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Commit b3ac022c authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

proc: turn signal_struct->count into "int nr_threads" 



No functional changes, just s/atomic_t count/int nr_threads/.

With the recent changes this counter has a single user, get_nr_threads()
And, none of its callers need the really accurate number of threads, not
to mention each caller obviously races with fork/exit.  It is only used to
report this value to the user-space, except first_tid() uses it to avoid
the unnecessary while_each_thread() loop in the unlikely case.

It is a bit sad we need a word in struct signal_struct for this, perhaps
we can change get_nr_threads() to approximate the number of threads using
signal->live and kill ->nr_threads later.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: default avatarRoland McGrath <roland@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent dd98acf7

include/linux/init_task.h

+1 −1
Original line number Diff line number Diff line
@@ -16,7 +16,7 @@ extern struct files_struct init_files; 
extern struct fs_struct init_fs;



#define INIT_SIGNALS(sig) {						\

	.count		= ATOMIC_INIT(1), 				\

	.nr_threads	= 1,						\

	.wait_chldexit	= __WAIT_QUEUE_HEAD_INITIALIZER(sig.wait_chldexit),\

	.shared_pending	= { 						\

		.list = LIST_HEAD_INIT(sig.shared_pending.list),	\

include/linux/sched.h

+2 −2
Original line number Diff line number Diff line
@@ -527,8 +527,8 @@ struct thread_group_cputimer { 
 */

struct signal_struct {

	atomic_t		sigcnt;

	atomic_t		count;

	atomic_t		live;

	int			nr_threads;



	wait_queue_head_t	wait_chldexit;	/* for wait4() */
@@ -2149,7 +2149,7 @@ extern bool current_is_single_threaded(void); 


static inline int get_nr_threads(struct task_struct *tsk)

{

	return atomic_read(&tsk->signal->count);

	return tsk->signal->nr_threads;

}



/* de_thread depends on thread_group_leader not being a pid based check */

kernel/exit.c

+1 −4
Original line number Diff line number Diff line
@@ -83,14 +83,10 @@ static void __exit_signal(struct task_struct *tsk) 
	struct sighand_struct *sighand;

	struct tty_struct *uninitialized_var(tty);



	BUG_ON(!sig);

	BUG_ON(!atomic_read(&sig->count));



	sighand = rcu_dereference_check(tsk->sighand,

					rcu_read_lock_held() ||

					lockdep_tasklist_lock_is_held());

	spin_lock(&sighand->siglock);

	atomic_dec(&sig->count);



	posix_cpu_timers_exit(tsk);

	if (group_dead) {
@@ -130,6 +126,7 @@ static void __exit_signal(struct task_struct *tsk) 
		sig->sum_sched_runtime += tsk->se.sum_exec_runtime;

	}



	sig->nr_threads--;

	__unhash_process(tsk, group_dead);



	/*

kernel/fork.c

+4 −4
Original line number Diff line number Diff line
@@ -877,9 +877,9 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 
	if (!sig)

		return -ENOMEM;



	atomic_set(&sig->sigcnt, 1);

	atomic_set(&sig->count, 1);

	sig->nr_threads = 1;

	atomic_set(&sig->live, 1);

	atomic_set(&sig->sigcnt, 1);

	init_waitqueue_head(&sig->wait_chldexit);

	if (clone_flags & CLONE_NEWPID)

		sig->flags |= SIGNAL_UNKILLABLE;
@@ -1256,9 +1256,9 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
	}



	if (clone_flags & CLONE_THREAD) {

		atomic_inc(&current->signal->sigcnt);

		atomic_inc(&current->signal->count);

		current->signal->nr_threads++;

		atomic_inc(&current->signal->live);

		atomic_inc(&current->signal->sigcnt);

		p->group_leader = current->group_leader;

		list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);

	}