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drm/nouveau/fence:: fix warning directly dereferencing a rcu pointer

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[ Upstream commit 5f35a624c1e30b5bae5023b3c256e94e0ad4f806 ]

Fix a sparse warning with this message
"warning:dereference of noderef expression". In this context it means we
are dereferencing a __rcu tagged pointer directly.

We should not be directly dereferencing a rcu pointer. To get a normal
(non __rcu tagged pointer) from a __rcu tagged pointer we are using the
function unrcu_pointer(...). The non __rcu tagged pointer then can be
dereferenced just like a normal pointer.

I tested with qemu with this command
qemu-system-x86_64 \
	-m 2G \
	-smp 2 \
	-kernel bzImage \
	-append "console=ttyS0 root=/dev/sda earlyprintk=serial net.ifnames=0" \
	-drive file=bullseye.img,format=raw \
	-net user,host=10.0.2.10,hostfwd=tcp:127.0.0.1:10021-:22 \
	-net nic,model=e1000 \
	-enable-kvm \
	-nographic \
	-pidfile vm.pid \
	2>&1 | tee vm.log
with lockdep enabled.

Fixes: 0ec5f02f0e2c ("drm/nouveau: prevent stale fence->channel pointers, and protect with rcu")
Signed-off-by: Abhinav Singh <singhabhinav9051571833@gmail.com>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231113191303.3277733-1-singhabhinav9051571833@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Abhinav Singh 2023-11-14 00:43:03 +05:30 committed by Ksawlii
parent 9eb8a943df
commit 4469e03fa9
1 changed files with 1 additions and 1 deletions
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2
drivers/gpu/drm/nouveau/nv04_fence.c
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@ -39,7 +39,7 @@ struct nv04_fence_priv {
static int
nv04_fence_emit(struct nouveau_fence *fence)
{
struct nvif_push *push = fence->channel->chan.push;
struct nvif_push *push = unrcu_pointer(fence->channel)->chan.push;
int ret = PUSH_WAIT(push, 2);
if (ret == 0) {
PUSH_NVSQ(push, NV_SW, 0x0150, fence->base.seqno);