Multiple issues with omapdrm

Wed Jun 5 03:43:49 PDT 2013

On Wed, Jun 5, 2013 at 4:59 AM, Tomi Valkeinen <tomi.valkeinen at ti.com> wrote:
> Hi,
>
> I did some testing with omapdrm on v3.10-rc1. Here are some issues I encountered.
> For most of them I don't have any idea where to even start looking for a problem,
> so I hope that you may have some ideas.
>
>
> dispc_runtime_get/put used in irq context
> =========================================
>
> dispc_runtime_get/put are used in irq context in omap_irq.c. I can hack
> around that with if (!in_atomic()), but I have no idea yet how to fix
> it properly.

Probably should have a flag/refcnt that is set when in the irq hander,
since we know that things are on in irq.

>
> drm_crtc warning
> ================
>
> I got this once when unloading the modules, but haven't happened since:
>
> drm_crtc.c line 3869
>
>         WARN_ON(!list_empty(&dev->mode_config.fb_list));
>
> As it only happened once, maybe some kind of race.
>

Hmm, this is new..  it is certain that there can be a fb with a
reference still around, waiting for a vblank/framedone.  But I think
it should already be removed from userspace perspective and no longer
on fb_list.  I think I need to go back and have a closer look at
2b677e8c0 where Daniel introduced that WARN_ON().

> omap_gem warning
> ================
>
> This happens on module unload:

oh, that is easy.. it is because the omap_fbdev.c does an unbalanced
omap_gem_get_paddr() to keep the fbcon fb from getting unmapped from
tiler (so if we have to restore fbcon mode in an opps, we don't have
to worry about grabbing mutexes or anything like that).  Maybe
somewhere in the cleanup it should do a put_paddr().  Otoh, I have
some skepticism about whether module unloading is really going to be
that reliable in practice, so meh..

