Fwd: WARNING ... drivers/gpu/drm/ttm/ttm_bo_vm.c...

Fwd: WARNING ... drivers/gpu/drm/ttm/ttm_bo_vm.c...

[Thomas Hellstrom]

Hi, David,

Are there any dev_mapping changes in 3.15 that could cause this?
Do we know what happens to vma->vm_file->f_mapping during fork?

Thanks,
/Thomas



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Date: 	Tue, 08 Apr 2014 03:29:26 +0200
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To: 	Thomas Hellstrom <thellstrom@vmware.com>
CC: 	Linux Kernel list <linux-kernel@vger.kernel.org>, Mailing-List
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Subject: 	WARNING ... drivers/gpu/drm/ttm/ttm_bo_vm.c...
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...
Command line: initrd=initrd.img
inst.stage2=hd:LABEL=Fedora\x20rawhide\x20x86_64  xdriver=modesetting
BOOT_IMAGE=vmlinuz
Kernel command line: initrd=initrd.img
inst.stage2=hd:LABEL=Fedora\x20rawhide\x20x86_64  xdriver=modesetting
BOOT_IMAGE=vmlinuz
...
------------[ cut here ]------------
WARNING: CPU: 1 PID: 1230 at drivers/gpu/drm/ttm/ttm_bo_vm.c:269
ttm_bo_vm_open+0x52/0x80 [ttm]()
CPU: 1 PID: 1230 Comm: Xorg Not tainted 3.15.0-0.rc0.git9.1.fc21.x86_64 #1
Call Trace:
 [<ffffffff817db690>] dump_stack+0x4d/0x66
 [<ffffffff81096b9d>] warn_slowpath_common+0x7d/0xa0
 [<ffffffff81096cca>] warn_slowpath_null+0x1a/0x20
 [<ffffffffa0250452>] ttm_bo_vm_open+0x52/0x80 [ttm]
 [<ffffffff810956fe>] copy_process.part.23+0x1b9e/0x1e90
 [<ffffffff81095bb6>] do_fork+0xc6/0x4b0
 [<ffffffff811de68f>] ? might_fault+0x5f/0xb0
 [<ffffffff817ef695>] ? sysret_check+0x22/0x5d
 [<ffffffff81096026>] SyS_clone+0x16/0x20
 [<ffffffff817efa49>] stub_clone+0x69/0x90
 [<ffffffff817ef669>] ? system_call_fastpath+0x16/0x1b
---[ end trace bc31de8c9c4c4d52 ]---
...

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poma

Re: WARNING ... drivers/gpu/drm/ttm/ttm_bo_vm.c...

[David Herrmann]

Hi Thomas

On Tue, Apr 8, 2014 at 7:11 AM, Thomas Hellstrom <thellstrom@vmware.com> wrote:
> Hi, David,
>
> Are there any dev_mapping changes in 3.15 that could cause this?
> Do we know what happens to vma->vm_file->f_mapping during fork?

Sorry, I was traveling. Yes, there have been changes, but I converted
all drivers properly. We now set file->f_mapping in drm_fops.c to
dev->anon_inode->i_mapping during open(). All the ttm stuff now sets
ttm->dev_mapping to the same during ttm init so I have no idea why
that assertion fails. The vmwgfx driver sets it correctly in
vmw_driver_load() and I cannot find any code changing it.

I also cannot reproduce it. Can you provide some more information?
Like what is vma->vm_file set to? What is ttm->dev_mapping? What is
drm_device->anon_inode->i_mapping? What is
&drm_device->anon_inode->i_data? All these should _always_ be the
same.

Btw., grep'ping for '_mapping' usually shows all related code, which I
reviewed and all looks good.

Thanks
David

Re: WARNING ... drivers/gpu/drm/ttm/ttm_bo_vm.c...

[Thomas Hellstrom]

Hi, David!

Thanks for the reply.

Actually I just got CC'd on the Fedora Bug. I haven't seen this either,
so I can't provide more info...

What I was thinking was that maybe after a fork, vma->vm_file->f_mapping
of the child process wasn't set to the same value as the
parent...

/Thomas



On 04/09/2014 08:54 PM, David Herrmann wrote:
> Hi Thomas
>
> On Tue, Apr 8, 2014 at 7:11 AM, Thomas Hellstrom <thellstrom@vmware.com> wrote:
>> Hi, David,
>>
>> Are there any dev_mapping changes in 3.15 that could cause this?
>> Do we know what happens to vma->vm_file->f_mapping during fork?
> Sorry, I was traveling. Yes, there have been changes, but I converted
> all drivers properly. We now set file->f_mapping in drm_fops.c to
> dev->anon_inode->i_mapping during open(). All the ttm stuff now sets
> ttm->dev_mapping to the same during ttm init so I have no idea why
> that assertion fails. The vmwgfx driver sets it correctly in
> vmw_driver_load() and I cannot find any code changing it.
>
> I also cannot reproduce it. Can you provide some more information?
> Like what is vma->vm_file set to? What is ttm->dev_mapping? What is
> drm_device->anon_inode->i_mapping? What is
> &drm_device->anon_inode->i_data? All these should _always_ be the
> same.
>
> Btw., grep'ping for '_mapping' usually shows all related code, which I
> reviewed and all looks good.
>
> Thanks
> David