[RFC 5/6]clean cpu state after hotremove CPU

Li Shaohua
2005-04-04T02:16:24Z

Clean up all CPU states including its runqueue and idle thread,
so we can use boot time code without any changes.
Note this makes /sys/devices/system/cpu/cpux/online unworkable.

Thanks,
Shaohua

---

linux-2.6.11-root/arch/i386/kernel/cpu/common.c | 12 ++++
linux-2.6.11-root/arch/i386/kernel/irq.c | 5 +
linux-2.6.11-root/arch/i386/kernel/process.c | 20 +++++++
linux-2.6.11-root/arch/i386/kernel/smpboot.c | 44 ++++++++++++++++-
linux-2.6.11-root/include/asm-i386/irq.h | 2
linux-2.6.11-root/kernel/exit.c | 59 +++++++++++++++++++++++
linux-2.6.11-root/kernel/sched.c | 61 +++++++++++++++++++++---
7 files changed, 195 insertions(+), 8 deletions(-)

diff -puN arch/i386/kernel/process.c~cpu_state_clean arch/i386/kernel/process.c
--- linux-2.6.11/arch/i386/kernel/process.c~cpu_state_clean 2005-03-31 10:50:27.000000000 +0800
+++ linux-2.6.11-root/arch/i386/kernel/process.c 2005-04-04 09:07:29.172936768 +0800
@@ -144,12 +144,32 @@ static void poll_idle (void)

#ifdef CONFIG_HOTPLUG_CPU
#include <asm/nmi.h>
+
+#ifdef CONFIG_STR_SMP
+extern void cpu_exit_clear(int);
+#endif
+
/* We don't actually take CPU down, just spin without interrupts. */
static inline void play_dead(void)
{
+#ifdef CONFIG_STR_SMP
+ cpu_exit_clear(_smp_processor_id());
+#endif
+
/* Ack it */
__get_cpu_var(cpu_state) = CPU_DEAD;

+#ifdef CONFIG_STR_SMP
+ /*
+ * With physical CPU hotplug, we should halt the CPU
+ * Note: release idle task struct requires the CPU doesn't
+ * touch stack or anything else.
+ */
+ local_irq_disable();
+ while (1)
+ __asm__ __volatile__ ("hlt": : :"memory");
+#endif
+
/* We shouldn't have to disable interrupts while dead, but
* some interrupts just don't seem to go away, and this makes
* it "work" for testing purposes. */
diff -puN arch/i386/kernel/smpboot.c~cpu_state_clean arch/i386/kernel/smpboot.c
--- linux-2.6.11/arch/i386/kernel/smpboot.c~cpu_state_clean 2005-03-31 10:50:27.000000000 +0800
+++ linux-2.6.11-root/arch/i386/kernel/smpboot.c 2005-04-04 09:05:41.699275248 +0800
@@ -794,8 +794,13 @@ static int __devinit do_boot_cpu(int api
int timeout, cpu;
unsigned long start_eip;
unsigned short nmi_high = 0, nmi_low = 0;
+ cpumask_t tmp_map;

- cpu = ++cpucount;
+ cpus_complement(tmp_map, cpu_present_map);
+ cpu = first_cpu(tmp_map);
+ if (cpu >= NR_CPUS)
+ return -ENODEV;
+ ++cpucount;
/*
* We can't use kernel_thread since we must avoid to
* reschedule the child.
@@ -867,13 +872,16 @@ static int __devinit do_boot_cpu(int api
inquire_remote_apic(apicid);
}
}
- x86_cpu_to_apicid[cpu] = apicid;
+
if (boot_error) {
/* Try to put things back the way they were before ... */
unmap_cpu_to_logical_apicid(cpu);
cpu_clear(cpu, cpu_callout_map); /* was set here (do_boot_cpu()) */
cpu_clear(cpu, cpu_initialized); /* was set by cpu_init() */
cpucount--;
+ } else {
+ x86_cpu_to_apicid[cpu] = apicid;
+ cpu_set(cpu, cpu_present_map);
}

/* mark "stuck" area as not stuck */
@@ -882,6 +890,37 @@ static int __devinit do_boot_cpu(int api
return boot_error;
}

