linux-kernel - Re: [PATCH] drm: fix call

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Date:   Thu, 25 Oct 2018 08:53:21 +0200
From:   Christian König <easy2remember.chk@...glemail.com>
To:     "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        Julia Lawall <julia.lawall@...6.fr>
Cc:     "kbuild-all@...org" <kbuild-all@...org>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm: fix call_kern.cocci warnings (fwd)

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

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@...6.fr>
>> Sent: Thursday, October 25, 2018 2:57 AM
>> To: Zhou, David(ChunMing) <David1.Zhou@....com>
>> Cc: kbuild-all@...org; intel-gfx@...ts.freedesktop.org; dri-
>> devel@...ts.freedesktop.org; Christian König
>> <easy2remember.chk@...glemail.com>; Gustavo Padovan
>> <gustavo@...ovan.org>; Maarten Lankhorst
>> <maarten.lankhorst@...ux.intel.com>; Sean Paul <sean@...rly.run>; David
>> Airlie <airlied@...ux.ie>; dri-devel@...ts.freedesktop.org; linux-
>> kernel@...r.kernel.org
>> 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@...el.com>
>> To: kbuild@...org
>> Cc: Julia Lawall <julia.lawall@...6.fr>
>> Subject: [PATCH] drm: fix call_kern.cocci warnings
>>
>> CC: kbuild-all@...org
>> CC: intel-gfx@...ts.freedesktop.org
>> CC: dri-devel@...ts.freedesktop.org
>> TO: Chunming Zhou <david1.zhou@....com>
>> CC: "Christian König" <easy2remember.chk@...glemail.com>
>> CC: Gustavo Padovan <gustavo@...ovan.org>
>> CC: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
>> CC: Sean Paul <sean@...rly.run>
>> CC: David Airlie <airlied@...ux.ie>
>> CC: dri-devel@...ts.freedesktop.org
>> CC: linux-kernel@...r.kernel.org
>>
>> From: kbuild test robot <fengguang.wu@...el.com>
>>
>> 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@....com>
>> Signed-off-by: kbuild test robot <fengguang.wu@...el.com>
>> ---
>>
>> 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;