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

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

[Julia Lawall]

[-- Attachment #1: Type: text/plain, Size: 2192 bytes --]

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@intel.com>
To: kbuild@01.org
Cc: Julia Lawall <julia.lawall@lip6.fr>
Subject: [PATCH] drm: fix call_kern.cocci warnings

CC: kbuild-all@01.org
CC: intel-gfx@lists.freedesktop.org
CC: dri-devel@lists.freedesktop.org
TO: Chunming Zhou <david1.zhou@amd.com>
CC: "Christian König" <easy2remember.chk@googlemail.com>
CC: Gustavo Padovan <gustavo@padovan.org>
CC: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
CC: Sean Paul <sean@poorly.run>
CC: David Airlie <airlied@linux.ie>
CC: dri-devel@lists.freedesktop.org
CC: linux-kernel@vger.kernel.org

From: kbuild test robot <fengguang.wu@intel.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@amd.com>
Signed-off-by: kbuild test robot <fengguang.wu@intel.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;

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

[Zhou, David(ChunMing)]

Reviewed-by: Chunming Zhou <david1.zhou@amd.com>

> -----Original Message-----
> From: Julia Lawall <julia.lawall@lip6.fr>
> Sent: Thursday, October 25, 2018 2:57 AM
> To: Zhou, David(ChunMing) <David1.Zhou@amd.com>
> Cc: kbuild-all@01.org; intel-gfx@lists.freedesktop.org; dri-
> devel@lists.freedesktop.org; Christian König
> <easy2remember.chk@googlemail.com>; Gustavo Padovan
> <gustavo@padovan.org>; Maarten Lankhorst
> <maarten.lankhorst@linux.intel.com>; Sean Paul <sean@poorly.run>; David
> Airlie <airlied@linux.ie>; dri-devel@lists.freedesktop.org; linux-
> kernel@vger.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@intel.com>
> To: kbuild@01.org
> Cc: Julia Lawall <julia.lawall@lip6.fr>
> Subject: [PATCH] drm: fix call_kern.cocci warnings
> 
> CC: kbuild-all@01.org
> CC: intel-gfx@lists.freedesktop.org
> CC: dri-devel@lists.freedesktop.org
> TO: Chunming Zhou <david1.zhou@amd.com>
> CC: "Christian König" <easy2remember.chk@googlemail.com>
> CC: Gustavo Padovan <gustavo@padovan.org>
> CC: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> CC: Sean Paul <sean@poorly.run>
> CC: David Airlie <airlied@linux.ie>
> CC: dri-devel@lists.freedesktop.org
> CC: linux-kernel@vger.kernel.org
> 
> From: kbuild test robot <fengguang.wu@intel.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@amd.com>
> Signed-off-by: kbuild test robot <fengguang.wu@intel.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;

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

[Christian König]

Am 25.10.18 um 03:28 schrieb Zhou, David(ChunMing):
> Reviewed-by: Chunming Zhou <david1.zhou@amd.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@lip6.fr>
>> Sent: Thursday, October 25, 2018 2:57 AM
>> To: Zhou, David(ChunMing) <David1.Zhou@amd.com>
>> Cc: kbuild-all@01.org; intel-gfx@lists.freedesktop.org; dri-
>> devel@lists.freedesktop.org; Christian König
>> <easy2remember.chk@googlemail.com>; Gustavo Padovan
>> <gustavo@padovan.org>; Maarten Lankhorst
>> <maarten.lankhorst@linux.intel.com>; Sean Paul <sean@poorly.run>; David
>> Airlie <airlied@linux.ie>; dri-devel@lists.freedesktop.org; linux-
>> kernel@vger.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@intel.com>
>> To: kbuild@01.org
>> Cc: Julia Lawall <julia.lawall@lip6.fr>
>> Subject: [PATCH] drm: fix call_kern.cocci warnings
>>
>> CC: kbuild-all@01.org
>> CC: intel-gfx@lists.freedesktop.org
>> CC: dri-devel@lists.freedesktop.org
>> TO: Chunming Zhou <david1.zhou@amd.com>
>> CC: "Christian König" <easy2remember.chk@googlemail.com>
>> CC: Gustavo Padovan <gustavo@padovan.org>
>> CC: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> CC: Sean Paul <sean@poorly.run>
>> CC: David Airlie <airlied@linux.ie>
>> CC: dri-devel@lists.freedesktop.org
>> CC: linux-kernel@vger.kernel.org
>>
>> From: kbuild test robot <fengguang.wu@intel.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@amd.com>
>> Signed-off-by: kbuild test robot <fengguang.wu@intel.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;

