[PATCH v3 4/6] pid: sprinkle tasklist_lock asserts

Mateusz Guzik
2025-02-01T16:31:35Z

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
---
kernel/pid.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/kernel/pid.c b/kernel/pid.c
index 924084713be8..2ae872f689a7 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -339,17 +339,23 @@ static struct pid **task_pid_ptr(struct task_struct *task, enum pid_type type)
*/
void attach_pid(struct task_struct *task, enum pid_type type)
{
- struct pid *pid = *task_pid_ptr(task, type);
+ struct pid *pid;
+
+ lockdep_assert_held_write(&tasklist_lock);
+
+ pid = *task_pid_ptr(task, type);
hlist_add_head_rcu(&task->pid_links[type], &pid->tasks[type]);
}

static void __change_pid(struct task_struct *task, enum pid_type type,
struct pid *new)
{
- struct pid **pid_ptr = task_pid_ptr(task, type);
- struct pid *pid;
+ struct pid **pid_ptr, *pid;
int tmp;

+ lockdep_assert_held_write(&tasklist_lock);
+
+ pid_ptr = task_pid_ptr(task, type);
pid = *pid_ptr;

hlist_del_rcu(&task->pid_links[type]);
@@ -386,6 +392,8 @@ void exchange_tids(struct task_struct *left, struct task_struct *right)
struct hlist_head *head1 = &pid1->tasks[PIDTYPE_PID];
struct hlist_head *head2 = &pid2->tasks[PIDTYPE_PID];

+ lockdep_assert_held_write(&tasklist_lock);
+
/* Swap the single entry tid lists */
hlists_swap_heads_rcu(head1, head2);

@@ -403,6 +411,7 @@ void transfer_pid(struct task_struct *old, struct task_struct *new,
enum pid_type type)
{
WARN_ON_ONCE(type == PIDTYPE_PID);
+ lockdep_assert_held_write(&tasklist_lock);
hlist_replace_rcu(&old->pid_links[type], &new->pid_links[type]);
}

--
2.43.0