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

[Christian KÃnig]

Am 25.10.18 um 03:28 schrieb Zhou, David(ChunMing):
> Reviewed-by: Chunming Zhou <david1.zhou@xxxxxxx>

NAK, GFP_ATOMIC should be avoided.

The correct solution is to move the allocation out of the spinlock or 
drop the lock and reacquire.

Christian.

> > -----Original Message-----
> > From: Julia Lawall <julia.lawall@xxxxxxx>
> > Sent: Thursday, October 25, 2018 2:57 AM
> > To: Zhou, David(ChunMing) <David1.Zhou@xxxxxxx>
> > Cc: kbuild-all@xxxxxx; intel-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-
> > devel@xxxxxxxxxxxxxxxxxxxxx; Christian KÃnig
> > <easy2remember.chk@xxxxxxxxxxxxxx>; Gustavo Padovan
> > <gustavo@xxxxxxxxxxx>; Maarten Lankhorst
> > <maarten.lankhorst@xxxxxxxxxxxxxxx>; Sean Paul <sean@xxxxxxxxxx>; David
> > Airlie <airlied@xxxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx; linux-
> > kernel@xxxxxxxxxxxxxxx
> > Subject: [PATCH] drm: fix call_kern.cocci warnings (fwd)
> >
> > 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 KÃnig" <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>
> > ---
> >
> > 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;