[cc += linux-pm] Hi Lyude,
First of all, thanks a lot for looking into this. On Mon, Jul 16, 2018 at 07:59:25PM -0400, Lyude Paul wrote: > In order to fix all of the spots that need to have runtime PM get/puts() > added, we need to ensure that it's possible for us to call > pm_runtime_get/put() in any context, regardless of how deep, since > almost all of the spots that are currently missing refs can potentially > get called in the runtime suspend/resume path. Otherwise, we'll try to > resume the GPU as we're trying to resume the GPU (and vice-versa) and > cause the kernel to deadlock. > > With this, it should be safe to call the pm runtime functions in any > context in nouveau with one condition: any point in the driver that > calls pm_runtime_get*() cannot hold any locks owned by nouveau that > would be acquired anywhere inside nouveau_pmops_runtime_resume(). > This includes modesetting locks, i2c bus locks, etc. [snip] > --- a/drivers/gpu/drm/nouveau/nouveau_drm.c > +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c > @@ -835,6 +835,8 @@ nouveau_pmops_runtime_suspend(struct device *dev) > return -EBUSY; > } > > + dev->power.disable_depth++; > + I'm not sure if that variable is actually private to the PM core. Grepping through the tree I only find a single occurrence where it's accessed outside the PM core and that's in amdgpu. So this looks a little fishy TBH. It may make sense to cc such patches to linux-pm to get Rafael & other folks involved with the PM core to comment. Also, the disable_depth variable only exists if the kernel was compiled with CONFIG_PM enabled, but I can't find a "depends on PM" or something like that in nouveau's Kconfig. Actually, if PM is not selected, all the nouveau_pmops_*() functions should be #ifdef'ed away, but oddly there's no #ifdef CONFIG_PM anywhere in nouveau_drm.c. Anywayn, if I understand the commit message correctly, you're hitting a pm_runtime_get_sync() in a code path that itself is called during a pm_runtime_get_sync(). Could you include stack traces in the commit message? My gut feeling is that this patch masks a deeper issue, e.g. if the runtime_resume code path does in fact directly poll outputs, that would seem wrong. Runtime resume should merely make the card accessible, i.e. reinstate power if necessary, put into PCI_D0, restore registers, etc. Output polling should be scheduled asynchronously. Thanks, Lukas _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
