Received: by 2002:a25:ad19:0:0:0:0:0 with SMTP id y25csp3991531ybi; Fri, 19 Jul 2019 12:44:11 -0700 (PDT) X-Google-Smtp-Source: APXvYqzlTE8rMpvoDqIlbKZMEWeBZ1xrkakfRiPZ2OtpcfVlWCjHCAfaenfu+vEJoXyyNP2aPKcL X-Received: by 2002:a63:5045:: with SMTP id q5mr47308182pgl.380.1563565451811; Fri, 19 Jul 2019 12:44:11 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1563565451; cv=none; d=google.com; s=arc-20160816; b=SwKSW43O/TgTW874hopI7hBmL6nUPV/ol9bmMyi/pYxxZUre4lJwpTrz0piOK/665L e/gGk/Xdo6CL5uOpAjl8HCwSfqLc+mqVm6GqzNECQQAb7L+N/azn/pvIc03jaP12ECsp VXpBsa8cfS+X7XfqSVe9gdzLXVk1Bmf5ne3ZY3ERoeyUnvtDdnP66XpBdsNJ0DbnAP2F 6QSP5d8k27A5meSec73s5wos3GJwlvFgfFRbKdsd3gHzwFsueuxkapOxhKzKXJSPgGux ttU2sTj4MW7sBD77NkwZc7PE0MhnrVbRxs4KF235C4ZrORhboRbv+lq4SePmom0UpV76 wUPQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:user-agent:in-reply-to :content-disposition:mime-version:references:message-id:subject:cc :to:from:date; bh=UI3Pn4+0UN9EF+YjeK0RGj0GcDuf9/enhI7WdykhHYo=; b=mACF/aZHnVhg1PaxGVX1OhN4IZnK2IhVgcTJUyz1HuBNfRFwYfaKyH8NkFzdCRCzju iUYIjXHAWLhbpyD/0XgrrRwHLqoa2Y/y2pJgezTkq6VMEPMNJT3OTYn50s5YBSjpAq2B nEDuEVmM7fFRBiaRJsKyC/Gptc7JHaKdBlZxk6bUrXAMde/sQH3kHs4ECJkB7amdBiZf swVQ9ldElL2rHGrnc5UcwV5jL8pIQ/Cd1cTOHXCKP/UtbKNFNFgyzqQeINl4y91QuTUg elobeXr0Hp3ik1fvwurm2ocRBk7xyHEEswXYt+PN7O22hPNEGYa/xn6JjjOna9JHv/na UzgQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id z26si201314pgv.462.2019.07.19.12.43.55; Fri, 19 Jul 2019 12:44:11 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726837AbfGSQOJ (ORCPT + 99 others); Fri, 19 Jul 2019 12:14:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54430 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729038AbfGSQOI (ORCPT ); Fri, 19 Jul 2019 12:14:08 -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 3E636300B916; Fri, 19 Jul 2019 16:14:08 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.136]) by smtp.corp.redhat.com (Postfix) with SMTP id 35F40646CF; Fri, 19 Jul 2019 16:14:05 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 19 Jul 2019 18:14:07 +0200 (CEST) Date: Fri, 19 Jul 2019 18:14:05 +0200 From: Oleg Nesterov To: "Joel Fernandes (Google)" Cc: linux-kernel@vger.kernel.org, Suren Baghdasaryan , kernel-team@android.com, Andrea Arcangeli , Andrew Morton , Christian Brauner , "Eric W. Biederman" , Tejun Heo Subject: Re: [PATCH RFC v1] pidfd: fix a race in setting exit_state for pidfd polling Message-ID: <20190719161404.GA24170@redhat.com> References: <20190717172100.261204-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190717172100.261204-1-joel@joelfernandes.org> 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 [10.5.110.49]); Fri, 19 Jul 2019 16:14:08 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org it seems that I missed something else... On 07/17, Joel Fernandes (Google) wrote: > > @@ -1156,10 +1157,11 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p) > ptrace_unlink(p); > > /* If parent wants a zombie, don't release it now */ > - state = EXIT_ZOMBIE; > + p->exit_state = EXIT_ZOMBIE; > if (do_notify_parent(p, p->exit_signal)) > - state = EXIT_DEAD; > - p->exit_state = state; > + p->exit_state = EXIT_DEAD; > + > + state = p->exit_state; > write_unlock_irq(&tasklist_lock); why do you think we also need to change wait_task_zombie() ? pidfd_poll() only needs the exit_state != 0 check, we know that it is not zero at this point. Why do we need to change exit_state before do_notify_parent() ? Oleg.