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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BF175C433EF for ; Tue, 10 May 2022 15:38:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243575AbiEJPl6 (ORCPT ); Tue, 10 May 2022 11:41:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47634 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346101AbiEJPjj (ORCPT ); Tue, 10 May 2022 11:39:39 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 8165D1F8C64 for ; Tue, 10 May 2022 08:35:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1652196904; 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=KAUYAL6xtEy1vEbUJu56EBQK32UGZSvLvF0XFVQ8Fq4=; b=Vm4suJuURI5PNU+Y2TBZngNsCqtwQrHaEL6jBYAJcz5vCyT31TjPDg/eEIjv36QaU/7SX1 4hBWptBOuHSgUlCqkWWMtbR79BixoQsvFXpTDW+SxgCWsDFmpd5oyoWqx4KNiiKemDiTT3 yLRh5PHvVchaREmBDHL7D6RHiVEZDQU= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-135-0inn2KGNM_GDY5x2WVygpg-1; Tue, 10 May 2022 11:35:03 -0400 X-MC-Unique: 0inn2KGNM_GDY5x2WVygpg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B03B6811E75; Tue, 10 May 2022 15:34:59 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.98]) by smtp.corp.redhat.com (Postfix) with SMTP id 8B237403579A; Tue, 10 May 2022 15:34:54 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 10 May 2022 17:34:59 +0200 (CEST) Date: Tue, 10 May 2022 17:34:53 +0200 From: Oleg Nesterov To: "Eric W. Biederman" Cc: linux-kernel@vger.kernel.org, rjw@rjwysocki.net, mingo@kernel.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, mgorman@suse.de, bigeasy@linutronix.de, Will Deacon , tj@kernel.org, linux-pm@vger.kernel.org, Peter Zijlstra , Richard Weinberger , Anton Ivanov , Johannes Berg , linux-um@lists.infradead.org, Chris Zankel , Max Filippov , linux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn , linux-ia64@vger.kernel.org Subject: Re: [PATCH v4 10/12] ptrace: Don't change __state Message-ID: <20220510153452.GA23707@redhat.com> References: <87a6bv6dl6.fsf_-_@email.froward.int.ebiederm.org> <20220505182645.497868-10-ebiederm@xmission.com> <20220510142202.GB23277@redhat.com> <87ee11wh6b.fsf@email.froward.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87ee11wh6b.fsf@email.froward.int.ebiederm.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 05/10, Eric W. Biederman wrote: > > > But I still think that a lockless > > > > if (!(task->jobctl & JOBCTL_PTRACE_FROZEN)) > > return; > > > > check at the start of ptrace_unfreeze_traced() makes sense to avoid > > lock_task_sighand() if possible. > > > > And ptrace_resume() can probably clear JOBCTL_PTRACE_FROZEN along with > > JOBCTL_TRACED to make this optimization work better. The same for > > ptrace_signal_wake_up(). > > What do you have that suggests that taking siglock there is a problem? Not necessarily a problem, but this optimization is free. If the tracee was resumed, it can compete for siglock with debugger. > What you propose will definitely work as an incremental change, and > in an incremental change we can explain why doing the stupid simple > thing is not good enough. OK. Oleg.