Date:	Thu, 8 Dec 2011 23:05:08 -0500
From:	Bobby Powers <bobbypowers@...il.com>
To:	Daniel Vetter <daniel.vetter@...ll.ch>
Cc:	Ben Widawsky <ben@...dawsk.net>, Dave Airlie <airlied@...il.com>,
	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] drm/i915: fix infinite recursion on unbind
 due to ilk vt-d w/a

On Tue, Dec 6, 2011 at 12:43 PM, Ben Widawsky <ben@...dawsk.net> wrote:
> On Tue, Dec 06, 2011 at 12:12:33PM +0100, Daniel Vetter wrote:
>> The recursion loop goes retire_requests->unbind->gpu_idle->retire_reqeusts.
>>
>> Every time we go through this we need a
>> - active object that can be retired
>> - and there are no other references to that object than the one from
>>   the active list, so that it gets unbound and freed immediately.
>> Otherwise the recursion stops. So the recursion is only limited by the
>> number of objects that fit these requirements sitting in the active list
>> any time retire_request is called.
>>
>> Issue exercised by tests/gem_unref_active_buffers from i-g-t.
>>
>> There's been a decent bikeshed discussion whether it wouldn't be
>> better to pass around a flag, but imo this is o.k. for such a limited
>> case that only supports a w/a.
>>
>> Signed-Off-by: Daniel Vetter <daniel.vetter@...ll.ch>
>> Reviewed-by: Chris Wilson <chris@...is-wilson> # we built better
>>       bikesheds, but this keeps the rain off for now
>> ---
>
> What about:
> http://lists.freedesktop.org/archives/intel-gfx/2011-October/012984.html
>
>
> Did someone prove that doesn't work?

This patch caused hard lockups for me after ~35 minutes of casual use
(twice).  I've attached the oopses.  I'm running a Fedora 16 machine,
Lenovo T420 (i5-2540M w/ VT-d enabled), and at each time had a Windows
7 KVM guest idling (not sure if that is relevant).  With this patch
reverted, I've had ~ 6 hours of oops free uptime.

Let me know what additional information I can provide, or if there is
anything I can test to help narrow the issue down.

yours,
Bobby

~~~

[bpowers@...a linux]$ lspci
00:00.0 Host bridge: Intel Corporation 2nd Generation Core Processor
Family DRAM Controller (rev 09)
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation
Core Processor Family Integrated Graphics Controller (rev 09)
00:16.0 Communication controller: Intel Corporation 6 Series/C200
Series Chipset Family MEI Controller #1 (rev 04)
00:19.0 Ethernet controller: Intel Corporation 82579LM Gigabit Network
Connection (rev 04)
00:1a.0 USB Controller: Intel Corporation 6 Series/C200 Series Chipset
Family USB Enhanced Host Controller #2 (rev 04)
00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset
Family High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset
Family PCI Express Root Port 1 (rev b4)
00:1c.1 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset
Family PCI Express Root Port 2 (rev b4)
00:1c.3 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset
Family PCI Express Root Port 4 (rev b4)
00:1c.4 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset
Family PCI Express Root Port 5 (rev b4)
00:1d.0 USB Controller: Intel Corporation 6 Series/C200 Series Chipset
Family USB Enhanced Host Controller #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation QM67 Express Chipset Family LPC
Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation 6 Series/C200 Series
Chipset Family 6 port SATA AHCI Controller (rev 04)
00:1f.3 SMBus: Intel Corporation 6 Series/C200 Series Chipset Family
SMBus Controller (rev 04)
03:00.0 Network controller: Intel Corporation Centrino Advanced-N 6205 (rev 34)
0d:00.0 System peripheral: Ricoh Co Ltd Device e823 (rev 08)
0d:00.3 FireWire (IEEE 1394): Ricoh Co Ltd FireWire Host Controller (rev 04)
[bpowers@...a linux]$ cat /proc/cpuinfo
processor	: 0
vendor_id	: GenuineIntel
cpu family	: 6
model		: 42
model name	: Intel(R) Core(TM) i5-2540M CPU @ 2.60GHz
stepping	: 7
microcode	: 0x18
cpu MHz		: 800.000
cache size	: 3072 KB
physical id	: 0
siblings	: 4
core id		: 0
cpu cores	: 2
apicid		: 0
initial apicid	: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 13
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx
rdtscp lm constant_tsc arch_perfmon pebs bts nopl xtopology
nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est
tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt
tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts
dts tpr_shadow vnmi flexpriority ept vpid
bogomips	: 5184.24
clflush size	: 64
cache_alignment	: 64
address sizes	: 36 bits physical, 48 bits virtual
power management:

[3 other processors omitted]

Download attachment "i915-list_add-corruption" of type "application/octet-stream" (14939 bytes)

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