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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 C3192C47404 for ; Wed, 9 Oct 2019 15:02:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9AEF220B7C for ; Wed, 9 Oct 2019 15:02:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731650AbfJIPCe (ORCPT ); Wed, 9 Oct 2019 11:02:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53100 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731072AbfJIPCe (ORCPT ); Wed, 9 Oct 2019 11:02:34 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 044B810C050B; Wed, 9 Oct 2019 15:02:34 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.44]) by smtp.corp.redhat.com (Postfix) with SMTP id CDA531001B30; Wed, 9 Oct 2019 15:02:32 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 9 Oct 2019 17:02:32 +0200 (CEST) Date: Wed, 9 Oct 2019 17:02:30 +0200 From: Oleg Nesterov To: Tejun Heo Cc: linux-kernel@vger.kernel.org, Roman Gushchin , Richard Purdie , Bruce Ashfield Subject: [PATCH] cgroup: freezer: call cgroup_enter_frozen() with preemption disabled in ptrace_stop() Message-ID: <20191009150230.GB12511@redhat.com> References: 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 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.65]); Wed, 09 Oct 2019 15:02:34 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ptrace_stop() does preempt_enable_no_resched() to avoid the preemption, but after that cgroup_enter_frozen() does spin_lock/unlock and this adds another preemption point. Reported-and-tested-by: Bruce Ashfield Fixes: 76f969e8948d ("cgroup: cgroup v2 freezer") Cc: stable@vger.kernel.org # v5.2+ Signed-off-by: Oleg Nesterov --- kernel/signal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/signal.c b/kernel/signal.c index 534fec2..f8eed86 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2205,8 +2205,8 @@ static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t */ preempt_disable(); read_unlock(&tasklist_lock); - preempt_enable_no_resched(); cgroup_enter_frozen(); + preempt_enable_no_resched(); freezable_schedule(); cgroup_leave_frozen(true); } else { -- 2.5.0