Date:	Wed, 26 Nov 2014 12:29:39 -0800
From:	Michael Marineau <mike@...ineau.org>
To:	Maarten Lankhorst <maarten.lankhorst@...onical.com>
Cc:	David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org,
	Ben Skeggs <bskeggs@...hat.com>,
	dri-devel@...ts.freedesktop.org
Subject: Re: 3.18-rc regression: drm/nouveau: use shared fences for readable objects

On Mon, Nov 24, 2014 at 11:43 PM, Maarten Lankhorst
<maarten.lankhorst@...onical.com> wrote:
> Hey,
>
> Op 22-11-14 om 21:16 schreef Michael Marineau:
>> On Nov 22, 2014 11:45 AM, "Michael Marineau" <mike@...ineau.org> wrote:
>>>
>>> On Nov 22, 2014 8:56 AM, "Maarten Lankhorst" <
>> maarten.lankhorst@...onical.com> wrote:
>>>> Hey,
>>>>
>>>> Op 22-11-14 om 01:19 schreef Michael Marineau:
>>>>> On Thu, Nov 20, 2014 at 12:53 AM, Maarten Lankhorst
>>>>> <maarten.lankhorst@...onical.com> wrote:
>>>>>> Op 20-11-14 om 05:06 schreef Michael Marineau:
>>>>>>> On Wed, Nov 19, 2014 at 12:10 AM, Maarten Lankhorst
>>>>>>> <maarten.lankhorst@...onical.com> wrote:
>>>>>>>> Hey,
>>>>>>>>
>>>>>>>> On 19-11-14 07:43, Michael Marineau wrote:
>>>>>>>>> On 3.18-rc kernel's I have been intermittently experiencing GPU
>>>>>>>>> lockups shortly after startup, accompanied with one or both of the
>>>>>>>>> following errors:
>>>>>>>>>
>>>>>>>>> nouveau E[   PFIFO][0000:01:00.0] read fault at 0x000734a000 [PTE]
>>>>>>>>> from PBDMA0/HOST_CPU on channel 0x007faa3000 [unknown]
>>>>>>>>> nouveau E[     DRM] GPU lockup - switching to software fbcon
>>>>>>>>>
>>>>>>>>> I was able to trace the issue with bisect to commit
>>>>>>>>> 809e9447b92ffe1346b2d6ec390e212d5307f61c "drm/nouveau: use shared
>>>>>>>>> fences for readable objects". The lockups appear to have cleared
>> up
>>>>>>>>> since reverting that and a few related followup commits:
>>>>>>>>>
>>>>>>>>> 809e9447: "drm/nouveau: use shared fences for readable objects"
>>>>>>>>> 055dffdf: "drm/nouveau: bump driver patchlevel to 1.2.1"
>>>>>>>>> e3be4c23: "drm/nouveau: specify if interruptible wait is desired
>> in
>>>>>>>>> nouveau_fence_sync"
>>>>>>>>> 15a996bb: "drm/nouveau: assign fence_chan->name correctly"
>>>>>>>> Weird. I'm not sure yet what causes it.
>>>>>>>>
>>>>>>>>
>> http://cgit.freedesktop.org/~mlankhorst/linux/commit/?h=fixed-fences-for-bisect&id=86be4f216bbb9ea3339843a5658d4c21162c7ee2
>>>>>>> Building a kernel from that commit gives me an entirely new
>> behavior:
>>>>>>> X hangs for at least 10-20 seconds at a time with brief moments of
>>>>>>> responsiveness before hanging again while gitk on the kernel repo
>>>>>>> loads. Otherwise the system is responsive. The head of that
>>>>>>> fixed-fences-for-bisect branch (1c6aafb5) which is the "use shared
>>>>>>> fences for readable objects" commit I originally bisected to does
>>>>>>> feature the complete lockups I was seeing before.
>>>>>> Ok for the sake of argument lets just assume they're separate bugs,
>> and we should look at xorg
>>>>>> hanging first.
>>>>>>
>>>>>> Is there anything in the dmesg when the hanging happens?
>>>>>>
>>>>>> And it's probably 15 seconds, if it's called through
>> nouveau_fence_wait.
