Name: Hot-plug CPU Boot Changes
Author: Rusty Russell
Status: Tested on 2.5.25, x86 SMP
D: This patch alters the boot sequence to "plug in" each CPU, one at a
D: time. You need the patch for each architecture, as well. The
D: interface used to be "smp_boot_cpus()", "smp_commence()", and each
D: arch implemented the "maxcpus" boot arg itself. With this patch,
D: it is:
D: smp_prepare_cpus(maxcpus): probe for cpus and set up cpu_possible(cpu).
D: __cpu_up(cpu): called *after* initcalls, for each cpu where
D: cpu_possible(cpu) is true.
D: smp_cpus_done(maxcpus): called after every cpu has been brought up
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.25/include/linux/notifier.h working-2.5.25-hotcpu/include/linux/notifier.h
--- linux-2.5.25/include/linux/notifier.h Mon Jun 24 00:55:28 2002
+++ working-2.5.25-hotcpu/include/linux/notifier.h Mon Jul 15 12:44:55 2002
@@ -58,5 +58,7 @@
#define SYS_HALT 0x0002 /* Notify of system halt */
#define SYS_POWER_OFF 0x0003 /* Notify of system power off */
+#define CPU_ONLINE 0x0002 /* CPU (unsigned)v coming up */
+
#endif /* __KERNEL__ */
#endif /* _LINUX_NOTIFIER_H */
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.25/include/linux/sched.h working-2.5.25-hotcpu/include/linux/sched.h
--- linux-2.5.25/include/linux/sched.h Sun Jul 7 02:12:24 2002
+++ working-2.5.25-hotcpu/include/linux/sched.h Mon Jul 15 12:44:55 2002
@@ -150,7 +150,6 @@
extern void update_one_process(struct task_struct *p, unsigned long user,
unsigned long system, int cpu);
extern void scheduler_tick(int user_tick, int system);
-extern void migration_init(void);
extern unsigned long cache_decay_ticks;
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.25/include/linux/smp.h working-2.5.25-hotcpu/include/linux/smp.h
--- linux-2.5.25/include/linux/smp.h Fri Jun 21 09:41:55 2002
+++ working-2.5.25-hotcpu/include/linux/smp.h Mon Jul 15 14:45:56 2002
@@ -32,19 +32,19 @@
/*
- * Boot processor call to load the other CPU's
+ * Prepare machine for booting other CPUs.
*/
-extern void smp_boot_cpus(void);
+extern void smp_prepare_cpus(unsigned int max_cpus);
/*
- * Processor call in. Must hold processors until ..
+ * Bring a CPU up
*/
-extern void smp_callin(void);
+extern int __cpu_up(unsigned int cpunum);
/*
- * Multiprocessors may now schedule
+ * Final polishing of CPUs
*/
-extern void smp_commence(void);
+extern void smp_cpus_done(unsigned int max_cpus);
/*
* Call a function on all other processors
@@ -71,6 +71,13 @@
#define MSG_RESCHEDULE 0x0003 /* Reschedule request from master CPU*/
#define MSG_CALL_FUNCTION 0x0004 /* Call function on all other CPUs */
+struct notifier_block;
+
+/* Need to know about CPUs going up/down? */
+extern int register_cpu_notifier(struct notifier_block *nb);
+extern void unregister_cpu_notifier(struct notifier_block *nb);
+
+int cpu_up(unsigned int cpu);
#else /* !SMP */
/*
@@ -92,6 +99,10 @@
#define __per_cpu_data
#define per_cpu(var, cpu) var
#define this_cpu(var) var
+
+/* Need to know about CPUs going up/down? */
+#define register_cpu_notifier(nb) 0
+#define unregister_cpu_notifier(nb) do { } while(0)
#endif /* !SMP */
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.25/init/main.c working-2.5.25-hotcpu/init/main.c
--- linux-2.5.25/init/main.c Thu Jun 20 01:28:52 2002
+++ working-2.5.25-hotcpu/init/main.c Mon Jul 15 12:44:55 2002
@@ -93,6 +93,35 @@
char *execute_command;
+/* Setup configured maximum number of CPUs to activate */
+static unsigned int max_cpus = UINT_MAX;
+
+/*
+ * Setup routine for controlling SMP activation
+ *
+ * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
+ * activation entirely (the MPS table probe still happens, though).
+ *
+ * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
+ * greater than 0, limits the maximum number of CPUs activated in
+ * SMP mode to <NUM>.
