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Subject[PATCH 3/4] 2.6.2-rc2-mm2 CPU Hotplug: The Core
Date
The actual CPU patch.  It's big, but almost all under
CONFIG_HOTPLUG_CPU, or macros which have same effect.

Particularly interested in Nick's views here: I tried to catch all the
places where the new scheduler might pull tasks onto an offline cpu.

Name: Hotplug CPU Patch: -mm Version
Author: Almost Everyone on the lhcs List
Status: Experimental
Depends: Hotcpu/use-kthread-simple.patch.gz
Depends: Hotcpu/drain_local_pages.patch.gz
Depends: Hotcpu/kstat-notifier-removal.patch.gz
Depends: Hotcpu/cpucontrol_macros.patch.gz
Depends: Module/module_kthread.patch.gz
Depends: Hotcpu/cpu_prepare.patch.gz
Depends: Hotcpu/zero-initializer-notifier-removal.patch.gz
Depends: Hotcpu/workqueue-cleanup.patch.gz
Depends: Hotcpu/kmod-affinity.patch.gz
Version: -mm

D: This is the arch-indep hotplug cpu code, contributed by Matt
D: Fleming, Zwane Mwaikambo, Dipankar Sarma, Joel Schopp,
D: Vatsa Vaddagiri and me.
D:
D: Changes are designed to be NOOPs: usually by explicit use of
D: CONFIG_HOTPLUG_CPU
D:
D: The way CPUs go down is:
D: 1) Userspace writes 0 to sysfs ("online" attrib).
D: 2) The cpucontrol mutex is grabbed.
D: 3) The task moves onto the cpu.
D: 4) cpu_online(cpu) is set to false.
D: 5) Tasks are migrated, cpus_allowed broken if required (not kernel threads)
D: 6) We move back off the cpu.
D: 7) CPU_OFFLINE notifier is called for the cpu (kernel threads clean up).
D: 8) Arch-specific __cpu_die() is called.
D: 9) CPU_DEAD notifier is called (caches drained, etc).
D: 10) hotplug script is run
D: 11) cpucontrol mutex released.
D:
D: CPUs go up as before, except with CONFIG_HOTPLUG_CPU, they can go
D: up after boot.
D:
D: Changes are:
D: - drivers/base/cpu.c: Add an "online" attribute.
D:
D: - drivers/scsi/scsi.c: drain the scsi_done_q into current CPU on CPU_DEAD
D:
D: - fs/buffer.c: release buffer heads from bh_lrus on CPU_DEAD
D:
D: - linux/cpu.h: Add cpu_down(). Add hotcpu_notifier convenience macro.
D: Add cpu_is_offline() for when you know a cpu was (once) online: this
D: is a constant if !CONFIG_HOTPLUG_CPU.
D:
D: - linux/interrupt.h: Add tasklet_kill_immediate for RCU tasklet takedown
D: on dead CPU.
D:
D: - linux/mmzip.h: keep pointer to kswapd, in case we need to move it.
D:
D: - linux/sched.h: Add migrate_all_tasks() for cpu-down. Add migrate_to_cpu
D: for kernel threads to escape. Add wake_idle_cpu() for i386 hotplug code.
D:
D: - kernel/cpu.c: Take cpucontrol lock around notifiers: notifiers have
D: no locking themselves. Implement cpu_down() and code to call
D: sbin_hotplug.
D:
D: - kernel/kmod.c: As a bound kernel thread, take care of case where
D: thread is going down, before keventd() CPU_OFFLINE notifier can
D: return.
D:
D: - kernel/kthread.c: Same as kmod.c, take care of race where CPU goes
D: down and we didn't get migrated.
D:
D: - kernel/rcupdate.c: Move rcu batch when cpu dies.
D:
D: - kernel/sched.c: Add wake_idle_cpu() for i386 hotplug.
D:
D: Check everywhere to make sure we never move tasks onto an
D: offline cpu: we'll just be fighting migrate_all_tasks().
D:
D: Change sched_migrate_task() to migrate_to_cpu and expose it
D: for hotplug cpu.
D:
D: Take hotplug lock in sys_sched_setaffinity.
D:
D: Return cpus_allowed masked by cpu_possible_map, not
D: cpu_online_map in sys_sched_getaffinity, otherwise tasks can't
D: know about whether they can run on currently-offline cpus.
D:
D: Implement migrate_all_tasks() to push tasks off the dying cpu.
D:
D: Add callbacks to stop migration thread.
D:
D: - kernel/softirq.c:
D: Handle case where interrupt tries to kick softirqd after it has exited.
D:
D: Implement tasklet_kill_immediate for RCU.
D:
D: Code to shut down ksoftirqd, and take over dead cpu's tasklets.
D:
D: - kernel/timer.c:
D: Code to migrate timers off dead CPU.
D:
D: - kernel/workqueue.c:
D: Keep all workqueue is list, with their name: when cpus come up
D: we need to create new threads for each one.
D:
D: Lock cpu hotplug in flush_workqueue for simplicity.
D:
D: create_workqueue_thread doesn't need name arg, now in struct.
D:
D: Lock cpu hotplug when creating and destroying workqueues.
D:
D: cleanup_workqueue_thread needs to block irqs: can now be called
D: on live workqueues.
D:
D: Implement callbacks to add and delete threads, and take over work.
D:
D: - mm/page_alloc.c:
D: Drain local pages on CPU which is dead.
D:
D: - mm/slab.c:
D: Move free_block decl, ac_entry and ac_data earlier in file.
D:
D: Stop reap timer on as cpu goes offline.
D:
D: Neaten list_for_each into list_for_each_entry.
D:
D: Free cache blocks and correct stats one CPU is dead.
D:
D: Make reap_timer_fnc terminate if cpu goes offline.
D:
D: - mm/swap.c:
D: Fix up committed stats and drain lru cache when cpu dead.
D:
D: - mm/vmscan.c:
D: Keep kswapd on cpus within node unless all CPUs go offline, and
D: restore when they come back.
D:
D: Record kswapd tasks for each pgdat upon creation.
D:
D: - net/core/dev.c:
D: Drain skb queues to this cpu when another cpu is dead.
D:
D: - net/core/flow.c:
D: Call __flow_cache_shrink() to shrink cache to zero when CPU dead.

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/drivers/base/cpu.c .22517-linux-2.6.2-rc2-mm2.updated/drivers/base/cpu.c
--- .22517-linux-2.6.2-rc2-mm2/drivers/base/cpu.c 2003-10-26 14:52:48.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/drivers/base/cpu.c 2004-02-01 01:08:03.000000000 +1100
@@ -7,6 +7,7 @@
#include <linux/init.h>
#include <linux/cpu.h>
#include <linux/topology.h>
+#include <linux/device.h>


struct sysdev_class cpu_sysdev_class = {
@@ -14,6 +15,46 @@ struct sysdev_class cpu_sysdev_class = {
};
EXPORT_SYMBOL(cpu_sysdev_class);

+#ifdef CONFIG_HOTPLUG_CPU
+static ssize_t show_online(struct sys_device *dev, char *buf)
+{
+ struct cpu *cpu = container_of(dev, struct cpu, sysdev);
+
+ return sprintf(buf, "%u\n", !!cpu_online(cpu->sysdev.id));
+}
+
+static ssize_t store_online(struct sys_device *dev, const char *buf,
+ size_t count)
+{
+ struct cpu *cpu = container_of(dev, struct cpu, sysdev);
+ ssize_t ret;
+
+ switch (buf[0]) {
+ case '0':
+ ret = cpu_down(cpu->sysdev.id);
+ break;
+ case '1':
+ ret = cpu_up(cpu->sysdev.id);
+ break;
+ default:
+ ret = -EINVAL;
+ }
+
+ if (ret >= 0)
+ ret = count;
+ return ret;
+}
+static SYSDEV_ATTR(online, 0600, show_online, store_online);
+
+static void __init register_cpu_control(struct cpu *cpu)
+{
+ sysdev_create_file(&cpu->sysdev, &attr_online);
+}
+#else /* ... !CONFIG_HOTPLUG_CPU */
+static void __init register_cpu_control(struct cpu *cpu)
+{
+}
+#endif /* CONFIG_HOTPLUG_CPU */

