Am 25.10.18 um 09:50 schrieb Maarten Lankhorst:
Op 24-10-18 om 20:57 schreef Julia Lawall:
The containing function is called with a spin_lock held, so GFP_KERNEL
can't be used.
julia
---------- Forwarded message ----------
Date: Tue, 23 Oct 2018 17:14:25 +0800
From: kbuild test robot <lkp@xxxxxxxxx>
To: kbuild@xxxxxx
Cc: Julia Lawall <julia.lawall@xxxxxxx>
Subject: [PATCH] drm: fix call_kern.cocci warnings
CC: kbuild-all@xxxxxx
CC: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
CC: dri-devel@xxxxxxxxxxxxxxxxxxxxx
TO: Chunming Zhou <david1.zhou@xxxxxxx>
CC: "Christian König" <easy2remember.chk@xxxxxxxxxxxxxx>
CC: Gustavo Padovan <gustavo@xxxxxxxxxxx>
CC: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
CC: Sean Paul <sean@xxxxxxxxxx>
CC: David Airlie <airlied@xxxxxxxx>
CC: dri-devel@xxxxxxxxxxxxxxxxxxxxx
CC: linux-kernel@xxxxxxxxxxxxxxx
From: kbuild test robot <fengguang.wu@xxxxxxxxx>
drivers/gpu/drm/drm_syncobj.c:202:4-14: ERROR: function drm_syncobj_find_signal_pt_for_point called on line 390 inside lock on line 389 but uses GFP_KERNEL
Find functions that refer to GFP_KERNEL but are called with locks held.
Semantic patch information:
The proposed change of converting the GFP_KERNEL is not necessarily the
correct one. It may be desired to unlock the lock, or to not call the
function under the lock in the first place.
Generated by: scripts/coccinelle/locks/call_kern.cocci
Fixes: 48197bc564c7 ("drm: add syncobj timeline support v9")
CC: Chunming Zhou <david1.zhou@xxxxxxx>
Signed-off-by: kbuild test robot <fengguang.wu@xxxxxxxxx>
The issue appears to be real and the patch looks sane. Chunming Zhou, do you want to fix it like this, or preallocate
a fence obj? If former, just ack. :)
Well, wait a second with that advise1
The problem here is that userspace (indirectly) controls when this
allocation is made. So what you could do is to construct some code to
force the kernel into doing a *lot* of GFP_ATOMIC allocations.
And when the kernel runs out of GFP_ATOMIC space, then well bad things
start to happen :)
Christian.
~Maarten
tree: git://anongit.freedesktop.org/drm/drm-tip drm-tip
head: 8d7ffd2298c607c3e1a16f94d51450d7940fd6a7
commit: 48197bc564c7a1888c86024a1ba4f956e0ec2300 [1968/2033] drm: add syncobj timeline support v9
:::::: branch date: 4 hours ago
:::::: commit date: 5 days ago
Please take the patch only if it's a positive warning. Thanks!
drm_syncobj.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -199,7 +199,7 @@ static struct dma_fence
(point <= syncobj->timeline)) {
struct drm_syncobj_stub_fence *fence =
kzalloc(sizeof(struct drm_syncobj_stub_fence),
- GFP_KERNEL);
+ GFP_ATOMIC);
if (!fence)
return NULL;
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