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 579EFEB64DD for ; Fri, 21 Jul 2023 21:23:59 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C24F08D0002; Fri, 21 Jul 2023 17:23:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BAF048D0001; Fri, 21 Jul 2023 17:23:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A279D8D0002; Fri, 21 Jul 2023 17:23:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 8F7A18D0001 for ; Fri, 21 Jul 2023 17:23:58 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 6018EC0401 for ; Fri, 21 Jul 2023 21:23:58 +0000 (UTC) X-FDA: 81036896556.11.546E568 Received: from wout3-smtp.messagingengine.com (wout3-smtp.messagingengine.com [64.147.123.19]) by imf18.hostedemail.com (Postfix) with ESMTP id EB12A1C0017 for ; Fri, 21 Jul 2023 21:23:55 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=arndb.de header.s=fm2 header.b=KIWSyr1g; dkim=pass header.d=messagingengine.com header.s=fm3 header.b=vEJWu1Be; dmarc=none; spf=pass (imf18.hostedemail.com: domain of arnd@arndb.de designates 64.147.123.19 as permitted sender) smtp.mailfrom=arnd@arndb.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1689974636; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=BXA5sL4xRNZhXccbqClwUqLOYCKhWLZB5FjhdMOfEyY=; b=AgX8RleUuXb9bGmauZniiq+ugMdrqrKP9Rdhpn/OAdMEY701qjRSdiS+fFIhFV1/UD7u2a YcHTJBHW81XEeRZDpsxbceE94t2HzpUKgqlJi03LV3IN/k9hjTNHOQ6bV8fjrG7vUoY+o1 D+2wm2QQt64GfG5UGECo+TZNRXvxv/M= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=arndb.de header.s=fm2 header.b=KIWSyr1g; dkim=pass header.d=messagingengine.com header.s=fm3 header.b=vEJWu1Be; dmarc=none; spf=pass (imf18.hostedemail.com: domain of arnd@arndb.de designates 64.147.123.19 as permitted sender) smtp.mailfrom=arnd@arndb.de ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1689974636; a=rsa-sha256; cv=none; b=YogpmHkJucTCtqWeZjDgVYO1e6SK2IuOuift57m7CDJanC2NBfnQSRybwdUsmFkdAK0cor mFj9MOPIWmJQfgNr12eOhD90XQysw8D4Y7TeYwzAjl/bIfDh3C+qWJOtSZYV6rLB0mxEcR k5MgAAU+0q8rM3aA7Grddn3N01l9soA= Received: from compute6.internal (compute6.nyi.internal [10.202.2.47]) by mailout.west.internal (Postfix) with ESMTP id 03BE53200A01; Fri, 21 Jul 2023 17:23:52 -0400 (EDT) Received: from imap51 ([10.202.2.101]) by compute6.internal (MEProxy); Fri, 21 Jul 2023 17:23:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arndb.de; h=cc :cc:content-type:content-type:date:date:from:from:in-reply-to :in-reply-to:message-id:mime-version:references:reply-to:sender :subject:subject:to:to; s=fm2; t=1689974632; x=1690061032; bh=BX A5sL4xRNZhXccbqClwUqLOYCKhWLZB5FjhdMOfEyY=; b=KIWSyr1gDGjK5zOe64 