From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755602AbdDLUxz (ORCPT ); Wed, 12 Apr 2017 16:53:55 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:35574 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755145AbdDLUxv (ORCPT ); Wed, 12 Apr 2017 16:53:51 -0400 Date: Wed, 12 Apr 2017 22:53:27 +0200 (CEST) From: Thomas Gleixner To: LKML cc: Peter Zijlstra , Ingo Molnar , Sebastian Siewior , Benjamin Herrenschmidt , "David S. Miller" , Fenghua Yu , Herbert Xu , Lai Jiangshan , Len Brown , Michael Ellerman , "Rafael J. Wysocki" , Tejun Heo , Tony Luck , Viresh Kumar , linux-ia64@vger.kernel.org Subject: [patch V 2 04/13] ia64/sn/hwperf: Replace racy task affinity logic In-Reply-To: <20170412201042.421132173@linutronix.de> Message-ID: References: <20170412200726.941336635@linutronix.de> <20170412201042.421132173@linutronix.de> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Subject: ia64/sn/hwperf: Replace racy task affinity logic From: Thomas Gleixner Date: Thu, 06 Apr 2017 14:56:18 +0200 sn_hwperf_op_cpu() which is invoked from an ioctl requires to run code on the requested 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. CPU hotplug and 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_safe() which guarantees to run the code on the requested CPU or to fail in case the CPU is offline. Signed-off-by: Thomas Gleixner Cc: Tony Luck Cc: Fenghua Yu Cc: linux-ia64@vger.kernel.org --- V2: Use the work function for real and remove the unused variable (reported by kbuild robot) arch/ia64/sn/kernel/sn2/sn_hwperf.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) Index: b/arch/ia64/sn/kernel/sn2/sn_hwperf.c =================================================================== --- a/arch/ia64/sn/kernel/sn2/sn_hwperf.c +++ b/arch/ia64/sn/kernel/sn2/sn_hwperf.c @@ -598,12 +598,17 @@ static void sn_hwperf_call_sal(void *inf op_info->ret = r; } +static long sn_hwperf_call_sal_work(void *info) +{ + sn_hwperf_call_sal(info); + return 0; +} + static int sn_hwperf_op_cpu(struct sn_hwperf_op_info *op_info) { u32 cpu; u32 use_ipi; int r = 0; - cpumask_t save_allowed; cpu = (op_info->a->arg & SN_HWPERF_ARG_CPU_MASK) >> 32; use_ipi = op_info->a->arg & SN_HWPERF_ARG_USE_IPI_MASK; @@ -629,13 +634,9 @@ static int sn_hwperf_op_cpu(struct sn_hw /* use an interprocessor interrupt to call SAL */ smp_call_function_single(cpu, sn_hwperf_call_sal, op_info, 1); - } - else { - /* migrate the task before calling SAL */ - save_allowed = current->cpus_allowed; - set_cpus_allowed_ptr(current, cpumask_of(cpu)); - sn_hwperf_call_sal(op_info); - set_cpus_allowed_ptr(current, &save_allowed); + } else { + /* Call on the target CPU */ + work_on_cpu_safe(cpu, sn_hwperf_call_sal_work, op_info); } } r = op_info->ret; From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Date: Wed, 12 Apr 2017 20:53:27 +0000 Subject: [patch V 2 04/13] ia64/sn/hwperf: Replace racy task affinity logic Message-Id: List-Id: References: <20170412200726.941336635@linutronix.de> <20170412201042.421132173@linutronix.de> In-Reply-To: <20170412201042.421132173@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: LKML Cc: Peter Zijlstra , Ingo Molnar , Sebastian Siewior , Benjamin Herrenschmidt , "David S. Miller" , Fenghua Yu , Herbert Xu , Lai Jiangshan , Len Brown , Michael Ellerman , "Rafael J. Wysocki" , Tejun Heo , Tony Luck , Viresh Kumar , linux-ia64@vger.kernel.org Subject: ia64/sn/hwperf: Replace racy task affinity logic From: Thomas Gleixner Date: Thu, 06 Apr 2017 14:56:18 +0200 sn_hwperf_op_cpu() which is invoked from an ioctl requires to run code on the requested 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. CPU hotplug and 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_safe() which guarantees to run the code on the requested CPU or to fail in case the CPU is offline. Signed-off-by: Thomas Gleixner Cc: Tony Luck Cc: Fenghua Yu Cc: linux-ia64@vger.kernel.org --- V2: Use the work function for real and remove the unused variable (reported by kbuild robot) arch/ia64/sn/kernel/sn2/sn_hwperf.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) Index: b/arch/ia64/sn/kernel/sn2/sn_hwperf.c =================================--- a/arch/ia64/sn/kernel/sn2/sn_hwperf.c +++ b/arch/ia64/sn/kernel/sn2/sn_hwperf.c @@ -598,12 +598,17 @@ static void sn_hwperf_call_sal(void *inf op_info->ret = r; } +static long sn_hwperf_call_sal_work(void *info) +{ + sn_hwperf_call_sal(info); + return 0; +} + static int sn_hwperf_op_cpu(struct sn_hwperf_op_info *op_info) { u32 cpu; u32 use_ipi; int r = 0; - cpumask_t save_allowed; cpu = (op_info->a->arg & SN_HWPERF_ARG_CPU_MASK) >> 32; use_ipi = op_info->a->arg & SN_HWPERF_ARG_USE_IPI_MASK; @@ -629,13 +634,9 @@ static int sn_hwperf_op_cpu(struct sn_hw /* use an interprocessor interrupt to call SAL */ smp_call_function_single(cpu, sn_hwperf_call_sal, op_info, 1); - } - else { - /* migrate the task before calling SAL */ - save_allowed = current->cpus_allowed; - set_cpus_allowed_ptr(current, cpumask_of(cpu)); - sn_hwperf_call_sal(op_info); - set_cpus_allowed_ptr(current, &save_allowed); + } else { + /* Call on the target CPU */ + work_on_cpu_safe(cpu, sn_hwperf_call_sal_work, op_info); } } r = op_info->ret;