drm/i915: Export a preallocate variant of i915_active_acquire()

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Sometimes we have to be very careful not to allocate underneath a mutex
(or spinlock) and yet still want to track activity. Enter
i915_active_acquire_for_context(). This raises the activity counter on
i915_active prior to use and ensures that the fence-tree contains a slot
for the context.

v2: Refactor active_lookup() so it can be called again before/after
locking to resolve contention. Since we protect the rbtree until we
idle, we can do a lockfree lookup, with the caveat that if another
thread performs a concurrent insertion, the rotations from the insert
may cause us to not find our target. A second pass holding the treelock
will find the target if it exists, or the place to perform our
insertion.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Thomas Hellström <thomas.hellstrom@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200731085015.32368-3-chris@chris-wilson.co.uk
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

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Chris Wilson 2020-07-31 09:50:11 +01:00 • committed by Joonas Lahtinen

parent 04240e30ed

commit 5d9341370f

4 changed files with 130 additions and 38 deletions

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2

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

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4

drivers/gpu/drm/i915/gt/intel_timeline.c

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150

drivers/gpu/drm/i915/i915_active.c

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12

drivers/gpu/drm/i915/i915_active.h

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