CjDoz6RYdvcy0EBMoGa/JdfwjIzcqn5BmUC9VCIKCw7NxZMfzt4z2Sa84XokZDHh D5UuaQEEeYlymRrPIp66kpzRRSIN/at++4LkuoNgOyR36Zhoc2rjzZ6KZwYlymge 0tEakJnvKGwlsyAYsg//PGS89t+lvztpDAo0kUyXnjMz+9ZC+0uLqc+K5RNwntKx Gv4AtsdcWzrAu4+yHh6VG7qXSeDWQ6aUHOw9xXjD0B3LCrKYHsAEJxG7xDVfwk77 6c+ZATLarJtSVzeAZdXzWXe2gYcEAzdls5VstykuKCV2YIwUkjQZhYbH48/ar0VE GnEg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:content-type:date:date :feedback-id:feedback-id:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:sender:subject :subject:to:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm3; t=1689974632; x=1690061032; bh=BXA5sL4xRNZhX ccbqClwUqLOYCKhWLZB5FjhdMOfEyY=; b=vEJWu1BeTLrHTDMqWmtuHU4Q7AyYu bd8BzeEIVML4QdPofZ/ZZS/RiGJ7LajTTSg3Jh4Btcxb8MpOjEvRkI+e6vsbr8LR Xn04DY3Kw9A6lpnISSTN91IJNkl7vxl/pHY7Xpa1/ijV4Vd2dgRWUTO4yiBo6vBP o2t8luG+lIf2+QaZyTrkrSqeE8ODIv4qfkSyUqYe7dXhj9pXGKhuWplSBI6tJX90 40jy6Am6cz1J5/XK8dCLFZ0vxqmM0bBY8wl1uSeV23QAX0b6xHvqVgGpKPjhuAX/ Ratl1Lx/lLyWcmFJUlA34do5XZDDiuieSs3trLcZWPLSwApDUc7KqmOfw== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedviedrhedvgdduheehucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepofgfggfkjghffffhvfevufgtsehttdertderredtnecuhfhrohhmpedftehr nhguuceuvghrghhmrghnnhdfuceorghrnhgusegrrhhnuggsrdguvgeqnecuggftrfgrth htvghrnhepffehueegteeihfegtefhjefgtdeugfegjeelheejueethfefgeeghfektdek teffnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomheprg hrnhgusegrrhhnuggsrdguvg X-ME-Proxy: Feedback-ID: i56a14606:Fastmail Received: by mailuser.nyi.internal (Postfix, from userid 501) id C7204B60089; Fri, 21 Jul 2023 17:23:50 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.9.0-alpha0-531-gfdfa13a06d-fm-20230703.001-gfdfa13a0 Mime-Version: 1.0 Message-Id: <02045e07-0f9a-49bf-b6ca-354cb67678f8@app.fastmail.com> In-Reply-To: <20230721185445.GS4253@hirez.programming.kicks-ass.net> References: <20230721102237.268073801@infradead.org> <20230721105744.022509272@infradead.org> <2a1f8ae6-ed2b-4fe8-85af-df64e9c84794@app.fastmail.com> <20230721185445.GS4253@hirez.programming.kicks-ass.net> Date: Fri, 21 Jul 2023 23:23:27 +0200 From: "Arnd Bergmann" To: "Peter Zijlstra" Cc: "Thomas Gleixner" , "Jens Axboe" , linux-kernel@vger.kernel.org, "Ingo Molnar" , "Darren Hart" , dave@stgolabs.net, andrealmeid@igalia.com, "Andrew Morton" , urezki@gmail.com, "Christoph Hellwig" , "Lorenzo Stoakes" , linux-api@vger.kernel.org, linux-mm@kvack.org, Linux-Arch , malteskarupke@web.de Subject: Re: [PATCH v1 05/14] futex: Add sys_futex_wake() Content-Type: text/plain X-Rspamd-Queue-Id: EB12A1C0017 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: hsbkgky3ptnmfsyzgbh5z9watz5w19t6 X-HE-Tag: 1689974635-603712 