From 0f1b92cbdd0309afae0af1963e8cccddb3d2eaff Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 30 Jan 2017 18:06:11 +0300 Subject: [PATCH] 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: Oleg Nesterov Signed-off-by: Pavel Tikhomirov Signed-off-by: Eric W. Biederman --- include/linux/sched.h | 3 +++ kernel/fork.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 35 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index d2334229167f..6261bfc12853 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -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; diff --git a/kernel/fork.c b/kernel/fork.c index 11c5c8ab827c..135b7a49ad59 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -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 -- 2.20.1