Messages in this thread Patch in this message | | | From | "Rafael J. Wysocki" <> | Subject | [PATCH 1/3] Disable CPU hotplug during suspend | Date | Thu, 27 Jul 2006 09:52:14 +0200 |
| |
The current suspend code has to be run on one CPU, so we use the CPU hotplug to take the non-boot CPUs offline on SMP machines. However, we should also make sure that these CPUs will not be enabled by someone else after we have disabled them.
The functions disable_nonboot_cpus() and enable_nonboot_cpus() are moved to kernel/cpu.c, because they now refer to some stuff in there that should better be static. Also it's better if disable_nonboot_cpus() returns an error instead of panicking if something goes wrong, and enable_nonboot_cpus() has no reason to panic(), because the CPUs may have been enabled by the userland before it tries to take them online.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> --- include/linux/cpu.h | 8 +++ include/linux/suspend.h | 8 --- kernel/cpu.c | 109 +++++++++++++++++++++++++++++++++++++++++------- kernel/power/Makefile | 2 kernel/power/disk.c | 7 ++- kernel/power/main.c | 10 +--- kernel/power/smp.c | 62 --------------------------- kernel/power/user.c | 14 +++--- 8 files changed, 121 insertions(+), 99 deletions(-)
Index: linux-2.6.18-rc2/include/linux/suspend.h =================================================================== --- linux-2.6.18-rc2.orig/include/linux/suspend.h 2006-07-26 08:52:42.000000000 +0200 +++ linux-2.6.18-rc2/include/linux/suspend.h 2006-07-27 08:01:29.000000000 +0200 @@ -57,14 +57,6 @@ static inline int software_suspend(void) } #endif /* CONFIG_PM */ -#ifdef CONFIG_SUSPEND_SMP -extern void disable_nonboot_cpus(void); -extern void enable_nonboot_cpus(void); -#else -static inline void disable_nonboot_cpus(void) {} -static inline void enable_nonboot_cpus(void) {} -#endif - void save_processor_state(void); void restore_processor_state(void); struct saved_context; Index: linux-2.6.18-rc2/kernel/power/smp.c =================================================================== --- linux-2.6.18-rc2.orig/kernel/power/smp.c 2006-07-26 08:52:42.000000000 +0200 +++ /dev/null 1970-01-01 00:00:00.000000000 +0000 @@ -1,62 +0,0 @@ -/* - * drivers/power/smp.c - Functions for stopping other CPUs. - * - * Copyright 2004 Pavel Machek <pavel@suse.cz> - * Copyright (C) 2002-2003 Nigel Cunningham <ncunningham@clear.net.nz> - * - * This file is released under the GPLv2. - */ - -#undef DEBUG - -#include <linux/smp_lock.h> -#include <linux/interrupt.h> -#include <linux/suspend.h> -#include <linux/module.h> -#include <linux/cpu.h> -#include <asm/atomic.h> -#include <asm/tlbflush.h> - -/* This is protected by pm_sem semaphore */ -static cpumask_t frozen_cpus; - -void disable_nonboot_cpus(void) -{ - int cpu, error; - - error = 0; - cpus_clear(frozen_cpus); - printk("Freezing cpus ...\n"); - for_each_online_cpu(cpu) { - if (cpu == 0) - continue; - error = cpu_down(cpu); - if (!error) { - cpu_set(cpu, frozen_cpus); - printk("CPU%d is down\n", cpu); - continue; - } - printk("Error taking cpu %d down: %d\n", cpu, error); - } - BUG_ON(raw_smp_processor_id() != 0); - if (error) - panic("cpus not sleeping"); -} - -void enable_nonboot_cpus(void) -{ - int cpu, error; - - printk("Thawing cpus ...