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Commit 0f1b92cb authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Eric W. Biederman
Browse files

introduce the walk_process_tree() helper 



Add the new helper to walk the process tree, the next patch adds a user.
Note that it visits the group leaders only, proc_visitor can do
for_each_thread itself or we can trivially extend walk_process_tree() to
do this.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent 015bb305

include/linux/sched.h

+3 −0
Original line number Diff line number Diff line
@@ -3053,6 +3053,9 @@ extern bool current_is_single_threaded(void); 
#define for_each_process_thread(p, t)	\

	for_each_process(p) for_each_thread(p, t)



typedef int (*proc_visitor)(struct task_struct *p, void *data);

void walk_process_tree(struct task_struct *top, proc_visitor, void *);



static inline int get_nr_threads(struct task_struct *tsk)

{

	return tsk->signal->nr_threads;

kernel/fork.c

+32 −0
Original line number Diff line number Diff line
@@ -2053,6 +2053,38 @@ SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 
}

#endif



void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)

{

	struct task_struct *leader, *parent, *child;

	int res;



	read_lock(&tasklist_lock);

	leader = top = top->group_leader;

down:

	for_each_thread(leader, parent) {

		list_for_each_entry(child, &parent->children, sibling) {

			res = visitor(child, data);

			if (res) {

				if (res < 0)

					goto out;

				leader = child;

				goto down;

			}

up:

			;

		}

	}



	if (leader != top) {

		child = leader;

		parent = child->real_parent;

		leader = parent->group_leader;

		goto up;

	}

out:

	read_unlock(&tasklist_lock);

}



#ifndef ARCH_MIN_MMSTRUCT_ALIGN

#define ARCH_MIN_MMSTRUCT_ALIGN 0

#endif