Commit 47e65328 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

[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: default avatarOleg Nesterov <oleg@tv-sign.ru>
Acked-By: default avatarEric Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 88531f72

include/linux/pid.h

+0 −1
Original line number Diff line number Diff line
@@ -4,7 +4,6 @@ 
enum pid_type

{

	PIDTYPE_PID,

	PIDTYPE_TGID,

	PIDTYPE_PGID,

	PIDTYPE_SID,

	PIDTYPE_MAX

include/linux/sched.h

+8 −3
Original line number Diff line number Diff line
@@ -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) \

kernel/exit.c

+1 −9
Original line number Diff line number Diff line
@@ -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).

kernel/fork.c

+3 −1
Original line number Diff line number Diff line
@@ -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++;

	}

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