[PATCH] Disable CPU hotplug during suspend

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>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 8fb344a..3fef7d6 100644 (file)
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -89,4 +89,12 @@ 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_ */

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 96e31aa..6e8a06c 100644 (file)
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -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;

diff --git a/kernel/cpu.c b/kernel/cpu.c
index f230f9a..32c9662 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -21,6 +21,11 @@ static DEFINE_MUTEX(cpu_bitmask_lock);
 
 static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain);
 
+/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
+ * Should always be manipulated under cpu_add_remove_lock
+ */
+static int cpu_hotplug_disabled;
+
 #ifdef CONFIG_HOTPLUG_CPU
 
 /* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
@@ -108,30 +113,25 @@ static int take_cpu_down(void *unused)
        return 0;
 }
 
-int cpu_down(unsigned int cpu)
+/* Requires cpu_add_remove_lock to be held */
+static int _cpu_down(unsigned int cpu)
 {
        int err;
        struct task_struct *p;
        cpumask_t old_allowed, tmp;
 
-       mutex_lock(&cpu_add_remove_lock);
-       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 */
@@ -179,22 +179,32 @@ 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 = 0;
+
+       mutex_lock(&cpu_add_remove_lock);
+       if (cpu_hotplug_disabled)
+               err = -EBUSY;
+       else
+               err = _cpu_down(cpu);
+
        mutex_unlock(&cpu_add_remove_lock);
        return err;
 }
 #endif /*CONFIG_HOTPLUG_CPU*/
 
-int __devinit cpu_up(unsigned int cpu)
+/* Requires cpu_add_remove_lock to be held */
+static int __devinit _cpu_up(unsigned int cpu)
 {
        int ret;
        void *hcpu = (void *)(long)cpu;
 
-       mutex_lock(&cpu_add_remove_lock);
-       if (cpu_online(cpu) || !cpu_present(cpu)) {
-               ret = -EINVAL;
-               goto out;
-       }
+       if (cpu_online(cpu) || !cpu_present(cpu))
+               return -EINVAL;
 
        ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
        if (ret == NOTIFY_BAD) {
@@ -219,7 +229,95 @@ out_notify:
        if (ret != 0)
                blocking_notifier_call_chain(&cpu_chain,
                                CPU_UP_CANCELED, hcpu);
+
+       return ret;
+}
+
+int __devinit cpu_up(unsigned int cpu)
+{
+       int err = 0;
+
+       mutex_lock(&cpu_add_remove_lock);
+       if (cpu_hotplug_disabled)
+               err = -EBUSY;
+       else
+               err = _cpu_up(cpu);
+
+       mutex_unlock(&cpu_add_remove_lock);
+       return err;
+}
+
+#ifdef CONFIG_SUSPEND_SMP
+static cpumask_t frozen_cpus;
+
+int disable_nonboot_cpus(void)
+{
+       int cpu, first_cpu, error;
+
+       mutex_lock(&cpu_add_remove_lock);
+       first_cpu = first_cpu(cpu_present_map);
+       if (!cpu_online(first_cpu)) {
+               error = _cpu_up(first_cpu);
+               if (error) {
+                       printk(KERN_ERR "Could not bring CPU%d up.\n",
+                               first_cpu);
+                       goto out;
+               }
+       }
+       error = set_cpus_allowed(current, cpumask_of_cpu(first_cpu));
+       if (error) {
+               printk(KERN_ERR "Could not run on CPU%d\n", first_cpu);
+               goto out;
+       }
+       /* 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
+        */
+       cpus_clear(frozen_cpus);
+       printk("Disabling non-boot CPUs ...\n");
+       for_each_online_cpu(cpu) {
+               if (cpu == first_cpu)
+                       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);
+               /* 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");
+       }
 out:
        mutex_unlock(&cpu_add_remove_lock);
-       return ret;
+       return error;
+}
+
+void enable_nonboot_cpus(void)
+{
+       int cpu, error;
+
+       /* Allow everyone to use the CPU hotplug again */
+       mutex_lock(&cpu_add_remove_lock);
+       cpu_hotplug_disabled = 0;
+       mutex_unlock(&cpu_add_remove_lock);
+
+       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

diff --git a/kernel/power/Makefile b/kernel/power/Makefile
index 8d0af3d..38725f5 100644 (file)
--- a/kernel/power/Makefile
+++ b/kernel/power/Makefile
@@ -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

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index e13e740..7c7b9b6 100644 (file)
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -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;

diff --git a/kernel/power/main.c b/kernel/power/main.c
index 6d295c7..4d40332 100644 (file)
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -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_t 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;

diff --git a/kernel/power/smp.c b/kernel/power/smp.c
deleted file mode 100644 (file)
index 5957312..0000000
--- a/kernel/power/smp.c
+++ /dev/null
@@ -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);
-}
-

diff --git a/kernel/power/user.c b/kernel/power/user.c
index 3f1539f..0ef5e4b 100644 (file)
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -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 *inode, struct file *filp,
                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;