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=-9.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,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 3F47BC43381 for ; Sat, 23 Feb 2019 21:34:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E21F20661 for ; Sat, 23 Feb 2019 21:34:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550957666; bh=sdaSjeIjJJaLaNZX971fccmQH49nOXGuFkBcNtt5siY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=tm9MMKSdYhSlYWvL5tFDyUP84J9IYMW6w/VtMFKkoaB5XuK7cjD8KnlKUXdoq8lGu yGM620eBRt+0cqIdGFZzwk68tZCTV2yXBhq9T7gt/eexaCSpOvh1cfCKMzXvVObinq R81cnrh4ZR12nF9pFnfgMRHcanVWsMoi9AF0+jec= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728414AbfBWVeY (ORCPT ); Sat, 23 Feb 2019 16:34:24 -0500 Received: from mail.kernel.org ([198.145.29.99]:39694 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728032AbfBWVEh (ORCPT ); Sat, 23 Feb 2019 16:04:37 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8595E20866; Sat, 23 Feb 2019 21:04:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550955876; bh=sdaSjeIjJJaLaNZX971fccmQH49nOXGuFkBcNtt5siY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iUpazdq1Unf+OOVwoQ20/Hib+alqNNe6QQcw4LEe4URj3uUqwCEXfSeXuitEF7yVk xDpNPINhLkpjCsN7g6EMqlkNr4XfuXP1Py3n9TTCeSJZK7IGksflT9l7Q10UMWj586 W5G8G3zbrZiMDdcU9ugN2tAqwCKhoqfVnv0GNSug= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Stephane Eranian , Kan Liang , Peter Zijlstra , Arnaldo Carvalho de Melo , Sasha Levin Subject: [PATCH AUTOSEL 4.20 09/72] perf core: Fix perf_proc_update_handler() bug Date: Sat, 23 Feb 2019 16:03:19 -0500 Message-Id: <20190223210422.199966-9-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190223210422.199966-1-sashal@kernel.org> References: <20190223210422.199966-1-sashal@kernel.org> MIME-Version: 1.0 X-Patchwork-Hint: Ignore 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 [ Upstream commit 1a51c5da5acc6c188c917ba572eebac5f8793432 ] 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 Signed-off-by: Sasha Levin --- 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 84530ab358c37..f113534bf22e9 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(); -- 2.19.1