/*
* register_cpu - Setup a driverfs device for a CPU.
@@ -34,6 +75,8 @@ int __init register_cpu(struct cpu *cpu,
error = sysfs_create_link(&root->sysdev.kobj,
&cpu->sysdev.kobj,
kobject_name(&cpu->sysdev.kobj));
+ if (!error)
+ register_cpu_control(cpu);
return error;
}

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/drivers/scsi/scsi.c .22517-linux-2.6.2-rc2-mm2.updated/drivers/scsi/scsi.c
--- .22517-linux-2.6.2-rc2-mm2/drivers/scsi/scsi.c 2004-01-31 17:28:10.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/drivers/scsi/scsi.c 2004-02-01 01:08:03.000000000 +1100
@@ -53,6 +53,8 @@
#include <linux/spinlock.h>
#include <linux/kmod.h>
#include <linux/interrupt.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>

#include <scsi/scsi_host.h>
#include "scsi.h"
@@ -1129,6 +1131,38 @@ int scsi_device_cancel(struct scsi_devic
return 0;
}

+#ifdef CONFIG_HOTPLUG_CPU
+static int scsi_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ int cpu = (unsigned long)hcpu;
+
+ switch(action) {
+ case CPU_DEAD:
+ /* Drain scsi_done_q. */
+ local_irq_disable();
+ list_splice_init(&per_cpu(scsi_done_q, cpu),
+ &__get_cpu_var(scsi_done_q));
+ raise_softirq_irqoff(SCSI_SOFTIRQ);
+ local_irq_enable();
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block __devinitdata scsi_cpu_nb = {
+ .notifier_call = scsi_cpu_notify,
+};
+
+#define register_scsi_cpu() register_cpu_notifier(&scsi_cpu_nb)
+#define unregister_scsi_cpu() unregister_cpu_notifier(&scsi_cpu_nb)
+#else
+#define register_scsi_cpu()
+#define unregister_scsi_cpu()
+#endif /* CONFIG_HOTPLUG_CPU */
+
MODULE_DESCRIPTION("SCSI core");
MODULE_LICENSE("GPL");

@@ -1163,6 +1197,7 @@ static int __init init_scsi(void)

devfs_mk_dir("scsi");
open_softirq(SCSI_SOFTIRQ, scsi_softirq, NULL);
+ register_scsi_cpu();
printk(KERN_NOTICE "SCSI subsystem initialized\n");
return 0;

@@ -1190,6 +1225,7 @@ static void __exit exit_scsi(void)
devfs_remove("scsi");
scsi_exit_procfs();
scsi_exit_queue();
+ unregister_scsi_cpu();
}

subsys_initcall(init_scsi);
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/fs/buffer.c .22517-linux-2.6.2-rc2-mm2.updated/fs/buffer.c
--- .22517-linux-2.6.2-rc2-mm2/fs/buffer.c 2004-01-31 17:28:12.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/fs/buffer.c 2004-02-01 01:08:03.000000000 +1100
@@ -2991,6 +2991,26 @@ init_buffer_head(void *data, kmem_cache_
}
}

+#ifdef CONFIG_HOTPLUG_CPU
+static void buffer_exit_cpu(int cpu)
+{
+ int i;
+ struct bh_lru *b = &per_cpu(bh_lrus, cpu);
+
+ for (i = 0; i < BH_LRU_SIZE; i++) {
+ brelse(b->bhs[i]);
+ b->bhs[i] = NULL;
+ }
+}
+
+static int buffer_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ if (action == CPU_DEAD)
+ buffer_exit_cpu((unsigned long)hcpu);
+ return NOTIFY_OK;
+}
+#endif /* CONFIG_HOTPLUG_CPU */

void __init buffer_init(void)
{
@@ -3008,6 +3028,7 @@ void __init buffer_init(void)
*/
nrpages = (nr_free_buffer_pages() * 10) / 100;
max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
+ hotcpu_notifier(buffer_cpu_notify, 0);
}

EXPORT_SYMBOL(__bforget);
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/include/linux/cpu.h .22517-linux-2.6.2-rc2-mm2.updated/include/linux/cpu.h
--- .22517-linux-2.6.2-rc2-mm2/include/linux/cpu.h 2004-01-31 17:28:19.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/include/linux/cpu.h 2004-02-01 01:08:03.000000000 +1100
@@ -21,6 +21,8 @@

#include <linux/sysdev.h>
#include <linux/node.h>
+#include <linux/compiler.h>
+#include <linux/cpumask.h>
#include <asm/semaphore.h>

struct cpu {
@@ -56,9 +58,19 @@ extern struct sysdev_class cpu_sysdev_cl
extern struct semaphore cpucontrol;
#define lock_cpu_hotplug() down(&cpucontrol)
#define unlock_cpu_hotplug() up(&cpucontrol)
+int cpu_down(unsigned int cpu);
+#define hotcpu_notifier(fn, pri) { \
+ static struct notifier_block fn##_nb = { fn, pri }; \
+ register_cpu_notifier(&fn##_nb); \
+}
+#define cpu_is_offline(cpu) unlikely(!cpu_online(cpu))
#else
#define lock_cpu_hotplug() do { } while (0)
#define unlock_cpu_hotplug() do { } while (0)
+#define hotcpu_notifier(fn, pri)
+
+/* CPUs don't go offline once they're online w/o CONFIG_HOTPLUG_CPU */
+#define cpu_is_offline(cpu) 0
#endif

#endif /* _LINUX_CPU_H_ */
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/include/linux/interrupt.h .22517-linux-2.6.2-rc2-mm2.updated/include/linux/interrupt.h
--- .22517-linux-2.6.2-rc2-mm2/include/linux/interrupt.h 2003-09-29 10:26:04.000000000 +1000
+++ .22517-linux-2.6.2-rc2-mm2.updated/include/linux/interrupt.h 2004-02-01 01:08:03.000000000 +1100
@@ -211,6 +211,7 @@ static inline void tasklet_hi_enable(str
}

extern void tasklet_kill(struct tasklet_struct *t);
+extern void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu);
extern void tasklet_init(struct tasklet_struct *t,
void (*func)(unsigned long), unsigned long data);

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/include/linux/mmzone.h .22517-linux-2.6.2-rc2-mm2.updated/include/linux/mmzone.h
--- .22517-linux-2.6.2-rc2-mm2/include/linux/mmzone.h 2004-01-31 17:28:19.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/include/linux/mmzone.h 2004-02-01 01:08:03.000000000 +1100
@@ -213,6 +213,7 @@ typedef struct pglist_data {
int node_id;
struct pglist_data *pgdat_next;
wait_queue_head_t kswapd_wait;
+ struct task_struct *kswapd;
} pg_data_t;

#define node_present_pages(nid) (NODE_DATA(nid)->node_present_pages)
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/include/linux/sched.h .22517-linux-2.6.2-rc2-mm2.updated/include/linux/sched.h
--- .22517-linux-2.6.2-rc2-mm2/include/linux/sched.h 2004-01-31 17:28:19.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/include/linux/sched.h 2004-02-01 01:08:03.000000000 +1100
@@ -634,6 +634,10 @@ extern void sched_balance_exec(void);
#define sched_balance_exec() {}
#endif

+/* Move tasks off this (offline) CPU onto another. */
+extern void migrate_all_tasks(void);
+/* Try to move me here, if possible. */
+void migrate_to_cpu(int dest_cpu);
extern void set_user_nice(task_t *p, long nice);
extern int task_prio(task_t *p);
extern int task_nice(task_t *p);
@@ -1010,6 +1014,8 @@ static inline void set_task_cpu(struct t
p->thread_info->cpu = cpu;
}

