From 260fc700cdc685bf67ece6d2c329c435fb6f5f70 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>
Date: Wed, 19 Jan 2022 14:37:41 +0100
Subject: dma-buf: Warn about dma_fence_chain container rules v2
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Git-commit: 270b48bb8da7452b4357d8726933beba72652310
Patch-mainline: v5.18-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
Chaining of dma_fence_chain objects is only allowed through the prev
fence and not through the contained fence.
Warn about that when we create a dma_fence_chain.
v2: fix comment style
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220204100429.2049-4-christian.koenig@amd.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/dma-buf/dma-fence-chain.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/dma-buf/dma-fence-chain.c b/drivers/dma-buf/dma-fence-chain.c
index 1b4cb3e5cec9..084c6927b735 100644
--- a/drivers/dma-buf/dma-fence-chain.c
+++ b/drivers/dma-buf/dma-fence-chain.c
@@ -254,5 +254,14 @@ void dma_fence_chain_init(struct dma_fence_chain *chain,
dma_fence_init(&chain->base, &dma_fence_chain_ops,
&chain->lock, context, seqno);
+
+ /*
+ * Chaining dma_fence_chain container together is only allowed through
+ * the prev fence and not through the contained fence.
+ *
+ * The correct way of handling this is to flatten out the fence
+ * structure into a dma_fence_array by the caller instead.
+ */
+ WARN_ON(dma_fence_is_chain(fence));
}
EXPORT_SYMBOL(dma_fence_chain_init);
--
2.38.1