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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91DF1CEBF66 for ; Fri, 27 Sep 2024 01:38:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 005CF6B009F; Thu, 26 Sep 2024 21:38:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EF8966B00A1; Thu, 26 Sep 2024 21:38:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D99026B00A2; Thu, 26 Sep 2024 21:38:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id BC5EB6B009F for ; Thu, 26 Sep 2024 21:38:15 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 69BBA1C5570 for ; Fri, 27 Sep 2024 01:38:15 +0000 (UTC) X-FDA: 82608807750.28.7EC5425 Received: from mail-qk1-f171.google.com (mail-qk1-f171.google.com [209.85.222.171]) by imf10.hostedemail.com (Postfix) with ESMTP id 3BC6FC0005 for ; Fri, 27 Sep 2024 01:38:13 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b="bB/RtVMZ"; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf10.hostedemail.com: domain of boqun.feng@gmail.com designates 209.85.222.171 as permitted sender) smtp.mailfrom=boqun.feng@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1727401003; a=rsa-sha256; cv=none; b=NpR4Qg+VdOhYIjpTjKwL2eKUzz5UfFiZSx1KOKhAeKkE/D5LFm0zkeoB2sOf0aenBy3OC7 BLvReCzdFvOSzLUr9pzcYaFR0PytDaN8QmpEM5621lDF9PWpECV6DgsMZhi0xOXbUCgZRq gBQG1+9WVPMZO0Odhys88zTxS+IyyQI= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b="bB/RtVMZ"; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf10.hostedemail.com: domain of boqun.feng@gmail.com designates 209.85.222.171 as permitted sender) smtp.mailfrom=boqun.feng@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1727401003; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Vlhv6vJ9/p0T/1mFJKv1z0EQJeECGsYyZGl1aUOn/r8=; b=KwxhlW97ve1TEzXVLQkpOo6HjxZ7+lY0NQUErRURi51aD3IsHGCqUD/BQA6J7l2UScfzoY +RnNQuJnUA9QljoadNWFFZIutHvstnt3vruF9zSDCSxM0Aau+7oKAWVb3bfpN94zlsEJNF Yh5hC66TXLFbAzAjaPvNcAIm7h9FJL4= Received: by mail-qk1-f171.google.com with SMTP id af79cd13be357-7acdd65fbceso130151585a.3 for ; Thu, 26 Sep 2024 18:38:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1727401092; x=1728005892; darn=kvack.org; h=content-transfer-encoding:subject:references:in-reply-to:message-id :cc:to:from:date:mime-version:feedback-id:from:to:cc:subject:date :message-id:reply-to; bh=Vlhv6vJ9/p0T/1mFJKv1z0EQJeECGsYyZGl1aUOn/r8=; b=bB/RtVMZh0lukIaFjp/YAvaxVjIENxhgsS/3D0WZvc0P2/IAdLU/ONkru9RUgVzzYN bFfi6lv2WxmsZ9fygj6kdgmT6lR7+RUZhRbWXI8V2UMcFjYXYae5jQcUpCOJIS6qr9pZ wFUx3sxtvF5clXNv1M1gcZ1hiuIcF8E7/CRk+No4IgFBv+lgwsZjL2Z/niczq9Omrxo0 vk6+XcI+FZSWOPNEdm0TPnnidR+U/IGvTsQWV049lv7gN6NgsqY60ZzA5LdP67eU2iy2 jceXg20Jdnez7kJ8Q4/Lro60FrIvJAQK8BN4m7xLccfkMZHYRcdLEl6SNBgquX3Gp/iS E7Nw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1727401092; x=1728005892; h=content-transfer-encoding:subject:references:in-reply-to:message-id :cc:to:from:date:mime-version:feedback-id:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=Vlhv6vJ9/p0T/1mFJKv1z0EQJeECGsYyZGl1aUOn/r8=; b=aVteadIQQYS9XHHKPGIcfR3tVPhGurmL60dY60SlSa1xta0N8pTc2K5gFAqMnQ0fiL /3BR2KOHz84oEnLaePjjPzkK/1c5yS3sdsGnUrBw8KuJeaERynemz59WNp+V+imZF8vX 4oF6I/WpSEWNalzn5k7q+6jI0v99aYi+bGi1y7/ePg5FkPZxjGhK4zb/idWHRH5WaSnM CNy7Va+tP2nu7i8WaA9JwunzwkJx982h81anT9M9mE0ooECHtRy/KpvU2By9UO9qGB+H hkO6u3bMR6nf33XAC6PSkczt3VYuS+ztWybGjb7CR9rN52mrJRqnYVJTjAI7GrxJmagV ospw== X-Forwarded-Encrypted: i=1; AJvYcCV1/EL36q0Lv0e1XPWKunm2VsMs5Jd+J1s5BGZ5agfSsL3oKapJzY2+An0rbbsy6PxdZGb+AkhGhg==@kvack.org X-Gm-Message-State: AOJu0YxhYdH2m8+ue/jlRHMHV933FDGIWb4HqBfFlGHGPJ3Ojjg3Fyvb FPQdw4A575X5RgZuRv3QNnHQibu4Nl1oFGJky5LeafBzax0Y/iPT X-Google-Smtp-Source: AGHT+IGGIx4GHXja8pTVUFJEvkYZ7hNl2HfLZkw22LyWg/l8WV2qX8Mb3nifflTKvhwohArNvVcLoQ== X-Received: by 2002:a05:620a:408e:b0:7a3:51ed:38c0 with SMTP id af79cd13be357-7ae3775f989mr306121985a.0.1727401092281; Thu, 26 Sep 2024 18:38:12 -0700 (PDT) Received: from fauth-a1-smtp.messagingengine.com (fauth-a1-smtp.messagingengine.com. [103.168.172.200]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7ae377f09bcsm42553085a.65.2024.09.26.18.38.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Sep 2024 18:38:11 -0700 (PDT) Received: from phl-compute-12.internal (phl-compute-12.phl.internal [10.202.2.52]) by mailfauth.phl.internal (Postfix) with ESMTP id 2B6821200043; Thu, 26 Sep 2024 21:38:11 -0400 (EDT) Received: from phl-imap-02 ([10.202.2.81]) by phl-compute-12.internal (MEProxy); Thu, 26 Sep 2024 21:38:11 -0400 X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeeftddrvddtkedggeekucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdggtfgfnhhsuhgsshgtrhhisggvpdfu rfetoffkrfgpnffqhgenuceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnh htshculddquddttddmnecujfgurhepofggfffhvfevkfgjfhfutgfgsehtjeertdertddt necuhfhrohhmpedfuehoqhhunhcuhfgvnhhgfdcuoegsohhquhhnrdhfvghnghesghhmrg hilhdrtghomheqnecuggftrfgrthhtvghrnhephfdvkeeukedtgeeugfegudejueetjedu heekhffhhedvudfgveehudefudffjeelnecuffhomhgrihhnpegvfhhfihgtihhoshdrtg homhenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfhhrohhmpegs ohhquhhnodhmvghsmhhtphgruhhthhhpvghrshhonhgrlhhithihqdeiledvgeehtdeige dqudejjeekheehhedvqdgsohhquhhnrdhfvghngheppehgmhgrihhlrdgtohhmsehfihig mhgvrdhnrghmvgdpnhgspghrtghpthhtohepvdeipdhmohguvgepshhmthhpohhuthdprh gtphhtthhopehnvggvrhgrjhdruhhprgguhhihrgihsegrmhgurdgtohhmpdhrtghpthht ohepmhgrrhhkrdhruhhtlhgrnhgusegrrhhmrdgtohhmpdhrtghpthhtohepmhgrthhhih gvuhdruggvshhnohihvghrshesvghffhhitghiohhsrdgtohhmpdhrtghpthhtohepjhhi rghnghhshhgrnhhlrghisehgmhgrihhlrdgtohhmpdhrtghpthhtohepkhgvnhhtrdhovh gvrhhsthhrvggvthesghhmrghilhdrtghomhdprhgtphhtthhopehmrghgvggurdhmihgt hhgrvghlsehgmhgrihhlrdgtohhmpdhrtghpthhtohepqhhirghnghdriihhrghnghduvd duudesghhmrghilhdrtghomhdprhgtphhtthhopehurhgviihkihesghhmrghilhdrtgho mhdprhgtphhtthhopehrohhsthgvughtsehgohhoughmihhsrdhorhhg X-ME-Proxy: Feedback-ID: iad51458e:Fastmail Received: by mailuser.phl.internal (Postfix, from userid 501) id DDF96B00067; Thu, 26 Sep 2024 21:38:10 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface MIME-Version: 1.0 Date: Fri, 27 Sep 2024 09:37:50 +0800 From: "Boqun Feng" To: "Mathieu Desnoyers" , "Linus Torvalds" Cc: "Jonas