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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 419FCC433E0 for ; Mon, 3 Aug 2020 19:27:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A426B22B45 for ; Mon, 3 Aug 2020 19:27:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="yDsb61D0"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="VVXBx0Zb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726615AbgHCT1o (ORCPT ); Mon, 3 Aug 2020 15:27:44 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:39108 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726889AbgHCT1j (ORCPT ); Mon, 3 Aug 2020 15:27:39 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1596482857; 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=bIfZVkgl4VVuKMo3PbC45J6WLkq9PVh31LMaoA7XSuQ=; b=yDsb61D0T2KVHL5+3IJvxPV7KgR6nyu3+1ZZpStsvdyU1xJv1JFNg4N12sumVDtBD4kD6s uVBbtCic+cw+eomU0RRogZYEhEkbyHpiwkjRVxv0gHs1s70xgh5iOG6okre1hOerCbzxZq GvlYAJFoJsRFO7/mSyW6OqVOusIaceUbAssm6IGADpx3fl9xrRtEfbBnjoHzWjhEUUQTXA yCFXTiucU7Il6u6SKWDIaKdzQPwrK0eU0u1/uJaD6KUrkKgxbiqbUb2M4Fb3dQW1fhSIx2 cNKI4ITsRE0rxj5g6nZclUHtmzHxRsDR+06GMAdDMVo4TsRHZ1WyaB/8FwHxWg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1596482857; 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=bIfZVkgl4VVuKMo3PbC45J6WLkq9PVh31LMaoA7XSuQ=; b=VVXBx0Zb0yel+Ld4MM02i6YTCyXdJqnmQzhhpnM8prGzxCuogsjeeG9TmCKzR+cvd0kY6Y vcH55OKZuzzX+vCQ== To: Heiko Carstens Cc: Sven Schnelle , Vincenzo Frascino , linux-kernel@vger.kernel.org, Peter Zijlstra , linux-s390@vger.kernel.org Subject: Re: [PATCH 2/2] s390: convert to GENERIC_VDSO In-Reply-To: <20200803184428.GA3973@osiris> References: <20200803055645.79042-1-svens@linux.ibm.com> <20200803055645.79042-3-svens@linux.ibm.com> <87ft93ncaa.fsf@nanos.tec.linutronix.de> <87a6zbn29n.fsf@nanos.tec.linutronix.de> <20200803184428.GA3973@osiris> Date: Mon, 03 Aug 2020 21:27:36 +0200 Message-ID: <873653mswn.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Heiko Carstens writes: > On Mon, Aug 03, 2020 at 06:05:24PM +0200, Thomas Gleixner wrote: >> +/** >> + * vdso_update_begin - Start of a VDSO update section >> + * >> + * Allows architecture code to safely update the architecture specific VDSO >> + * data. >> + */ >> +void vdso_update_begin(void) >> +{ >> + struct vdso_data *vdata = __arch_get_k_vdso_data(); >> + >> + raw_spin_lock(&timekeeper_lock); >> + vdso_write_begin(vdata); >> +} > > I would assume that this only works if vdso_update_begin() is called > with irqs disabled, otherwise it could deadlock, no? Yes. > Maybe something like: > > void vdso_update_begin(unsigned long *flags) > { > struct vdso_data *vdata = __arch_get_k_vdso_data(); > > raw_spin_lock_irqsave(&timekeeper_lock, *flags); > vdso_write_begin(vdata); Shudder. Why not returning flags? > } > > void vdso_update_end(unsigned long *flags) Ditto, why pointer and not value? > { > struct vdso_data *vdata = __arch_get_k_vdso_data(); > > vdso_write_end(vdata); > __arch_sync_vdso_data(vdata); > raw_spin_unlock_irqrestore(&timekeeper_lock, *flags); > } > > ? Just wondering. Thought about that briefly, but then hated the flags thing and delegated it to the caller. Lockdep will yell if that lock is taken with interrupts enabled :) But aside of the pointer vs. value thing, I'm fine with doing it in the functions. Thanks, tglx