+/* Wake up a CPU from idle */
+void wake_idle_cpu(unsigned int cpu);
#else

static inline unsigned int task_cpu(struct task_struct *p)
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/kernel/cpu.c .22517-linux-2.6.2-rc2-mm2.updated/kernel/cpu.c
--- .22517-linux-2.6.2-rc2-mm2/kernel/cpu.c 2004-01-31 17:28:20.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/kernel/cpu.c 2004-02-01 01:08:03.000000000 +1100
@@ -1,14 +1,17 @@
/* CPU control.
- * (C) 2001 Rusty Russell
+ * (C) 2001, 2002, 2003, 2004 Rusty Russell
+ *
* This code is licenced under the GPL.
*/
#include <linux/proc_fs.h>
#include <linux/smp.h>
#include <linux/init.h>
-#include <linux/notifier.h>
#include <linux/sched.h>
#include <linux/unistd.h>
+#include <linux/kmod.h> /* for hotplug_path */
#include <linux/cpu.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
#include <asm/semaphore.h>

/* This protects CPUs going up and down... */
@@ -19,14 +22,150 @@ static struct notifier_block *cpu_chain;
/* Need to know about CPUs going up/down? */
int register_cpu_notifier(struct notifier_block *nb)
{
- return notifier_chain_register(&cpu_chain, nb);
+ int ret;
+
+ if ((ret = down_interruptible(&cpucontrol)) != 0)
+ return ret;
+ ret = notifier_chain_register(&cpu_chain, nb);
+ up(&cpucontrol);
+ return ret;
}
+EXPORT_SYMBOL(register_cpu_notifier);

void unregister_cpu_notifier(struct notifier_block *nb)
{
- notifier_chain_unregister(&cpu_chain,nb);
+ down(&cpucontrol);
+ notifier_chain_unregister(&cpu_chain, nb);
+ up(&cpucontrol);
+}
+EXPORT_SYMBOL(unregister_cpu_notifier);
+
+#ifdef CONFIG_HOTPLUG_CPU
+static inline void check_for_tasks(int cpu)
+{
+ struct task_struct *p;
+
+ write_lock_irq(&tasklist_lock);
+ for_each_process(p) {
+ if (task_cpu(p) == cpu)
+ printk(KERN_WARNING "Task %s is on cpu %d, "
+ "not dying\n", p->comm, cpu);
+ }
+ write_unlock_irq(&tasklist_lock);
+}
+
+/* Notify userspace when a cpu event occurs, by running '/sbin/hotplug
+ * cpu' with certain environment variables set. */
+static int cpu_run_sbin_hotplug(unsigned int cpu, const char *action)
+{
+ char *argv[3], *envp[5], cpu_str[12], action_str[32];
+ int i;
+
+ sprintf(cpu_str, "CPU=%d", cpu);
+ sprintf(action_str, "ACTION=%s", action);
+ /* FIXME: Add DEVPATH. --RR */
+
+ i = 0;
+ argv[i++] = hotplug_path;
+ argv[i++] = "cpu";
+ argv[i] = NULL;
+
+ i = 0;
+ /* minimal command environment */
+ envp [i++] = "HOME=/";
+ envp [i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
+ envp [i++] = cpu_str;
+ envp [i++] = action_str;
+ envp [i] = NULL;
+
+ return call_usermodehelper(argv[0], argv, envp, 0);
+}
+
+static inline int cpu_down_check(unsigned int cpu, cpumask_t mask)
+{
+ if (!cpu_online(cpu))
+ return -EINVAL;
+
+ cpu_clear(cpu, mask);
+ if (any_online_cpu(mask) == NR_CPUS)
+ return -EBUSY;
+
+ return 0;
}

+static inline int cpu_disable(int cpu)
+{
+ int ret;
+
+ ret = __cpu_disable();
+ if (ret < 0)
+ return ret;
+
+ /* Everyone looking at cpu_online() should be doing so with
+ * preemption disabled. */
+ synchronize_kernel();
+ BUG_ON(cpu_online(cpu));
+ return 0;
+}
+
+int cpu_down(unsigned int cpu)
+{
+ int err, rc;
+ void *vcpu = (void *)(long)cpu;
+ cpumask_t oldmask, mask;
+
+ if ((err = down_interruptible(&cpucontrol)) != 0)
+ return err;
+
+ /* There has to be another cpu for this task. */
+ oldmask = current->cpus_allowed;
+ if ((err = cpu_down_check(cpu, oldmask)) != 0)
+ goto out;
+
+ /* Schedule ourselves on the dying CPU. */
+ set_cpus_allowed(current, cpumask_of_cpu(cpu));
+
+ if ((err = cpu_disable(cpu)) != 0)
+ goto out_allowed;
+
+ /* Move other tasks off to other CPUs (simple since they are
+ not running now). */
+ migrate_all_tasks();
+
+ /* Move off dying CPU, which will revert to idle process. */
+ cpus_clear(mask);
+ cpus_complement(mask);
+ cpu_clear(cpu, mask);
+ set_cpus_allowed(current, mask);
+
+ /* Tell kernel threads to go away: they can't fail here. */
+ rc = notifier_call_chain(&cpu_chain, CPU_OFFLINE, vcpu);
+ BUG_ON(rc == NOTIFY_BAD);
+
+ check_for_tasks(cpu);
+
+ /* This actually kills the CPU. */
+ __cpu_die(cpu);
+
+ /* CPU is completely dead: tell everyone. Too late to complain. */
+ rc = notifier_call_chain(&cpu_chain, CPU_DEAD, vcpu);
+ BUG_ON(rc == NOTIFY_BAD);
+
+ cpu_run_sbin_hotplug(cpu, "offline");
+
+ out_allowed:
+ set_cpus_allowed(current, oldmask);
+ out:
+ up(&cpucontrol);
+ return err;
+}
+#else
+static inline int cpu_run_sbin_hotplug(unsigned int cpu, const char *action)
+{
+ return 0;
+}
+#endif /*CONFIG_HOTPLUG_CPU*/
+
int __devinit cpu_up(unsigned int cpu)
{
int ret;
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/kernel/kmod.c .22517-linux-2.6.2-rc2-mm2.updated/kernel/kmod.c
--- .22517-linux-2.6.2-rc2-mm2/kernel/kmod.c 2004-01-31 17:28:20.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/kernel/kmod.c 2004-02-01 01:08:03.000000000 +1100
@@ -34,6 +34,7 @@
#include <linux/security.h>
#include <linux/mount.h>
#include <linux/kernel.h>
+#include <linux/cpu.h>
#include <asm/uaccess.h>

extern int max_threads;
@@ -170,6 +171,12 @@ static int ____call_usermodehelper(void

/* We can run anywhere, unlike our parent keventd(). */
set_cpus_allowed(current, CPU_MASK_ALL);
+ /* As a kernel thread which was bound to a specific cpu,
+ migrate_all_tasks wouldn't touch us. Avoid running child
+ on dying CPU. */
+ if (cpu_is_offline(smp_processor_id()))
+ migrate_to_cpu(any_online_cpu(CPU_MASK_ALL));
+
retval = -EPERM;
if (current->fs->root)
retval = execve(sub_info->path, sub_info->argv,sub_info->envp);
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/kernel/kthread.c .22517-linux-2.6.2-rc2-mm2.updated/kernel/kthread.c
--- .22517-linux-2.6.2-rc2-mm2/kernel/kthread.c 2004-01-31 17:28:20.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/kernel/kthread.c 2004-02-01 01:08:03.000000000 +1100
@@ -12,6 +12,7 @@
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/unistd.h>
+#include <linux/cpu.h>
#include <asm/semaphore.h>

struct kthread_create_info
@@ -39,7 +40,7 @@ static int kthread(void *_create)
threadfn = create->threadfn;
data = create->data;

- /* Block and flush all signals (in case we're not from keventd). */
+ /* Block and flush all signals. */
sigfillset(&blocked);
sigprocmask(SIG_BLOCK, &blocked, NULL);
flush_signals(current);
@@ -47,6 +48,12 @@ static int kthread(void *_create)
/* By default we can run anywhere, unlike keventd. */
set_cpus_allowed(current, CPU_MASK_ALL);

