Re: Warnings in DRM code when removing/unbinding a driver

[Daniel Vetter]

On Wed, Dec 18, 2019 at 7:08 PM John Garry <john.garry@xxxxxxxxxx> wrote:
>
> +
>
> So the v5.4 kernel does not have this issue.
>
> I have bisected the initial occurrence to:
>
> commit 37a48adfba6cf6e87df9ba8b75ab85d514ed86d8
> Author: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Date:   Fri Sep 6 14:20:53 2019 +0200
>
>      drm/vram: Add kmap ref-counting to GEM VRAM objects
>
>      The kmap and kunmap operations of GEM VRAM buffers can now be called
>      in interleaving pairs. The first call to drm_gem_vram_kmap() maps the
>      buffer's memory to kernel address space and the final call to
>      drm_gem_vram_kunmap() unmaps the memory. Intermediate calls to these
>      functions increment or decrement a reference counter.
>
> So this either exposes or creates the issue.

Yeah that's just shooting the messenger. Like I said, for most drivers
you can pretty much assume that their unload sequence has been broken
since forever. It's not often tested, and especially the hotunbind
from a device (as opposed to driver unload) stuff wasn't even possible
to get right until just recently.
-Daniel

>
> John
>
> >> On Mon, 2019-12-16 at 17:23 +0000, John Garry wrote:
> >>> Hi all,
> >>>
> >>> Enabling CONFIG_DEBUG_TEST_DRIVER_REMOVE causes many warns on a system
> >>> with the HIBMC hw:
> >>>
> >>> [   27.788806] WARNING: CPU: 24 PID: 1 at
> >>> drivers/gpu/drm/drm_gem_vram_helper.c:564
> >>> bo_driver_move_notify+0x8c/0x98
> >>
> >> A total shot in the dark. This might make no sense,
> >> but it's worth a try:
> >
> > Thanks for the suggestion, but still the same splat.
> >
> > I haven't had a chance to analyze the problem myself. But perhaps we
> > should just change over the device-managed interface, as Daniel mentioned.
> >
> >>
> >> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
> >> b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
> >> index 2fd4ca91a62d..69bb0e29da88 100644
> >> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
> >> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
> >> @@ -247,9 +247,8 @@ static int hibmc_unload(struct drm_device *dev)
> >>   {
> >>          struct hibmc_drm_private *priv = dev->dev_private;
> >> -       hibmc_fbdev_fini(priv);
> >> -
> >>          drm_atomic_helper_shutdown(dev);
> >> +       hibmc_fbdev_fini(priv);
> >>          if (dev->irq_enabled)
> >>                  drm_irq_uninstall(dev);
> >>
> >> Hope it helps,
> >> Ezequiel
> >>
> >
> > Thanks,
> > John
> >
> > [EOM]
> >
> >>> [   27.798969] Modules linked in:
> >>> [   27.802018] CPU: 24 PID: 1 Comm: swapper/0 Tainted: G    B
> >>>    5.5.0-rc1-dirty #565
> >>> [   27.810358] Hardware name: Huawei D06 /D06, BIOS Hisilicon D06 UEFI
> >>> RC0 - V1.16.01 03/15/2019
> >>> [   27.818872] pstate: 20c00009 (nzCv daif +PAN +UAO)
> >>> [   27.823654] pc : bo_driver_move_notify+0x8c/0x98
> >>> [   27.828262] lr : bo_driver_move_notify+0x40/0x98
> >>> [   27.832868] sp : ffff00236f0677e0
> >>> [   27.836173] x29: ffff00236f0677e0 x28: ffffa0001454e5e0
> >>> [   27.841476] x27: ffff002366e52128 x26: ffffa000149e67b0
> >>> [   27.846779] x25: ffff002366e523e0 x24: ffff002336936120
> >>> [   27.852082] x23: ffff0023346f4010 x22: ffff002336936128
