diff options
| -rw-r--r-- | fs/exec.c | 5 | ||||
| -rw-r--r-- | include/linux/pid.h | 1 | ||||
| -rw-r--r-- | include/linux/rculist.h | 21 | ||||
| -rw-r--r-- | kernel/pid.c | 19 |
4 files changed, 42 insertions, 4 deletions
diff --git a/fs/exec.c b/fs/exec.c index 06b4c550af5d..9b60f927afd7 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1186,11 +1186,8 @@ static int de_thread(struct task_struct *tsk) /* Become a process group leader with the old leader's pid. * The old leader becomes a thread of the this thread group. - * Note: The old leader also uses this pid until release_task - * is called. Odd but simple and correct. */ - tsk->pid = leader->pid; - change_pid(tsk, PIDTYPE_PID, task_pid(leader)); + exchange_tids(tsk, leader); transfer_pid(leader, tsk, PIDTYPE_TGID); transfer_pid(leader, tsk, PIDTYPE_PGID); transfer_pid(leader, tsk, PIDTYPE_SID); diff --git a/include/linux/pid.h b/include/linux/pid.h index cc896f0fc4e3..2159ffca63fc 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -102,6 +102,7 @@ extern void attach_pid(struct task_struct *task, enum pid_type); extern void detach_pid(struct task_struct *task, enum pid_type); extern void change_pid(struct task_struct *task, enum pid_type, struct pid *pid); +extern void exchange_tids(struct task_struct *task, struct task_struct *old); extern void transfer_pid(struct task_struct *old, struct task_struct *new, enum pid_type); diff --git a/include/linux/rculist.h b/include/linux/rculist.h index 8214cdc715f2..67867e0d4cec 100644 --- a/include/linux/rculist.h +++ b/include/linux/rculist.h @@ -506,6 +506,27 @@ static inline void hlist_replace_rcu(struct hlist_node *old, WRITE_ONCE(old->pprev, LIST_POISON2); } +/** + * hlists_swap_heads_rcu - swap the lists the hlist heads point to + * @left: The hlist head on the left + * @right: The hlist head on the right + * + * The lists start out as [@left ][node1 ... ] and + [@right ][node2 ... ] + * The lists end up as [@left ][node2 ... ] + * [@right ][node1 ... ] + */ +static inline void hlists_swap_heads_rcu(struct hlist_head *left, struct hlist_head *right) +{ + struct hlist_node *node1 = left->first; + struct hlist_node *node2 = right->first; + + rcu_assign_pointer(left->first, node2); + rcu_assign_pointer(right->first, node1); + WRITE_ONCE(node2->pprev, &left->first); + WRITE_ONCE(node1->pprev, &right->first); +} + /* * return the first or the next element in an RCU protected hlist */ diff --git a/kernel/pid.c b/kernel/pid.c index c835b844aca7..6d5d0a5bda82 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -363,6 +363,25 @@ void change_pid(struct task_struct *task, enum pid_type type, attach_pid(task, type); } +void exchange_tids(struct task_struct *left, struct task_struct *right) +{ + struct pid *pid1 = left->thread_pid; + struct pid *pid2 = right->thread_pid; + struct hlist_head *head1 = &pid1->tasks[PIDTYPE_PID]; + struct hlist_head *head2 = &pid2->tasks[PIDTYPE_PID]; + + /* Swap the single entry tid lists */ + hlists_swap_heads_rcu(head1, head2); + + /* Swap the per task_struct pid */ + rcu_assign_pointer(left->thread_pid, pid2); + rcu_assign_pointer(right->thread_pid, pid1); + + /* Swap the cached value */ + WRITE_ONCE(left->pid, pid_nr(pid2)); + WRITE_ONCE(right->pid, pid_nr(pid1)); +} + /* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */ void transfer_pid(struct task_struct *old, struct task_struct *new, enum pid_type type) |