+ */
+static int __init nosmp(char *str)
+{
+ max_cpus = 0;
+ return 1;
+}
+
+__setup("nosmp", nosmp);
+
+static int __init maxcpus(char *str)
+{
+ get_option(&str, &max_cpus);
+ return 1;
+}
+
+__setup("maxcpus=", maxcpus);
+
static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
@@ -273,6 +302,7 @@
#endif
static inline void setup_per_cpu_areas(void) { }
+static inline void smp_prepare_cpus(unsigned int maxcpus) { }
#else
@@ -303,11 +333,27 @@
/* Called by boot processor to activate the rest. */
static void __init smp_init(void)
{
+ unsigned int i;
+
+ /* FIXME: This should be done in userspace --RR */
+ for (i = 0; i < NR_CPUS; i++) {
+ if (num_online_cpus() >= max_cpus)
+ break;
+ if (cpu_possible(i) && !cpu_online(i)) {
+ printk("Bringing up %i\n", i);
+ cpu_up(i);
+ }
+ }
+
+ /* Any cleanup work */
+ printk("CPUS done %u\n", max_cpus);
+ smp_cpus_done(max_cpus);
+#if 0
/* Get other processors into their bootup holding patterns. */
- smp_boot_cpus();
smp_threads_ready=1;
smp_commence();
+#endif
}
#endif
@@ -402,14 +448,12 @@
check_bugs();
printk("POSIX conformance testing by UNIFIX\n");
- init_idle(current, smp_processor_id());
-
/*
* We count on the initial thread going ok
* Like idlers init is an unlocked kernel thread, which will
* make syscalls (and thus be locked).
*/
- smp_init();
+ init_idle(current, smp_processor_id());
/* Do the rest non-__init'ed, we're now alive */
rest_init();
@@ -441,12 +485,6 @@
static void __init do_basic_setup(void)
{
/*
- * Let the per-CPU migration threads start up:
- */
-#if CONFIG_SMP
- migration_init();
-#endif
- /*
* Tell the world that we're going to be the grim
* reaper of innocent orphaned children.
*
@@ -490,7 +528,10 @@
static char * argv_sh[] = { "sh", NULL, };
lock_kernel();
+ /* Sets up cpus_possible() */
+ smp_prepare_cpus(max_cpus);
do_basic_setup();
+ smp_init();
prepare_namespace();
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.25/kernel/Makefile working-2.5.25-hotcpu/kernel/Makefile
--- linux-2.5.25/kernel/Makefile Mon Jun 10 16:03:56 2002
+++ working-2.5.25-hotcpu/kernel/Makefile Mon Jul 15 12:44:55 2002
@@ -17,6 +17,7 @@
sysctl.o capability.o ptrace.o timer.o user.o \
signal.o sys.o kmod.o context.o futex.o platform.o
+obj-$(CONFIG_SMP) += cpu.o
obj-$(CONFIG_UID16) += uid16.o
obj-$(CONFIG_MODULES) += ksyms.o
obj-$(CONFIG_PM) += pm.o
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.25/kernel/cpu.c working-2.5.25-hotcpu/kernel/cpu.c
--- linux-2.5.25/kernel/cpu.c Thu Jan 1 10:00:00 1970
+++ working-2.5.25-hotcpu/kernel/cpu.c Mon Jul 15 14:34:49 2002
@@ -0,0 +1,54 @@
+/* CPU control.
+ * (C) 2001 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 <asm/semaphore.h>
+
+/* This protects CPUs going up and down... */
+DECLARE_MUTEX(cpucontrol);
+
+static struct notifier_block *cpu_chain = NULL;
+
+/* Need to know about CPUs going up/down? */
+int register_cpu_notifier(struct notifier_block *nb)
+{
+ return notifier_chain_register(&cpu_chain, nb);
+}
+
+void unregister_cpu_notifier(struct notifier_block *nb)
+{
+ notifier_chain_unregister(&cpu_chain,nb);
+}
+
+int __devinit cpu_up(unsigned int cpu)
+{
+ int ret;
+
+ if ((ret = down_interruptible(&cpucontrol)) != 0)
+ return ret;
+
+ if (cpu_online(cpu)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ /* Arch-specific enabling code. */
+ ret = __cpu_up(cpu);
+ if (ret != 0) goto out;
+ if (!cpu_online(cpu))
+ BUG();
+
+ /* Now call notifier in preparation. */
+ printk("CPU %u IS NOW UP!\n", cpu);
+ notifier_call_chain(&cpu_chain, CPU_ONLINE, (void *)cpu);
+
+ out:
+ up(&cpucontrol);
+ return ret;
+}
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.25/kernel/sched.c working-2.5.25-hotcpu/kernel/sched.c
--- linux-2.5.25/kernel/sched.c Sun Jul 7 02:12:24 2002
+++ working-2.5.25-hotcpu/kernel/sched.c Mon Jul 15 12:44:55 2002
@@ -26,6 +26,8 @@
#include <linux/interrupt.h>
#include <linux/completion.h>
#include <linux/kernel_stat.h>
+#include <linux/notifier.h>
+#include <linux/delay.h>
/*
* Convert user-nice values [ -20 ... 0 ... 19 ]
@@ -1752,9 +1756,11 @@
migration_req_t req;
runqueue_t *rq;
+#if 0 /* FIXME: Grab cpu_lock, return error on this case. --RR */
new_mask &= cpu_online_map;
if (!new_mask)
BUG();
+#endif
preempt_disable();
rq = task_rq_lock(p, &flags);
@@ -1787,8 +1793,6 @@
preempt_enable();
}
-static __initdata int master_migration_thread;
-
static int migration_thread(void * bind_cpu)
{
int cpu = (int) (long) bind_cpu;
@@ -1800,15 +1804,7 @@
sigfillset(¤t->blocked);
set_fs(KERNEL_DS);
- /*
- * The first migration thread is started on the boot CPU, it
- * migrates the other migration threads to their destination CPUs.
