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-rw-r--r--lib/is_single_threaded.c62
1 files changed, 36 insertions, 26 deletions
diff --git a/lib/is_single_threaded.c b/lib/is_single_threaded.c
index f1ed2fe76c65..2762516e0a5e 100644
--- a/lib/is_single_threaded.c
+++ b/lib/is_single_threaded.c
@@ -12,34 +12,44 @@
#include <linux/sched.h>
-/**
- * is_single_threaded - Determine if a thread group is single-threaded or not
- * @p: A task in the thread group in question
- *
- * This returns true if the thread group to which a task belongs is single
- * threaded, false if it is not.
+/*
+ * Returns true if the task does not share ->mm with another thread/process.
*/
-bool is_single_threaded(struct task_struct *p)
+bool is_single_threaded(struct task_struct *task)
{
- struct task_struct *g, *t;
- struct mm_struct *mm = p->mm;
-
- if (atomic_read(&p->signal->count) != 1)
- goto no;
-
- if (atomic_read(&p->mm->mm_users) != 1) {
- read_lock(&tasklist_lock);
- do_each_thread(g, t) {
- if (t->mm == mm && t != p)
- goto no_unlock;
- } while_each_thread(g, t);
- read_unlock(&tasklist_lock);
- }
+ struct mm_struct *mm = task->mm;
+ struct task_struct *p, *t;
+ bool ret;
+
+ might_sleep();
+
+ if (atomic_read(&task->signal->live) != 1)
+ return false;
- return true;
+ if (atomic_read(&mm->mm_users) == 1)
+ return true;
+
+ ret = false;
+ down_write(&mm->mmap_sem);
+ rcu_read_lock();
+ for_each_process(p) {
+ if (unlikely(p->flags & PF_KTHREAD))
+ continue;
+ if (unlikely(p == task->group_leader))
+ continue;
+
+ t = p;
+ do {
+ if (unlikely(t->mm == mm))
+ goto found;
+ if (likely(t->mm))
+ break;
+ } while_each_thread(p, t);
+ }
+ ret = true;
+found:
+ rcu_read_unlock();
+ up_write(&mm->mmap_sem);
-no_unlock:
- read_unlock(&tasklist_lock);
-no:
- return false;
+ return ret;
}