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introduce the walk_process_tree() helper

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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: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Oleg Nesterov 2017-01-30 18:06:11 +03:00 committed by Eric W. Biederman
parent 015bb305b8
commit 0f1b92cbdd
2 changed files with 35 additions and 0 deletions
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3
include/linux/sched.h
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@ -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;

32
kernel/fork.c
View file

@ -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