Arvind.Yadav@....com>
Subject: [PATCH v4 6/6] dma-buf: Check status of enable-signaling bit on debug

Fence signaling must be enabled to make sure that
the dma_fence_is_signaled() function ever returns true.
Since drivers and implementations sometimes mess this up,
this ensures correct behaviour when DMABUF_DEBUG_ENABLE_SIGNALING
is used during debugging.
This should make any implementation bugs resulting in not
signaled fences much more obvious.

Signed-off-by: Arvind Yadav <Arvind.Yadav@....com>
---

Changes in v1,v2 :
1- Addressing Christian's comment to replace
CONFIG_DEBUG_WW_MUTEX_SLOWPATH instead of CONFIG_DEBUG_FS.
2- As per Christian's comment moving this patch at last so
The version of this patch is also changed and previously
it was [PATCH 1/4]

Changes in v3: 
1 - Adding new config DMABUF_DEBUG_ENABLE_SIGNALING.
2 - Replace CONFIG_DEBUG_WW_MUTEX_SLOWPATH to new
CONFIG_DMABUF_DEBUG_ENABLE_SIGNALING.

---
 drivers/dma-buf/Kconfig   | 7 +++++++
 include/linux/dma-fence.h | 5 +++++
 2 files changed, 12 insertions(+)

diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
index e4dc53a36428..c991e6a51510 100644
--- a/drivers/dma-buf/Kconfig
+++ b/drivers/dma-buf/Kconfig
@@ -65,6 +65,13 @@ config DMABUF_SELFTESTS
 	default n
 	depends on DMA_SHARED_BUFFER
 
+config DMABUF_DEBUG_ENABLE_SIGNALING
+	bool "DMA Fence enable signaling debug checks"
+	default n
+	depends on DMA_SHARED_BUFFER
+	help
+	  This option enables additional checks for software signaling of fence.
+
 menuconfig DMABUF_HEAPS
 	bool "DMA-BUF Userland Memory Heaps"
 	select DMA_SHARED_BUFFER
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 775cdc0b4f24..01e1fa4d3cec 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -428,6 +428,11 @@ dma_fence_is_signaled_locked(struct dma_fence *fence)
 static inline bool
 dma_fence_is_signaled(struct dma_fence *fence)
 {
+#ifdef CONFIG_DMABUF_DEBUG_ENABLE_SIGNALING
+	if (!test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags))
+		return false;
+#endif
+
 	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
 		return true;
 
-- 
2.25.1