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=-5.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, 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 3872DC4363C for ; Thu, 8 Oct 2020 14:07:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE1872184D for ; Thu, 8 Oct 2020 14:07:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="dGWchd14" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730459AbgJHOH5 (ORCPT ); Thu, 8 Oct 2020 10:07:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53300 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730175AbgJHOH5 (ORCPT ); Thu, 8 Oct 2020 10:07:57 -0400 Received: from mail-il1-x144.google.com (mail-il1-x144.google.com [IPv6:2607:f8b0:4864:20::144]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F32F5C061755 for ; Thu, 8 Oct 2020 07:07:56 -0700 (PDT) Received: by mail-il1-x144.google.com with SMTP id l16so5743015ilt.13 for ; Thu, 08 Oct 2020 07:07:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=diM16rALesHaCmwXGl03a1r60jg62usWEYSJ8E59HcQ=; b=dGWchd14Qhgki7wTp4s3wAGENm3BnuFx6wwLUm9CyWKSzpBBScby8wM1IW687+3qyq b5qbTGQ08HSpX32nGgwQNyO9GCZvRuW7cMsovzjzOVC6kg/2fzVWgmGmG/ddhqzq8iGV 4oxVGZTcpsHEFRUYpvc/wqaKWillCTtAkMW/V/WVFwmVkRF2lkAA7xPV2ZPFn3raUpGu 8E9XTe1cgYx+vUUyXPyBl5Co7f+CgMUavAAHBCkivdsBZmluS/Ohbvu1NGxVOwlXRfGF NmxrprhTSQq92ENFloJfFX6/vo1Q04mGIfwTvhmvCLs22gXIOjF0qBBrxZClYVG37VdU cEnA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=diM16rALesHaCmwXGl03a1r60jg62usWEYSJ8E59HcQ=; b=j9//t7J1wsiVGKDiy5aDSx0DJfQJenGdPstiZp4wjH3dmIBSzgWnUYOSXhupC5T1IH +mQ7lrqPbUGqP6rjvMfBrK0V8pDJI93Nyjpym6hMGZ1pkof8sps1ZnPg55rq8gMNKCVO EIjpsPymWiSkJjDv7nWfbYkOiAL8pjnBVusBXyflpdypBI+j/2DCJAAlZLdcyuTIBh8P EKTdoRS8YntbtooMU1lNoWKum34AmVwO2iM26l7/OtxCBpOeMsuUUm23Yo4E5mmfRVb2 o6GyRbdjQH8dikLwPELJKSsEluymzZKSg5vrFOXHZE4081mMqSFaaCekzIwueuPX/b8o EJ5Q== X-Gm-Message-State: AOAM532aWki6maXpAdt/YtJmgjCE3aH3JjngreimVxC4GQckjW4pcfHg mFquV62JKgdZJGrbWe1DjfJusA== X-Google-Smtp-Source: ABdhPJzN0O4GYXwVtzshMhwu2JGkqvxiOKnf/9fN5dg8j/tlNarx0Pyra0Nc6zri58QPeCAPvroKXg== X-Received: by 2002:a92:6e05:: with SMTP id j5mr6436063ilc.248.1602166076312; Thu, 08 Oct 2020 07:07:56 -0700 (PDT) Received: from [192.168.1.30] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id t10sm2279646iog.49.2020.10.08.07.07.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 08 Oct 2020 07:07:55 -0700 (PDT) Subject: Re: [PATCH 4/6] kernel: add support for TIF_NOTIFY_SIGNAL To: Oleg Nesterov Cc: linux-kernel@vger.kernel.org, io-uring@vger.kernel.org, peterz@infradead.org, tglx@linutronix.de References: <20201005150438.6628-1-axboe@kernel.dk> <20201005150438.6628-5-axboe@kernel.dk> <20201008135325.GG9995@redhat.com> From: Jens Axboe Message-ID: Date: Thu, 8 Oct 2020 08:07:55 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201008135325.GG9995@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/8/20 7:53 AM, Oleg Nesterov wrote: > On 10/05, Jens Axboe wrote: >> >> static inline int signal_pending(struct task_struct *p) >> { >> +#ifdef 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); >> } > > perhaps we can add test_tsk_thread_mask() later... Yeah would be nice, and I bet there are a lot of cases in the kernel that test multiple bits like that. >> static inline void restore_saved_sigmask_unless(bool interrupted) >> { >> - if (interrupted) >> + if (interrupted) { >> +#ifdef TIF_NOTIFY_SIGNAL >> + WARN_ON(!test_thread_flag(TIF_SIGPENDING) && >> + !test_thread_flag(TIF_NOTIFY_SIGNAL)); >> +#else >> WARN_ON(!test_thread_flag(TIF_SIGPENDING)); >> - else >> +#endif >> + } else { >> restore_saved_sigmask(); >> + } > > I'd suggest to simply do > > - WARN_ON(!test_thread_flag(TIF_SIGPENDING)); > + WARN_ON(!signal_pending(current); Ah yes, that's much better. I'll make the edit. >> --- a/kernel/entry/kvm.c >> +++ b/kernel/entry/kvm.c >> @@ -8,6 +8,9 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work) >> do { >> int ret; >> >> + if (ti_work & _TIF_NOTIFY_SIGNAL) >> + tracehook_notify_signal(); > > Can't really comment this change, but to me it would be more safe to > simply return -EINTR. > > Or perhaps even better, treat _TIF_NOTIFY_SIGNAL and _TIF_SIGPENDING > equally: > > - if (ti_work & _TIF_SIGPENDING) { > + if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) { > kvm_handle_signal_exit(vcpu); > return -EINTR; Not sure I follow your logic here. Why treat it any different than NOTIFY_RESUME from this perspective? -- Jens Axboe