Re: [PATCH] drm: fix call_kern.cocci warnings (fwd)

[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. :)

~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;