- */
- if (cpu != master_migration_thread) {
- while (!cpu_rq(master_migration_thread)->migration_thread)
- yield();
- set_cpus_allowed(current, 1UL << cpu);
- }
+ set_cpus_allowed(current, 1UL << cpu);
printk("migration_task %d on cpu=%d\n", cpu, smp_processor_id());
ret = setscheduler(0, SCHED_FIFO, ¶m);
@@ -1865,27 +1861,31 @@
}
}
-void __init migration_init(void)
+static int migration_call(struct notifier_block *nfb,
+ unsigned long action,
+ void *hcpu)
{
- int cpu;
-
- master_migration_thread = smp_processor_id();
- current->cpus_allowed = 1UL << master_migration_thread;
-
- for (cpu = 0; cpu < NR_CPUS; cpu++) {
- if (!cpu_online(cpu))
- continue;
- if (kernel_thread(migration_thread, (void *) (long) cpu,
- CLONE_FS | CLONE_FILES | CLONE_SIGNAL) < 0)
- BUG();
+ switch (action) {
+ case CPU_ONLINE:
+ printk("Starting migration thread for cpu %li\n",
+ (long)hcpu);
+ kernel_thread(migration_thread, hcpu,
+ CLONE_FS | CLONE_FILES | CLONE_SIGNAL);
+ break;
}
- current->cpus_allowed = -1L;
+ return NOTIFY_OK;
+}
- for (cpu = 0; cpu < NR_CPUS; cpu++) {
- if (!cpu_online(cpu))
- continue;
- while (!cpu_rq(cpu)->migration_thread)
- schedule_timeout(2);
- }
+static struct notifier_block migration_notifier = { &migration_call, NULL, 0 };
+
+int __init migration_init(void)
+{
+ /* Start one for boot CPU. */
+ migration_call(&migration_notifier, CPU_ONLINE,
+ (void *)smp_processor_id());
+ register_cpu_notifier(&migration_notifier);
+ return 0;
}
+
+__initcall(migration_init);
#endif
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.25/kernel/softirq.c working-2.5.25-hotcpu/kernel/softirq.c
--- linux-2.5.25/kernel/softirq.c Sun Jul 7 02:12:24 2002
+++ working-2.5.25-hotcpu/kernel/softirq.c Mon Jul 15 12:44:55 2002
@@ -17,6 +17,7 @@
#include <linux/init.h>
#include <linux/tqueue.h>
#include <linux/percpu.h>
+#include <linux/notifier.h>
/*
- No shared variables, all the data are CPU local.
@@ -397,20 +398,32 @@
}
}
-static __init int spawn_ksoftirqd(void)
+static int __devinit cpu_callback(struct notifier_block *nfb,
+ unsigned long action,
+ void *hcpu)
{
- int cpu;
+ int hotcpu = (unsigned long)hcpu;
- for (cpu = 0; cpu < NR_CPUS; cpu++) {
- if (!cpu_online(cpu))
- continue;
- if (kernel_thread(ksoftirqd, (void *) (long) cpu,
- CLONE_FS | CLONE_FILES | CLONE_SIGNAL) < 0)
- printk("spawn_ksoftirqd() failed for cpu %d\n", cpu);
- else
- while (!ksoftirqd_task(cpu))
- yield();
- }
+ if (action == CPU_ONLINE) {
+ if (kernel_thread(ksoftirqd, hcpu,
+ CLONE_FS | CLONE_FILES | CLONE_SIGNAL) < 0) {
+ printk("ksoftirqd for %i failed\n", hotcpu);
+ return NOTIFY_BAD;
+ }
+
+ while (!ksoftirqd_task(hotcpu))
+ yield();
+ return NOTIFY_OK;
+ }
+ return NOTIFY_BAD;
+}
+
+static struct notifier_block cpu_nfb = { &cpu_callback, NULL, 0 };
+
+static __init int spawn_ksoftirqd(void)
+{
+ cpu_callback(&cpu_nfb, CPU_ONLINE, (void *)smp_processor_id());
+ register_cpu_notifier(&cpu_nfb);
return 0;
}
-- Anyone who quotes me in their sig is an idiot. -- Rusty Russell. - 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/