> >>> [   27.857385] x21: ffffa000149c15c0 x20: ffff0023369361f8
> >>> [   27.862687] x19: ffff002336936000 x18: 0000000000001258
> >>> [   27.867989] x17: 0000000000001190 x16: 00000000000011d0
> >>> [   27.873292] x15: 0000000000001348 x14: ffffa00012d68190
> >>> [   27.878595] x13: 0000000000000006 x12: 1ffff40003241f91
> >>> [   27.883897] x11: ffff940003241f91 x10: dfffa00000000000
> >>> [   27.889200] x9 : ffff940003241f92 x8 : 0000000000000001
> >>> [   27.894502] x7 : ffffa0001920fc88 x6 : ffff940003241f92
> >>> [   27.899804] x5 : ffff940003241f92 x4 : ffff0023369363a0
> >>> [   27.905107] x3 : ffffa00010c104b8 x2 : dfffa00000000000
> >>> [   27.910409] x1 : 0000000000000003 x0 : 0000000000000001
> >>> [   27.915712] Call trace:
> >>> [   27.918151]  bo_driver_move_notify+0x8c/0x98
> >>> [   27.922412]  ttm_bo_cleanup_memtype_use+0x54/0x100
> >>> [   27.927194]  ttm_bo_put+0x3a0/0x5d0
> >>> [   27.930673]  drm_gem_vram_object_free+0xc/0x18
> >>> [   27.935109]  drm_gem_object_free+0x34/0xd0
> >>> [   27.939196]  drm_gem_object_put_unlocked+0xc8/0xf0
> >>> [   27.943978]  hibmc_user_framebuffer_destroy+0x20/0x40
> >>> [   27.949020]  drm_framebuffer_free+0x48/0x58
> >>> [   27.953194]  drm_mode_object_put.part.1+0x90/0xe8
> >>> [   27.957889]  drm_mode_object_put+0x28/0x38
> >>> [   27.961976]  hibmc_fbdev_fini+0x54/0x78
> >>> [   27.965802]  hibmc_unload+0x2c/0xd0
> >>> [   27.969281]  hibmc_pci_remove+0x2c/0x40
> >>> [   27.973109]  pci_device_remove+0x6c/0x140
> >>> [   27.977110]  really_probe+0x174/0x548
> >>> [   27.980763]  driver_probe_device+0x7c/0x148
> >>> [   27.984936]  device_driver_attach+0x94/0xa0
> >>> [   27.989109]  __driver_attach+0xa8/0x110
> >>> [   27.992935]  bus_for_each_dev+0xe8/0x158
> >>> [   27.996849]  driver_attach+0x30/0x40
> >>> [   28.000415]  bus_add_driver+0x234/0x2f0
> >>> [   28.004241]  driver_register+0xbc/0x1d0
> >>> [   28.008067]  __pci_register_driver+0xbc/0xd0
> >>> [   28.012329]  hibmc_pci_driver_init+0x20/0x28
> >>> [   28.016590]  do_one_initcall+0xb4/0x254
> >>> [   28.020417]  kernel_init_freeable+0x27c/0x328
> >>> [   28.024765]  kernel_init+0x10/0x118
> >>> [   28.028245]  ret_from_fork+0x10/0x18
> >>> [   28.031813] ---[ end trace 35a83b71b657878d ]---
> >>> [   28.036503] ------------[ cut here ]------------
> >>> [   28.041115] WARNING: CPU: 24 PID: 1 at
> >>> drivers/gpu/drm/drm_gem_vram_helper.c:40
> >>> ttm_buffer_object_destroy+0x4c/0x80
> >>> [   28.051537] Modules linked in:
> >>> [   28.054585] CPU: 24 PID: 1 Comm: swapper/0 Tainted: G    B   W
> >>>    5.5.0-rc1-dirty #565
> >>> [   28.062924] Hardware name: Huawei D06 /D06, BIOS Hisilicon D06 UEFI
> >>> RC0 - V1.16.01 03/15/2019
> >>>
> >>> [snip]
> >>>
> >>> Indeed, simply unbinding the device from the driver causes the same sort
> >>> of issue:
> >>>
> >>> root@(none)$ cd ./bus/pci/drivers/hibmc-drm/
> >>> root@(none)$ ls
> >>> 0000:05:00.0  bind          new_id        remove_id     uevent
> >>> unbind
> >>> root@(none)$ echo 0000\:05\:00.0 > unbind
> >>> [  116.074352] ------------[ cut here ]------------
> >>> [  116.078978] WARNING: CPU: 17 PID: 1178 at
> >>> drivers/gpu/drm/drm_gem_vram_helper.c:40
> >>> ttm_buffer_object_destroy+0x4c/0x80
> >>> [  116.089661] Modules linked in:
