The patch titled
Subject: get_task_mm: check PF_KTHREAD lockless
has been added to the -mm mm-unstable branch. Its filename is
get_task_mm-check-pf_kthread-lockless.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/get_task_mm-check-pf_kthread-lockless.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: get_task_mm: check PF_KTHREAD lockless
Date: Wed, 26 Jun 2024 21:10:17 +0200
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@xxxxxxxxxx
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/fork.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
--- a/kernel/fork.c~get_task_mm-check-pf_kthread-lockless
+++ a/kernel/fork.c
@@ -1536,14 +1536,13 @@ struct mm_struct *get_task_mm(struct tas
{
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;
}
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
memcg-mm_update_next_owner-kill-the-retry-logic.patch
memcg-mm_update_next_owner-move-for_each_thread-into-try_to_set_owner.patch
get_task_mm-check-pf_kthread-lockless.patch
zap_pid_ns_processes-dont-send-sigkill-to-sub-threads.patch
coredump-simplify-zap_process.patch
