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=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 C7EF8C3815B for ; Wed, 15 Apr 2020 21:10:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF28E2076D for ; Wed, 15 Apr 2020 21:10:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2442314AbgDOVKN (ORCPT ); Wed, 15 Apr 2020 17:10:13 -0400 Received: from foss.arm.com ([217.140.110.172]:52514 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2442222AbgDOVFb (ORCPT ); Wed, 15 Apr 2020 17:05:31 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CEA0E113E; Wed, 15 Apr 2020 14:05:26 -0700 (PDT) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id E99283F6C4; Wed, 15 Apr 2020 14:05:25 -0700 (PDT) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com Subject: [PATCH v3 2/9] sched/debug: Make sd->flags sysctl read-only Date: Wed, 15 Apr 2020 22:05:05 +0100 Message-Id: <20200415210512.805-3-valentin.schneider@arm.com> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20200415210512.805-1-valentin.schneider@arm.com> References: <20200415210512.805-1-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Writing to the sysctl of a sched_domain->flags directly updates the value of the field, and goes nowhere near update_top_cache_domain(). This means that the cached domain pointers can end up containing stale data (e.g. the domain pointed to doesn't have the relevant flag set anymore). Explicit domain walks that check for flags will be affected by the write, but this won't be in sync with the cached pointers which will still point to the domains that were cached at the last sched_domain build. In other words, writing to this interface is playing a dangerous game. It could be made to trigger an update of the cached sched_domain pointers when written to, but this does not seem to be worth the trouble. Make it read-only. Signed-off-by: Valentin Schneider --- kernel/sched/debug.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index a562df57a86e..00796b0a2723 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -258,7 +258,7 @@ sd_alloc_ctl_domain_table(struct sched_domain *sd) set_table_entry(&table[2], "busy_factor", &sd->busy_factor, sizeof(int), 0644, proc_dointvec_minmax); set_table_entry(&table[3], "imbalance_pct", &sd->imbalance_pct, sizeof(int), 0644, proc_dointvec_minmax); set_table_entry(&table[4], "cache_nice_tries", &sd->cache_nice_tries, sizeof(int), 0644, proc_dointvec_minmax); - set_table_entry(&table[5], "flags", &sd->flags, sizeof(int), 0644, proc_dointvec_minmax); + set_table_entry(&table[5], "flags", &sd->flags, sizeof(int), 0444, proc_dointvec_minmax); set_table_entry(&table[6], "max_newidle_lb_cost", &sd->max_newidle_lb_cost, sizeof(long), 0644, proc_doulongvec_minmax); set_table_entry(&table[7], "name", sd->name, CORENAME_MAX_SIZE, 0444, proc_dostring); /* &table[8] is terminator */ -- 2.24.0