Commit 8ac5dc66 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Andrew Morton
Browse files

get_task_mm: check PF_KTHREAD lockless 

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.

Link: https://lkml.kernel.org/r/20240626191017.GA20031@redhat.com


Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent d73d0035

kernel/fork.c

+5 −6
Original line number Diff line number Diff line
@@ -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

	if (mm)

		mmget(mm);

	}

	task_unlock(task);

	return mm;

}