> >>> [  116.092711] CPU: 17 PID: 1178 Comm: sh Tainted: G    B   W
> >>> 5.5.0-rc1-dirty #565
> >>> [  116.100704] Hardware name: Huawei D06 /D06, BIOS Hisilicon D06 UEFI
> >>> RC0 - V1.16.01 03/15/2019
> >>> [  116.109218] pstate: 20400009 (nzCv daif +PAN -UAO)
> >>> [  116.114001] pc : ttm_buffer_object_destroy+0x4c/0x80
> >>> [  116.118956] lr : ttm_buffer_object_destroy+0x18/0x80
> >>> [  116.123910] sp : ffff0022e6cef8e0
> >>> [  116.127215] x29: ffff0022e6cef8e0 x28: ffff00231b1fb000
> >>> [  116.132519] x27: 0000000000000000 x26: ffff00231b1fb000
> >>> [  116.137821] x25: ffff0022e6cefdc0 x24: 0000000000002480
> >>> [  116.143124] x23: ffff0023682b6ab0 x22: ffff0023682b6800
> >>> [  116.148427] x21: ffff0023682b6800 x20: 0000000000000000
> >>> [  116.153730] x19: ffff0023682b6800 x18: 0000000000000000
> >>> [  116.159032] x17: 000000000000000000000000001
> >>> [  116.185545] x7 : ffff0023682b6b07 x6 : ffff80046d056d61
> >>> [  116.190848] x5 : ffff80046d056d61 x4 : ffff0023682b6ba0
> >>> [  116.196151] x3 : ffffa00010197338 x2 : dfffa00000000000
> >>> [  116.201453] x1 : 0000000000000003 x0 : 0000000000000001
> >>> [  116.206756] Call trace:
> >>> [  116.209195]  ttm_buffer_object_destroy+0x4c/0x80
> >>> [  116.213803]  ttm_bo_release_list+0x184/0x220
> >>> [  116.218064]  ttm_bo_put+0x410/0x5d0
> >>> [  116.221544]  drm_gem_vram_object_free+0xc/0x18
> >>> [  116.225979]  drm_gem_object_free+0x34/0xd0
> >>> [  116.230066]  drm_gem_object_put_unlocked+0xc8/0xf0
> >>> [  116.234848]  hibmc_user_framebuffer_destroy+0x20/0x40
> >>> [  116.239890]  drm_framebuffer_free+0x48/0x58
> >>> [  116.244064]  drm_mode_object_put.part.1+0x90/0xe8
> >>> [  116.248759]  drm_mode_object_put+0x28/0x38
> >>> [  116.252846]  hibmc_fbdev_fini+0x54/0x78
> >>> [  116.256672]  hibmc_unload+0x2c/0xd0
> >>> [  116.260151]  hibmc_pci_remove+0x2c/0x40
> >>> [  116.263979]  pci_device_remove+0x6c/0x140
> >>> [  116.267980]  device_release_driver_internal+0x134/0x250
> >>> [  116.273196]  device_driver_detach+0x28/0x38
> >>> [  116.277369]  unbind_store+0xfc/0x150
> >>> [  116.280934]  drv_attr_store+0x48/0x60
> >>> [  116.284589]  sysfs_kf_write+0x80/0xb0
> >>> [  116.288241]  kernfs_fop_write+0x1d4/0x320
> >>> [  116.292243]  __vfs_write+0x54/0x98
> >>> [  116.295635]  vfs_write+0xe8/0x270
> >>> [  116.298940]  ksys_write+0xc8/0x180
> >>> [  116.302333]  __arm64_sys_write+0x40/0x50
> >>> [  116.306248]  el0_svc_common.constprop.0+0xa4/0x1f8
> >>> [  116.311029]  el0_svc_handler+0x34/0xb0
> >>> [  116.314770]  el0_sync_handler+0x10c/0x1c8
> >>> [  116.318769]  el0_sync+0x140/0x180
> >>> [  116.322074] ---[ end trace e60e43d0e316b5c8 ]---
> >>> [  116.326868] ------------[ cut here ]------------
> >>>
> >>>
> >>> dmesg and .config is here:
> >>> https://pastebin.com/4P5yaZBS
> >>>
> >>> I'm not sure if this is a HIBMC driver issue or issue with the
> >>> framework.
> >>>
> >>> john
> >>>
> >>>
> >>> _______________________________________________
> >>> dri-devel mailing list
> >>> dri-devel@xxxxxxxxxxxxxxxxxxxxx
> >>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >>
> >>
> >
> > _______________________________________________
> > Linuxarm mailing list
> > Linuxarm@xxxxxxxxxx
> > http://hulk.huawei.com/mailman/listinfo/linuxarm
> > .
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch