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b=djEG01Z03mYMCo6cGpoxgBOctC+8R09k+5yhS2FWuRaTQKORUCzKReDXfyVe+ly9L U60FnjgoNpoW5qqYO+q/+fsHhyl27CC2cnM5UK5sfAkAt5ufz1+DgT4O8eSaBNDD2s ryBMQZF6Eur9NS9JbE9XqXJQWt4/ksA0r+Sq7a6kh4VDNjIbV66ZQcEMNOxJZsRyBU ut2P7VOo0atxYVLSlqadbPQ8HAYOWT6e4a9Vb0+CEMB+S0269r8W/qDkl2zhtdgNHj HSbdlpjAta/H/3XEXjzAidptaz3Ci9H2V52zYY8cxDMQg8z0z6Rd1fwZO+arPHIP9Z 0Wf3jJslP3Low== Date: Tue, 17 Sep 2024 08:37:04 +0100 From: Will Deacon To: "Christoph Lameter (Ampere)" Cc: kernel test robot , Christoph Lameter via B4 Relay , Thomas Gleixner , Catalin Marinas , Peter Zijlstra , Ingo Molnar , Waiman Long , Boqun Feng , oe-kbuild-all@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org Subject: Re: [PATCH v3] Avoid memory barrier in read_seqcount() through load acquire Message-ID: <20240917073703.GB27290@willie-the-truck> References: <20240912-seq_optimize-v3-1-8ee25e04dffa@gentwo.org> <202409132135.ki3Mp5EA-lkp@intel.com> <766fe92a-13da-f299-0ecf-f8a477d58a79@gentwo.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <766fe92a-13da-f299-0ecf-f8a477d58a79@gentwo.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 9A6CE40003 X-Stat-Signature: tmcug87ppkbg1ckqkx8smdkdze5tgfsb X-Rspam-User: X-HE-Tag: 1726558631-346166 X-HE-Meta: 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 NAPwPGP4 NrnOioPLIgrO1kG2udfE/1qnIGGM7sd/7eU7l4AqasT69mSOOykEWU16DGE++oziHlcGHgT2PZK3cPtuS5n6CBwPKYa8Otti33wGkVz7lc0C3ijydPJa2nRyhLyCUMjw7bb27s3sVPDq6Yup8QWRIEIUZEM5yWMOR8SzbsugTi82hsui8mlbACgx00tdyMTUjMMLh5XgLO87AuAOtrTBWc3eJBfbmtx39IXF5NVzSR+2Dc1AUu8jvE1Kn/UkFjgdqQ5nVJtTbquX0+v56mL+gUSax7r/qxNQxa4a+WzNE3Kj8q8WbnMoRWXEWTzd/hRIbtI7MwWwfe30++CpbRAnMHB15LMPFAG2r/sgsnCCOCGaHL2y+kNdaaMLZv91rHSeHdUik/+b7ZbxoE1HOtbWF0YzORcAkMI81fQK7ZlmOfk0EeFgNXysohZJaF7XJxg5KTS0Mq0R/cIHyv6Q5/xHVeNOPq1rcKyg4Ehyd X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 16, 2024 at 10:52:18AM -0700, Christoph Lameter (Ampere) wrote: > 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 > 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 > --- > 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(>->tlb.seqno); > + return seqprop_sequence(>->tlb.seqno, false); > } Yikes, why is the driver using the seqlock internals here? It's a bit of a pity, as a quick grep suggest that this is the _only_ user of 'seqcount_mutex_t', yet it's still having to work around the API. Will