From patchwork Thu Feb 23 07:44:15 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 9587853 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 8FF34604A2 for ; Thu, 23 Feb 2017 07:44:40 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7CEBB285E2 for ; Thu, 23 Feb 2017 07:44:40 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 71D3328684; Thu, 23 Feb 2017 07:44:40 +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=-4.1 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_MED,T_DKIM_INVALID autolearn=ham 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 E1D87285E2 for ; Thu, 23 Feb 2017 07:44:39 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 5FB0D6E988; Thu, 23 Feb 2017 07:44:39 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from mail-wr0-x243.google.com (mail-wr0-x243.google.com [IPv6:2a00:1450:400c:c0c::243]) by gabe.freedesktop.org (Postfix) with ESMTPS id D3E726E97F for ; Thu, 23 Feb 2017 07:44:35 +0000 (UTC) Received: by mail-wr0-x243.google.com with SMTP id s27so2936474wrb.0 for ; Wed, 22 Feb 2017 23:44:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references; bh=IizsGcXgf3NjN5omcMxJqgSAvK/xZ1qY+uo8H0u3JjE=; b=tzb89TESXLZtsDAVPn2TIY7/060d9SekESKPjMGTa+jGCG63gnhcaJ7Q5ByUdvisFy Vze4INm6l1Z6QXxbfp/J/+x3XLP1XmN2trolOII9byw3dpFajx+jn3bKxWSa06li9MyA PgIRik4ouRmdh9hkSVMH7cQRrE70gEIuCtLNy0tud6Ds/OtJOw4RyHl1wiEMGXBsUymB QBRZjvN92EiAyUL52ILvn9MsVKj3MwMyFK15vHDgBkTuMh1/Jonr0MC0dEbUk7agRSXG 2x0Sc+iXcV/UpBbea+omBcOgztikqWvDwwKTtZzD9mmLrVZYiG6wZV1mMQurJ16jiD+M JW6w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :in-reply-to:references; bh=IizsGcXgf3NjN5omcMxJqgSAvK/xZ1qY+uo8H0u3JjE=; b=AYl/ffkfp8b4of32QO8n53foduRvHy2VcMAEB3pEBpwL/F16NU16VxBNIafVkgBmnM k6DbmjvifSFD1NIk8AzBnqpE9jmhu+Z3QCRyJdOb3A0VyqFfGtHt9BLeT4IZHHf85OHL U335bxidCWe7zyREneoRvm6cOZ5Q9dz0lOvdCZsFmDZA0J8AM+k1Cr2aTYrhlOYGOkGZ 6SiV4b9LSCXsD8Cdhm7YD3e4szS+HatePr5Ox6hoKJjRPK1L8Ze4xGmlXiLR1wmjm/UR tDMAilmBcc0Fjgpd2XD6jNhQE8Y1NnSI0+RBcQb62flY3lhNsdXgn5d7cf752m7SVbMV 6pxw== X-Gm-Message-State: AMke39nu1WDMiYZ10YgtIKj9pRF/H6Q9IYRlRIaIs14yYAzJ3IhgDW308byJynAMbyAeaw== X-Received: by 10.223.162.205 with SMTP id t13mr30341434wra.155.1487835874489; Wed, 22 Feb 2017 23:44:34 -0800 (PST) Received: from haswell.alporthouse.com ([78.156.65.138]) by smtp.gmail.com with ESMTPSA id 186sm5655906wmw.24.2017.02.22.23.44.32 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 Feb 2017 23:44:33 -0800 (PST) From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Thu, 23 Feb 2017 07:44:15 +0000 Message-Id: <20170223074422.4125-10-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170223074422.4125-1-chris@chris-wilson.co.uk> References: <20170223074422.4125-1-chris@chris-wilson.co.uk> Subject: [Intel-gfx] [PATCH v4 09/16] drm/i915: Take a reference whilst processing the signaler request X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" X-Virus-Scanned: ClamAV using ClamSMTP The plan in the near-future is to allow requests to be removed from the signaler. We can no longer then rely on holding a reference to the request for the duration it is in the signaling tree, and instead must obtain a reference to the request for the current operation using RCU. Signed-off-by: Chris Wilson Reviewed-by: Tvrtko Ursulin --- drivers/gpu/drm/i915/intel_breadcrumbs.c | 22 +++++++++++++++------- drivers/gpu/drm/i915/intel_ringbuffer.h | 2 +- 2 files changed, 16 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c index d5bf4c0b2deb..a35d59d00bfb 100644 --- a/drivers/gpu/drm/i915/intel_breadcrumbs.c +++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c @@ -496,7 +496,11 @@ static int intel_breadcrumbs_signaler(void *arg) * need to wait for a new interrupt from the GPU or for * a new client. */ - request = READ_ONCE(b->first_signal); + rcu_read_lock(); + request = rcu_dereference(b->first_signal); + if (request) + request = i915_gem_request_get_rcu(request); + rcu_read_unlock(); if (signal_complete(request)) { local_bh_disable(); dma_fence_signal(&request->fence); @@ -515,24 +519,28 @@ static int intel_breadcrumbs_signaler(void *arg) * the oldest before picking the next one. */ spin_lock_irq(&b->lock); - if (request == b->first_signal) { + if (request == rcu_access_pointer(b->first_signal)) { struct rb_node *rb = rb_next(&request->signaling.node); - b->first_signal = rb ? to_signaler(rb) : NULL; + rcu_assign_pointer(b->first_signal, + rb ? to_signaler(rb) : NULL); } rb_erase(&request->signaling.node, &b->signals); spin_unlock_irq(&b->lock); i915_gem_request_put(request); } else { - if (kthread_should_stop()) + if (kthread_should_stop()) { + GEM_BUG_ON(request); break; + } schedule(); if (kthread_should_park()) kthread_parkme(); } + i915_gem_request_put(request); } while (1); __set_current_state(TASK_RUNNING); @@ -597,7 +605,7 @@ void intel_engine_enable_signaling(struct drm_i915_gem_request *request) rb_link_node(&request->signaling.node, parent, p); rb_insert_color(&request->signaling.node, &b->signals); if (first) - smp_store_mb(b->first_signal, request); + rcu_assign_pointer(b->first_signal, request); spin_unlock(&b->lock); @@ -670,7 +678,7 @@ void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine) /* The engines should be idle and all requests accounted for! */ WARN_ON(READ_ONCE(b->first_wait)); WARN_ON(!RB_EMPTY_ROOT(&b->waiters)); - WARN_ON(READ_ONCE(b->first_signal)); + WARN_ON(rcu_access_pointer(b->first_signal)); WARN_ON(!RB_EMPTY_ROOT(&b->signals)); if (!IS_ERR_OR_NULL(b->signaler)) @@ -691,7 +699,7 @@ bool intel_breadcrumbs_busy(struct intel_engine_cs *engine) busy |= intel_engine_flag(engine); } - if (b->first_signal) { + if (rcu_access_pointer(b->first_signal)) { wake_up_process(b->signaler); busy |= intel_engine_flag(engine); } diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h index 04e7d5a9ee3a..fbf34af7bc77 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.h +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h @@ -242,7 +242,7 @@ struct intel_engine_cs { struct rb_root signals; /* sorted by retirement */ struct intel_wait *first_wait; /* oldest waiter by retirement */ struct task_struct *signaler; /* used for fence signalling */ - struct drm_i915_gem_request *first_signal; + struct drm_i915_gem_request __rcu *first_signal; struct timer_list fake_irq; /* used after a missed interrupt */ struct timer_list hangcheck; /* detect missed interrupts */