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=-16.7 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 7C218C43387 for ; Fri, 11 Jan 2019 01:17:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4411020872 for ; Fri, 11 Jan 2019 01:17:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="dlf7+xIO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729034AbfAKBRW (ORCPT ); Thu, 10 Jan 2019 20:17:22 -0500 Received: from mail-pg1-f196.google.com ([209.85.215.196]:39287 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726369AbfAKBRV (ORCPT ); Thu, 10 Jan 2019 20:17:21 -0500 Received: by mail-pg1-f196.google.com with SMTP id w6so5583729pgl.6 for ; Thu, 10 Jan 2019 17:17:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=pBrZ3CioDf9IPnu/iao9blT0tnYCjnN+XUWIYCmnjVI=; b=dlf7+xIONI6JaeCr8BxqmLQXVnJ/3Il58Z3oHS0X5j688A5xlpM18FUDkNb+ICs0Ux QfhaWjixCTKBWuOPDLU2Puee/o0ollIgBSS7kpri8euDCc9ZpypPkZA4SkrF+3KdfKrm xUm8OyG2U5WIpRWCh8s4py/JMzLtjq9iE5RVfSYPEldPIaSgdxcXQ0Fwz/Wyd8t44n+n ShTxsFs3/fq9PsdY6/UgdS9a2y1oJgdbYpEQFA1N/6uea8uLyhelz6r+SavatbSYggMN uWeU2Z6urDdtL71avRcbGsGVjRkw3XFwt0FvrwnElrroTeJf9ZQ3rh60JXiC2aH5Xwjt HQNw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=pBrZ3CioDf9IPnu/iao9blT0tnYCjnN+XUWIYCmnjVI=; b=cZ03uDwXXpM5xgCfl2O3OWHIPlLmjkmTuK0w2tIzTXfKmiS/yTZ8IAud8Nkw7Fv5SW FiJAKeVkoIQymCMG1MuY6DaE85JzHjjIH6imQwkYdUxu6oZrl8ywGPReiL/2nYt4UMA5 YQO2mD+HOmFWPfa/s8ytQtN1SkLRrpjuSO6xfDgPO0a+eTCc0QyAjx7PlmMXrI8Iw2O7 FBZ/SFEGvJBp62JV0O79enT1qfYGIOcHQ4+MbgOwNSKeCDzcRkx1XcBt1FaUW8YBUPxz YhxAqN18eXHyiZwkePX9jFOLkIfnacWpA5uz5A8tPC4P/Q6l5jTBk+9hDqPgAMwqkCNO MGRg== X-Gm-Message-State: AJcUukcA6i/lktaMFIGQY4JCHz4iCraTG4px1hanV1sfjqOR943cVfer WO9odsVUMi2qr//JOwaUVuYta1LNAEOS2A== X-Google-Smtp-Source: ALg8bN6xHkb+R89hc+bzgrI1nBBCvO1djpQnbcNJb4y33X7QX0osetByPWxSxAF5EH3H9ICQqYQAWA== X-Received: by 2002:a62:6047:: with SMTP id u68mr12252161pfb.239.1547169440216; Thu, 10 Jan 2019 17:17:20 -0800 (PST) Received: from localhost ([104.133.9.99]) by smtp.gmail.com with ESMTPSA id x12sm96711363pgr.55.2019.01.10.17.17.19 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 10 Jan 2019 17:17:19 -0800 (PST) From: Stephane Eranian To: linux-kernel@vger.kernel.org Cc: peterz@infradead.org, mingo@elte.hu, ak@linux.intel.com, kan.liang@intel.com, jolsa@redhat.com, acme@redhat.com Subject: [PATCH] perf/core: fix perf_proc_update_handler() bug Date: Thu, 10 Jan 2019 17:17:16 -0800 Message-Id: <1547169436-6266-1-git-send-email-eranian@google.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Stephane Eranian --- 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(); -- 2.7.4