From 47e65328a7b1cdfc4e3102e50d60faf94ebba7d3 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:25 -0800 Subject: [PATCH] [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 Acked-By: Eric Biederman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/pid.h | 1 - include/linux/sched.h | 11 ++++++++--- kernel/exit.c | 10 +--------- kernel/fork.c | 4 +++- 4 files changed, 12 insertions(+), 14 deletions(-) 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 @@ struct task_struct { /* 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 @@ extern void wait_task_inactive(task_t * p); #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 @@ static void __unhash_process(struct task_struct *p) { 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 @@ static void __unhash_process(struct task_struct *p) list_del_init(&p->tasks); __get_cpu_var(process_counts)--; } - + list_del_rcu(&p->thread_group); remove_parent(p); } @@ -964,13 +963,6 @@ asmlinkage long sys_exit(int error_code) 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 @@ static task_t *copy_process(unsigned long clone_flags, * 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 @@ static task_t *copy_process(unsigned long clone_flags, 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 @@ static task_t *copy_process(unsigned long clone_flags, 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++; } -- 2.7.4