From c01e8da2cdb99303547d25b3dbffa3afec56738a Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 3 Feb 2020 09:41:48 +0000 Subject: drm/i915: Initialise basic fence before acquiring seqno Inside the intel_timeline_get_seqno(), we currently track the retirement of the old cachelines by listening to the new request. This requires that the new request is ready to be used and so requires a minimum bit of initialisation prior to getting the new seqno. Fixes: b1e3177bd1d8 ("drm/i915: Coordinate i915_active with its own mutex") Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Matthew Auld Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20200203094152.4150550-2-chris@chris-wilson.co.uk (cherry picked from commit 855e39e65cfc33a73724f1cc644ffc5754864a20) Signed-off-by: Jani Nikula --- drivers/gpu/drm/i915/i915_request.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) (limited to 'drivers/gpu/drm/i915/i915_request.c') diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c index 78a5f5d3c070..f56b046a32de 100644 --- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -595,6 +595,8 @@ static void __i915_request_ctor(void *arg) i915_sw_fence_init(&rq->submit, submit_notify); i915_sw_fence_init(&rq->semaphore, semaphore_notify); + dma_fence_init(&rq->fence, &i915_fence_ops, &rq->lock, 0, 0); + rq->file_priv = NULL; rq->capture_list = NULL; @@ -653,25 +655,30 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp) } } - ret = intel_timeline_get_seqno(tl, rq, &seqno); - if (ret) - goto err_free; - rq->i915 = ce->engine->i915; rq->context = ce; rq->engine = ce->engine; rq->ring = ce->ring; rq->execution_mask = ce->engine->mask; + kref_init(&rq->fence.refcount); + rq->fence.flags = 0; + rq->fence.error = 0; + INIT_LIST_HEAD(&rq->fence.cb_list); + + ret = intel_timeline_get_seqno(tl, rq, &seqno); + if (ret) + goto err_free; + + rq->fence.context = tl->fence_context; + rq->fence.seqno = seqno; + RCU_INIT_POINTER(rq->timeline, tl); RCU_INIT_POINTER(rq->hwsp_cacheline, tl->hwsp_cacheline); rq->hwsp_seqno = tl->hwsp_seqno; rq->rcustate = get_state_synchronize_rcu(); /* acts as smp_mb() */ - dma_fence_init(&rq->fence, &i915_fence_ops, &rq->lock, - tl->fence_context, seqno); - /* We bump the ref for the fence chain */ i915_sw_fence_reinit(&i915_request_get(rq)->submit); i915_sw_fence_reinit(&i915_request_get(rq)->semaphore); -- cgit v1.2.3 From 0b1570b7ffe68dfefa07cb092a0723f898bb8184 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 27 Feb 2020 08:57:14 +0000 Subject: drm/i915: Protect i915_request_await_start from early waits We need to be extremely careful inside i915_request_await_start() as it needs to walk the list of requests in the foreign timeline with very little protection. As we hold our own timeline mutex, we can not nest inside the signaler's timeline mutex, so all that remains is our RCU protection. However, to be safe we need to tell the compiler that we may be traversing the list only under RCU protection, and furthermore we need to start declaring requests as elements of the timeline from their construction. Fixes: 9ddc8ec027a3 ("drm/i915: Eliminate the trylock for awaiting an earlier request") Fixes: 6a79d848403d ("drm/i915: Lock signaler timeline while navigating") Signed-off-by: Chris Wilson Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20200227085723.1961649-11-chris@chris-wilson.co.uk (cherry picked from commit d22d2d073ef859b346bc32cb25299262e3973769) Signed-off-by: Jani Nikula --- drivers/gpu/drm/i915/i915_request.c | 41 +++++++++++++++++++++++++------------ 1 file changed, 28 insertions(+), 13 deletions(-) (limited to 'drivers/gpu/drm/i915/i915_request.c') diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c index f56b046a32de..dcaa85a91090 100644 --- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -275,7 +275,7 @@ bool i915_request_retire(struct i915_request *rq) spin_unlock_irq(&rq->lock); remove_from_client(rq); - list_del(&rq->link); + list_del_rcu(&rq->link); intel_context_exit(rq->context); intel_context_unpin(rq->context); @@ -721,6 +721,8 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp) rq->infix = rq->ring->emit; /* end of header; start of user payload */ intel_context_mark_active(ce); + list_add_tail_rcu(&rq->link, &tl->requests); + return rq; err_unwind: @@ -777,13 +779,23 @@ i915_request_await_start(struct i915_request *rq, struct i915_request *signal) GEM_BUG_ON(i915_request_timeline(rq) == rcu_access_pointer(signal->timeline)); + if (i915_request_started(signal)) + return 0; + fence = NULL; rcu_read_lock(); spin_lock_irq(&signal->lock); - if (!i915_request_started(signal) && - !list_is_first(&signal->link, - &rcu_dereference(signal->timeline)->requests)) { - struct i915_request *prev = list_prev_entry(signal, link); + do { + struct list_head *pos = READ_ONCE(signal->link.prev); + struct i915_request *prev; + + /* Confirm signal has not been retired, the link is valid */ + if (unlikely(i915_request_started(signal))) + break; + + /* Is signal the earliest request on its timeline? */ + if (pos == &rcu_dereference(signal->timeline)->requests) + break; /* * Peek at the request before us in the timeline. That @@ -791,13 +803,18 @@ i915_request_await_start(struct i915_request *rq, struct i915_request *signal) * after acquiring a reference to it, confirm that it is * still part of the signaler's timeline. */ - if (i915_request_get_rcu(prev)) { - if (list_next_entry(prev, link) == signal) - fence = &prev->fence; - else - i915_request_put(prev); + prev = list_entry(pos, typeof(*prev), link); + if (!i915_request_get_rcu(prev)) + break; + + /* After the strong barrier, confirm prev is still attached */ + if (unlikely(READ_ONCE(prev->link.next) != &signal->link)) { + i915_request_put(prev); + break; } - } + + fence = &prev->fence; + } while (0); spin_unlock_irq(&signal->lock); rcu_read_unlock(); if (!fence) @@ -1242,8 +1259,6 @@ __i915_request_add_to_timeline(struct i915_request *rq) 0); } - list_add_tail(&rq->link, &timeline->requests); - /* * Make sure that no request gazumped us - if it was allocated after * our i915_request_alloc() and called __i915_request_add() before -- cgit v1.2.3