[PATCH] pids: kill PIDTYPE_TGID
This patch kills PIDTYPE_TGID pid_type thus saving one hash table in
kernel/pid.c and speeding up subthreads create/destroy a bit. It is also a
preparation for the further tref/pids rework.
This patch adds 'struct list_head thread_group' to 'struct task_struct'
instead.
We don't detach group leader from PIDTYPE_PID namespace until another
thread inherits it's ->pid == ->tgid, so we are safe wrt premature
free_pidmap(->tgid) call.
Currently there are no users of find_task_by_pid_type(PIDTYPE_TGID).
Should the need arise, we can use find_task_by_pid()->group_leader.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-By: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/pid.h b/include/linux/pid.h
index 099e70e..5b9082c 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -4,7 +4,6 @@
enum pid_type
{
PIDTYPE_PID,
- PIDTYPE_TGID,
PIDTYPE_PGID,
PIDTYPE_SID,
PIDTYPE_MAX
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a913fca..99855f6 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -752,6 +752,7 @@
/* PID/PID hash table linkage. */
struct pid pids[PIDTYPE_MAX];
+ struct list_head thread_group;
struct completion *vfork_done; /* for vfork() */
int __user *set_child_tid; /* CLONE_CHILD_SETTID */
@@ -1192,13 +1193,17 @@
#define while_each_thread(g, t) \
while ((t = next_thread(t)) != g)
-extern task_t * FASTCALL(next_thread(const task_t *p));
-
#define thread_group_leader(p) (p->pid == p->tgid)
+static inline task_t *next_thread(task_t *p)
+{
+ return list_entry(rcu_dereference(p->thread_group.next),
+ task_t, thread_group);
+}
+
static inline int thread_group_empty(task_t *p)
{
- return list_empty(&p->pids[PIDTYPE_TGID].pid_list);
+ return list_empty(&p->thread_group);
}
#define delay_group_leader(p) \
diff --git a/kernel/exit.c b/kernel/exit.c
index aea23e7..22399ca 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -51,7 +51,6 @@
{
nr_threads--;
detach_pid(p, PIDTYPE_PID);
- detach_pid(p, PIDTYPE_TGID);
if (thread_group_leader(p)) {
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);
@@ -59,7 +58,7 @@
list_del_init(&p->tasks);
__get_cpu_var(process_counts)--;
}
-
+ list_del_rcu(&p->thread_group);
remove_parent(p);
}
@@ -964,13 +963,6 @@
do_exit((error_code&0xff)<<8);
}
-task_t fastcall *next_thread(const task_t *p)
-{
- return pid_task(p->pids[PIDTYPE_TGID].pid_list.next, PIDTYPE_TGID);
-}
-
-EXPORT_SYMBOL(next_thread);
-
/*
* Take down every thread in the group. This is called by fatal signals
* as well as by sys_exit_group (below).
diff --git a/kernel/fork.c b/kernel/fork.c
index 12cdd9f..bc551ef 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1112,6 +1112,7 @@
* We dont wake it up yet.
*/
p->group_leader = p;
+ INIT_LIST_HEAD(&p->thread_group);
INIT_LIST_HEAD(&p->ptrace_children);
INIT_LIST_HEAD(&p->ptrace_list);
@@ -1165,7 +1166,9 @@
retval = -EAGAIN;
goto bad_fork_cleanup_namespace;
}
+
p->group_leader = current->group_leader;
+ list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
if (current->signal->group_stop_count > 0) {
/*
@@ -1213,7 +1216,6 @@
list_add_tail(&p->tasks, &init_task.tasks);
__get_cpu_var(process_counts)++;
}
- attach_pid(p, PIDTYPE_TGID, p->tgid);
attach_pid(p, PIDTYPE_PID, p->pid);
nr_threads++;
}