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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CE059C74A5B for ; Wed, 29 Mar 2023 23:55:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230176AbjC2Xzs (ORCPT ); Wed, 29 Mar 2023 19:55:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55856 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231288AbjC2Xzr (ORCPT ); Wed, 29 Mar 2023 19:55:47 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 713151FD2 for ; Wed, 29 Mar 2023 16:55:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1680134100; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=YDvzU53CPeswLit/FMHu3YOxwiNaBZwdjQxKehJieKw=; b=KpIdcd0gkaSTioCNr4d1uGjOOrF73EuXGl4XHnRkB8stP2uGbqsZavAqKG2ylau/SEF8cg XIivhYRuChbUARFUvIsBLpkgzB47HcvDlDA0XcF2z85E54II7gbDFAXiPQIhc/pFppj3G2 MJTa/2sle19+8Rj2Vnko5RmCeunnALc= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-658-gjbwPLEMPuu8BeS56HR0nQ-1; Wed, 29 Mar 2023 19:54:56 -0400 X-MC-Unique: gjbwPLEMPuu8BeS56HR0nQ-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C88EE3C0DDA1; Wed, 29 Mar 2023 23:54:55 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.161]) by smtp.corp.redhat.com (Postfix) with SMTP id AFE50492C3E; Wed, 29 Mar 2023 23:54:51 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 30 Mar 2023 01:54:48 +0200 (CEST) Date: Thu, 30 Mar 2023 01:54:43 +0200 From: Oleg Nesterov To: Gregory Price Cc: Arnd Bergmann , Gregory Price , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Linux-Arch , avagin@gmail.com, Peter Zijlstra , Andy Lutomirski , krisman@collabora.com, Thomas Gleixner , Jonathan Corbet , shuah , Catalin Marinas , Will Deacon , Mark Rutland , tongtiangen@huawei.com, Robin Murphy Subject: Re: [PATCH v14 1/4] asm-generic,arm64: create task variant of access_ok Message-ID: <20230329235442.GA10790@redhat.com> References: <20230328164811.2451-1-gregory.price@memverge.com> <20230328164811.2451-2-gregory.price@memverge.com> <20230329151515.GA913@redhat.com> <9a456346-e207-44e1-873e-40d21334e01b@app.fastmail.com> <20230329160322.GA4477@redhat.com> <20230329171322.GB4477@redhat.com> <20230329175850.GA8425@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 03/29, Gregory Price wrote: > > Last note on this before I push up another patch set. > > The change from __get_user to get_user also introduces a call to > might_fault() which adds a larger callstack for every syscall / > dispatch. This turns into a might_sleep and might_reschedule, which > represent a very different pattern of execution from before. might_fault() is nop unless CONFIG_PROVE_LOCKING || DEBUG_ATOMIC_SLEEP. Again, I won't really argue with task_access_ok(). Just I am not sure 2/4 gives enough justification for this new helper with unclear semantics (until we ensure that access_ok() doesn't depend on current). Oleg.