Messages in this thread |  | | Subject | Re: Warnings in DRM code when removing/unbinding a driver | From | John Garry <> | Date | Thu, 19 Dec 2019 10:03:33 +0000 |
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On 19/12/2019 09:54, Daniel Vetter wrote: > On Wed, Dec 18, 2019 at 7:08 PM John Garry <john.garry@huawei.com> wrote: >> >> + >> >> So the v5.4 kernel does not have this issue. >> >> I have bisected the initial occurrence to: >> >> commit 37a48adfba6cf6e87df9ba8b75ab85d514ed86d8 >> Author: Thomas Zimmermann <tzimmermann@suse.de> >> 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.
OK, so it exposes it.
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.
Do you think it's worth trying to fix this for 5.5 and earlier, or just switch to the device-managed interface for 5.6 and forget about 5.5 and earlier?
Thanks, John
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