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get_task_mm: check PF_KTHREAD lockless

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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: Oleg Nesterov <oleg@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2024-06-26 21:10:17 +02:00 committed by Andrew Morton
parent d73d003521
commit 8ac5dc6659
1 changed files with 5 additions and 6 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

11
kernel/fork.c
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@ -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;
}