+ /* As a kernel thread which was bound to a specific cpu,
+ migrate_all_tasks wouldn't touch us. Avoid running on
+ dying CPU. */
+ if (cpu_is_offline(smp_processor_id()))
+ migrate_to_cpu(any_online_cpu(CPU_MASK_ALL));
+
/* OK, tell user we're spawned, wait for stop or wakeup */
__set_current_state(TASK_INTERRUPTIBLE);
complete(&create->started);
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/kernel/rcupdate.c .22517-linux-2.6.2-rc2-mm2.updated/kernel/rcupdate.c
--- .22517-linux-2.6.2-rc2-mm2/kernel/rcupdate.c 2003-10-09 18:03:02.000000000 +1000
+++ .22517-linux-2.6.2-rc2-mm2.updated/kernel/rcupdate.c 2004-02-01 01:08:03.000000000 +1100
@@ -154,6 +154,60 @@ out_unlock:
}


+#ifdef CONFIG_HOTPLUG_CPU
+
+/* warning! helper for rcu_offline_cpu. do not use elsewhere without reviewing
+ * locking requirements, the list it's pulling from has to belong to a cpu
+ * which is dead and hence not processing interrupts.
+ */
+static void rcu_move_batch(struct list_head *list)
+{
+ struct list_head *entry;
+ int cpu = smp_processor_id();
+
+ local_irq_disable();
+ while (!list_empty(list)) {
+ entry = list->next;
+ list_del(entry);
+ list_add_tail(entry, &RCU_nxtlist(cpu));
+ }
+ local_irq_enable();
+}
+
+static void rcu_offline_cpu(int cpu)
+{
+ /* if the cpu going offline owns the grace period
+ * we can block indefinitely waiting for it, so flush
+ * it here
+ */
+ spin_lock_irq(&rcu_ctrlblk.mutex);
+ if (!rcu_ctrlblk.rcu_cpu_mask)
+ goto unlock;
+
+ cpu_clear(cpu, rcu_ctrlblk.rcu_cpu_mask);
+ if (cpus_empty(rcu_ctrlblk.rcu_cpu_mask)) {
+ rcu_ctrlblk.curbatch++;
+ /* We may avoid calling start batch if
+ * we are starting the batch only
+ * because of the DEAD CPU (the current
+ * CPU will start a new batch anyway for
+ * the callbacks we will move to current CPU).
+ * However, we will avoid this optimisation
+ * for now.
+ */
+ rcu_start_batch(rcu_ctrlblk.maxbatch);
+ }
+unlock:
+ spin_unlock_irq(&rcu_ctrlblk.mutex);
+
+ rcu_move_batch(&RCU_curlist(cpu));
+ rcu_move_batch(&RCU_nxtlist(cpu));
+
+ tasklet_kill_immediate(&RCU_tasklet(cpu), cpu);
+}
+
+#endif
+
/*
* This does the RCU processing work from tasklet context.
*/
@@ -214,7 +268,11 @@ static int __devinit rcu_cpu_notify(stru
case CPU_UP_PREPARE:
rcu_online_cpu(cpu);
break;
- /* Space reserved for CPU_OFFLINE :) */
+#ifdef CONFIG_HOTPLUG_CPU
+ case CPU_DEAD:
+ rcu_offline_cpu(cpu);
+ break;
+#endif
default:
break;
}
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/kernel/sched.c .22517-linux-2.6.2-rc2-mm2.updated/kernel/sched.c
--- .22517-linux-2.6.2-rc2-mm2/kernel/sched.c 2004-01-31 17:28:20.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/kernel/sched.c 2004-02-01 01:08:03.000000000 +1100
@@ -508,6 +508,12 @@ static inline void resched_task(task_t *
#endif
}

+/* Wake up a CPU from idle */
+void wake_idle_cpu(unsigned int cpu)
+{
+ resched_task(cpu_rq(cpu)->idle);
+}
+
/**
* task_curr - is this task currently executing on a CPU?
* @p: the task in question.
@@ -723,7 +729,8 @@ static int try_to_wake_up(task_t * p, un
goto out_activate;

if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)
- || task_running(rq, p)))
+ || task_running(rq, p)
+ || cpu_is_offline(this_cpu)))
goto out_activate;

/* Passive load balancing */
@@ -1112,25 +1119,21 @@ enum idle_type
};

#ifdef CONFIG_SMP
-#ifdef CONFIG_NUMA
-/*
- * If dest_cpu is allowed for this process, migrate the task to it.
- * This is accomplished by forcing the cpu_allowed mask to only
- * allow dest_cpu, which will force the cpu onto dest_cpu. Then
- * the cpu_allowed mask is restored.
- */
-static void sched_migrate_task(task_t *p, int dest_cpu)
+
+#if defined(CONFIG_NUMA) || defined(CONFIG_HOTPLUG_CPU)
+/* If dest_cpu is allowed for this process, migrate us to it. */
+void migrate_to_cpu(int dest_cpu)
{
runqueue_t *rq;
migration_req_t req;
unsigned long flags;

- rq = task_rq_lock(p, &flags);
- if (!cpu_isset(dest_cpu, p->cpus_allowed))
+ rq = task_rq_lock(current, &flags);
+ if (!cpu_isset(dest_cpu, current->cpus_allowed))
goto out;

/* force the process onto the specified CPU */
- if (migrate_task(p, dest_cpu, &req)) {
+ if (migrate_task(current, dest_cpu, &req)) {
/* Need to wait for migration thread. */
task_rq_unlock(rq, &flags);
wake_up_process(rq->migration_thread);
@@ -1140,7 +1143,9 @@ static void sched_migrate_task(task_t *p
out:
task_rq_unlock(rq, &flags);
}
+#endif /* CONFIG_NUMA || CONFIG_HOTPLUG_CPU */

+#ifdef CONFIG_NUMA
/*
* Find the least loaded CPU. Slightly favor the current CPU by
* setting its runqueue length as the minimum to start.
@@ -1185,7 +1190,7 @@ void sched_balance_exec(void)
if (domain->flags & SD_FLAG_EXEC) {
new_cpu = sched_best_cpu(current, domain);
if (new_cpu != this_cpu)
- sched_migrate_task(current, new_cpu);
+ migrate_task_to_cpu(current, new_cpu);
}
}
#endif /* CONFIG_NUMA */
@@ -1597,6 +1602,10 @@ static inline void idle_balance(int this
{
struct sched_domain *domain = this_sched_domain();

+ /* CPU going down is a special case: we don't pull more tasks here */
+ if (cpu_is_offline(this_cpu))
+ return;
+
do {
if (unlikely(!domain->groups))
/* hasn't been setup yet */
@@ -1701,6 +1710,10 @@ static void rebalance_tick(int this_cpu,
unsigned long j = jiffies + CPU_OFFSET(this_cpu);
struct sched_domain *domain = this_sched_domain();

+ /* CPU going down is a special case: we don't pull more tasks here */
+ if (cpu_is_offline(this_cpu))
+ return;
+
/* Run through all this CPU's domains */
do {
unsigned long interval;
@@ -2623,11 +2636,13 @@ asmlinkage long sys_sched_setaffinity(pi
if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
return -EFAULT;

+ lock_cpu_hotplug();
read_lock(&tasklist_lock);

p = find_process_by_pid(pid);
if (!p) {
read_unlock(&tasklist_lock);
+ unlock_cpu_hotplug();
return -ESRCH;
}

@@ -2648,6 +2663,7 @@ asmlinkage long sys_sched_setaffinity(pi

out_unlock:
put_task_struct(p);
+ unlock_cpu_hotplug();
return retval;
}

@@ -2677,7 +2693,7 @@ asmlinkage long sys_sched_getaffinity(pi
goto out_unlock;

retval = 0;
- cpus_and(mask, p->cpus_allowed, cpu_online_map);
+ cpus_and(mask, p->cpus_allowed, cpu_possible_map);

out_unlock:
read_unlock(&tasklist_lock);
@@ -3058,6 +3074,9 @@ static void __migrate_task(struct task_s
/* Affinity changed (again). */
if (!cpu_isset(dest_cpu, p->cpus_allowed))
goto out;
+ /* CPU went down. */
+ if (cpu_is_offline(dest_cpu))
+ goto out;

set_task_cpu(p, dest_cpu);
if (p->array) {
@@ -3123,6 +3142,72 @@ static int migration_thread(void * data)
return 0;
}

