From 8413502238168561acf1e2137eaea6af4004e506 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 6 Jan 2020 11:42:33 +0000 Subject: drm/i915/gt: Drop mutex serialisation between context pin/unpin The last remaining reason for serialising the pin/unpin of the intel_context is to ensure that our preallocated wakerefs are not consumed too early (i.e. the unpin of the previous phase does not emit the idle barriers for this phase before we even submit). All of the other operations within the context pin/unpin are supposed to be atomic... Therefore, we can reduce the serialisation to being just on the i915_active.preallocated_barriers itself and drop the nested pin_mutex from intel_context_unpin(). Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Maarten Lankhorst Reviewed-by: Maarten Lankhorst Link: https://patchwork.freedesktop.org/patch/msgid/20200106114234.2529613-5-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/gt/intel_context.c | 24 +++++++++++------------- drivers/gpu/drm/i915/i915_active.c | 19 +++++++++++++++---- 2 files changed, 26 insertions(+), 17 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c index 4d0bc1478ccd..5ea8305fd633 100644 --- a/drivers/gpu/drm/i915/gt/intel_context.c +++ b/drivers/gpu/drm/i915/gt/intel_context.c @@ -86,22 +86,20 @@ err: void intel_context_unpin(struct intel_context *ce) { - if (likely(atomic_add_unless(&ce->pin_count, -1, 1))) + if (!atomic_dec_and_test(&ce->pin_count)) return; - /* We may be called from inside intel_context_pin() to evict another */ - intel_context_get(ce); - mutex_lock_nested(&ce->pin_mutex, SINGLE_DEPTH_NESTING); - - if (likely(atomic_dec_and_test(&ce->pin_count))) { - CE_TRACE(ce, "retire\n"); - - ce->ops->unpin(ce); - - intel_context_active_release(ce); - } + CE_TRACE(ce, "unpin\n"); + ce->ops->unpin(ce); - mutex_unlock(&ce->pin_mutex); + /* + * Once released, we may asynchronously drop the active reference. + * As that may be the only reference keeping the context alive, + * take an extra now so that it is not freed before we finish + * dereferencing it. + */ + intel_context_get(ce); + intel_context_active_release(ce); intel_context_put(ce); } diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c index cfe09964622b..f3da5c06f331 100644 --- a/drivers/gpu/drm/i915/i915_active.c +++ b/drivers/gpu/drm/i915/i915_active.c @@ -605,12 +605,15 @@ int i915_active_acquire_preallocate_barrier(struct i915_active *ref, struct intel_engine_cs *engine) { intel_engine_mask_t tmp, mask = engine->mask; + struct llist_node *pos = NULL, *next; struct intel_gt *gt = engine->gt; - struct llist_node *pos, *next; int err; GEM_BUG_ON(i915_active_is_idle(ref)); - GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers)); + + /* Wait until the previous preallocation is completed */ + while (!llist_empty(&ref->preallocated_barriers)) + cond_resched(); /* * Preallocate a node for each physical engine supporting the target @@ -653,16 +656,24 @@ int i915_active_acquire_preallocate_barrier(struct i915_active *ref, GEM_BUG_ON(rcu_access_pointer(node->base.fence) != ERR_PTR(-EAGAIN)); GEM_BUG_ON(barrier_to_engine(node) != engine); - llist_add(barrier_to_ll(node), &ref->preallocated_barriers); + next = barrier_to_ll(node); + next->next = pos; + if (!pos) + pos = next; intel_engine_pm_get(engine); } + GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers)); + llist_add_batch(next, pos, &ref->preallocated_barriers); + return 0; unwind: - llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) { + while (pos) { struct active_node *node = barrier_from_ll(pos); + pos = pos->next; + atomic_dec(&ref->count); intel_engine_pm_put(barrier_to_engine(node)); -- cgit v1.2.3