>>>>>> Try changing else if (!ret) to else if (WARN_ON(!ret)) in that
>> function, and see if you get some dmesg spam. :)
>>>>> Adding the WARN_ON to 86be4f21 repots the following:
>>>>>
>>>>> [ 1188.676073] ------------[ cut here ]------------
>>>>> [ 1188.676161] WARNING: CPU: 1 PID: 474 at
>>>>> drivers/gpu/drm/nouveau/nouveau_fence.c:359
>>>>> nouveau_fence_wait.part.9+0x33/0x40 [nouveau]()
>>>>> [ 1188.676166] Modules linked in: rndis_host cdc_ether usbnet mii bnep
>>>>> ecb btusb bluetooth rfkill bridge stp llc hid_generic usb_storage
>>>>> joydev mousedev hid_apple usbhid bcm5974 nls_iso8859_1 nls_cp437 vfat
>>>>> fat nouveau snd_hda_codec_hdmi coretemp x86_pkg_temp_thermal
>>>>> intel_powerclamp kvm_intel kvm iTCO_wdt crct10dif_pclmul
>>>>> iTCO_vendor_support crc32c_intel evdev aesni_intel mac_hid aes_x86_64
>>>>> lrw glue_helper ablk_helper applesmc snd_hda_codec_cirrus cryptd
>>>>> input_polldev snd_hda_codec_generic mxm_wmi led_class wmi microcode
>>>>> hwmon snd_hda_intel ttm snd_hda_controller lpc_ich i2c_i801 mfd_core
>>>>> snd_hda_codec i2c_algo_bit snd_hwdep drm_kms_helper snd_pcm sbs drm
>>>>> apple_gmux i2ccore snd_timer snd agpgart mei_me soundcore sbshc mei
>>>>> video xhci_hcd usbcore usb_common apple_bl button battery ac efivars
>>>>> autofs4
>>>>> [ 1188.676300]  efivarfs
>>>>> [ 1188.676308] CPU: 1 PID: 474 Comm: Xorg Tainted: G        W
>>>>> 3.17.0-rc2-nvtest+ #147
>>>>> [ 1188.676313] Hardware name: Apple Inc.
>>>>> MacBookPro11,3/Mac-2BD1B31983FE1663, BIOS
>>>>> MBP112.88Z.0138.B11.1408291503 08/29/2014
>>>>> [ 1188.676316]  0000000000000009 ffff88045daebce8 ffffffff814f0c09
>>>>> 0000000000000000
>>>>> [ 1188.676325]  ffff88045daebd20 ffffffff8104ea5d ffff88006a6c1468
>>>>> 00000000fffffff0
>>>>> [ 1188.676333]  0000000000000000 0000000000000000 ffff88006a6c1000
>>>>> ffff88045daebd30
>>>>> [ 1188.676341] Call Trace:
>>>>> [ 1188.676356]  [<ffffffff814f0c09>] dump_stack+0x4d/0x66
>>>>> [ 1188.676369]  [<ffffffff8104ea5d>] warn_slowpath_common+0x7d/0xa0
>>>>> [ 1188.676377]  [<ffffffff8104eb3a>] warn_slowpath_null+0x1a/0x20
>>>>> [ 1188.676439]  [<ffffffffc04dd523>]
>>>>> nouveau_fence_wait.part.9+0x33/0x40 [nouveau]
>>>>> [ 1188.676496]  [<ffffffffc04ddfe6>] nouveau_fence_wait+0x16/0x30
>> [nouveau]
>>>>> [ 1188.676552]  [<ffffffffc04e598f>]
>>>>> nouveau_gem_ioctl_cpu_prep+0xef/0x1f0 [nouveau]
>>>>> [ 1188.676578]  [<ffffffffc01c2f4c>] drm_ioctl+0x1ec/0x660 [drm]
>>>>> [ 1188.676590]  [<ffffffff814f9026>] ?
