From 2c4704756cab7cfa031ada4dab361562f0e357c0 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Tue, 26 Sep 2017 13:06:43 -0500 Subject: pids: Move the pgrp and session pid pointers from task_struct to signal_struct To access these fields the code always has to go to group leader so going to signal struct is no loss and is actually a fundamental simplification. This saves a little bit of memory by only allocating the pid pointer array once instead of once for every thread, and even better this removes a few potential races caused by the fact that group_leader can be changed by de_thread, while signal_struct can not. Signed-off-by: "Eric W. Biederman" --- kernel/pid.c | 45 ++++++++++++++++++++++----------------------- 1 file changed, 22 insertions(+), 23 deletions(-) (limited to 'kernel/pid.c') diff --git a/kernel/pid.c b/kernel/pid.c index d0de2b59f86f..f8486d2e2346 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -265,27 +265,35 @@ struct pid *find_vpid(int nr) } EXPORT_SYMBOL_GPL(find_vpid); +static struct pid **task_pid_ptr(struct task_struct *task, enum pid_type type) +{ + return (type == PIDTYPE_PID) ? + &task->thread_pid : + (type == __PIDTYPE_TGID) ? + &task->signal->leader_pid : + &task->signal->pids[type]; +} + /* * attach_pid() must be called with the tasklist_lock write-held. */ void attach_pid(struct task_struct *task, enum pid_type type) { - struct pid_link *link = &task->pids[type]; - hlist_add_head_rcu(&link->node, &link->pid->tasks[type]); + struct pid *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_link *link; + struct pid **pid_ptr = task_pid_ptr(task, type); struct pid *pid; int tmp; - link = &task->pids[type]; - pid = link->pid; + pid = *pid_ptr; - hlist_del_rcu(&link->node); - link->pid = new; + hlist_del_rcu(&task->pid_links[type]); + *pid_ptr = new; for (tmp = PIDTYPE_MAX; --tmp >= 0; ) if (!hlist_empty(&pid->tasks[tmp])) @@ -310,8 +318,9 @@ void change_pid(struct task_struct *task, enum pid_type type, void transfer_pid(struct task_struct *old, struct task_struct *new, enum pid_type type) { - new->pids[type].pid = old->pids[type].pid; - hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node); + if (type == PIDTYPE_PID) + new->thread_pid = old->thread_pid; + hlist_replace_rcu(&old->pid_links[type], &new->pid_links[type]); } struct task_struct *pid_task(struct pid *pid, enum pid_type type) @@ -322,7 +331,7 @@ struct task_struct *pid_task(struct pid *pid, enum pid_type type) first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]), lockdep_tasklist_lock_is_held()); if (first) - result = hlist_entry(first, struct task_struct, pids[(type)].node); + result = hlist_entry(first, struct task_struct, pid_links[(type)]); } return result; } @@ -360,9 +369,7 @@ struct pid *get_task_pid(struct task_struct *task, enum pid_type type) { struct pid *pid; rcu_read_lock(); - if (type != PIDTYPE_PID) - task = task->group_leader; - pid = get_pid(rcu_dereference(task->pids[type].pid)); + pid = get_pid(rcu_dereference(*task_pid_ptr(task, type))); rcu_read_unlock(); return pid; } @@ -420,16 +427,8 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type, rcu_read_lock(); if (!ns) ns = task_active_pid_ns(current); - if (likely(pid_alive(task))) { - struct pid *pid; - if (type == PIDTYPE_PID) - pid = task_pid(task); - else if (type == __PIDTYPE_TGID) - pid = task_tgid(task); - else - pid = rcu_dereference(task->group_leader->pids[type].pid); - nr = pid_nr_ns(pid, ns); - } + if (likely(pid_alive(task))) + nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns); rcu_read_unlock(); return nr; -- cgit v1.2.3-59-g8ed1b