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=-5.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 57270C433E7 for ; Thu, 15 Oct 2020 14:47:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F1B53218AC for ; Thu, 15 Oct 2020 14:47:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="TCrc40N7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389258AbgJOOrZ (ORCPT ); Thu, 15 Oct 2020 10:47:25 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:29905 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389384AbgJOOrV (ORCPT ); Thu, 15 Oct 2020 10:47:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602773240; 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=fzjpDAV5F3Ar6lYBMyYyeWD2zEgRpW1GmqDCDHO9pf0=; b=TCrc40N7RXFM23vA4Tb7GV1tV75OEB2bRuBnR1pyggSdi/c/zeEhAptJZ09vAUSrlWFBRd eSXbUcK1QhviyPLw+yKeyE83y/guQoMhv0IFFefcFvfCcc6UGNCqGu+e6C7AmVfqRXHNKj CP/TNrV++SgLYScrj+0COWutmDDK/+s= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-25-4lWrHLouM0WfDg-0bt7_VQ-1; Thu, 15 Oct 2020 10:47:18 -0400 X-MC-Unique: 4lWrHLouM0WfDg-0bt7_VQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2673086ABDB; Thu, 15 Oct 2020 14:47:17 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.193.8]) by smtp.corp.redhat.com (Postfix) with SMTP id 77FB475125; Thu, 15 Oct 2020 14:47:15 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 15 Oct 2020 16:47:16 +0200 (CEST) Date: Thu, 15 Oct 2020 16:47:14 +0200 From: Oleg Nesterov To: Jens Axboe Cc: linux-kernel@vger.kernel.org, io-uring@vger.kernel.org, peterz@infradead.org, tglx@linutronix.de Subject: Re: [PATCH 3/5] kernel: add support for TIF_NOTIFY_SIGNAL Message-ID: <20201015144713.GJ24156@redhat.com> References: <20201015131701.511523-1-axboe@kernel.dk> <20201015131701.511523-4-axboe@kernel.dk> <20201015143151.GB24156@redhat.com> <5d231aa1-b8c7-ae4e-90bb-211f82b57547@kernel.dk> <20201015143728.GE24156@redhat.com> <788b31b7-6acc-cc85-5e91-d0c2538341b7@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <788b31b7-6acc-cc85-5e91-d0c2538341b7@kernel.dk> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 10/15, Jens Axboe wrote: > > On 10/15/20 8:37 AM, Oleg Nesterov wrote: > > On 10/15, Jens Axboe wrote: > >> > >> On 10/15/20 8:31 AM, Oleg Nesterov wrote: > >>> On 10/15, Jens Axboe wrote: > >>>> > >>>> static inline int signal_pending(struct task_struct *p) > >>>> { > >>>> +#if defined(CONFIG_GENERIC_ENTRY) && defined(TIF_NOTIFY_SIGNAL) > >>>> + /* > >>>> + * TIF_NOTIFY_SIGNAL isn't really a signal, but it requires the same > >>>> + * behavior in terms of ensuring that we break out of wait loops > >>>> + * so that notify signal callbacks can be processed. > >>>> + */ > >>>> + if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL))) > >>>> + return 1; > >>>> +#endif > >>>> return task_sigpending(p); > >>>> } > >>> > >>> I don't understand why does this version requires CONFIG_GENERIC_ENTRY. > >>> > >>> Afaics, it is very easy to change all the non-x86 arches to support > >>> TIF_NOTIFY_SIGNAL, but it is not trivial to change them all to use > >>> kernel/entry/common.c ? > >> > >> I think that Thomas wants to gate TIF_NOTIFY_SIGNAL on conversion to > >> the generic entry code? > > > > Then I think TIF_NOTIFY_SIGNAL will be never fully supported ;) > > That is indeed a worry. From a functionality point of view, with the > major archs supporting it, I'm not too worried about that side. But it > does mean that we'll be stuck with the ifdeffery forever, which isn't > great. plus we can't kill the ugly JOBCTL_TASK_WORK. Oleg.