On Mon, 06 Nov 2023, Janusz Krzysztofik <janusz.krzysztofik@xxxxxxxxxxxxxxx> wrote: > Object debugging tools were sporadically reporting illegal attempts to > free a still active i915 VMA object from when parking a GPU tile believed > to be idle. > > [161.359441] ODEBUG: free active (active state 0) object: ffff88811643b958 object type: i915_active hint: __i915_vma_active+0x0/0x50 [i915] > [161.360082] WARNING: CPU: 5 PID: 276 at lib/debugobjects.c:514 debug_print_object+0x80/0xb0 > ... > [161.360304] CPU: 5 PID: 276 Comm: kworker/5:2 Not tainted 6.5.0-rc1-CI_DRM_13375-g003f860e5577+ #1 > [161.360314] Hardware name: Intel Corporation Rocket Lake Client Platform/RocketLake S UDIMM 6L RVP, BIOS RKLSFWI1.R00.3173.A03.2204210138 04/21/2022 > [161.360322] Workqueue: i915-unordered __intel_wakeref_put_work [i915] > [161.360592] RIP: 0010:debug_print_object+0x80/0xb0 > ... > [161.361347] debug_object_free+0xeb/0x110 > [161.361362] i915_active_fini+0x14/0x130 [i915] > [161.361866] release_references+0xfe/0x1f0 [i915] > [161.362543] i915_vma_parked+0x1db/0x380 [i915] > [161.363129] __gt_park+0x121/0x230 [i915] > [161.363515] ____intel_wakeref_put_last+0x1f/0x70 [i915] > > That has been tracked down to be happening when another thread was > deactivating the VMA inside __active_retire() helper, after the VMA's > active counter was already decremented to 0, but before deactivation of > the VMA's object was reported to the object debugging tools. Root cause > has been identified as premature release of last wakeref for the GPU tile > to which the active VMA belonged. > > In case of single tile platforms, an engine associated with a request that > uses the VMA is keeping the tile's wakeref long enough for that VMA to be > deactivated on time, before it is going to be freed. However, on multi- > tile platforms, a request may use a VMA from a tile other than the one > that hosts the request's engine, then, not protected with the engine's > wakeref. > > Get an extra wakeref for the VMA's tile when activating it, and put that > wakeref only after the VMA is deactivated. However, exclude GGTT from > that processing path, otherwise the GPU never goes idle. Since > __i915_vma_retire() may be called from atomic contexts, use async variant > of wakeref put. > > Closes: https://gitlab.freedesktop.org/drm/intel/issues/8875 > Fixes: Fixes: 213c43676beb ("drm/i915/mtl: Remove the 'force_probe' requirement for Meteor Lake") I get the motivation, but this is hardly true. Also, double Fixes. BR, Jani. > Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@xxxxxxxxxxxxxxx> > --- > drivers/gpu/drm/i915/i915_vma.c | 18 ++++++++++++++++-- > 1 file changed, 16 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c > index d09aad34ba37f..70c68f614c6db 100644 > --- a/drivers/gpu/drm/i915/i915_vma.c > +++ b/drivers/gpu/drm/i915/i915_vma.c > @@ -34,6 +34,7 @@ > #include "gt/intel_engine.h" > #include "gt/intel_engine_heartbeat.h" > #include "gt/intel_gt.h" > +#include "gt/intel_gt_pm.h" > #include "gt/intel_gt_requests.h" > #include "gt/intel_tlb.h" > > @@ -103,12 +104,25 @@ static inline struct i915_vma *active_to_vma(struct i915_active *ref) > > static int __i915_vma_active(struct i915_active *ref) > { > - return i915_vma_tryget(active_to_vma(ref)) ? 0 : -ENOENT; > + struct i915_vma *vma = active_to_vma(ref); > + > + if (!i915_vma_tryget(vma)) > + return -ENOENT; > + > + if (!i915_vma_is_ggtt(vma)) > + intel_gt_pm_get(vma->vm->gt); > + > + return 0; > } > > static void __i915_vma_retire(struct i915_active *ref) > { > - i915_vma_put(active_to_vma(ref)); > + struct i915_vma *vma = active_to_vma(ref); > + > + if (!i915_vma_is_ggtt(vma)) > + intel_gt_pm_put_async(vma->vm->gt); > + > + i915_vma_put(vma); > } > > static struct i915_vma * -- Jani Nikula, Intel