+#ifdef CONFIG_HOTPLUG_CPU
+/* migrate_all_tasks - function to migrate all the tasks from the
+ * current cpu caller must have already scheduled this to the target
+ * cpu via set_cpus_allowed */
+void migrate_all_tasks(void)
+{
+ struct task_struct *tsk, *t;
+ int dest_cpu, src_cpu;
+ unsigned int node;
+
+ /* We're nailed to this CPU. */
+ src_cpu = smp_processor_id();
+
+ /* lock out everyone else intentionally */
+ write_lock_irq(&tasklist_lock);
+
+ /* watch out for per node tasks, let's stay on this node */
+ node = cpu_to_node(src_cpu);
+
+ do_each_thread(t, tsk) {
+ cpumask_t mask;
+ if (tsk == current)
+ continue;
+
+ if (task_cpu(tsk) != src_cpu)
+ continue;
+
+ /* Figure out where this task should go (attempting to
+ * keep it on-node), and check if it can be migrated
+ * as-is. NOTE that kernel threads bound to more than
+ * one online cpu will be migrated. */
+ mask = node_to_cpumask(node);
+ cpus_and(mask, mask, tsk->cpus_allowed);
+ dest_cpu = any_online_cpu(mask);
+ if (dest_cpu == NR_CPUS)
+ dest_cpu = any_online_cpu(tsk->cpus_allowed);
+ if (dest_cpu == NR_CPUS) {
+ /* Kernel threads which are bound to specific
+ * processors need to look after themselves
+ * with their own callbacks. Exiting tasks
+ * can have mm NULL too. */
+ if (tsk->mm == NULL && !(tsk->flags & PF_EXITING))
+ continue;
+
+ cpus_clear(tsk->cpus_allowed);
+ cpus_complement(tsk->cpus_allowed);
+ dest_cpu = any_online_cpu(tsk->cpus_allowed);
+
+ /* Don't tell them about moving exiting tasks,
+ since they never leave kernel. */
+ if (!(tsk->flags & PF_EXITING)
+ && printk_ratelimit())
+ printk(KERN_INFO "process %d (%s) no "
+ "longer affine to cpu%d\n",
+ tsk->pid, tsk->comm, src_cpu);
+ }
+
+ get_task_struct(tsk);
+ __migrate_task(tsk, dest_cpu);
+ put_task_struct(tsk);
+ } while_each_thread(t, tsk);
+
+ write_unlock_irq(&tasklist_lock);
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
/*
* migration_call - callback that gets triggered when a CPU is added.
* Here we can start up the necessary migration thread for the new CPU.
@@ -3145,14 +3230,26 @@ static int migration_call(struct notifie
/* Strictly unneccessary, as first user will wake it. */
wake_up_process(cpu_rq(cpu)->migration_thread);
break;
+#ifdef CONFIG_HOTPLUG_CPU
+ case CPU_UP_CANCELED:
+ /* Unbind it from offline cpu so it can run. Fall thru. */
+ kthread_bind(cpu_rq(cpu)->migration_thread,smp_processor_id());
+ case CPU_OFFLINE:
+ kthread_stop(cpu_rq(cpu)->migration_thread);
+ cpu_rq(cpu)->migration_thread = NULL;
+ break;
+
+ case CPU_DEAD:
+ BUG_ON(cpu_rq(cpu)->nr_running != 0);
+ break;
+#endif
}
return NOTIFY_OK;
}

-/*
- * We want this after the other threads, so they can use set_cpus_allowed
- * from their CPU_OFFLINE callback
- */
+/* Want this after the other threads, so they can use set_cpus_allowed
+ * from their CPU_OFFLINE callback, and also so everyone is off
+ * runqueue so we know it's empty. */
static struct notifier_block __devinitdata migration_notifier = {
.notifier_call = migration_call,
.priority = -10,
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/kernel/softirq.c .22517-linux-2.6.2-rc2-mm2.updated/kernel/softirq.c
--- .22517-linux-2.6.2-rc2-mm2/kernel/softirq.c 2004-01-31 17:28:20.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/kernel/softirq.c 2004-02-01 01:08:03.000000000 +1100
@@ -104,7 +104,11 @@ restart:
local_irq_disable();

pending = local_softirq_pending();
- if (pending && --max_restart)
+ /*
+ * If ksoftirqd is dead transiently during cpu offlining
+ * continue to process from interrupt context.
+ */
+ if (pending && (--max_restart || !__get_cpu_var(ksoftirqd)))
goto restart;
if (pending)
wakeup_softirqd();
@@ -344,6 +348,58 @@ static int ksoftirqd(void * __bind_cpu)
return 0;
}

+#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * tasklet_kill_immediate is called to remove a tasklet which can already be
+ * scheduled for execution on @cpu.
+ *
+ * Unlike tasklet_kill, this function removes the tasklet
+ * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
+ *
+ * When this function is called, @cpu must be in the CPU_DEAD state.
+ */
+void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
+{
+ struct tasklet_struct **i;
+
+ BUG_ON(cpu_online(cpu));
+ BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));
+
+ if (!test_bit(TASKLET_STATE_SCHED, &t->state))
+ return;
+
+ /* CPU is dead, so no lock needed. */
+ for (i = &per_cpu(tasklet_vec, cpu).list; *i; i = &(*i)->next) {
+ if (*i == t) {
+ *i = t->next;
+ return;
+ }
+ }
+ BUG();
+}
+
+static void takeover_tasklets(unsigned int cpu)
+{
+ struct tasklet_struct **i;
+
+ /* CPU is dead, so no lock needed. */
+ local_irq_disable();
+
+ /* Find end, append list for that CPU. */
+ for (i = &__get_cpu_var(tasklet_vec).list; *i; i = &(*i)->next);
+ *i = per_cpu(tasklet_vec, cpu).list;
+ per_cpu(tasklet_vec, cpu).list = NULL;
+ raise_softirq_irqoff(TASKLET_SOFTIRQ);
+
+ for (i = &__get_cpu_var(tasklet_hi_vec).list; *i; i = &(*i)->next);
+ *i = per_cpu(tasklet_hi_vec, cpu).list;
+ per_cpu(tasklet_hi_vec, cpu).list = NULL;
+ raise_softirq_irqoff(HI_SOFTIRQ);
+
+ local_irq_enable();
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
static int __devinit cpu_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
@@ -367,6 +423,21 @@ static int __devinit cpu_callback(struct
case CPU_ONLINE:
wake_up_process(per_cpu(ksoftirqd, hotcpu));
break;
+#ifdef CONFIG_HOTPLUG_CPU
+ case CPU_UP_CANCELED:
+ /* Unbind so it can run. Fall thru. */
+ kthread_bind(per_cpu(ksoftirqd, hotcpu), smp_processor_id());
+ case CPU_OFFLINE:
+ p = per_cpu(ksoftirqd, hotcpu);
+ per_cpu(ksoftirqd, hotcpu) = NULL;
+ /* Must set to NULL before interrupt tries to wake it */
+ barrier();
+ kthread_stop(p);
+ break;
+ case CPU_DEAD:
+ takeover_tasklets(hotcpu);
+ break;
+#endif /* CONFIG_HOTPLUG_CPU */
}
return NOTIFY_OK;
}
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/kernel/timer.c .22517-linux-2.6.2-rc2-mm2.updated/kernel/timer.c
--- .22517-linux-2.6.2-rc2-mm2/kernel/timer.c 2004-01-26 16:15:09.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/kernel/timer.c 2004-02-01 01:08:03.000000000 +1100
@@ -1223,7 +1223,74 @@ static void __devinit init_timers_cpu(in

