The patch titled
kernel/pid.c: update comment on find_task_by_pid_ns
has been added to the -mm tree. Its filename is
kernel-pidc-update-comment-on-find_task_by_pid_ns.patch
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------------------------------------------------------
Subject: kernel/pid.c: update comment on find_task_by_pid_ns
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
tasklist_lock does protect the task and its pid, it can't go away. The
problem is that find_pid_ns() itself is unsafe without rcu lock, it can
race with copy_process()->free_pid(any_pid).
Protecting copy_process()->free_pid(any_pid) with tasklist_lock would make
it possible to call find_task_by_pid_ns() under tasklist safely, but we
don't do so because we are trying to get rid of the read_lock sites of
tasklist_lock.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/pid.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN kernel/pid.c~kernel-pidc-update-comment-on-find_task_by_pid_ns kernel/pid.c
--- a/kernel/pid.c~kernel-pidc-update-comment-on-find_task_by_pid_ns
+++ a/kernel/pid.c
@@ -376,7 +376,7 @@ struct task_struct *pid_task(struct pid
EXPORT_SYMBOL(pid_task);
/*
- * Must be called under rcu_read_lock() or with tasklist_lock read-held.
+ * Must be called under rcu_read_lock().
*/
struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
{
_
Patches currently in -mm which might be from penguin-kernel@xxxxxxxxxxxxxxxxxxx are
origin.patch
linux-next.patch
kernel-pidc-update-comment-on-find_task_by_pid_ns.patch
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