From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753844AbdDOOTs (ORCPT ); Sat, 15 Apr 2017 10:19:48 -0400 Received: from terminus.zytor.com ([65.50.211.136]:60815 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751541AbdDOOTp (ORCPT ); Sat, 15 Apr 2017 10:19:45 -0400 Date: Sat, 15 Apr 2017 07:18:36 -0700 From: tip-bot for Thomas Gleixner Message-ID: Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org, mingo@kernel.org, hpa@zytor.com, davem@davemloft.net Reply-To: linux-kernel@vger.kernel.org, tglx@linutronix.de, davem@davemloft.net, hpa@zytor.com, mingo@kernel.org In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sparc/sysfs: Replace racy task affinity logic Git-Commit-ID: ea875ec94eafb858990f3fe9528501f983105653 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: ea875ec94eafb858990f3fe9528501f983105653 Gitweb: http://git.kernel.org/tip/ea875ec94eafb858990f3fe9528501f983105653 Author: Thomas Gleixner AuthorDate: Thu, 13 Apr 2017 10:17:07 +0200 Committer: Thomas Gleixner CommitDate: Sat, 15 Apr 2017 12:20:54 +0200 sparc/sysfs: Replace racy task affinity logic The mmustat_enable sysfs file accessor functions must run code on the target CPU. This is achieved by temporarily setting the affinity of the calling user space thread to the requested CPU and reset it to the original affinity afterwards. That's racy vs. concurrent affinity settings for that thread resulting in code executing on the wrong CPU and overwriting the new affinity setting. Replace it by using work_on_cpu() which guarantees to run the code on the requested CPU. Protection against CPU hotplug is not required as the open sysfs file already prevents the removal from the CPU offline callback. Using the hotplug protected version would actually be wrong because it would deadlock against a CPU hotplug operation of the CPU associated to the sysfs file in progress. Signed-off-by: Thomas Gleixner Acked-by: David S. Miller Cc: fenghua.yu@intel.com Cc: tony.luck@intel.com Cc: herbert@gondor.apana.org.au Cc: rjw@rjwysocki.net Cc: peterz@infradead.org Cc: benh@kernel.crashing.org Cc: bigeasy@linutronix.de Cc: jiangshanlai@gmail.com Cc: sparclinux@vger.kernel.org Cc: viresh.kumar@linaro.org Cc: mpe@ellerman.id.au Cc: tj@kernel.org Cc: lenb@kernel.org Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1704131001270.2408@nanos Signed-off-by: Thomas Gleixner --- arch/sparc/kernel/sysfs.c | 39 +++++++++++---------------------------- 1 file changed, 11 insertions(+), 28 deletions(-) diff --git a/arch/sparc/kernel/sysfs.c b/arch/sparc/kernel/sysfs.c index d63fc61..5fd352b 100644 --- a/arch/sparc/kernel/sysfs.c +++ b/arch/sparc/kernel/sysfs.c @@ -98,27 +98,7 @@ static struct attribute_group mmu_stat_group = { .name = "mmu_stats", }; -/* XXX convert to rusty's on_one_cpu */ -static unsigned long run_on_cpu(unsigned long cpu, - unsigned long (*func)(unsigned long), - unsigned long arg) -{ - cpumask_t old_affinity; - unsigned long ret; - - cpumask_copy(&old_affinity, ¤t->cpus_allowed); - /* should return -EINVAL to userspace */ - if (set_cpus_allowed_ptr(current, cpumask_of(cpu))) - return 0; - - ret = func(arg); - - set_cpus_allowed_ptr(current, &old_affinity); - - return ret; -} - -static unsigned long read_mmustat_enable(unsigned long junk) +static long read_mmustat_enable(void *data __maybe_unused) { unsigned long ra = 0; @@ -127,11 +107,11 @@ static unsigned long read_mmustat_enable(unsigned long junk) return ra != 0; } -static unsigned long write_mmustat_enable(unsigned long val) +static long write_mmustat_enable(void *data) { - unsigned long ra, orig_ra; + unsigned long ra, orig_ra, *val = data; - if (val) + if (*val) ra = __pa(&per_cpu(mmu_stats, smp_processor_id())); else ra = 0UL; @@ -142,7 +122,8 @@ static unsigned long write_mmustat_enable(unsigned long val) static ssize_t show_mmustat_enable(struct device *s, struct device_attribute *attr, char *buf) { - unsigned long val = run_on_cpu(s->id, read_mmustat_enable, 0); + long val = work_on_cpu(s->id, read_mmustat_enable, NULL); + return sprintf(buf, "%lx\n", val); } @@ -150,13 +131,15 @@ static ssize_t store_mmustat_enable(struct device *s, struct device_attribute *attr, const char *buf, size_t count) { - unsigned long val, err; - int ret = sscanf(buf, "%lu", &val); + unsigned long val; + long err; + int ret; + ret = sscanf(buf, "%lu", &val); if (ret != 1) return -EINVAL; - err = run_on_cpu(s->id, write_mmustat_enable, val); + err = work_on_cpu(s->id, write_mmustat_enable, &val); if (err) return -EIO;