base->timer_jiffies = jiffies;
}
-
+
+#ifdef CONFIG_HOTPLUG_CPU
+static int migrate_timer_list(tvec_base_t *new_base, struct list_head *head)
+{
+ struct timer_list *timer;
+
+ while (!list_empty(head)) {
+ timer = list_entry(head->next, struct timer_list, entry);
+ /* We're locking backwards from __mod_timer order here,
+ beware deadlock. */
+ if (!spin_trylock(&timer->lock))
+ return 0;
+ list_del(&timer->entry);
+ internal_add_timer(new_base, timer);
+ timer->base = new_base;
+ spin_unlock(&timer->lock);
+ }
+ return 1;
+}
+
+static void __devinit migrate_timers(int cpu)
+{
+ tvec_base_t *old_base;
+ tvec_base_t *new_base;
+ int i;
+
+ BUG_ON(cpu_online(cpu));
+ old_base = &per_cpu(tvec_bases, cpu);
+ new_base = &get_cpu_var(tvec_bases);
+ printk("migrate_timers: offlined base %p\n", old_base);
+
+ local_irq_disable();
+again:
+ /* Prevent deadlocks via ordering by old_base < new_base. */
+ if (old_base < new_base) {
+ spin_lock(&new_base->lock);
+ spin_lock(&old_base->lock);
+ } else {
+ spin_lock(&old_base->lock);
+ spin_lock(&new_base->lock);
+ }
+
+ if (old_base->running_timer)
+ BUG();
+ for (i = 0; i < TVR_SIZE; i++)
+ if (!migrate_timer_list(new_base, old_base->tv1.vec + i))
+ goto unlock_again;
+ for (i = 0; i < TVN_SIZE; i++)
+ if (!migrate_timer_list(new_base, old_base->tv2.vec + i)
+ || !migrate_timer_list(new_base, old_base->tv3.vec + i)
+ || !migrate_timer_list(new_base, old_base->tv4.vec + i)
+ || !migrate_timer_list(new_base, old_base->tv5.vec + i))
+ goto unlock_again;
+ spin_unlock(&old_base->lock);
+ spin_unlock(&new_base->lock);
+ local_irq_enable();
+ put_cpu_var(tvec_bases);
+ return;
+
+unlock_again:
+ /* Avoid deadlock with __mod_timer, by backing off. */
+ spin_unlock(&old_base->lock);
+ spin_unlock(&new_base->lock);
+ cpu_relax();
+ goto again;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
static int __devinit timer_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
@@ -1232,6 +1299,11 @@ static int __devinit timer_cpu_notify(st
case CPU_UP_PREPARE:
init_timers_cpu(cpu);
break;
+#ifdef CONFIG_HOTPLUG_CPU
+ case CPU_DEAD:
+ migrate_timers(cpu);
+ break;
+#endif
default:
break;
}
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/kernel/workqueue.c .22517-linux-2.6.2-rc2-mm2.updated/kernel/workqueue.c
--- .22517-linux-2.6.2-rc2-mm2/kernel/workqueue.c 2004-01-31 17:28:20.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/kernel/workqueue.c 2004-02-01 01:08:03.000000000 +1100
@@ -22,6 +22,8 @@
#include <linux/completion.h>
#include <linux/workqueue.h>
#include <linux/slab.h>
+#include <linux/cpu.h>
+#include <linux/notifier.h>
#include <linux/kthread.h>

/*
@@ -55,8 +57,22 @@ struct cpu_workqueue_struct {
*/
struct workqueue_struct {
struct cpu_workqueue_struct cpu_wq[NR_CPUS];
+ const char *name;
+ struct list_head list;
};

+#ifdef CONFIG_HOTPLUG_CPU
+/* All the workqueues on the system, for hotplug cpu to add/remove
+ threads to each one as cpus come/go. Protected by cpucontrol
+ sem. */
+static LIST_HEAD(workqueues);
+#define add_workqueue(wq) list_add(&(wq)->list, &workqueues)
+#define del_workqueue(wq) list_del(&(wq)->list)
+#else
+#define add_workqueue(wq)
+#define del_workqueue(wq)
+#endif /* CONFIG_HOTPLUG_CPU */
+
/* Preempt must be disabled. */
static void __queue_work(struct cpu_workqueue_struct *cwq,
struct work_struct *work)
@@ -210,6 +226,7 @@ void flush_workqueue(struct workqueue_st

might_sleep();

+ lock_cpu_hotplug();
for (cpu = 0; cpu < NR_CPUS; cpu++) {
DEFINE_WAIT(wait);
long sequence_needed;
@@ -231,11 +248,10 @@ void flush_workqueue(struct workqueue_st
finish_wait(&cwq->work_done, &wait);
spin_unlock_irq(&cwq->lock);
}
+ unlock_cpu_hotplug();
}

-static int create_workqueue_thread(struct workqueue_struct *wq,
- const char *name,
- int cpu)
+static int create_workqueue_thread(struct workqueue_struct *wq, int cpu)
{
struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu;
struct task_struct *p;
@@ -249,7 +265,7 @@ static int create_workqueue_thread(struc
init_waitqueue_head(&cwq->more_work);
init_waitqueue_head(&cwq->work_done);

- p = kthread_create(worker_thread, cwq, "%s/%d", name, cpu);
+ p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
if (IS_ERR(p))
return PTR_ERR(p);
cwq->thread = p;
@@ -268,14 +284,19 @@ struct workqueue_struct *create_workqueu
if (!wq)
return NULL;

+ wq->name = name;
+ /* We don't need the distraction of CPUs appearing and vanishing. */
+ lock_cpu_hotplug();
for (cpu = 0; cpu < NR_CPUS; cpu++) {
if (!cpu_online(cpu))
continue;
- if (create_workqueue_thread(wq, name, cpu) < 0)
+ if (create_workqueue_thread(wq, cpu) < 0)
destroy = 1;
else
wake_up_process(wq->cpu_wq[cpu].thread);
}
+ add_workqueue(wq);
+
/*
* Was there any error during startup? If yes then clean up:
*/
@@ -283,16 +304,23 @@ struct workqueue_struct *create_workqueu
destroy_workqueue(wq);
wq = NULL;
}
+ unlock_cpu_hotplug();
return wq;
}

static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
{
struct cpu_workqueue_struct *cwq;
+ unsigned long flags;
+ struct task_struct *p;

cwq = wq->cpu_wq + cpu;
- if (cwq->thread)
- kthread_stop(cwq->thread);
+ spin_lock_irqsave(&cwq->lock, flags);
+ p = cwq->thread;
+ cwq->thread = NULL;
+ spin_unlock_irqrestore(&cwq->lock, flags);
+ if (p)
+ kthread_stop(p);
}

void destroy_workqueue(struct workqueue_struct *wq)
@@ -301,10 +329,14 @@ void destroy_workqueue(struct workqueue_

flush_workqueue(wq);

+ /* We don't need the distraction of CPUs appearing and vanishing. */
+ lock_cpu_hotplug();
for (cpu = 0; cpu < NR_CPUS; cpu++) {
if (cpu_online(cpu))
cleanup_workqueue_thread(wq, cpu);
}
+ list_del(&wq->list);
+ unlock_cpu_hotplug();
kfree(wq);
}

