linux-kernel - Re: [PATCH v3] Avoid memory barrier in read

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Message-ID: <766fe92a-13da-f299-0ecf-f8a477d58a79@gentwo.org>
Date: Mon, 16 Sep 2024 10:52:18 -0700 (PDT)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: kernel test robot <lkp@...el.com>
cc: Christoph Lameter via B4 Relay <devnull+cl.gentwo.org@...nel.org>, 
    Thomas Gleixner <tglx@...utronix.de>, 
    Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
    Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
    Waiman Long <longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>, 
    oe-kbuild-all@...ts.linux.dev, linux-mm@...ck.org, 
    linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
    linux-arch@...r.kernel.org
Subject: Re: [PATCH v3] Avoid memory barrier in read_seqcount() through load
 acquire

On Fri, 13 Sep 2024, kernel test robot wrote:

> >> drivers/gpu/drm/i915/gt/intel_tlb.h:21:47: error: macro "seqprop_sequence" requires 2 arguments, but only 1 given

>From 15d86bc9589f16947c5fb0f34d2947eacd48f853 Mon Sep 17 00:00:00 2001
From: Christoph Lameter <cl@...two.org>
Date: Mon, 16 Sep 2024 10:44:16 -0700
Subject: [PATCH] Update Intel DRM use of seqprop_sequence

One of Intels drivers uses seqprop_sequence() for its tlb sequencing.
We added a parameter so that we can use acquire. Its pretty safe to
assume that this will work without acquire.

Signed-off-by: Christoph Lameter <cl@...ux.com>
---
 drivers/gpu/drm/i915/gt/intel_tlb.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_tlb.h b/drivers/gpu/drm/i915/gt/intel_tlb.h
index 337327af92ac..81998c4cd4fb 100644
--- a/drivers/gpu/drm/i915/gt/intel_tlb.h
+++ b/drivers/gpu/drm/i915/gt/intel_tlb.h
@@ -18,7 +18,7 @@ void intel_gt_fini_tlb(struct intel_gt *gt);

 static inline u32 intel_gt_tlb_seqno(const struct intel_gt *gt)
 {
-	return seqprop_sequence(&gt->tlb.seqno);
+	return seqprop_sequence(&gt->tlb.seqno, false);
 }

 static inline u32 intel_gt_next_invalidate_tlb_full(const struct intel_gt *gt)
-- 
2.39.5