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 018A3FD2D92 for ; Tue, 10 Mar 2026 11:58:03 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id AAE2910E6F8; Tue, 10 Mar 2026 11:57:50 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=lankhorst.se header.i=@lankhorst.se header.b="XKKxE+3a"; dkim-atps=neutral Received: from lankhorst.se (unknown [141.105.120.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id 24C1110E6DF; Tue, 10 Mar 2026 11:57:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=lankhorst.se; s=default; t=1773143866; bh=GM99HYLF97WpfYfNVigw6iCS9l1p6bU3FfLbJKUNlsE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XKKxE+3aF3SAv6wcuzyBvs1cMEJVoKpMuVaidXgMEw/owkOdP/sQ/A5zyEygry3al 5t8iNWr/JUHCR9cTCMucoM/w6WGKEzLni+KTx6taKQHDoA9xiZBgfFzdekRMp6wbue ykLhcfRmbRKz1UxD29gxFygsEKnh9JMCS+UXZxJRpe7mTf8HCgfARCr5vUPU1Mr3am ajN2Mf6aHOMl/lgOlNqWPJGRCcNV9jhIroygl45cm77gRmNW25k4LGSFN13lCPVCUG De+L17rK0dq10jqrgXGoOUrAtViLfMLPb7kmQ3iPAZzEJgMpj0iyDX/rlZ1YOdSCJW OLqasz4xamZdw== From: Maarten Lankhorst To: intel-xe@lists.freedesktop.org, intel-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org, Sebastian Andrzej Siewior , Maarten Lankhorst Subject: [PATCH v7 26/26] drm/i915/gt: Add a spinlock to prevent starvation of irq_work. Date: Tue, 10 Mar 2026 12:57:08 +0100 Message-ID: <20260310115709.2276203-27-dev@lankhorst.se> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260310115709.2276203-1-dev@lankhorst.se> References: <20260310115709.2276203-1-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 */ -- 2.51.0