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: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx>
---
arch/sh/kernel/smp.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
index f624174..2470c83 100644
--- a/arch/sh/kernel/smp.c
+++ b/arch/sh/kernel/smp.c
@@ -123,7 +123,6 @@ void native_play_dead(void)
int __cpu_disable(void)
{
unsigned int cpu = smp_processor_id();
- struct task_struct *p;
int ret;
ret = mp_ops->cpu_disable(cpu);
@@ -153,11 +152,7 @@ int __cpu_disable(void)
flush_cache_all();
local_flush_tlb_all();
- read_lock(&tasklist_lock);
- for_each_process(p)
- if (p->mm)
- cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
- read_unlock(&tasklist_lock);
+ clear_tasks_mm_cpumask(cpu);
return 0;
}
--
1.7.9.2
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>