[PATCH 01/49] cyclic-ids
Chris Wilson
chris at chris-wilson.co.uk
Tue Aug 4 21:29:33 UTC 2020
---
drivers/gpu/drm/i915/gt/intel_engine_types.h | 1 +
drivers/gpu/drm/i915/gt/intel_lrc.c | 10 +++++++++-
2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
index c400aaa2287b..bfa0199b7a2c 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
@@ -330,6 +330,7 @@ struct intel_engine_cs {
atomic_t fw_active;
unsigned long context_tag;
+ unsigned long context_last;
struct rb_node uabi_node;
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 417f6b0c6c61..e53a5c8af7b0 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1355,7 +1355,15 @@ __execlists_schedule_in(struct i915_request *rq)
ce->lrc.ccid = ce->tag;
} else {
/* We don't need a strict matching tag, just different values */
- unsigned int tag = ffs(READ_ONCE(engine->context_tag));
+ unsigned int tag;
+
+ /* Cyclically allocate unused ids */
+ tag = GENMASK(BITS_PER_LONG - 1,
+ engine->context_last++ % BITS_PER_LONG);
+
+ tag = ffs(READ_ONCE(engine->context_tag) & tag);
+ if (tag == 0)
+ tag = ffs(READ_ONCE(engine->context_tag));
GEM_BUG_ON(tag == 0 || tag >= BITS_PER_LONG);
clear_bit(tag - 1, &engine->context_tag);
--
2.20.1
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