From patchwork Sat Aug 17 15:30:22 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 11099165 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D98811399 for ; Sat, 17 Aug 2019 15:30:49 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CA64D212BE for ; Sat, 17 Aug 2019 15:30:49 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id BE7D726E4F; Sat, 17 Aug 2019 15:30:49 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=unavailable version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 5AB00212BE for ; Sat, 17 Aug 2019 15:30:49 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id ACF796EA23; Sat, 17 Aug 2019 15:30:47 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id CE1E0897F6; Sat, 17 Aug 2019 15:30:45 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from haswell.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 18173855-1500050 for multiple; Sat, 17 Aug 2019 16:30:23 +0100 From: Chris Wilson To: dri-devel@lists.freedesktop.org Subject: [PATCH v2] dma-fence: Store the timestamp in the same union as the cb_list Date: Sat, 17 Aug 2019 16:30:22 +0100 Message-Id: <20190817153022.5749-1-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.23.0.rc1 In-Reply-To: <20190817144736.7826-6-chris@chris-wilson.co.uk> References: <20190817144736.7826-6-chris@chris-wilson.co.uk> MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org, =?utf-8?q?Christian_K=C3=B6nig?= Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP The timestamp and the cb_list are mutually exclusive, the cb_list can only be added to prior to being signaled (and once signaled we drain), while the timestamp is only valid upon being signaled. Both the timestamp and the cb_list are only valid while the fence is alive, and as soon as no references are held can be replaced by the rcu_head. By reusing the union for the timestamp, we squeeze the base dma_fence struct to 64 bytes on x86-64. v2: Sort the union chronologically Suggested-by: Christian König Signed-off-by: Chris Wilson Cc: Christian König Acked-by: Christian König . --- drivers/dma-buf/dma-fence.c | 16 +++++++------- drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 13 ++++++------ drivers/gpu/drm/vmwgfx/vmwgfx_fence.c | 3 +++ include/linux/dma-fence.h | 23 ++++++++++++++++----- 4 files changed, 37 insertions(+), 18 deletions(-) diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c index 8a6d0250285d..2c136aee3e79 100644 --- a/drivers/dma-buf/dma-fence.c +++ b/drivers/dma-buf/dma-fence.c @@ -129,6 +129,7 @@ EXPORT_SYMBOL(dma_fence_context_alloc); int dma_fence_signal_locked(struct dma_fence *fence) { struct dma_fence_cb *cur, *tmp; + struct list_head cb_list; lockdep_assert_held(fence->lock); @@ -136,16 +137,16 @@ int dma_fence_signal_locked(struct dma_fence *fence) &fence->flags))) return -EINVAL; + /* Stash the cb_list before replacing it with the timestamp */ + list_replace(&fence->cb_list, &cb_list); + fence->timestamp = ktime_get(); set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags); trace_dma_fence_signaled(fence); - if (!list_empty(&fence->cb_list)) { - list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) { - INIT_LIST_HEAD(&cur->node); - cur->func(fence, cur); - } - INIT_LIST_HEAD(&fence->cb_list); + list_for_each_entry_safe(cur, tmp, &cb_list, node) { + INIT_LIST_HEAD(&cur->node); + cur->func(fence, cur); } return 0; @@ -231,7 +232,8 @@ void dma_fence_release(struct kref *kref) trace_dma_fence_destroy(fence); - if (WARN(!list_empty(&fence->cb_list), + if (WARN(!list_empty(&fence->cb_list) && + !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags), "Fence %s:%s:%llx:%llx released with pending signals!\n", fence->ops->get_driver_name(fence), fence->ops->get_timeline_name(fence), diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c index 2bc9c460e78d..09c68dda2098 100644 --- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c +++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c @@ -114,18 +114,18 @@ __dma_fence_signal__timestamp(struct dma_fence *fence, ktime_t timestamp) } static void -__dma_fence_signal__notify(struct dma_fence *fence) +__dma_fence_signal__notify(struct dma_fence *fence, + const struct list_head *list) { struct dma_fence_cb *cur, *tmp; lockdep_assert_held(fence->lock); lockdep_assert_irqs_disabled(); - list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) { + list_for_each_entry_safe(cur, tmp, list, node) { INIT_LIST_HEAD(&cur->node); cur->func(fence, cur); } - INIT_LIST_HEAD(&fence->cb_list); } void intel_engine_breadcrumbs_irq(struct intel_engine_cs *engine) @@ -187,11 +187,12 @@ void intel_engine_breadcrumbs_irq(struct intel_engine_cs *engine) list_for_each_safe(pos, next, &signal) { struct i915_request *rq = list_entry(pos, typeof(*rq), signal_link); - - __dma_fence_signal__timestamp(&rq->fence, timestamp); + struct list_head cb_list; spin_lock(&rq->lock); - __dma_fence_signal__notify(&rq->fence); + list_replace(&rq->fence.cb_list, &cb_list); + __dma_fence_signal__timestamp(&rq->fence, timestamp); + __dma_fence_signal__notify(&rq->fence, &cb_list); spin_unlock(&rq->lock); i915_request_put(rq); diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c index 434dfadb0e52..178a6cd1a06f 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c @@ -185,6 +185,9 @@ static long vmw_fence_wait(struct dma_fence *f, bool intr, signed long timeout) spin_lock(f->lock); + if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &f->flags)) + goto out; + if (intr && signal_pending(current)) { ret = -ERESTARTSYS; goto out; diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h index 2ce4d877d33e..8b4a5aaa6848 100644 --- a/include/linux/dma-fence.h +++ b/include/linux/dma-fence.h @@ -65,17 +65,30 @@ struct dma_fence_cb; struct dma_fence { spinlock_t *lock; const struct dma_fence_ops *ops; - /* We clear the callback list on kref_put so that by the time we - * release the fence it is unused. No one should be adding to the cb_list - * that they don't themselves hold a reference for. + /* + * We clear the callback list on kref_put so that by the time we + * release the fence it is unused. No one should be adding to the + * cb_list that they don't themselves hold a reference for. + * + * The lifetime of the timestamp is similarly tied to both the + * rcu freelist and the cb_list. The timestamp is only set upon + * signaling while simultaneously notifying the cb_list. Ergo, we + * only use either the cb_list of timestamp. Upon destruction, + * neither are accessible, and so we can use the rcu. This means + * that the cb_list is *only* valid until the signal bit is set, + * and to read either you *must* hold a reference to the fence. + * + * Listed in chronological order. */ union { - struct rcu_head rcu; struct list_head cb_list; + /* @cb_list replaced by @timestamp on dma_fence_signal() */ + ktime_t timestamp; + /* @timestamp replaced by @rcu on dma_fence_release() */ + struct rcu_head rcu; }; u64 context; u64 seqno; - ktime_t timestamp; unsigned long flags; struct kref refcount; int error;