diff mbox series

drm: fix call_kern.cocci warnings (fwd)

Message ID alpine.DEB.2.21.1810241955110.3776@hadrien (mailing list archive)
State New, archived
Headers show
Series drm: fix call_kern.cocci warnings (fwd) | expand

Commit Message

Julia Lawall Oct. 24, 2018, 6:57 p.m. UTC 
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(-)

Comments

Chunming Zhou Oct. 25, 2018, 1:28 a.m. UTC | #1 
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;
Maarten Lankhorst Oct. 25, 2018, 7:50 a.m. UTC | #2 
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;
Maarten Lankhorst Oct. 25, 2018, 7:51 a.m. UTC | #3 
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. :)
Christian König Oct. 25, 2018, 7:57 a.m. UTC | #4 
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.
diff mbox series

Patch

--- 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;