From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp06.in.ibm.com (e28smtp06.in.ibm.com [59.145.155.6]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e28smtp06.in.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 05B11B810F for ; Fri, 30 Oct 2009 16:23:10 +1100 (EST) Received: from d28relay05.in.ibm.com (d28relay05.in.ibm.com [9.184.220.62]) by e28smtp06.in.ibm.com (8.14.3/8.13.1) with ESMTP id n9U5N41N001273 for ; Fri, 30 Oct 2009 10:53:04 +0530 Received: from d28av01.in.ibm.com (d28av01.in.ibm.com [9.184.220.63]) by d28relay05.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id n9U5N4sS2076754 for ; Fri, 30 Oct 2009 10:53:04 +0530 Received: from d28av01.in.ibm.com (loopback [127.0.0.1]) by d28av01.in.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id n9U5N3eV007480 for ; Fri, 30 Oct 2009 10:53:04 +0530 Subject: [PATCH v5 4/4] pseries: Serialize cpu hotplug operations during deactivate Vs deallocate To: Nathan Fontenot , Benjamin Herrenschmidt From: Gautham R Shenoy Date: Fri, 30 Oct 2009 10:53:04 +0530 Message-ID: <20091030052304.25493.41341.stgit@sofia.in.ibm.com> In-Reply-To: <20091030052106.25493.42109.stgit@sofia.in.ibm.com> References: <20091030052106.25493.42109.stgit@sofia.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Arun R Bharadwaj , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Ingo Molnar List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Currently the cpu-allocation/deallocation process comprises of two steps: - Set the indicators and to update the device tree with DLPAR node information. - Online/offline the allocated/deallocated CPU. This is achieved by writing to the sysfs tunables "probe" during allocation and "release" during deallocation. At the sametime, the userspace can independently online/offline the CPUs of the system using the sysfs tunable "online". It is quite possible that when a userspace tool offlines a CPU for the purpose of deallocation and is in the process of updating the device tree, some other userspace tool could bring the CPU back online by writing to the "online" sysfs tunable thereby causing the deallocate process to fail. The solution to this is to serialize writes to the "probe/release" sysfs tunable with the writes to the "online" sysfs tunable. This patch employs a mutex to provide this serialization, which is a no-op on all architectures except PPC_PSERIES Signed-off-by: Gautham R Shenoy --- arch/powerpc/platforms/pseries/dlpar.c | 28 +++++++++++++++++++++++----- drivers/base/cpu.c | 2 ++ include/linux/cpu.h | 13 +++++++++++++ 3 files changed, 38 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/platforms/pseries/dlpar.c b/arch/powerpc/platforms/pseries/dlpar.c index 8e04a69..b6fc6ab 100644 --- a/arch/powerpc/platforms/pseries/dlpar.c +++ b/arch/powerpc/platforms/pseries/dlpar.c @@ -501,6 +501,18 @@ int release_drc(u32 drc_index) } #ifdef CONFIG_HOTPLUG_CPU +static DEFINE_MUTEX(pseries_cpu_hotplug_mutex); + +void cpu_hotplug_driver_lock() +{ + mutex_lock(&pseries_cpu_hotplug_mutex); +} + +void cpu_hotplug_driver_unlock() +{ + mutex_unlock(&pseries_cpu_hotplug_mutex); +} + static ssize_t cpu_probe_store(struct class *class, const char *buf, size_t count) { @@ -509,18 +521,19 @@ static ssize_t cpu_probe_store(struct class *class, const char *buf, char *cpu_name; int rc; + cpu_hotplug_driver_lock(); rc = strict_strtoul(buf, 0, &drc_index); if (rc) - return -EINVAL; + goto out; rc = acquire_drc(drc_index); if (rc) - return -EINVAL; + goto out; dn = configure_connector(drc_index); if (!dn) { release_drc(drc_index); - return -EINVAL; + goto out; } /* fixup dn name */ @@ -529,7 +542,8 @@ static ssize_t cpu_probe_store(struct class *class, const char *buf, if (!cpu_name) { free_cc_nodes(dn); release_drc(drc_index); - return -ENOMEM; + rc = -ENOMEM; + goto out; } sprintf(cpu_name, "/cpus/%s", dn->full_name); @@ -541,6 +555,8 @@ static ssize_t cpu_probe_store(struct class *class, const char *buf, release_drc(drc_index); rc = online_node_cpus(dn); +out: + cpu_hotplug_driver_unlock(); return rc ? -EINVAL : count; } @@ -562,6 +578,7 @@ static ssize_t cpu_release_store(struct class *class, const char *buf, return -EINVAL; } + cpu_hotplug_driver_lock(); rc = offline_node_cpus(dn); if (rc) @@ -570,7 +587,7 @@ static ssize_t cpu_release_store(struct class *class, const char *buf, rc = release_drc(*drc_index); if (rc) { of_node_put(dn); - return -EINVAL; + goto out; } rc = remove_device_tree_nodes(dn); @@ -579,6 +596,7 @@ static ssize_t cpu_release_store(struct class *class, const char *buf, of_node_put(dn); out: + cpu_hotplug_driver_unlock(); return rc ? -EINVAL : count; } diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index e62a4cc..07c3f05 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -35,6 +35,7 @@ static ssize_t __ref store_online(struct sys_device *dev, struct sysdev_attribut struct cpu *cpu = container_of(dev, struct cpu, sysdev); ssize_t ret; + cpu_hotplug_driver_lock(); switch (buf[0]) { case '0': ret = cpu_down(cpu->sysdev.id); @@ -49,6 +50,7 @@ static ssize_t __ref store_online(struct sys_device *dev, struct sysdev_attribut default: ret = -EINVAL; } + cpu_hotplug_driver_unlock(); if (ret >= 0) ret = count; diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 4753619..b0ad4e1 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -115,6 +115,19 @@ extern void put_online_cpus(void); #define unregister_hotcpu_notifier(nb) unregister_cpu_notifier(nb) int cpu_down(unsigned int cpu); +#ifdef CONFIG_PPC_PSERIES +extern void cpu_hotplug_driver_lock(void); +extern void cpu_hotplug_driver_unlock(void); +#else +static inline void cpu_hotplug_driver_lock(void) +{ +} + +static inline void cpu_hotplug_driver_unlock(void) +{ +} +#endif + #else /* CONFIG_HOTPLUG_CPU */ #define get_online_cpus() do { } while (0)