Oberhauser" , linux-kernel@vger.kernel.org, rcu@vger.kernel.org, linux-mm@kvack.org, lkmm@lists.linux.dev, "Paul E. McKenney" , "Frederic Weisbecker" , "Neeraj Upadhyay" , "Joel Fernandes" , "Josh Triplett" , "Uladzislau Rezki (Sony)" , rostedt , "Lai Jiangshan" , Zqiang , "Peter Zijlstra" , "Ingo Molnar" , "Will Deacon" , "Waiman Long" , "Mark Rutland" , "Thomas Gleixner" , "Kent Overstreet" , "Vlastimil Babka" , maged.michael@gmail.com, "Neeraj Upadhyay" Message-Id: In-Reply-To: <0b262fe5-2fc5-478d-bf66-f208723238d5@efficios.com> References: <4167e6f5-4ff9-4aaa-915e-c1e692ac785a@efficios.com> <48992c9f-6c61-4716-977c-66e946adb399@efficios.com> <2b2aea37-06fe-40cb-8458-9408406ebda6@efficios.com> <55633835-242c-4d7f-875b-24b16f17939c@huaweicloud.com> <54487a36-f74c-46c3-aed7-fc86eaaa9ca2@huaweicloud.com> <0b262fe5-2fc5-478d-bf66-f208723238d5@efficios.com> Subject: Re: [RFC PATCH 1/4] hazptr: Add initial implementation of hazard pointers Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 3BC6FC0005 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 5xymsft1xz7xyu9beoetsxa4rbj5dhwd X-HE-Tag: 1727401093-166958 X-HE-Meta: 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 XXLlVGtq 6t2mnjdQT0X1li1JouR176/t/smJJ8ea8Vqk0AbkuekffvsIV0lalI9m8lY1N+/DmNMq+QeVGak5KcPpgGaNW4xsEUbn416XHSA6na7EBWGz+kAVaqRPHmJOjlNBFz5o/CP/7O3/8loJBtHc3CHP5ntet8VlGjmQHbUZbCzrBsC84lSgRL4vmqWDKqTcsuoVdFgGmbxn0VVpzSbDMAhbZhKfJ88VICT2TDGLQZRI5Z6vF8nNZz+tKRkaZMH1HZH32KzpHov2x4sbVCHaCm28HURzXHPTZbFVHgC0eK7PgtYU+5J0BIbSm9mprfO8LpkRH16opvYXSiivG/bkoxkYSbVq5s1l0HWUftfpOxidb0Rt2ilEXa9cmn6xbGMiIPYBsZfEhgfEhM7E+L7UVYGLC5Vsx6GndFYzAnNnOnLfIiL1dhl9/TZsw9MuZw/QyM5bftIUn1C0m1ZTznxQ= 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 Fri, Sep 27, 2024, at 9:30 AM, Mathieu Desnoyers wrote: > On 2024-09-27 02:01, Boqun Feng wrote: >> #define ADDRESS_EQ(var, expr) \ >> ({ \ >> bool _____cmp_res = (unsigned long)(var) == (unsigned long)(expr); \ >> \ >> OPTIMIZER_HIDE_VAR(var); \ >> _____cmp_res; \ >> }) > > If the goal is to ensure gcc uses the register populated by the > second, I'm afraid it does not work. AFAIU, "hiding" the dependency > chain does not prevent the SSA GVN optimization from combining the > registers as being one and choosing one arbitrary source. "hiding" > the dependency chain before or after the comparison won't help here. > > int fct_hide_var_compare(void) > { > int *a, *b; > > do { > a = READ_ONCE(p); > asm volatile ("" : : : "memory"); > b = READ_ONCE(p); > } while (!ADDRESS_EQ(a, b)); Note that ADDRESS_EQ() only hide first parameter, so this should be ADDRESS_EQ(b, a). Regards, Boqun > return *b; > } > > gcc 14.2 x86-64: > > fct_hide_var_compare: > mov rax,QWORD PTR [rip+0x0] # 67 > mov rdx,QWORD PTR [rip+0x0] # 6e > cmp rax,rdx > jne 60 > mov eax,DWORD PTR [rax] > ret > main: > xor eax,eax > ret > > gcc 14.2.0 ARM64: > > fct_hide_var_compare: > adrp x0, .LANCHOR0 > add x0, x0, :lo12:.LANCHOR0 > .L12: > ldr x1, [x0] > ldr x2, [x0] > cmp x1, x2 > bne .L12 > ldr w0, [x1] > ret > p: > .zero 8 > > > -- > Mathieu Desnoyers > EfficiOS Inc. > https://www.efficios.com