From 6c81e21a4742385c00713137c6fdcade0412e93c Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Wed, 25 Mar 2020 13:00:59 +0000 Subject: [PATCH] drm/i915/gt: Stage the transfer of the virtual breadcrumb We move the virtual breadcrumb from one physical engine to the next, if the next virtual request is scheduled on a new physical engine. Since the virtual context can only be in one signal queue, we need it to track the current physical engine for the new breadcrumbs. However, to move the list we need both breadcrumb locks -- and since we cannot take both at the same time (unless we are careful and always ensure consistent ordering) stage the movement of the signaler via the current virtual request. Closes: https://gitlab.freedesktop.org/drm/intel/issues/1510 Fixes: 6d06779e8672 ("drm/i915: Load balancing across a virtual engine") Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20200325130059.30600-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/gt/intel_lrc.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index d49baade0986..b12355048501 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -1663,7 +1663,7 @@ static bool virtual_matches(const struct virtual_engine *ve, } static void virtual_xfer_breadcrumbs(struct virtual_engine *ve, - struct intel_engine_cs *engine) + struct i915_request *rq) { struct intel_engine_cs *old = ve->siblings[0]; @@ -1671,9 +1671,19 @@ static void virtual_xfer_breadcrumbs(struct virtual_engine *ve, spin_lock(&old->breadcrumbs.irq_lock); if (!list_empty(&ve->context.signal_link)) { - list_move_tail(&ve->context.signal_link, - &engine->breadcrumbs.signalers); - intel_engine_signal_breadcrumbs(engine); + list_del_init(&ve->context.signal_link); + + /* + * We cannot acquire the new engine->breadcrumbs.irq_lock + * (as we are holding a breadcrumbs.irq_lock already), + * so attach this request to the signaler on submission. + * The queued irq_work will occur when we finally drop + * the engine->active.lock after dequeue. + */ + set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &rq->fence.flags); + + /* Also transfer the pending irq_work for the old breadcrumb. */ + intel_engine_signal_breadcrumbs(rq->engine); } spin_unlock(&old->breadcrumbs.irq_lock); } @@ -2045,7 +2055,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine) engine); if (!list_empty(&ve->context.signals)) - virtual_xfer_breadcrumbs(ve, engine); + virtual_xfer_breadcrumbs(ve, rq); /* * Move the bound engine to the top of the list -- 2.11.0