\n"); - for_each_cpu_mask(cpu, frozen_cpus) { - error = cpu_up(cpu); - if (!error) { - printk("CPU%d is up\n", cpu); - continue; - } - printk("Error taking cpu %d up: %d\n", cpu, error); - panic("Not enough cpus"); - } - cpus_clear(frozen_cpus); -} - Index: linux-2.6.18-rc2/kernel/power/disk.c =================================================================== --- linux-2.6.18-rc2.orig/kernel/power/disk.c 2006-07-26 08:52:49.000000000 +0200 +++ linux-2.6.18-rc2/kernel/power/disk.c 2006-07-27 08:06:15.000000000 +0200 @@ -18,6 +18,7 @@ #include <linux/fs.h> #include <linux/mount.h> #include <linux/pm.h> +#include <linux/cpu.h> #include "power.h" @@ -72,7 +73,10 @@ static int prepare_processes(void) int error; pm_prepare_console(); - disable_nonboot_cpus(); + + error = disable_nonboot_cpus(); + if (error) + goto enable_cpus; if (freeze_processes()) { error = -EBUSY; @@ -84,6 +88,7 @@ static int prepare_processes(void) return 0; thaw: thaw_processes(); +enable_cpus: enable_nonboot_cpus(); pm_restore_console(); return error; Index: linux-2.6.18-rc2/kernel/power/main.c =================================================================== --- linux-2.6.18-rc2.orig/kernel/power/main.c 2006-07-26 08:52:42.000000000 +0200 +++ linux-2.6.18-rc2/kernel/power/main.c 2006-07-27 08:06:09.000000000 +0200 @@ -16,6 +16,7 @@ #include <linux/init.h> #include <linux/pm.h> #include <linux/console.h> +#include <linux/cpu.h> #include "power.h" @@ -51,7 +52,7 @@ void pm_set_ops(struct pm_ops * ops) static int suspend_prepare(suspend_state_t state) { - int error = 0; + int error; unsigned int free_pages; if (!pm_ops || !pm_ops->enter) @@ -59,12 +60,9 @@ static int suspend_prepare(suspend_state pm_prepare_console(); - disable_nonboot_cpus(); - - if (num_online_cpus() != 1) { - error = -EPERM; + error = disable_nonboot_cpus(); + if (error) goto Enable_cpu; - } if (freeze_processes()) { error = -EAGAIN; Index: linux-2.6.18-rc2/kernel/power/user.c =================================================================== --- linux-2.6.18-rc2.orig/kernel/power/user.c 2006-07-26 08:52:49.000000000 +0200 +++ linux-2.6.18-rc2/kernel/power/user.c 2006-07-27 08:05:56.000000000 +0200 @@ -19,6 +19,7 @@ #include <linux/swapops.h> #include <linux/pm.h> #include <linux/fs.h> +#include <linux/cpu.h> #include <asm/uaccess.h> @@ -139,12 +140,15 @@ static int snapshot_ioctl(struct inode * if (data->frozen) break; down(&pm_sem); - disable_nonboot_cpus(); - if (freeze_processes()) { - thaw_processes(); - enable_nonboot_cpus(); - error = -EBUSY; + error = disable_nonboot_cpus(); + if (!error) { + error = freeze_processes(); + if (error) { + thaw_processes(); + error = -EBUSY; + } } + enable_nonboot_cpus(); up(&pm_sem); if (!error) data->frozen = 1; Index: linux-2.6.18-rc2/include/linux/cpu.h =================================================================== --- linux-2.6.18-rc2.orig/include/linux/cpu.h 2006-07-16 11:38:15.000000000 +0200 +++ linux-2.6.18-rc2/include/linux/cpu.h 2006-07-27 08:05:35.000000000 +0200 @@ -95,4 +95,12 @@ int cpu_down(unsigned int cpu); static inline int cpu_is_offline(int cpu) { return 0; } #endif +#ifdef CONFIG_SUSPEND_SMP +extern int disable_nonboot_cpus(void); +extern void enable_nonboot_cpus(void); +#else +static inline int disable_nonboot_cpus(void) { return 0; } +static inline void enable_nonboot_cpus(void) {} +#endif + #endif /* _LINUX_CPU_H_ */ Index: linux-2.6.18-rc2/kernel/cpu.c =================================================================== --- linux-2.6.18-rc2.orig/kernel/cpu.c 2006-07-16 11:38:16.000000000 +0200 +++ linux-2.6.18-rc2/kernel/cpu.c 2006-07-27 08:15:35.000000000 +0200 @@ -20,6 +20,11 @@ static DEFINE_MUTEX(cpucontrol); static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain); +/* If set, cpu_up and cpu_down will return -EPERM and do nothing. + * Should always be manipulated with the cpucontrol mutex locked. + */ +static int cpu_hotplug_disabled; + #ifdef CONFIG_HOTPLUG_CPU static struct task_struct *lock_cpu_hotplug_owner; static int lock_cpu_hotplug_depth; @@ -116,32 +121,25 @@ static int take_cpu_down(void *unused) return 0; } -int cpu_down(unsigned int cpu) +/* Requires the cpucontrol mutex to be locked */ +static int __cpu_down(unsigned int cpu) { int err; struct task_struct *p; cpumask_t old_allowed, tmp; - if ((err = lock_cpu_hotplug_interruptible()) != 0) - return err; - - if (num_online_cpus() == 1) { - err = -EBUSY; - goto out; - } + if (num_online_cpus() == 1) + return -EBUSY; - if (!cpu_online(cpu)) { - err = -EINVAL; - goto out; - } + if (!cpu_online(cpu)) + return -EINVAL; err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE, (void *)(long)cpu); if (err == NOTIFY_BAD) { printk("%s: attempt to take down CPU %u failed\n", __FUNCTION__, cpu); - err = -EINVAL; - goto out; + return -EINVAL; } /* Ensure that we are not runnable on dying cpu */ @@ -186,7 +184,22 @@ out_thread: err = kthread_stop(p); out_allowed: set_cpus_allowed(current, old_allowed); -out: + return err; +} + +int cpu_down(unsigned int cpu) +{ + int err; + + err = lock_cpu_hotplug_interruptible(); + if (err) + return err; + + if (cpu_hotplug_disabled) + err = -EPERM; + else + err = __cpu_down(cpu); + unlock_cpu_hotplug(); return err; } @@ -200,6 +213,11 @@ int __devinit cpu_up(unsigned int cpu) if ((ret = lock_cpu_hotplug_interruptible()) != 0) return ret; + if (cpu_hotplug_disabled) { + ret = -EPERM; + goto out; + } + if (cpu_online(cpu) || !cpu_present(cpu)) { ret = -EINVAL; goto out; @@ -230,3 +248,64 @@ out: unlock_cpu_hotplug(); return ret; } + +#ifdef CONFIG_SUSPEND_SMP +static cpumask_t frozen_cpus; + +int disable_nonboot_cpus(void) +{ + int cpu, error = 0; + + /* We take down all of the non-boot CPUs in one shot to avoid races + * with the userspace trying to use the CPU hotplug at the same time + */ + lock_cpu_hotplug(); + cpus_clear(frozen_cpus); + printk("Disabling non-boot CPUs ...\n"); + for_each_online_cpu(cpu) { + if (cpu == 0) + continue; + error = __cpu_down(cpu); + if (!error) { + cpu_set(cpu, frozen_cpus); + printk("CPU%d is down\n", cpu); + } else { + printk(KERN_ERR "Error taking CPU%d down: %d\n", + cpu, error); + break; + } + } + if (!error) { + BUG_ON(num_online_cpus() > 1); + BUG_ON(raw_smp_processor_id() != 0); + /* Make sure the CPUs won't be enabled by someone else */ + cpu_hotplug_disabled = 1; + } else { + printk(KERN_ERR "Non-boot CPUs are not disabled"); + } + unlock_cpu_hotplug(); + return error; +} + +void enable_nonboot_cpus(void) +{ + int cpu, error; + + /* Allow everyone to use the CPU hotplug again */ + lock_cpu_hotplug(); + cpu_hotplug_disabled = 0; + unlock_cpu_hotplug(); + + printk("Enabling non-boot CPUs ...\n"); + for_each_cpu_mask(cpu, frozen_cpus) { + error = cpu_up(cpu); + if (!error) { + printk("CPU%d is up\n", cpu); + continue; + } + printk(KERN_WARNING "Error taking CPU%d up: %d\n", + cpu, error); + } + cpus_clear(frozen_cpus); +} +#endif Index: linux-2.6.18-rc2/kernel/power/Makefile =================================================================== --- linux-2.6.18-rc2.orig/kernel/power/Makefile 2006-06-18 03:49:35.000000000 +0200 +++ linux-2.6.18-rc2/kernel/power/Makefile 2006-07-27 08:07:28.000000000 +0200 @@ -7,6 +7,4 @@ obj-y := main.o process.o console.o obj-$(CONFIG_PM_LEGACY) += pm.o obj-$(CONFIG_SOFTWARE_SUSPEND) += swsusp.o disk.o snapshot.o swap.o user.o -obj-$(CONFIG_SUSPEND_SMP) += smp.o - obj-$(CONFIG_MAGIC_SYSRQ) += poweroff.o - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |