diff options
Diffstat (limited to 'kernel/cpu.c')
| -rw-r--r-- | kernel/cpu.c | 57 |
1 files changed, 56 insertions, 1 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index 2060c6e5702..a4eb5227a19 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -10,13 +10,18 @@ #include <linux/sched.h> #include <linux/unistd.h> #include <linux/cpu.h> +#include <linux/oom.h> +#include <linux/rcupdate.h> #include <linux/export.h> +#include <linux/bug.h> #include <linux/kthread.h> #include <linux/stop_machine.h> #include <linux/mutex.h> #include <linux/gfp.h> #include <linux/suspend.h> +#include "smpboot.h" + #ifdef CONFIG_SMP /* Serializes the updates to cpu_online_mask, cpu_present_mask */ static DEFINE_MUTEX(cpu_add_remove_lock); @@ -171,6 +176,47 @@ void __ref unregister_cpu_notifier(struct notifier_block *nb) } EXPORT_SYMBOL(unregister_cpu_notifier); +/** + * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU + * @cpu: a CPU id + * + * This function walks all processes, finds a valid mm struct for each one and + * then clears a corresponding bit in mm's cpumask. While this all sounds + * trivial, there are various non-obvious corner cases, which this function + * tries to solve in a safe manner. + * + * Also note that the function uses a somewhat relaxed locking scheme, so it may + * be called only for an already offlined CPU. + */ +void clear_tasks_mm_cpumask(int cpu) +{ + struct task_struct *p; + + /* + * This function is called after the cpu is taken down and marked + * offline, so its not like new tasks will ever get this cpu set in + * their mm mask. -- Peter Zijlstra + * Thus, we may use rcu_read_lock() here, instead of grabbing + * full-fledged tasklist_lock. + */ + WARN_ON(cpu_online(cpu)); + rcu_read_lock(); + for_each_process(p) { + struct task_struct *t; + + /* + * Main thread might exit, but other threads may still have + * a valid mm. Find one. + */ + t = find_lock_task_mm(p); + if (!t) + continue; + cpumask_clear_cpu(cpu, mm_cpumask(t->mm)); + task_unlock(t); + } + rcu_read_unlock(); +} + static inline void check_for_tasks(int cpu) { struct task_struct *p; @@ -295,11 +341,19 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) int ret, nr_calls = 0; void *hcpu = (void *)(long)cpu; unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0; + struct task_struct *idle; if (cpu_online(cpu) || !cpu_present(cpu)) return -EINVAL; cpu_hotplug_begin(); + + idle = idle_thread_get(cpu); + if (IS_ERR(idle)) { + ret = PTR_ERR(idle); + goto out; + } + ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls); if (ret) { nr_calls--; @@ -309,7 +363,7 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) } /* Arch-specific enabling code. */ - ret = __cpu_up(cpu); + ret = __cpu_up(cpu, idle); if (ret != 0) goto out_notify; BUG_ON(!cpu_online(cpu)); @@ -320,6 +374,7 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) out_notify: if (ret != 0) __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL); +out: cpu_hotplug_done(); return ret; |