[Nouveau] [Bug 76732] Kworker using 100% CPU

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=76732

--- Comment #32 from Dale Hamel <daleha at gmail.com> ---
I can confirm that v3.8-rc6 ( a few commits before the bad commit ) works fine
for me.

(In reply to comment #0)
> Loading the nouveau driver leads to a kworker constantly using  100% of a
> CPU core.
> 
> PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
> 211 root      20   0       0      0      0 R 100.0  0.0   2:51.00 kworker/1:1
> 
> Powertop suggests the problem comes from nouveau_connector_hotplug_work.
> 
> I noticed this problem first occurred in kernel 3.9 and still persists in
> 3.14 rc8. In kernel 3.8 the problem did not occur. Some time ago, trying to
> figure out the cause, i also tried a kernel bisect.
> 
> 
> git bisect start
> # bad: [c1be5a5b1b355d40e6cf79cc979eb66dafa24ad1] Linux 3.9
> git bisect bad c1be5a5b1b355d40e6cf79cc979eb66dafa24ad1
> # good: [19f949f52599ba7c3f67a5897ac6be14bfcb1200] Linux 3.8
> git bisect good 19f949f52599ba7c3f67a5897ac6be14bfcb1200
> # good: [d778df51c09264076fe0208c099ef7d428f21790] mm: vmscan: save work
> scanning (almost) empty LRU lists
> git bisect good d778df51c09264076fe0208c099ef7d428f21790
> # bad: [ee89f81252179dcbf6cd65bd48299f5e52292d88] Merge branch
> 'for-3.9/core' of git://git.kernel.dk/linux-block
> git bisect bad ee89f81252179dcbf6cd65bd48299f5e52292d88
> # good: [69086a78bdc973ec0b722be790b146e84ba8a8c4] Merge branch 'for-linus'
> of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
> git bisect good 69086a78bdc973ec0b722be790b146e84ba8a8c4
> # bad: [ed5dc2372dba46e0ecd08791b1a0399d313e5cff] Merge tag
> 'mmc-updates-for-3.9-rc1' of git://
> git.kernel.org/pub/scm/linux/kernel/git/cjb/mmc
> git bisect bad ed5dc2372dba46e0ecd08791b1a0399d313e5cff
> # bad: [1f3a574a4bfe86ebf7d51fac37e0668397372fd8] Merge branch
> 'drm-nouveau-next' of
> git://anongit.freedesktop.org/git/nouveau/linux-2.6into drm-next
> git bisect bad 1f3a574a4bfe86ebf7d51fac37e0668397372fd8
> # good: [cd17ef4114ad5c514b17e6a0bb02a309ab90b692] Merge tag
> 'drm-intel-next-2013-02-01' of git://
> people.freedesktop.org/~danvet/drm-intel into drm-next
> git bisect good cd17ef4114ad5c514b17e6a0bb02a309ab90b692
> # good: [210561ffd72d00eccf12c0131b8024d5436bae95] intel/iommu: force
> writebuffer-flush quirk on Gen 4 Chipsets
> git bisect good 210561ffd72d00eccf12c0131b8024d5436bae95
> # good: [0f0800661a125ddb038462570c869fe6f8ab5737] drm/nouveau/gpio: pass
> number of on-die gpio lines to base
> git bisect good 0f0800661a125ddb038462570c869fe6f8ab5737
> # good: [35f8badc1cf652381fa3f82c1fbea39f4dbe87fd] drm: Don't set the
> plane->fb to NULL on successfull set_plane
> git bisect good 35f8badc1cf652381fa3f82c1fbea39f4dbe87fd
> # good: [31a34aa421032cfe3b2b892c929e7539e747a7ac] drm/nouveau/i2c: aux
> channels not necessarily on nvio
> git bisect good 31a34aa421032cfe3b2b892c929e7539e747a7ac
> # bad: [0a0afd282fd715dd63d64b243299a64da14f8e8d] drm/nv50-/disp: move DP
> link training to core and train from supervisor
> git bisect bad 0a0afd282fd715dd63d64b243299a64da14f8e8d
> # good: [ac8cc241a81941932da44993242e68c62e115ec7] drm/nv50/devinit:
> reverse the logic for running encoder init scripts
> git bisect good ac8cc241a81941932da44993242e68c62e115ec7
> # good: [7dcd060c0e6e4f76ce7eea94c66437ce8f546530] drm/nouveau/i2c: create
> proper chipset-specific class implementations
> git bisect good 7dcd060c0e6e4f76ce7eea94c66437ce8f546530
> # good: [5cc027f6b1ec651c18a4322ed3e30c6e9cf01e96] drm/nv50-/disp: handle
> supervisor tasks from workqueue
> git bisect good 5cc027f6b1ec651c18a4322ed3e30c6e9cf01e96
> # first bad commit: [0a0afd282fd715dd63d64b243299a64da14f8e8d]
> drm/nv50-/disp: move DP link training to core and train from supervisor
> 
> 
> 
> 
> 0a0afd282fd715dd63d64b243299a64da14f8e8d is the first bad commit
> commit 0a0afd282fd715dd63d64b243299a64da14f8e8d
> Author: Ben Skeggs <bskeggs at redhat.com>
> Date:   Mon Feb 18 23:17:53 2013 -0500
> 
>     drm/nv50-/disp: move DP link training to core and train from supervisor
> 
>     We need to be able to do link training for PIOR-connected ANX9805 from
>     the third supervisor handler (due to script ordering in the bios, can't
>     have the "user" call train because some settings are overwritten from
>     the modesetting bios scripts).
> 
>     This moves link training for SOR-connected DP encoders to the second
>     supervisor interrupt, *before* we call the modesetting scripts (yes,
>     different ordering from PIOR is necessary).  This is useful since we
>     should now be able to remove some hacks to workaround races between
>     the supervisor and link training paths.
> 
>     Signed-off-by: Ben Skeggs <bskeggs at redhat.com>
> 
> :040000 040000 8f2f2d8ea35eae1b6e6ff981761be02a8818bac3
> 2994eb54c689056254c241fe78a3af8d0b61d1df M    drivers

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