+#ifdef CONFIG_STR_SMP
+extern void do_exit_idle(void);
+extern void cpu_uninit(void);
+void cpu_exit_clear(int cpu)
+{
+ int sibling;
+ cpucount --;
+
+ cpu_uninit();
+
+ irq_ctx_exit(cpu);
+
+ cpu_clear(cpu, cpu_callout_map);
+ cpu_clear(cpu, cpu_callin_map);
+ cpu_clear(cpu, cpu_present_map);
+
+ x86_cpu_to_apicid[cpu] = BAD_APICID;
+
+ for_each_cpu_mask(sibling, cpu_sibling_map[cpu])
+ cpu_clear(cpu, cpu_sibling_map[sibling]);
+ cpus_clear(cpu_sibling_map[cpu]);
+
+ phys_proc_id[cpu] = BAD_APICID;
+
+ cpu_clear(cpu, smp_commenced_mask);
+
+ unmap_cpu_to_logical_apicid(cpu);
+
+ do_exit_idle();
+}
+#endif
static void smp_tune_scheduling (void)
{
unsigned long cachesize; /* kB */
@@ -1104,6 +1143,7 @@ void __devinit smp_prepare_boot_cpu(void
{
cpu_set(smp_processor_id(), cpu_online_map);
cpu_set(smp_processor_id(), cpu_callout_map);
+ cpu_set(smp_processor_id(), cpu_present_map);
}

#ifdef CONFIG_HOTPLUG_CPU
diff -puN arch/i386/kernel/cpu/common.c~cpu_state_clean arch/i386/kernel/cpu/common.c
--- linux-2.6.11/arch/i386/kernel/cpu/common.c~cpu_state_clean 2005-03-31 10:50:27.000000000 +0800
+++ linux-2.6.11-root/arch/i386/kernel/cpu/common.c 2005-03-31 10:50:27.000000000 +0800
@@ -621,3 +621,15 @@ void __devinit cpu_init (void)
clear_used_math();
mxcsr_feature_mask_init();
}
+
+#ifdef CONFIG_STR_SMP
+void __devinit cpu_uninit(void)
+{
+ int cpu = smp_processor_id();
+ cpu_clear(cpu, cpu_initialized);
+
+ /* lazy TLB state */
+ per_cpu(cpu_tlbstate, cpu).state = 0;
+ per_cpu(cpu_tlbstate, cpu).active_mm = &init_mm;
+}
+#endif
diff -puN include/asm-i386/irq.h~cpu_state_clean include/asm-i386/irq.h
--- linux-2.6.11/include/asm-i386/irq.h~cpu_state_clean 2005-03-31 10:50:27.000000000 +0800
+++ linux-2.6.11-root/include/asm-i386/irq.h 2005-03-31 10:50:27.000000000 +0800
@@ -29,9 +29,11 @@ extern void release_vm86_irqs(struct tas

#ifdef CONFIG_4KSTACKS
extern void irq_ctx_init(int cpu);
+ extern void irq_ctx_exit(int cpu);
# define __ARCH_HAS_DO_SOFTIRQ
#else
# define irq_ctx_init(cpu) do { } while (0)
+# define irq_ctx_exit(cpu) do { } while (0)
#endif

#ifdef CONFIG_IRQBALANCE
diff -puN arch/i386/kernel/irq.c~cpu_state_clean arch/i386/kernel/irq.c
--- linux-2.6.11/arch/i386/kernel/irq.c~cpu_state_clean 2005-03-31 10:50:27.000000000 +0800
+++ linux-2.6.11-root/arch/i386/kernel/irq.c 2005-03-31 10:50:27.000000000 +0800
@@ -153,6 +153,11 @@ void irq_ctx_init(int cpu)
cpu,hardirq_ctx[cpu],softirq_ctx[cpu]);
}

+void irq_ctx_exit(int cpu)
+{
+ hardirq_ctx[cpu] = NULL;
+}
+
extern asmlinkage void __do_softirq(void);

asmlinkage void do_softirq(void)
diff -puN kernel/exit.c~cpu_state_clean kernel/exit.c
--- linux-2.6.11/kernel/exit.c~cpu_state_clean 2005-03-31 10:50:27.000000000 +0800
+++ linux-2.6.11-root/kernel/exit.c 2005-03-31 10:50:27.000000000 +0800
@@ -845,6 +845,65 @@ fastcall NORET_TYPE void do_exit(long co
for (;;) ;
}

+#ifdef CONFIG_STR_SMP
+void do_exit_idle(void)
+{
+ struct task_struct *tsk = current;
+ int group_dead;
+
+ BUG_ON(tsk->pid);
+ BUG_ON(tsk->mm);
+
+ if (tsk->io_context)
+ exit_io_context();
+ tsk->flags |= PF_EXITING;
+ tsk->it_virt_expires = cputime_zero;
+ tsk->it_prof_expires = cputime_zero;
+ tsk->it_sched_expires = 0;
+
+ acct_update_integrals(tsk);
+ update_mem_hiwater(tsk);
+ group_dead = atomic_dec_and_test(&tsk->signal->live);
+ if (group_dead) {
+ del_timer_sync(&tsk->signal->real_timer);
+ acct_process(-1);
+ }
+ exit_mm(tsk);
+
+ exit_sem(tsk);
+ __exit_files(tsk);
+ __exit_fs(tsk);
+ exit_namespace(tsk);
+ exit_thread();
+ exit_keys(tsk);
+
+ if (group_dead && tsk->signal->leader)
+ disassociate_ctty(1);
+
+ module_put(tsk->thread_info->exec_domain->module);
+ if (tsk->binfmt)
+ module_put(tsk->binfmt->module);
+
+ tsk->exit_code = -1;
+ tsk->exit_state = EXIT_DEAD;
+
+ /* in release_task */
+ atomic_dec(&tsk->user->processes);
+ write_lock_irq(&tasklist_lock);
+ __exit_signal(tsk);
+ __exit_sighand(tsk);
+ write_unlock_irq(&tasklist_lock);
+ release_thread(tsk);
+ put_task_struct(tsk);
+
+ tsk->flags |= PF_DEAD;
+#ifdef CONFIG_NUMA
+ mpol_free(tsk->mempolicy);
+ tsk->mempolicy = NULL;
+#endif
+}
+#endif
+
NORET_TYPE void complete_and_exit(struct completion *comp, long code)
{
if (comp)
diff -puN kernel/sched.c~cpu_state_clean kernel/sched.c
--- linux-2.6.11/kernel/sched.c~cpu_state_clean 2005-03-31 10:50:27.000000000 +0800
+++ linux-2.6.11-root/kernel/sched.c 2005-04-04 09:06:40.362357104 +0800
@@ -4028,6 +4028,58 @@ void __devinit init_idle(task_t *idle, i
}

/*
+ * Initial dummy domain for early boot and for hotplug cpu. Being static,
+ * it is initialized to zero, so all balancing flags are cleared which is
+ * what we want.
+ */
+static struct sched_domain sched_domain_dummy;
+
+#ifdef CONFIG_STR_SMP
+static void __devinit exit_idle(int cpu)
+{
+ runqueue_t *rq = cpu_rq(cpu);
+ struct task_struct *p = rq->idle;
+ int j, k;
+ prio_array_t *array;
+
+ /* init runqueue */
+ spin_lock_init(&rq->lock);
+ rq->active = rq->arrays;
+ rq->expired = rq->arrays + 1;
+ rq->best_expired_prio = MAX_PRIO;
+
+ rq->prev_mm = NULL;
+ rq->curr = rq->idle = NULL;
+ rq->expired_timestamp = 0;
+
+ rq->sd = &sched_domain_dummy;
+ rq->cpu_load = 0;
+ rq->active_balance = 0;
+ rq->push_cpu = 0;
+ rq->migration_thread = NULL;
+ INIT_LIST_HEAD(&rq->migration_queue);
+ atomic_set(&rq->nr_iowait, 0);
+
+ for (j = 0; j < 2; j++) {
+ array = rq->arrays + j;
+ for (k = 0; k < MAX_PRIO; k++) {
+ INIT_LIST_HEAD(array->queue + k);
+ __clear_bit(k, array->bitmap);
+ }
+ // delimiter for bitsearch
+ __set_bit(MAX_PRIO, array->bitmap);
+ }
+ /* Destroy IDLE thread.
+ * it's safe now, the CPU is in busy loop
+ */
+ if (p->active_mm)
+ mmdrop(p->active_mm);
+ p->active_mm = NULL;
+ put_task_struct(p);
+}
+#endif
+
+/*
* In a system that switches off the HZ timer nohz_cpu_mask
* indicates which cpus entered this state. This is used
* in the rcu update to wait only for active cpus. For system
@@ -4432,6 +4484,9 @@ static int migration_call(struct notifie
complete(&req->done);
}
spin_unlock_irq(&rq->lock);
+#ifdef CONFIG_STR_SMP
+ exit_idle(cpu);
+#endif
break;
#endif
}
@@ -4834,12 +4889,6 @@ static void __devinit arch_destroy_sched

#endif /* ARCH_HAS_SCHED_DOMAIN */

-/*
- * Initial dummy domain for early boot and for hotplug cpu. Being static,
- * it is initialized to zero, so all balancing flags are cleared which is
- * what we want.
- */
-static struct sched_domain sched_domain_dummy;

#ifdef CONFIG_HOTPLUG_CPU
/*
_