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=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 94A17C433DB for ; Mon, 29 Mar 2021 14:33:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 65E3D61959 for ; Mon, 29 Mar 2021 14:33:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230391AbhC2Ocq (ORCPT ); Mon, 29 Mar 2021 10:32:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46076 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230339AbhC2Ocm (ORCPT ); Mon, 29 Mar 2021 10:32:42 -0400 Received: from mail-ot1-x333.google.com (mail-ot1-x333.google.com [IPv6:2607:f8b0:4864:20::333]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 28D72C061574 for ; Mon, 29 Mar 2021 07:32:31 -0700 (PDT) Received: by mail-ot1-x333.google.com with SMTP id t23-20020a0568301e37b02901b65ab30024so12465358otr.4 for ; Mon, 29 Mar 2021 07:32:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6pd5+1lyxF0IpfUFm+C/Q0BotbJ7mj/8xSGsdykFryU=; b=WOGPfNiBH1rBOn7rKEj2te7OWuckEUpvJ+NQWbuqa1LLPtC8ni5+XceiDdRhii9Ezo M3ZPxxLkR1FXKmahCW23aHCLAWw+1OTM6ecK7JG1myf3fkFFkHbKy3NxP5RvTvpov7Y9 EsByzRGNkr3bhxp3Sv7v6YCoNu0qTBw+quXgG6uVUGQ8KuWIX4x/qiDMmEaufKVIHUXm 6yyKWYP37AglSKbupam4uq5h1Nmct7LqgHslu+LbupQAHibZM9OqxzCSknm9Ae0xDYpl o0BLDukK5niYeGEuiSDb/YFoa+1gQZhKm0HpxsyBbqblfmPZjrQumWmzZOKLO9gjRBmK Nx5g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6pd5+1lyxF0IpfUFm+C/Q0BotbJ7mj/8xSGsdykFryU=; b=sTa3Ujz3PCKC4vjDEbpzSeKL5Uum9m14ROWRVnP4yKMxMMwWTOXjH1JmB5x3MW+LFa +lMcOtyge1pnQD0Zc6m99JK2+pj8ybLWPcuJhAO4WTdAG9d6Qp6eX74QX1e4u47i1ReF sxmMvBcykxUjqKwBn8C1/iyGtY8+Pz5nBLoVu6ArNStJgE15sdJ6cbQKLwbbUS1Amijp CGvE/9hvyfVKuK2EFOALyS0MStFAKGkdfx4bHUc560qFGvoJ1FdGTJBsEvI1J34BOCzP zmf7FqU7bYeNTzV9q+4Xyvgm3lGbgqiY39650UzwsA3A5tU1QZU/4b/clrUwVQtWkEMs jyZg== X-Gm-Message-State: AOAM532XzGFuDZvfIez7PwcjfkKTkB9BM0DckQMcJ8ipB2/uzU6Cm7wA tpm1N6TypSsQ67QTUcOsPlIGVZSYxKMnrUEHUe0rJg== X-Google-Smtp-Source: ABdhPJxXlJbzmAzqT33taumiK8BdMN/OkVmDMWa6AP1XrX+5I2Yys/7Pp8HpnlAdCIy2hzJQig2Zesc70wVcHKDSdNI= X-Received: by 2002:a05:6830:148c:: with SMTP id s12mr23773028otq.251.1617028350375; Mon, 29 Mar 2021 07:32:30 -0700 (PDT) MIME-Version: 1.0 References: <20210324112503.623833-1-elver@google.com> <20210324112503.623833-7-elver@google.com> <20210329142705.GA24849@redhat.com> In-Reply-To: <20210329142705.GA24849@redhat.com> From: Marco Elver Date: Mon, 29 Mar 2021 16:32:18 +0200 Message-ID: Subject: Re: [PATCH v3 06/11] perf: Add support for SIGTRAP on perf events To: Oleg Nesterov Cc: Peter Zijlstra , Alexander Shishkin , Arnaldo Carvalho de Melo , Ingo Molnar , Jiri Olsa , Mark Rutland , Namhyung Kim , Thomas Gleixner , Alexander Potapenko , Al Viro , Arnd Bergmann , Christian Brauner , Dmitry Vyukov , Jann Horn , Jens Axboe , Matt Morehouse , Peter Collingbourne , Ian Rogers , kasan-dev , linux-arch , linux-fsdevel , LKML , "the arch/x86 maintainers" , "open list:KERNEL SELFTEST FRAMEWORK" , Jiri Olsa Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, 29 Mar 2021 at 16:27, Oleg Nesterov wrote: > On 03/29, Peter Zijlstra wrote: > > > > On Thu, Mar 25, 2021 at 09:14:39AM +0100, Marco Elver wrote: > > > @@ -6395,6 +6395,13 @@ static void perf_sigtrap(struct perf_event *event) > > > { > > > struct kernel_siginfo info; > > > > > > + /* > > > + * This irq_work can race with an exiting task; bail out if sighand has > > > + * already been released in release_task(). > > > + */ > > > + if (!current->sighand) > > > + return; > > This is racy. If "current" has already passed exit_notify(), current->parent > can do release_task() and destroy current->sighand right after the check. > > > Urgh.. I'm not entirely sure that check is correct, but I always forget > > the rules with signal. It could be we ought to be testing PF_EXISTING > > instead. > > Agreed, PF_EXISTING check makes more sense in any case, the exiting task > can't receive the signal anyway. Thanks for confirming. I'll switch to just checking PF_EXITING (PF_EXISTING does not exist :-)). Thanks, -- Marco