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=-10.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,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 DB8F8C31680 for ; Mon, 21 Jan 2019 18:35:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AA0F421726 for ; Mon, 21 Jan 2019 18:35:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548095744; bh=sh0cfqRPiFqBaAnRx3+vVxdOrbDoMF6AbsktLhaVg14=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ZhOuvIHuOwoIF/XAm0fSxdLUjwO3C5FC8jiQrLCna5yioJ8wEiIJPe/4g6ISwqR8T 4FyxXG4fwW7cBoY+QohYXwmVwZh/wHEhL8qFJrWnmBTaASiPNPnZZT47MmIcNSPl7p AVzq8UZb3shO5KlqhbRqfB9vEcBDkXUi7RLvG+T4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728223AbfAUSfn (ORCPT ); Mon, 21 Jan 2019 13:35:43 -0500 Received: from mail.kernel.org ([198.145.29.99]:43042 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728173AbfAUSfm (ORCPT ); Mon, 21 Jan 2019 13:35:42 -0500 Received: from quaco.ghostprotocols.net (unknown [179.97.41.186]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CFC6F21721; Mon, 21 Jan 2019 18:35:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548095741; bh=sh0cfqRPiFqBaAnRx3+vVxdOrbDoMF6AbsktLhaVg14=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vOXpgvWIKtOdc5SMdBvEtGnENvRj31Eaf5EP7fDhIBYKkOE2eMU4dXjLApRDJ0cnJ zZhJzcvmWqnpIJHaafWlTjYq8Gl12t0AMlTBbhweDChj3iNRb+SCHqP2oUtFFdoGEi ZRmFuKTkST+lmBzAWmlbOxCsgYA9oEBenTUfw3i4= From: Arnaldo Carvalho de Melo To: Ingo Molnar Cc: Clark Williams , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Stephane Eranian , Andi Kleen , Jiri Olsa , Arnaldo Carvalho de Melo , Kan Liang , Peter Zijlstra Subject: [PATCH 3/7] perf core: Fix perf_proc_update_handler() bug Date: Mon, 21 Jan 2019 15:35:03 -0300 Message-Id: <20190121183507.23490-4-acme@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190121183507.23490-1-acme@kernel.org> References: <20190121183507.23490-1-acme@kernel.org> 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 From: Stephane Eranian The perf_proc_update_handler() handles /proc/sys/kernel/perf_event_max_sample_rate syctl variable. When the PMU IRQ handler timing monitoring is disabled, i.e, when /proc/sys/kernel/perf_cpu_time_max_percent is equal to 0 or 100, then no modification to sysctl_perf_event_sample_rate is allowed to prevent possible hang from wrong values. The problem is that the test to prevent modification is made after the sysctl variable is modified in perf_proc_update_handler(). You get an error: $ echo 10001 >/proc/sys/kernel/perf_event_max_sample_rate echo: write error: invalid argument But the value is still modified causing all sorts of inconsistencies: $ cat /proc/sys/kernel/perf_event_max_sample_rate 10001 This patch fixes the problem by moving the parsing of the value after the test. Committer testing: # echo 100 > /proc/sys/kernel/perf_cpu_time_max_percent # echo 10001 > /proc/sys/kernel/perf_event_max_sample_rate -bash: echo: write error: Invalid argument # cat /proc/sys/kernel/perf_event_max_sample_rate 10001 # Signed-off-by: Stephane Eranian Reviewed-by: Andi Kleen Reviewed-by: Jiri Olsa Tested-by: Arnaldo Carvalho de Melo Cc: Kan Liang Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1547169436-6266-1-git-send-email-eranian@google.com Signed-off-by: Arnaldo Carvalho de Melo --- kernel/events/core.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 3cd13a30f732..e5ede6918050 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -436,18 +436,18 @@ int perf_proc_update_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { - int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); - - if (ret || !write) - return ret; - + int ret; + int perf_cpu = sysctl_perf_cpu_time_max_percent; /* * If throttling is disabled don't allow the write: */ - if (sysctl_perf_cpu_time_max_percent == 100 || - sysctl_perf_cpu_time_max_percent == 0) + if (write && (perf_cpu == 100 || perf_cpu == 0)) return -EINVAL; + ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + if (ret || !write) + return ret; + max_samples_per_tick = DIV_ROUND_UP(sysctl_perf_event_sample_rate, HZ); perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate; update_perf_cpu_limits(); -- 2.20.1