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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,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 BFF6CC28D1E for ; Thu, 6 Jun 2019 10:22:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A1BB120872 for ; Thu, 6 Jun 2019 10:22:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728364AbfFFKWZ (ORCPT ); Thu, 6 Jun 2019 06:22:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60226 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727469AbfFFKWY (ORCPT ); Thu, 6 Jun 2019 06:22:24 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4E50F30872D2; Thu, 6 Jun 2019 10:22:13 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.159]) by smtp.corp.redhat.com (Postfix) with SMTP id B97096918F; Thu, 6 Jun 2019 10:22:05 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 6 Jun 2019 12:22:11 +0200 (CEST) Date: Thu, 6 Jun 2019 12:22:03 +0200 From: Oleg Nesterov To: Linus Torvalds Cc: Andrew Morton , Deepa Dinamani , Linux List Kernel Mailing , Arnd Bergmann , Davidlohr Bueso , Jens Axboe , Davidlohr Bueso , e@80x24.org, Jason Baron , linux-fsdevel , linux-aio@kvack.org, omar.kilani@gmail.com, Thomas Gleixner , stable , Al Viro , "Eric W. Biederman" , David Laight Subject: Re: [PATCH -mm 0/1] signal: simplify set_user_sigmask/restore_user_sigmask Message-ID: <20190606102203.GA31870@redhat.com> References: <20190522032144.10995-1-deepa.kernel@gmail.com> <20190529161157.GA27659@redhat.com> <20190604134117.GA29963@redhat.com> <20190605155801.GA25165@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 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Thu, 06 Jun 2019 10:22:24 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/05, Linus Torvalds wrote: > > On Wed, Jun 5, 2019 at 8:58 AM Oleg Nesterov wrote: > > > > To simplify the review, please see the code with this patch applied. > > I am using epoll_pwait() as an example because it looks very simple. > > I like it. > > However. > > I think I'd like it even more if we just said "we don't need > restore_saved_sigmask AT ALL". ^^^^^^^^^^^^^^^^^^^^^ Did you mean restore_saved_sigmask_unless() introduced by this patch? If yes: > Which would be fairly easy to do with something like the attached... I don't think so, > --- a/arch/x86/entry/common.c > +++ b/arch/x86/entry/common.c > @@ -160,7 +160,7 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags) > klp_update_patch_state(current); > > /* deal with pending signal delivery */ > - if (cached_flags & _TIF_SIGPENDING) > + if (cached_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK)) > do_signal(regs); ... > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -2877,6 +2877,7 @@ int set_user_sigmask(const sigset_t __user *usigmask, sigset_t *set, > > *oldset = current->blocked; > set_current_blocked(set); > + set_thread_flag(TIF_RESTORE_SIGMASK); This will re-introduce the problem fixed by the previous patch. Yes, do_signal() does restore_saved_sigmask() at the end, but only if get_signal() returns false. This means that restore_saved_sigmask()->set_current_blocked(saved_mask) should restore ->blocked (and may be clear TIF_SIGPENDING) before ret-from-syscall. Or I misunderstood? Oleg.