From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3BE2FC43458 for ; Thu, 2 Jul 2026 08:08:50 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id EBBBF10F224; Thu, 2 Jul 2026 08:08:47 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=lankhorst.se header.i=@lankhorst.se header.b="jRkhdNqt"; dkim-atps=neutral Received: from lankhorst.se (unknown [141.105.120.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id DB14B10F216; Thu, 2 Jul 2026 08:08:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=lankhorst.se; s=default; t=1782979723; bh=Smwtu6CwhUCwK5agwnez+Jaqs++M2OVTTW4z7GIcls4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jRkhdNqt428OUt2VBrVpqYbRuG0Hu7R5b0/H0LzhPCYShbec7RAqTHrXCGwcapdx+ 6RqL7DYdv+4suUtX0hrm0v1tSQ1kIdI1FRZBuw+n8gA2Rb8KLCaO6O4Hgam7O1ONiP vQJO9il8uVUz7eE8W/txDgroJ5nkbmbqU//epxMhmoyLcgxAvT+qmv7SutMtfdKHjX POEhC7o9IB7Di5DPIkduoLQcNfnI5V2md/w20TSa9vgI9hQ3JA2VQgLwBv1jRAOTUi nGSxKyEJ52+yZztMDiRSMXHqLPP6FfONkDGW75g+x9s+WFn9tZ3m7zgF118Kb3B8+D Q8n3KAgDoP0ng== From: Maarten Lankhorst To: intel-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org, Sebastian Andrzej Siewior , Maarten Lankhorst Subject: [PATCH 7/7] drm/i915/gt: Add a spinlock to prevent starvation of irq_work. Date: Thu, 2 Jul 2026 10:09:13 +0200 Message-ID: <20260702080913.434121-8-dev@lankhorst.se> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260702080913.434121-1-dev@lankhorst.se> References: <20260702080913.434121-1-dev@lankhorst.se> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" From: Sebastian Andrzej Siewior IRQ-Work (FIFO-1) will be preempted by the threaded-interrupt (FIFO-50) and the interrupt will poll on signaler_active while the irq-work can't make progress. Solve this by adding a spinlock to prevent starvation and force completion. Signed-off-by: Maarten Lankhorst --- drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 8 +++++++- drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h | 1 + 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c index c10ac0ab3bfa8..c2b174bfa1418 100644 --- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c +++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c @@ -209,6 +209,7 @@ static void signal_irq_work(struct irq_work *work) intel_breadcrumbs_disarm_irq(b); rcu_read_lock(); + spin_lock(&b->signaler_active_sync); atomic_inc(&b->signaler_active); list_for_each_entry_rcu(ce, &b->signalers, signal_link) { struct i915_request *rq; @@ -246,6 +247,7 @@ static void signal_irq_work(struct irq_work *work) } } atomic_dec(&b->signaler_active); + spin_unlock(&b->signaler_active_sync); rcu_read_unlock(); llist_for_each_safe(signal, sn, signal) { @@ -290,6 +292,7 @@ intel_breadcrumbs_create(struct intel_engine_cs *irq_engine) init_llist_head(&b->signaled_requests); spin_lock_init(&b->irq_lock); + spin_lock_init(&b->signaler_active_sync); init_irq_work(&b->irq_work, signal_irq_work); b->irq_engine = irq_engine; @@ -487,8 +490,11 @@ void intel_context_remove_breadcrumbs(struct intel_context *ce, if (release) intel_context_put(ce); - while (atomic_read(&b->signaler_active)) + while (atomic_read(&b->signaler_active)) { + spin_lock(&b->signaler_active_sync); + spin_unlock(&b->signaler_active_sync); cpu_relax(); + } } static void print_signals(struct intel_breadcrumbs *b, struct drm_printer *p) diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h b/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h index bdf09fd67b6e7..28dae32628aab 100644 --- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h +++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h @@ -40,6 +40,7 @@ struct intel_breadcrumbs { struct list_head signalers; struct llist_head signaled_requests; atomic_t signaler_active; + spinlock_t signaler_active_sync; spinlock_t irq_lock; /* protects the interrupt from hardirq context */ struct irq_work irq_work; /* for use from inside irq_lock */ -- 2.53.0