Acked-by: Dave Airlie <airlied@xxxxxxxxxx> On Tue, 5 Nov 2019 at 21:06, Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> wrote: > > Dave, ping for Acked-by here so we can merge? You already gave an > early ack in IRC while travelling. > > Regards, Joonas > > Quoting Joonas Lahtinen (2019-08-30 13:50:53) > > To ensure cross-driver locking compatibility, document the expected > > guidelines for implementing the GEM locking in i915. Note that this > > is a description of how things should end up after being reworked, > > and does not reflect the current state of things. > > > > Signed-off-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> > > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > Cc: Dave Airlie <airlied@xxxxxxxxxx> > > Cc: Matthew Auld <matthew.auld@xxxxxxxxx> > > Cc: Abdiel Janulgue <abdiel.janulgue@xxxxxxxxxxxxxxx> > > Cc: CQ Tang <cq.tang@xxxxxxxxx> > > --- > > Documentation/gpu/i915.rst | 45 ++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 45 insertions(+) > > > > diff --git a/Documentation/gpu/i915.rst b/Documentation/gpu/i915.rst > > index e249ea7b0ec7..63a72d10f2c7 100644 > > --- a/Documentation/gpu/i915.rst > > +++ b/Documentation/gpu/i915.rst > > @@ -320,6 +320,51 @@ for execution also include a list of all locations within buffers that > > refer to GPU-addresses so that the kernel can edit the buffer correctly. > > This process is dubbed relocation. > > > > +Locking Guidelines > > +------------------ > > + > > +**NOTE:** This is a description of how the locking should be after > > +refactoring is done. Does not necessarily reflect what the locking > > +looks like while WIP. > > + > > +#. All locking rules and interface contracts with cross-driver interfaces > > + (dma-buf, dma_fence) need to be followed. > > + > > +#. No struct_mutex anywhere in the code > > + > > +#. dma_resv will be the outermost lock (when needed) and ww_acquire_ctx > > + is to be hoisted at highest level and passed down within i915_gem_ctx > > + in the call chain > > + > > +#. While holding lru/memory manager (buddy, drm_mm, whatever) locks > > + system memory allocations are not allowed > > + > > + * Enforce this by priming lockdep (with fs_reclaim). If we > > + allocate memory while holding these looks we get a rehash > > + of the shrinker vs. struct_mutex saga, and that would be > > + real bad. > > + > > +#. Do not nest different lru/memory manager locks within each other. > > + Take them in turn to update memory allocations, relying on the object’s > > + dma_resv ww_mutex to serialize against other operations. > > + > > +#. The suggestion for lru/memory managers locks is that they are small > > + enough to be spinlocks. > > + > > +#. All features need to come with exhaustive kernel selftests and/or > > + IGT tests when appropriate > > + > > +#. All LMEM uAPI paths need to be fully restartable (_interruptible() > > + for all locks/waits/sleeps) > > + > > + * Error handling validation through signal injection. > > + Still the best strategy we have for validating GEM uAPI > > + corner cases. > > + Must be excessively used in the IGT, and we need to check > > + that we really have full path coverage of all error cases. > > + > > + * -EDEADLK handling with ww_mutex > > + > > GEM BO Management Implementation Details > > ---------------------------------------- > > > > -- > > 2.20.1 > > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
