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 58251C79FB7 for ; Wed, 9 Sep 2026 16:34:52 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 1538210F223; Wed, 9 Sep 2026 16:34:52 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="gdl/E96f"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 890DB10F21E; Wed, 9 Sep 2026 16:34:50 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 4779E42A69; Wed, 9 Sep 2026 16:34:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 000EE1F00898; Wed, 9 Sep 2026 16:34:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788971690; bh=65NxpK4aAjHY4erwa0huEmvlMddwj01kuPWOjahOQEM=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=gdl/E96fZ5yoOsbocU+eJ0fmdN0EjHb2ryVc+my3+TXRG93x8BcgbWYA0ZR0LOCaU HGKzv3TS/qL30b1PrFm+FW1mA67VZ7cbZS2Sppl3Di4BUIE+BBSqdAKi0+73gPIotH t/F9YWkOikcVsvC7hVvLIuO1s1BC978dIAcFvAhtooMOqDRe+B/SX8ToKwjcIwDZF0 e+R/fn/ZqnVHz05GG2MOBdLkLHHNHGBzO32IYrc+t/3ew8xlQoImy7AdPT0fX4+rxt lMsFo2+UXyoQLfMDPWIZDMipqb+Tx9lDeNud2kxuma47Nq1wvFHz6ZQE0vRh3XY2fE 30oCjpvKXzb6A== From: sashiko-bot@kernel.org Subject: Re: [PATCH v2 12/13] drm/i915/dsb: Add tracepoints for DSB commit To: "Ville Syrjala" Cc: intel-xe@lists.freedesktop.org, intel-gfx@lists.freedesktop.org In-Reply-To: <20260909161730.12969-13-ville.syrjala@linux.intel.com> References: <20260909161730.12969-1-ville.syrjala@linux.intel.com> <20260909161730.12969-13-ville.syrjala@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Wed, 09 Sep 2026 16:34:49 +0000 Message-Id: <20260909163450.000EE1F00898@smtp.kernel.org> X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" Thank you for your contribution! Sashiko AI review found 2 potential issue(= s) to consider: - [High] Calling `intel_get_crtc_scanline()` inside the tracepoint's `TP_fa= st_assign` block acquires a sleeping lock while in atomic context, causing = a kernel panic on PREEMPT_RT. - [Medium] The `intel_dsb_done` tracepoint is conditionally called only whe= n a userspace vblank event is present, leading to unbalanced commit/done tr= ace events for background updates. -- commit b6804a525207ea31e82f537e553534efcdaa5b8f Author: Ville Syrj=C3=A4l=C3=A4 drm/i915/dsb: Add tracepoints for DSB commit =20 This commit adds new tracepoints intel_dsb_commit and intel_dsb_done to tra= ck when the display state buffer performs operations on the hardware. > diff --git a/drivers/gpu/drm/i915/display/intel_display_trace.h b/drivers= /gpu/drm/i915/display/intel_display_trace.h > index 504d105935bc0..06cf662931fe3 100644 > --- a/drivers/gpu/drm/i915/display/intel_display_trace.h > +++ b/drivers/gpu/drm/i915/display/intel_display_trace.h [ ... ] > @@ -681,6 +682,56 @@ TRACE_EVENT(intel_fbc_nuke, > __entry->frame, __entry->scanline) > ); > =20 > +TRACE_EVENT(intel_dsb_commit, > + TP_PROTO(struct intel_crtc *crtc, enum intel_dsb_id dsb_id), > + TP_ARGS(crtc, dsb_id), > + > + TP_STRUCT__entry( > + __string(dev, __dev_name_kms(crtc)) > + __field(char, pipe_name) > + __field(u32, dsb_id) > + __field(u32, frame) > + __field(u32, scanline) > + ), > + > + TP_fast_assign( > + __assign_str(dev); > + __entry->pipe_name =3D pipe_name(crtc->pipe); > + __entry->dsb_id =3D dsb_id; > + __entry->frame =3D intel_crtc_get_vblank_counter(crtc); > + __entry->scanline =3D intel_get_crtc_scanline(crtc); [Severity: High] Does calling intel_get_crtc_scanline() from within a TP_fast_assign block cause issues on preempt-rt kernels? When this tracepoint is active, TP_fast_assign executes in an atomic context (RCU read-side critical section with preemption disabled). intel_get_crtc_scanline() eventually acquires uncore->lock: intel_get_crtc_scanline() intel_vblank_section_enter() uncore->lock (spinlock_t) On preempt-rt, spinlock_t becomes a sleepable rt_mutex, which will cause a scheduling while atomic panic. > + ), > + > + TP_printk("dev %s, pipe %c, DSB %d, frame=3D%u, scanline=3D%u", > + __get_str(dev), __entry->pipe_name, __entry->dsb_id, > + __entry->frame, __entry->scanline) > +); > + > +TRACE_EVENT(intel_dsb_done, > + TP_PROTO(struct intel_crtc *crtc, enum intel_dsb_id dsb_id), > + TP_ARGS(crtc, dsb_id), > + > + TP_STRUCT__entry( > + __string(dev, __dev_name_kms(crtc)) > + __field(char, pipe_name) > + __field(u32, dsb_id) > + __field(u32, frame) > + __field(u32, scanline) > + ), > + > + TP_fast_assign( > + __assign_str(dev); > + __entry->pipe_name =3D pipe_name(crtc->pipe); > + __entry->dsb_id =3D dsb_id; > + __entry->frame =3D intel_crtc_get_vblank_counter(crtc); > + __entry->scanline =3D intel_get_crtc_scanline(crtc); [Severity: High] This appears to have the same preempt-rt issue as the intel_dsb_commit tracepoint where it acquires a sleeping lock while in atomic context. > + ), > + > + TP_printk("dev %s, pipe %c, DSB %d, frame=3D%u, scanline=3D%u", > + __get_str(dev), __entry->pipe_name, __entry->dsb_id, > + __entry->frame, __entry->scanline) > +); > + [ ... ] > diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i= 915/display/intel_dsb.c > index 8e01e1eed291e..299d778520a22 100644 > --- a/drivers/gpu/drm/i915/display/intel_dsb.c > +++ b/drivers/gpu/drm/i915/display/intel_dsb.c [ ... ] > @@ -1124,6 +1127,8 @@ void intel_dsb_irq_handler(struct intel_display *di= splay, > spin_lock(&display->drm->event_lock); > =20 > if (crtc->dsb_event) { > + trace_intel_dsb_done(crtc, dsb_id); > + [Severity: Medium] Will this lead to unbalanced commit/done trace events for background update= s? The trace_intel_dsb_done() tracepoint is conditionally called only when a userspace vblank event is present. If a commit completes in hardware without an associated vblank event, the irq handler will skip emitting the completion tracepoint. > /* > * Update vblank counter/timestamp in case it > * hasn't been done yet for this frame. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260909161730.1296= 9-1-ville.syrjala@linux.intel.com?part=3D12