On 11/21/23 06:50, Danilo Krummrich wrote:
On 11/13/23 20:13, Abhinav Singh wrote:
This patch fixes 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.
Signed-off-by: Abhinav Singh <singhabhinav9051571833@xxxxxxxxx>
Applied, thanks!
There are a few more such occurrences. [1][2] Plan to fix them as well?
[1]
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/nouveau/nv10_fence.c#L35
[2]
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/nouveau/nv84_fence.c#L88
---
v1 -> v2 : Replaced the rcu_dereference(...) with unrcu_pointer(...) and
also removed the rcu locking and unlocking function call.
v2 -> v3 : Changed the description of the patch to match it with the
actual
implementation.
drivers/gpu/drm/nouveau/nv04_fence.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/nouveau/nv04_fence.c
b/drivers/gpu/drm/nouveau/nv04_fence.c
index 5b71a5a5cd85..cdbc75e3d1f6 100644
--- a/drivers/gpu/drm/nouveau/nv04_fence.c
+++ b/drivers/gpu/drm/nouveau/nv04_fence.c
@@ -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);
Thanks a lot for merging this.
Yeah sure I will submit the patch for the issues soon.
Regards,
Abhinav Singh
