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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 78457C43441 for ; Tue, 27 Nov 2018 10:56:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E63B21104 for ; Tue, 27 Nov 2018 10:56:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="bzWbqT6J" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E63B21104 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=armlinux.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730946AbeK0VyN (ORCPT ); Tue, 27 Nov 2018 16:54:13 -0500 Received: from pandora.armlinux.org.uk ([78.32.30.218]:57750 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730932AbeK0VyN (ORCPT ); Tue, 27 Nov 2018 16:54:13 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2014; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=MxYiCzVt/FhorUWOmxeQ2pTQEgyDcHOGa+63bpz66Q0=; b=bzWbqT6JYd1DjysobM6mucFgh ZKISozLGdqCWM/pzH/B6IimOWBQ1E4iUuDnrGk2Juwmm43Jt8jbsVYGy8yvJsMONlE1Y71fV0XSxw vyYh8iQWh3vycpAH/MJBv/k23xk5pPtLH97E3CyVPZeFP8QtpJcyao3nx1xYOED0CCCIw=; Received: from n2100.armlinux.org.uk ([2002:4e20:1eda:1:214:fdff:fe10:4f86]:34242) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.90_1) (envelope-from ) id 1gRb2X-0006T5-Bv; Tue, 27 Nov 2018 10:56:25 +0000 Received: from linux by n2100.armlinux.org.uk with local (Exim 4.90_1) (envelope-from ) id 1gRb2U-0002XP-AV; Tue, 27 Nov 2018 10:56:22 +0000 Date: Tue, 27 Nov 2018 10:56:20 +0000 From: Russell King - ARM Linux To: Rafael David Tinoco Cc: Vladimir Murzin , Vincent Whitchurch , Nick Desaulniers , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Masahiro Yamada , Mathieu Desnoyers , Thomas Gleixner , Timothy E Baldwin , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] arm: always update thread_info->syscall Message-ID: <20181127105620.GD30658@n2100.armlinux.org.uk> References: <20181126225335.10477-1-rafael.tinoco@linaro.org> <20181126233303.GZ30658@n2100.armlinux.org.uk> <20181126234111.GA30658@n2100.armlinux.org.uk> <20181126234456.GB30658@n2100.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 27, 2018 at 08:30:32AM -0200, Rafael David Tinoco wrote: > On 11/26/18 9:44 PM, Russell King - ARM Linux wrote: > >On Mon, Nov 26, 2018 at 11:41:11PM +0000, Russell King - ARM Linux wrote: > >>On Mon, Nov 26, 2018 at 11:33:03PM +0000, Russell King - ARM Linux wrote: > >>>On Mon, Nov 26, 2018 at 08:53:35PM -0200, Rafael David Tinoco wrote: > >>>>Right now, only way for task->thread_info->syscall to be updated is if > >>>>if _TIF_SYSCALL_WORK is set in current's task thread_info->flags > >>>>(similar to what has_syscall_work() checks for arm64). > >>>> > >>>>This means that "->syscall" will only be updated if we are tracing the > >>>>syscalls through ptrace, for example. This is NOT the same behavior as > >>>>arm64, when pt_regs->syscallno is updated in the beginning of svc0 > >>>>handler for *every* syscall entry. > >>> > >>>So when was it decided that the syscall number will always be required > >>>(we need it to know how far back this has to be backported). > >> > >>PS, I rather object to the fact that the required behaviour seems to > >>change, arch maintainers aren't told about it until... some test is > >>created at some random point in the future which then fails. > >> > >>Surely there's a better way to communicate changes in requirements > >>than discovery-by-random-bug-report ? > > > >Final comment for tonight - the commit introducing /proc/*/syscall says: > > > > This adds /proc/PID/syscall and /proc/PID/task/TID/syscall magic files. > > These use task_current_syscall() to show the task's current system call > > number and argument registers, stack pointer and PC. For a task blocked > > but not in a syscall, the file shows "-1" in place of the syscall number, > > followed by only the SP and PC. For a task that's not blocked, it shows > > "running". > > > >Please validate that a blocked task does indeed show -1 with your patch > >applied. > > Will do. This is done in an upper level (collect_syscall <- > task_current_syscall <- proc_pid_syscall): > > if (!try_get_task_stack(target)) { > /* Task has no stack, so the task isn't in a syscall. */ > *sp = *pc = 0; > *callno = -1; > return 0; > } > > I think only missing part for arm was that one, but will confirm, after > fixing usage of "r7" for obtaining "scno". Will send a v2 in this thread. There's another question - what's the expected behaviour when we restart a syscall using the restartblock mechanism? Is the syscall number expected to be __NR_restart_syscall or the original syscall number? I can't find anywhere that this detail is specified (damn the lack of API documentation - I'm tempted to say that we won't implement this until it gets documented properly, and that test can continue failing until such time that happens.) -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up