[PATCH] get_task_mm: check PF_KTHREAD lockless
From: Oleg Nesterov
Date: Wed Jun 26 2024 - 15:12:07 EST
Nowadays PF_KTHREAD is sticky and it was never protected by ->alloc_lock.
Move the PF_KTHREAD check outside of task_lock() section to make this code
more understandable.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
kernel/fork.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index 4c361d2bdc12..d3dc623a1247 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1536,14 +1536,13 @@ struct mm_struct *get_task_mm(struct task_struct *task)
{
struct mm_struct *mm;
+ if (task->flags & PF_KTHREAD)
+ return NULL;
+
task_lock(task);
mm = task->mm;
- if (mm) {
- if (task->flags & PF_KTHREAD)
- mm = NULL;
- else
- mmget(mm);
- }
+ if (mm)
+ mmget(mm);
task_unlock(task);
return mm;
}
--
2.25.1.362.g51ebf55