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=-7.3 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 7005AC433ED for ; Tue, 13 Apr 2021 17:17:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 40BA4613B6 for ; Tue, 13 Apr 2021 17:17:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344578AbhDMRSN (ORCPT ); Tue, 13 Apr 2021 13:18:13 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:23162 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231131AbhDMRSL (ORCPT ); Tue, 13 Apr 2021 13:18:11 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618334270; 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=M6s9zDeT8gTkZ68rPedGR2Yu+AcsSpDjVHkAnNA1XnQ=; b=L02TZ62PLbZs/tCOGL9RASOS1EtXC4Gkz+1XlunO8HFq0J9YfoLuLOt9kmrrg0MabAjoim LpOuCKFYE57qiD7PJd9ix+C4orayAo9v1yVKYQJYeFZiSyNrW6N6vYyaF+B4V9XQAl8ti5 nLAfwaPhyss3dqMTjZeSrRN9uDkvW1w= 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-245-DRx9Ca9OMcuoX-JS6b7WlQ-1; Tue, 13 Apr 2021 13:17:48 -0400 X-MC-Unique: DRx9Ca9OMcuoX-JS6b7WlQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AD2F364159; Tue, 13 Apr 2021 17:17:47 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.195.154]) by smtp.corp.redhat.com (Postfix) with SMTP id CA3D96062F; Tue, 13 Apr 2021 17:17:45 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 13 Apr 2021 19:17:47 +0200 (CEST) Date: Tue, 13 Apr 2021 19:17:43 +0200 From: Oleg Nesterov To: Igor Zhbanov Cc: linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Mutual debugging of 2 processes can stuck in unkillable stopped state Message-ID: <20210413171741.GA7672@redhat.com> References: <20210329164900.GB24849@redhat.com> <4124a89e-a62e-0c51-1f46-8409867a626a@omprussia.ru> <20210329173848.GC24849@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 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org Hi Igor, sorry for delay... On 04/12, Igor Zhbanov wrote: > > Hi Oleg, > > So what is the cause of this problem? The cause is clear. And well known ;) And again, this has almost nothing to do with the mutual debugging. The tracee sleeps in ptrace_stop(). You send SIGKILL. This wakes the tracee up, it dequeues the signal, calls do_exit(), and stops again in PTRACE_EVENT_EXIT. With SIGKILL in signal->shared_pending. This all looks as if the tracee doesn't react to SIGKILL. The only problem is that any change can break something which relies on the current behaviour :/ I'll write another email on this. Oleg.