@@ -345,8 +377,78 @@ int current_is_keventd(void)
return 0;
}

+#ifdef CONFIG_HOTPLUG_CPU
+/* Take the work from this (downed) CPU. */
+static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
+{
+ struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu;
+ LIST_HEAD(list);
+ struct work_struct *work;
+
+ spin_lock_irq(&cwq->lock);
+ printk("Workqueue %s: %i\n", wq->name, list_empty(&cwq->worklist));
+ list_splice_init(&cwq->worklist, &list);
+
+ while (!list_empty(&list)) {
+ printk("Taking work for %s\n", wq->name);
+ work = list_entry(list.next,struct work_struct,entry);
+ list_del(&work->entry);
+ __queue_work(wq->cpu_wq + smp_processor_id(), work);
+ }
+ spin_unlock_irq(&cwq->lock);
+}
+
+/* We're holding the cpucontrol mutex here */
+static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
+ unsigned long action,
+ void *hcpu)
+{
+ unsigned int hotcpu = (unsigned long)hcpu;
+ struct workqueue_struct *wq;
+
+ switch (action) {
+ case CPU_UP_PREPARE:
+ /* Create a new workqueue thread for it. */
+ list_for_each_entry(wq, &workqueues, list) {
+ if (create_workqueue_thread(wq, hotcpu) < 0) {
+ printk("workqueue for %i failed\n", hotcpu);
+ return NOTIFY_BAD;
+ }
+ }
+ break;
+
+ case CPU_ONLINE:
+ /* Kick off worker threads. */
+ list_for_each_entry(wq, &workqueues, list)
+ wake_up_process(wq->cpu_wq[hotcpu].thread);
+ break;
+
+ case CPU_UP_CANCELED:
+ list_for_each_entry(wq, &workqueues, list) {
+ /* Unbind so it can run. */
+ kthread_bind(wq->cpu_wq[hotcpu].thread,
+ smp_processor_id());
+ cleanup_workqueue_thread(wq, hotcpu);
+ }
+ break;
+
+ case CPU_OFFLINE:
+ list_for_each_entry(wq, &workqueues, list)
+ take_over_work(wq, hotcpu);
+ list_for_each_entry(wq, &workqueues, list)
+ cleanup_workqueue_thread(wq, hotcpu);
+ break;
+ case CPU_DEAD:
+ break;
+ }
+
+ return NOTIFY_OK;
+}
+#endif
+
void init_workqueues(void)
{
+ hotcpu_notifier(workqueue_cpu_callback, 0);
keventd_wq = create_workqueue("events");
BUG_ON(!keventd_wq);
}
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/mm/page_alloc.c .22517-linux-2.6.2-rc2-mm2.updated/mm/page_alloc.c
--- .22517-linux-2.6.2-rc2-mm2/mm/page_alloc.c 2004-02-01 01:08:00.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/mm/page_alloc.c 2004-02-01 01:08:03.000000000 +1100
@@ -1538,9 +1538,27 @@ struct seq_operations vmstat_op = {

#endif /* CONFIG_PROC_FS */

+#ifdef CONFIG_HOTPLUG_CPU
+static int page_alloc_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ int cpu = (unsigned long)hcpu;
+ long *count;
+
+ if (action == CPU_DEAD) {
+ /* Drain local pagecache count. */
+ count = &per_cpu(nr_pagecache_local, cpu);
+ atomic_add(*count, &nr_pagecache);
+ *count = 0;
+ drain_local_pages(cpu);
+ }
+ return NOTIFY_OK;
+}
+#endif /* CONFIG_HOTPLUG_CPU */

void __init page_alloc_init(void)
{
+ hotcpu_notifier(page_alloc_cpu_notify, 0);
}

/*
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/mm/slab.c .22517-linux-2.6.2-rc2-mm2.updated/mm/slab.c
--- .22517-linux-2.6.2-rc2-mm2/mm/slab.c 2004-01-31 17:28:20.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/mm/slab.c 2004-02-01 01:08:03.000000000 +1100
@@ -521,9 +521,19 @@ enum {
static DEFINE_PER_CPU(struct timer_list, reap_timers);

static void reap_timer_fnc(unsigned long data);
-
+static void free_block (kmem_cache_t* cachep, void** objpp, int len);
static void enable_cpucache (kmem_cache_t *cachep);

+static inline void ** ac_entry(struct array_cache *ac)
+{
+ return (void**)(ac+1);
+}
+
+static inline struct array_cache *ac_data(kmem_cache_t *cachep)
+{
+ return cachep->array[smp_processor_id()];
+}
+
/* Cal the num objs, wastage, and bytes left over for a given slab size. */
static void cache_estimate (unsigned long gfporder, size_t size,
int flags, size_t *left_over, unsigned int *num)
@@ -578,27 +588,33 @@ static void start_cpu_timer(int cpu)
}
}

-/*
- * Note: if someone calls kmem_cache_alloc() on the new
- * cpu before the cpuup callback had a chance to allocate
- * the head arrays, it will oops.
- * Is CPU_ONLINE early enough?
- */
+#ifdef CONFIG_HOTPLUG_CPU
+static void stop_cpu_timer(int cpu)
+{
+ struct timer_list *rt = &per_cpu(reap_timers, cpu);
+
+ if (rt->function) {
+ del_timer_sync(rt);
+ WARN_ON(timer_pending(rt));
+ rt->function = NULL;
+ }
+}
+#endif
+
static int __devinit cpuup_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
long cpu = (long)hcpu;
- struct list_head *p;
+ kmem_cache_t* cachep;

switch (action) {
case CPU_UP_PREPARE:
down(&cache_chain_sem);
- list_for_each(p, &cache_chain) {
+ list_for_each_entry(cachep, &cache_chain, next) {
int memsize;
struct array_cache *nc;

- kmem_cache_t* cachep = list_entry(p, kmem_cache_t, next);
memsize = sizeof(void*)*cachep->limit+sizeof(struct array_cache);
nc = kmalloc(memsize, GFP_KERNEL);
if (!nc)
@@ -618,22 +634,32 @@ static int __devinit cpuup_callback(stru
up(&cache_chain_sem);
break;
case CPU_ONLINE:
- if (g_cpucache_up == FULL)
- start_cpu_timer(cpu);
+ start_cpu_timer(cpu);
break;
+
+#ifdef CONFIG_HOTPLUG_CPU
+ case CPU_OFFLINE:
+ stop_cpu_timer(cpu);
+ break;
+
case CPU_UP_CANCELED:
+ case CPU_DEAD:
down(&cache_chain_sem);
-
- list_for_each(p, &cache_chain) {
+ list_for_each_entry(cachep, &cache_chain, next) {
struct array_cache *nc;
- kmem_cache_t* cachep = list_entry(p, kmem_cache_t, next);

+ spin_lock_irq(&cachep->spinlock);
+ /* cpu is dead; no one can alloc from it. */
nc = cachep->array[cpu];
cachep->array[cpu] = NULL;
+ cachep->free_limit -= cachep->batchcount;
+ free_block(cachep, ac_entry(nc), nc->avail);
+ spin_unlock_irq(&cachep->spinlock);
kfree(nc);
}
up(&cache_chain_sem);
break;
+#endif /* CONFIG_HOTPLUG_CPU */
}
return NOTIFY_OK;
bad:
@@ -643,16 +669,6 @@ bad:

static struct notifier_block cpucache_notifier = { &cpuup_callback, NULL, 0 };

-static inline void ** ac_entry(struct array_cache *ac)
-{
- return (void**)(ac+1);
-}
-
-static inline struct array_cache *ac_data(kmem_cache_t *cachep)
-{
- return cachep->array[smp_processor_id()];
-}
-
/* Initialisation.
* Called after the gfp() functions have been enabled, and before smp_init().
*/
@@ -1378,7 +1394,6 @@ static void smp_call_function_all_cpus(v
preempt_enable();
}

-static void free_block (kmem_cache_t* cachep, void** objpp, int len);
static void drain_array_locked(kmem_cache_t* cachep,
struct array_cache *ac, int force);

@@ -1499,6 +1514,9 @@ int kmem_cache_destroy (kmem_cache_t * c
return 1;
}

+ /* no cpu_online check required here since we clear the percpu
+ * array on cpu offline and set this to NULL.
+ */
for (i = 0; i < NR_CPUS; i++)
kfree(cachep->array[i]);

@@ -2590,7 +2608,8 @@ static void reap_timer_fnc(unsigned long
struct timer_list *rt = &__get_cpu_var(reap_timers);

cache_reap();
- mod_timer(rt, jiffies + REAPTIMEOUT_CPUC + cpu);
+ if (!cpu_is_offline(cpu))
+ mod_timer(rt, jiffies + REAPTIMEOUT_CPUC + cpu);
}

#ifdef CONFIG_PROC_FS
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/mm/swap.c .22517-linux-2.6.2-rc2-mm2.updated/mm/swap.c
--- .22517-linux-2.6.2-rc2-mm2/mm/swap.c 2004-01-10 13:59:39.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/mm/swap.c 2004-02-01 01:08:03.000000000 +1100
@@ -27,6 +27,9 @@
#include <linux/module.h>
#include <linux/percpu_counter.h>
#include <linux/percpu.h>
+#include <linux/cpu.h>
+#include <linux/notifier.h>
+#include <linux/init.h>

