Commit 73863ab0 authored by Anton Vorontsov's avatar Anton Vorontsov Committed by Linus Torvalds

powerpc: use clear_tasks_mm_cpumask()

Current CPU hotplug code has some task->mm handling issues:

1. Working with task->mm w/o getting mm or grabing the task lock is
   dangerous as ->mm might disappear (exit_mm() assigns NULL under
   task_lock(), so tasklist lock is not enough).

   We can't use get_task_mm()/mmput() pair as mmput() might sleep,
   so we must take the task lock while handle its mm.

2. Checking for process->mm is not enough because process' main
   thread may exit or detach its mm via use_mm(), but other threads
   may still have a valid mm.

   To fix this we would need to use find_lock_task_mm(), which would
   walk up all threads and returns an appropriate task (with task
   lock held).

clear_tasks_mm_cpumask() has all the issues fixed, so let's use it.
Suggested-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarAnton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3eaa73bd
...@@ -333,9 +333,7 @@ static int __cpuinit mmu_context_cpu_notify(struct notifier_block *self, ...@@ -333,9 +333,7 @@ static int __cpuinit mmu_context_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu) unsigned long action, void *hcpu)
{ {
unsigned int cpu = (unsigned int)(long)hcpu; unsigned int cpu = (unsigned int)(long)hcpu;
#ifdef CONFIG_HOTPLUG_CPU
struct task_struct *p;
#endif
/* We don't touch CPU 0 map, it's allocated at aboot and kept /* We don't touch CPU 0 map, it's allocated at aboot and kept
* around forever * around forever
*/ */
...@@ -358,12 +356,7 @@ static int __cpuinit mmu_context_cpu_notify(struct notifier_block *self, ...@@ -358,12 +356,7 @@ static int __cpuinit mmu_context_cpu_notify(struct notifier_block *self,
stale_map[cpu] = NULL; stale_map[cpu] = NULL;
/* We also clear the cpu_vm_mask bits of CPUs going away */ /* We also clear the cpu_vm_mask bits of CPUs going away */
read_lock(&tasklist_lock); clear_tasks_mm_cpumask(cpu);
for_each_process(p) {
if (p->mm)
cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
}
read_unlock(&tasklist_lock);
break; break;
#endif /* CONFIG_HOTPLUG_CPU */ #endif /* CONFIG_HOTPLUG_CPU */
} }
......
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