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

[Maarten Lankhorst]

Op 25-10-18 om 08:53 schreef Christian König:
> Am 25.10.18 um 03:28 schrieb Zhou, David(ChunMing):
>> Reviewed-by: Chunming Zhou <david1.zhou@amd.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. 
Yeah +1. Especially in a case like this where it's obvious to prevent. :)

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

[Koenig, Christian]

Am 25.10.18 um 09:51 schrieb Maarten Lankhorst:
> Op 25-10-18 om 08:53 schreef Christian König:
>> Am 25.10.18 um 03:28 schrieb Zhou, David(ChunMing):
>>> Reviewed-by: Chunming Zhou <david1.zhou@amd.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.
> Yeah +1. Especially in a case like this where it's obvious to prevent. :)

Another possibility would to not allocate the dummy fence at all.

E.g. we just need a global instance of that which is always signaled and 
has a reference count of +1.

Christian.

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

[zhoucm1]

will send a fix soon.


Thanks,

David


On 2018年10月25日 15:57, Koenig, Christian wrote:
> Am 25.10.18 um 09:51 schrieb Maarten Lankhorst:
>> Op 25-10-18 om 08:53 schreef Christian König:
>>> Am 25.10.18 um 03:28 schrieb Zhou, David(ChunMing):
>>>> Reviewed-by: Chunming Zhou <david1.zhou@amd.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.
>> Yeah +1. Especially in a case like this where it's obvious to prevent. :)
> Another possibility would to not allocate the dummy fence at all.
>
> E.g. we just need a global instance of that which is always signaled and
> has a reference count of +1.
>
> Christian.

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@intel.com>
> To: kbuild@01.org
> Cc: Julia Lawall <julia.lawall@lip6.fr>
> Subject: [PATCH] drm: fix call_kern.cocci warnings
>
> CC: kbuild-all@01.org
> CC: intel-gfx@lists.freedesktop.org
> CC: dri-devel@lists.freedesktop.org
> TO: Chunming Zhou <david1.zhou@amd.com>
> CC: "Christian König" <easy2remember.chk@googlemail.com>
> CC: Gustavo Padovan <gustavo@padovan.org>
> CC: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> CC: Sean Paul <sean@poorly.run>
> CC: David Airlie <airlied@linux.ie>
> CC: dri-devel@lists.freedesktop.org
> CC: linux-kernel@vger.kernel.org
>
> From: kbuild test robot <fengguang.wu@intel.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@amd.com>
> Signed-off-by: kbuild test robot <fengguang.wu@intel.com>
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;

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

[Christian König]

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@intel.com>
>> To: kbuild@01.org
>> Cc: Julia Lawall <julia.lawall@lip6.fr>
>> Subject: [PATCH] drm: fix call_kern.cocci warnings
>>
>> CC: kbuild-all@01.org
>> CC: intel-gfx@lists.freedesktop.org
>> CC: dri-devel@lists.freedesktop.org
>> TO: Chunming Zhou <david1.zhou@amd.com>
>> CC: "Christian König" <easy2remember.chk@googlemail.com>
>> CC: Gustavo Padovan <gustavo@padovan.org>
>> CC: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> CC: Sean Paul <sean@poorly.run>
>> CC: David Airlie <airlied@linux.ie>
>> CC: dri-devel@lists.freedesktop.org
>> CC: linux-kernel@vger.kernel.org
>>
>> From: kbuild test robot <fengguang.wu@intel.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@amd.com>
>> Signed-off-by: kbuild test robot <fengguang.wu@intel.com>
> 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;
>