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 F0359CCD183 for ; Fri, 3 Oct 2025 14:41:02 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 9956F10E127; Fri, 3 Oct 2025 14:41:00 +0000 (UTC) Received: from lankhorst.se (lankhorst.se [141.105.120.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6130C10E125; Fri, 3 Oct 2025 14:40:59 +0000 (UTC) From: Maarten Lankhorst To: intel-gfx@lists.freedesktop.org Cc: intel-xe@lists.freedesktop.org, Maarten Lankhorst , Tvrtko Ursulin , Luca Abeni , Steven Rostedt , Sebastian Andrzej Siewior , Jani Nikula Subject: [CI 1/2] drm/i915: Disable tracepoints for PREEMPT_RT Date: Fri, 3 Oct 2025 16:40:55 +0200 Message-ID: <20251003144054.112239-3-dev@lankhorst.se> X-Mailer: git-send-email 2.51.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Luca Abeni reported this: | BUG: scheduling while atomic: kworker/u8:2/15203/0x00000003 | CPU: 1 PID: 15203 Comm: kworker/u8:2 Not tainted 4.19.1-rt3 #10 | Call Trace: | rt_spin_lock+0x3f/0x50 | gen6_read32+0x45/0x1d0 [i915] | g4x_get_vblank_counter+0x36/0x40 [i915] | trace_event_raw_event_i915_pipe_update_start+0x7d/0xf0 [i915] The tracing events use trace_intel_pipe_update_start() among other events use functions acquire spinlock_t locks which are transformed into sleeping locks on PREEMPT_RT. A few trace points use intel_get_crtc_scanline(), others use ->get_vblank_counter() wich also might acquire a sleeping locks on PREEMPT_RT. At the time the arguments are evaluated within trace point, preemption is disabled and so the locks must not be acquired on PREEMPT_RT. Based on this I don't see any other way than disable trace points on PREMPT_RT. [mlankhorst] The original patch was insufficient, and since the tracing infrastructure does not allow for partial disabling of tracepoints. Completely disable tracing for the entire i915 driver in PREEMPT_RT, a separate fix for display tracepoints on xe is added to make those work. Cc: Tvrtko Ursulin Reported-by: Luca Abeni Cc: Steven Rostedt Co-developed-by: Sebastian Andrzej Siewior Acked-by: Jani Nikula Link: https://lore.kernel.org/r/20250828090944.101069-1-dev@lankhorst.se Signed-off-by: Maarten Lankhorst --- drivers/gpu/drm/i915/Makefile | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile index 78a45a6681df3..6d7800e25e554 100644 --- a/drivers/gpu/drm/i915/Makefile +++ b/drivers/gpu/drm/i915/Makefile @@ -13,6 +13,11 @@ subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror # drivers. Define I915 when building i915. subdir-ccflags-y += -DI915 +# FIXME: Disable tracepoints on i915 for PREEMPT_RT, unfortunately +# it's an all or nothing flag. You cannot selectively disable +# only some tracepoints. +subdir-ccflags-$(CONFIG_PREEMPT_RT) += -DNOTRACE + subdir-ccflags-y += -I$(src) # Please keep these build lists sorted! -- 2.51.0