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pid: sprinkle tasklist_lock asserts

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They cost nothing on production kernels and document the requirement of
holding the tasklist_lock lock in respective routines.

Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20250206164415.450051-4-mjguzik@gmail.com
Acked-by: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Mateusz Guzik
2025-02-06 17:44:12 +01:00
committed by Christian Brauner
parent 6731cd97e6
commit 74198dc206
1 changed files with 12 additions and 3 deletions
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15
kernel/pid.c
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@@ -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]);
}