X-HE-Meta: U2FsdGVkX1/an9EAJ391tnRV5hSOP/3RSMDtY1ylLIzevJtfHZlL6VWDQoRZwUU/Tp0heFMaGQxkz/EvjvGvXp1d5amkvHctbTWMY59zwDiJ4A6XarxyBmgkN8T3n8GpBuRXSAfk0dMICMSOegwvw+OtRJeyk1WcfM+x0NPv04picSvqRqm+6JDVm9NFejKVGMQPEROlVTZ35NjwsVDMHl2WJmWbayfXRNerOzohUFAacId26aAzdI7gILnN4opmkUoi0qxhTrzDWNkG9nyCuLPRQYHXdmb4k2mHksATJ9Y7FkC1mzWJtrB5nMmsA0f4OSecJfG+mAbhwjkyoO2Aygk40aIkpttfPeyy9J3vP8SZ/jqlBX1bg4MvcwKgZYPVwWPESWxkOT2HOnclIUAdwpKFPUrJjToe+dYiLag/KtXGYKbRpawETWpAd5RpOIqREBy27leftqerp+qvkkSYIJg9YTLoTIYfgcpdQT6nPWBP/zUwzBYGiDHPpnxtFWkpjnm6XU/PQ03bxba6axKN5NFVECJDhgCaQDyIQpSlANB6cR6BEU0v7Wz3sWfmHXmMG13BfRDo3ZstP6tRFt5It4xJ7Y6Qk8hXcyi/yHQ652JZBXl4xmCiNbj5pI5M8c4W+cK37WXDBokUTHiZxZiDEQ33CHk3rzxNQpO3H1LvlS6akwspOwdBIq0PwGBziEpqWUxGhcQcVlUofrW24XmSju+Bog5oOCzd/E92UdKx14Qol5FTvkAmkyquvXBl7LVAfC/uFh+Dja3JITtmxWo3NJtk3/Pjn38E5t3i3it9KU8MC4lAyjNsolYNHgegs+PGFW5XtcGieT7RzLaHRB0/tTYIpEAD04s2LrXnHAu9x0hT3ZE1s9GiYiT46ylSSPdVCV+uL3XOBzcTubK2svBGZWz9r/yZbLXwSHZKuP6QgPjC3cCwQRwCLJOclLWgMLwiDEMtKn8dh/5XAubFyGe YcJFye8Z 8N380cmTVi1qEBVCoXEqtXauHCuzraLC/3wwOalhY7rBRuEfal/IoB8G8XF/6oXTS/BMTvo4zcrhkg3QFvZRKNtEK+urbtuXH+wkowSWU1iQSvxab9Xcb6rMWz1sOQXN1g1xUeisnq4pUA6iYPqUylkaRfSD7QTdA7WyRNiSiLyQC+sYy7jm73HtaU47jK8fkNwyRypZyJ06iHPPLCPOsovQsV6QW2ht7KIiv 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: On Fri, Jul 21, 2023, at 20:54, Peter Zijlstra wrote: > On Fri, Jul 21, 2023 at 05:41:20PM +0200, Arnd Bergmann wrote: >> On Fri, Jul 21, 2023, at 12:22, Peter Zijlstra wrote: >> > --- a/kernel/sys_ni.c >> > +++ b/kernel/sys_ni.c >> > @@ -87,6 +87,7 @@ COND_SYSCALL_COMPAT(set_robust_list); >> > COND_SYSCALL(get_robust_list); >> > COND_SYSCALL_COMPAT(get_robust_list); >> > COND_SYSCALL(futex_waitv); >> > +COND_SYSCALL(futex_wake); >> > COND_SYSCALL(kexec_load); >> > COND_SYSCALL_COMPAT(kexec_load); >> > COND_SYSCALL(init_module); >> >> This is fine for the moment, but I wonder if we should start making >> futex mandatory at some point. Right now, sparc32 with CONFIG_SMP >> cannot support futex because of the lack of atomics in early >> sparc processors, but sparc32 glibc actually requires futexes >> and consequently only works on uniprocessor machines, on sparc64 >> compat mode, or on Leon3 with out of tree patches. > > PARISC is another 'fun' case. I had to look up how that works, but as far as I can tell, the parisc code actually has a chance of working, as the userspace atomics go through the light-weight syscall that shares a hashed lock with the actual futex syscall. On sparc32 I think it's worse because userspace assumes that atomic instructions are supported while the kernel assumes they are not. Arnd