/* How many pages do we try to swap or page in/out together? */
int page_cluster;
@@ -381,7 +384,43 @@ void vm_acct_memory(long pages)
preempt_enable();
}
EXPORT_SYMBOL(vm_acct_memory);
-#endif
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void lru_drain_cache(unsigned int cpu)
+{
+ struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
+
+ /* CPU is dead, so no locking needed. */
+ if (pagevec_count(pvec)) {
+ printk("pagevec_count for %u is %u\n",
+ cpu, pagevec_count(pvec));
+ __pagevec_lru_add(pvec);
+ }
+ pvec = &per_cpu(lru_add_active_pvecs, cpu);
+ if (pagevec_count(pvec)) {
+ printk("active pagevec_count for %u is %u\n",
+ cpu, pagevec_count(pvec));
+ __pagevec_lru_add_active(pvec);
+ }
+}
+
+/* Drop the CPU's cached committed space back into the central pool. */
+static int cpu_swap_callback(struct notifier_block *nfb,
+ unsigned long action,
+ void *hcpu)
+{
+ long *committed;
+
+ committed = &per_cpu(committed_space, (long)hcpu);
+ if (action == CPU_DEAD) {
+ atomic_add(*committed, &vm_committed_space);
+ *committed = 0;
+ lru_drain_cache((long)hcpu);
+ }
+ return NOTIFY_OK;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+#endif /* CONFIG_SMP */

#ifdef CONFIG_SMP
void percpu_counter_mod(struct percpu_counter *fbc, long amount)
@@ -420,4 +459,5 @@ void __init swap_setup(void)
* Right now other parts of the system means that we
* _really_ don't want to cluster much more
*/
+ hotcpu_notifier(cpu_swap_callback, 0);
}
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/mm/vmscan.c .22517-linux-2.6.2-rc2-mm2.updated/mm/vmscan.c
--- .22517-linux-2.6.2-rc2-mm2/mm/vmscan.c 2004-01-31 17:28:20.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/mm/vmscan.c 2004-02-01 01:08:03.000000000 +1100
@@ -30,6 +30,8 @@
#include <linux/backing-dev.h>
#include <linux/rmap-locking.h>
#include <linux/topology.h>
+#include <linux/cpu.h>
+#include <linux/notifier.h>

#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
@@ -1105,13 +1107,54 @@ int shrink_all_memory(int nr_pages)
}
#endif

+#ifdef CONFIG_HOTPLUG_CPU
+/* It's optimal to keep kswapds on the same CPUs as their memory, but
+ not required for correctness. So if the last cpu in a node goes
+ away, let them run anywhere, and as the first one comes back,
+ restore their cpu bindings. */
+static int __devinit cpu_callback(struct notifier_block *nfb,
+ unsigned long action,
+ void *hcpu)
+{
+ pg_data_t *pgdat;
+ unsigned int hotcpu = (unsigned long)hcpu;
+ cpumask_t mask;
+
+ if (action == CPU_OFFLINE) {
+ /* Make sure that kswapd never becomes unschedulable. */
+ for_each_pgdat(pgdat) {
+ mask = node_to_cpumask(pgdat->node_id);
+ if (any_online_cpu(mask) == NR_CPUS) {
+ cpus_complement(mask);
+ set_cpus_allowed(pgdat->kswapd, mask);
+ }
+ }
+ }
+
+ if (action == CPU_ONLINE) {
+ for_each_pgdat(pgdat) {
+ mask = node_to_cpumask(pgdat->node_id);
+ cpu_clear(hotcpu, mask);
+ if (any_online_cpu(mask) == NR_CPUS) {
+ cpu_set(hotcpu, mask);
+ /* One of our CPUs came back: restore mask */
+ set_cpus_allowed(pgdat->kswapd, mask);
+ }
+ }
+ }
+ return NOTIFY_OK;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
static int __init kswapd_init(void)
{
pg_data_t *pgdat;
swap_setup();
for_each_pgdat(pgdat)
- kernel_thread(kswapd, pgdat, CLONE_KERNEL);
+ pgdat->kswapd
+ = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL));
total_memory = nr_free_pagecache_pages();
+ hotcpu_notifier(cpu_callback, 0);
return 0;
}

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/net/core/dev.c .22517-linux-2.6.2-rc2-mm2.updated/net/core/dev.c
--- .22517-linux-2.6.2-rc2-mm2/net/core/dev.c 2004-01-31 17:28:21.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/net/core/dev.c 2004-02-01 01:08:03.000000000 +1100
@@ -105,6 +105,7 @@
#include <linux/kmod.h>
#include <linux/module.h>
#include <linux/kallsyms.h>
+#include <linux/cpu.h>
#include <linux/netpoll.h>
#ifdef CONFIG_NET_RADIO
#include <linux/wireless.h> /* Note : will define WIRELESS_EXT */
@@ -3080,6 +3081,52 @@ int unregister_netdevice(struct net_devi
return 0;
}

+#ifdef CONFIG_HOTPLUG_CPU
+static int dev_cpu_callback(struct notifier_block *nfb,
+ unsigned long action,
+ void *ocpu)
+{
+ struct sk_buff **list_skb;
+ struct net_device **list_net;
+ struct sk_buff *skb;
+ unsigned int cpu, oldcpu = (unsigned long)ocpu;
+ struct softnet_data *sd, *oldsd;
+
+ if (action != CPU_DEAD)
+ return NOTIFY_OK;
+
+ local_irq_disable();
+ cpu = smp_processor_id();
+ sd = &per_cpu(softnet_data, cpu);
+ oldsd = &per_cpu(softnet_data, oldcpu);
+
+ /* Find end of our completion_queue. */
+ list_skb = &sd->completion_queue;
+ while (*list_skb)
+ list_skb = &(*list_skb)->next;
+ /* Append completion queue from offline CPU. */
+ *list_skb = oldsd->completion_queue;
+ oldsd->completion_queue = NULL;
+
+ /* Find end of our output_queue. */
+ list_net = &sd->output_queue;
+ while (*list_net)
+ list_net = &(*list_net)->next_sched;
+ /* Append output queue from offline CPU. */
+ *list_net = oldsd->output_queue;
+ oldsd->output_queue = NULL;
+
+ raise_softirq_irqoff(NET_TX_SOFTIRQ);
+ local_irq_enable();
+
+ /* Process offline CPU's input_pkt_queue */
+ while ((skb = __skb_dequeue(&oldsd->input_pkt_queue)))
+ netif_rx(skb);
+
+ return NOTIFY_OK;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+

/*
* Initialize the DEV module. At boot time this walks the device list and
@@ -3144,6 +3191,7 @@ static int __init net_dev_init(void)
#ifdef CONFIG_NET_SCHED
pktsched_init();
#endif
+ hotcpu_notifier(dev_cpu_callback, 0);
rc = 0;
out:
return rc;
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .22517-linux-2.6.2-rc2-mm2/net/core/flow.c .22517-linux-2.6.2-rc2-mm2.updated/net/core/flow.c
--- .22517-linux-2.6.2-rc2-mm2/net/core/flow.c 2004-01-31 17:28:21.000000000 +1100
+++ .22517-linux-2.6.2-rc2-mm2.updated/net/core/flow.c 2004-02-01 01:08:03.000000000 +1100
@@ -326,6 +326,17 @@ static void __devinit flow_cache_cpu_pre
tasklet_init(tasklet, flow_cache_flush_tasklet, 0);
}

+#ifdef CONFIG_HOTPLUG_CPU
+static int flow_cache_cpu(struct notifier_block *nfb,
+ unsigned long action,
+ void *hcpu)
+{
+ if (action == CPU_DEAD)
+ __flow_cache_shrink((unsigned long)hcpu, 0);
+ return NOTIFY_OK;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
static int __init flow_cache_init(void)
{
int i;
@@ -350,6 +361,7 @@ static int __init flow_cache_init(void)
for_each_cpu(i)
flow_cache_cpu_prepare(i);

+ hotcpu_notifier(flow_cache_cpu, 0);
return 0;
}

--
Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
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