BR,
-R

>
> [   30.167480] ------------[ cut here ]------------
> [   30.167724] WARNING: at drivers/gpu/drm/omapdrm/omap_gem.c:1318 omap_gem_free_object+0x24c/0x25c [omapdrm]()
> [   30.182952] Modules linked in: omapdrm(-) drm_kms_helper drm panel_taal panel_tfp410 panel_generic_dpi omapdss
> [   30.183166] CPU: 0 PID: 6 Comm: kworker/u4:0 Not tainted 3.10.0-rc1-00004-g8ed4760 #110
> [   30.183166] Workqueue: omapdrm apply_worker [omapdrm]
> [   30.207641] Backtrace:
> [   30.210296] [<c00189ac>] (dump_backtrace+0x0/0x10c) from [<c0018b48>] (show_stack+0x18/0x1c)
> [   30.219299]  r6:bf0e5988 r5:00000009 r4:00000000 r3:eb872080
> [   30.225433] [<c0018b30>] (show_stack+0x0/0x1c) from [<c0520c04>] (dump_stack+0x20/0x28)
> [   30.234039] [<c0520be4>] (dump_stack+0x0/0x28) from [<c0041fb8>] (warn_slowpath_common+0x54/0x74)
> [   30.243530] [<c0041f64>] (warn_slowpath_common+0x0/0x74) from [<c0041ffc>] (warn_slowpath_null+0x24/0x2c)
> [   30.243774]  r8:ebfab99c r7:ebb41800 r6:ebb41830 r5:ebefce40 r4:ebefce40
> r3:00000009
> [   30.262176] [<c0041fd8>] (warn_slowpath_null+0x0/0x2c) from [<bf0e5988>] (omap_gem_free_object+0x24c/0x25c [omapdrm])
> [   30.273498] [<bf0e573c>] (omap_gem_free_object+0x0/0x25c [omapdrm]) from [<bf080c0c>] (drm_gem_object_free+0x30/0x38 [drm])
> [   30.285675] [<bf080bdc>] (drm_gem_object_free+0x0/0x38 [drm]) from [<bf0e196c>] (omap_plane_post_apply+0x108/0x10c [omapdrm])
> [   30.285675] [<bf0e1864>] (omap_plane_post_apply+0x0/0x10c [omapdrm]) from [<bf0e100c>] (apply_worker+0x68/0x188 [omapdrm])
> [   30.309509]  r6:ebae5c6c r5:ebae5c5c r4:ebae5c5c
> [   30.312042] [<bf0e0fa4>] (apply_worker+0x0/0x188 [omapdrm]) from [<c005ef10>] (process_one_work+0x1b8/0x4e8)
> [   30.325012] [<c005ed58>] (process_one_work+0x0/0x4e8) from [<c005f654>] (worker_thread+0x138/0x388)
> [   30.325378] [<c005f51c>] (worker_thread+0x0/0x388) from [<c0066070>] (kthread+0xac/0xb8)
> [   30.343292] [<c0065fc4>] (kthread+0x0/0xb8) from [<c00146e8>] (ret_from_fork+0x14/0x2c)
> [   30.351837]  r7:00000000 r6:00000000 r5:c0065fc4 r4:eb843d54
> [   30.352111] ---[ end trace 78317663d3b4807c ]---
>
>
> Deadlock at module unload
> =========================
> When removing the modules, there's a dealock. This is the last line printed:
>
> [   30.399200] [drm] Module unloaded
>
> Then, when the deadlock detection kicks in:
>
> [  240.962432] INFO: task rmmod:894 blocked for more than 120 seconds.
> [  240.962432] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [  240.977508] rmmod           D c0524964     0   894    884 0x00000000
> [  240.981719] Backtrace:
> [  240.987274] [<c05245ec>] (__schedule+0x0/0x7e8) from [<c0524eb0>] (schedule+0x38/0x78)
> [  240.995819] [<c0524e78>] (schedule+0x0/0x78) from [<c05251ac>] (schedule_preempt_disabled+0x28/0x38)
> [  241.005706] [<c0525184>] (schedule_preempt_disabled+0x0/0x38) from [<c05238c4>] (mutex_lock_nested+0x1b8/0x3a8)
> [  241.016693]  r4:c07f5bf8 r3:eb978180
> [  241.020812] [<c052370c>] (mutex_lock_nested+0x0/0x3a8) from [<c033c9d0>] (driver_detach+0x4c/0xc0)
> [  241.021026] [<c033c984>] (driver_detach+0x0/0xc0) from [<c033bd24>] (bus_remove_driver+0x94/0xfc)
> [  241.040100]  r6:c07f5b38 r5:bf0ec410 r4:00000000 r3:00000000
> [  241.042633] [<c033bc90>] (bus_remove_driver+0x0/0xfc) from [<c033d054>] (driver_unregister+0x58/0x78)
> [  241.056060]  r6:c07c28a4 r5:bf0ec410 r4:00000000 r3:eb978180
> [  241.062164] [<c033cffc>] (driver_unregister+0x0/0x78) from [<c033ddc0>] (platform_driver_unregister+0x14/0x18)
> [  241.072875]  r5:bf0ebc18 r4:c07c2860
> [  241.075439] [<c033ddac>] (platform_driver_unregister+0x0/0x18) from [<bf0df2c8>] (pdev_remove+0x48/0x54 [omapdrm])
> [  241.087921] [<bf0df280>] (pdev_remove+0x0/0x54 [omapdrm]) from [<c033dc38>] (platform_drv_remove+0x20/0x24)
> [  241.098327]  r4:c07c2870 r3:bf0df280
> [  241.100860] [<c033dc18>] (platform_drv_remove+0x0/0x24) from [<c033bfc4>] (__device_release_driver+0x78/0xd4)
> [  241.112792] [<c033bf4c>] (__device_release_driver+0x0/0xd4) from [<c033ca40>] (driver_detach+0xbc/0xc0)
> [  241.113159]  r5:bf0ebc18 r4:c07c2870
> [  241.122833] [<c033c984>] (driver_detach+0x0/0xc0) from [<c033bd24>] (bus_remove_driver+0x94/0xfc)
> [  241.136108]  r6:c07f5b38 r5:bf0ebc18 r4:00000000 r3:00000000
> [  241.142211] [<c033bc90>] (bus_remove_driver+0x0/0xfc) from [<c033d054>] (driver_unregister+0x58/0x78)
> [  241.152069]  r6:00000880 r5:bf0ebc18 r4:00000000 r3:00000000
> [  241.153472] [<c033cffc>] (driver_unregister+0x0/0x78) from [<c033ddc0>] (platform_driver_unregister+0x14/0x18)
> [  241.168823]  r5:bf0ec4a0 r4:00000000
> [  241.171356] [<c033ddac>] (platform_driver_unregister+0x0/0x18) from [<bf0e9bb8>] (omap_drm_fini+0x28/0x3c [omapdrm])
> [  241.183990] [<bf0e9b90>] (omap_drm_fini+0x0/0x3c [omapdrm]) from [<c009ef10>] (SyS_delete_module+0x154/0x288)
> [  241.194610] [<c009edbc>] (SyS_delete_module+0x0/0x288) from [<c0014620>] (ret_fast_syscall+0x0/0x48)
> [  241.204345]  r7:00000081 r6:006d7264 r5:70616d6f r4:0001aac4
> [  241.206726] 3 locks held by rmmod/894:
> [  241.214416]  #0:  (&__lockdep_no_validate__){......}, at: [<c033c9d0>] driver_detach+0x4c/0xc0
> [  241.223693]  #1:  (&__lockdep_no_validate__){......}, at: [<c033c9dc>] driver_detach+0x58/0xc0
> [  241.232940]  #2:  (&__lockdep_no_validate__){......}, at: [<c033c9d0>] driver_detach+0x4c/0xc0
>
>  Tomi
>