>> _raw_spin_unlock_irqrestore+0x36/0x70
>>>>> [ 1188.676600]  [<ffffffff81094f6d>] ? trace_hardirqs_on+0xd/0x10
>>>>> [ 1188.676655]  [<ffffffffc04da5b4>] nouveau_drm_ioctl+0x54/0xc0
>> [nouveau]
>>>>> [ 1188.676663]  [<ffffffff811a8950>] do_vfs_ioctl+0x300/0x520
>>>>> [ 1188.676671]  [<ffffffff814f9e55>] ? sysret_check+0x22/0x5d
>>>>> [ 1188.676677]  [<ffffffff811a8bb1>] SyS_ioctl+0x41/0x80
>>>>> [ 1188.676683]  [<ffffffff814f9e29>] system_call_fastpath+0x16/0x1b
>>>>> [ 1188.676688] ---[ end trace 6f7a510865b4674f ]---
>>>>>
>>>>> Here are the fence events that fired during that particular
>> fence_wait:
>>>>>             Xorg   474 [004]  1173.667645: fence:fence_wait_start:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56910
>>>>>             Xorg   474 [004]  1173.667647: fence:fence_enable_signal:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56910
>>>>>          swapper     0 [007]  1173.667688: fence:fence_signaled:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56900
>>>>>          swapper     0 [007]  1173.667692: fence:fence_destroy:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56900
>>>>>          swapper     0 [007]  1173.667839: fence:fence_signaled:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56901
>>>>>          swapper     0 [007]  1173.667842: fence:fence_destroy:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56901
>>>>>          swapper     0 [007]  1173.668021: fence:fence_signaled:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56902
>>>>>          swapper     0 [007]  1173.668482: fence:fence_signaled:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56903
>>>>>          swapper     0 [007]  1173.668485: fence:fence_destroy:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56903
>>>>>          swapper     0 [007]  1173.668489: fence:fence_signaled:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56904
>>>>>          swapper     0 [007]  1173.668496: fence:fence_signaled:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56905
>>>>>          swapper     0 [007]  1173.668499: fence:fence_destroy:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56905
>>>>>          swapper     0 [007]  1173.668502: fence:fence_signaled:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56906
>>>>>          swapper     0 [007]  1173.668505: fence:fence_signaled:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56907
>>>>>          swapper     0 [007]  1173.668508: fence:fence_destroy:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56907
>>>>>          swapper     0 [007]  1173.668511: fence:fence_signaled:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56908
>>>>>          swapper     0 [007]  1173.668513: fence:fence_destroy:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56908
>>>>>      kworker/4:1    80 [004]  1173.676265: fence:fence_destroy:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56896
>>>>>      kworker/4:1    80 [004]  1173.676273: fence:fence_destroy:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56898
>>>>>      kworker/4:1    80 [004]  1173.676277: fence:fence_destroy:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56902
>>>>>      kworker/4:1    80 [004]  1173.676280: fence:fence_destroy:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56904
>>>>>             Xorg   474 [001]  1188.676067: fence:fence_wait_end:
>>>>> driver=nouveau timeline=Xorg[474] context=2 seqno=56910
>>>>>
>>>>> I assume that excludes the context you really want so the full fence
>>>>> event log and corresponding dmesg output are attached.
>>>> Yep, the trace events are useful. The fence is emitted and presumably
>> no event is fired after emission.
>>>> Lets find out if the nvif crap is buggy or it's a result of some other
>> issue, what happens when you change:
>>>> .wait = fence_default_wait,
>>>> to
>>>> .wait = nouveau_fence_wait_legacy,
>>>> in nouveau_fence.c?
>>> That change works just fine.
>> The xorg hangs also appear to be resolved by db1cf46 "drm/nouveau: use rcu
>> in nouveau_gem_ioctl_cpu_prep"
>>
> Oh right, I just remembered what was going on there..
> the .wait was a workaround for a bug in the nvif interface. The hangs should be resolved by applying
> 7caa63c04029c5882865867470c106ef73eafb2b
>
> Can you confirm?
>
> Could you also confirm that 1c6aafb5f1b84fa5 "drm/nouveau: use shared fences for readable objects, EDITED" with the
> above commit applied is the first broken commit?
>
> ~Maarten
>

I don't follow, 7caa63c04029c5882865867470c106ef73eafb2b precedes
those other commits so there is nothing to apply. Just for kicks I
tried reverting it but that made no difference in behavior. Did you
mean something else?

-- 
Michael Marineau
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