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exit: reparent: introduce find_child_reaper() 

find_new_reaper() does 2 completely different things.  Not only it finds a
reaper, it also updates pid_ns->child_reaper or kills the whole namespace
if the caller is ->child_reaper.

Now that has_child_subreaper logic doesn't depend on child_reaper check we
can move that pid_ns code into a separate helper.  IMHO this makes the
code more clean, and this allows the next changes.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Sterling Alexander <stalexan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2014-12-10 15:55:11 -08:00 committed by Linus Torvalds
parent 175aed3f8d
commit 1109909c7d
1 changed files with 35 additions and 21 deletions
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56
kernel/exit.c
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@ -459,6 +459,34 @@ static void exit_mm(struct task_struct *tsk)
clear_thread_flag(TIF_MEMDIE);
}
static struct task_struct *find_child_reaper(struct task_struct *father)
__releases(&tasklist_lock)
__acquires(&tasklist_lock)
{
struct pid_namespace *pid_ns = task_active_pid_ns(father);
struct task_struct *reaper = pid_ns->child_reaper;
if (likely(reaper != father))
return reaper;
for_each_thread(father, reaper) {
if (reaper->flags & PF_EXITING)
continue;
pid_ns->child_reaper = reaper;
return reaper;
}
write_unlock_irq(&tasklist_lock);
if (unlikely(pid_ns == &init_pid_ns)) {
panic("Attempted to kill init! exitcode=0x%08x\n",
father->signal->group_exit_code ?: father->exit_code);
}
zap_pid_ns_processes(pid_ns);
write_lock_irq(&tasklist_lock);
return father;
}
/*
* When we die, we re-parent all our children, and try to:
* 1. give them to another thread in our thread group, if such a member exists
@ -466,33 +494,17 @@ static void exit_mm(struct task_struct *tsk)
* child_subreaper for its children (like a service manager)
* 3. give it to the init process (PID 1) in our pid namespace
*/
static struct task_struct *find_new_reaper(struct task_struct *father)
__releases(&tasklist_lock)
__acquires(&tasklist_lock)
static struct task_struct *find_new_reaper(struct task_struct *father,
struct task_struct *child_reaper)
{
struct pid_namespace *pid_ns = task_active_pid_ns(father);
struct task_struct *thread;
for_each_thread(father, thread) {
if (thread->flags & PF_EXITING)
continue;
if (unlikely(pid_ns->child_reaper == father))
pid_ns->child_reaper = thread;
return thread;
}
if (unlikely(pid_ns->child_reaper == father)) {
write_unlock_irq(&tasklist_lock);
if (unlikely(pid_ns == &init_pid_ns)) {
panic("Attempted to kill init! exitcode=0x%08x\n",
father->signal->group_exit_code ?:
father->exit_code);
}
zap_pid_ns_processes(pid_ns);
write_lock_irq(&tasklist_lock);
}
if (father->signal->has_child_subreaper) {
struct task_struct *reaper;
/*
@ -501,7 +513,7 @@ static struct task_struct *find_new_reaper(struct task_struct *father)
* namespace, this is safe because all its threads are dead.
*/
for (reaper = father;
!same_thread_group(reaper, pid_ns->child_reaper);
!same_thread_group(reaper, child_reaper);
reaper = reaper->real_parent) {
/* call_usermodehelper() descendants need this check */
if (reaper == &init_task)
@ -515,7 +527,7 @@ static struct task_struct *find_new_reaper(struct task_struct *father)
}
}
return pid_ns->child_reaper;
return child_reaper;
}
/*
@ -552,7 +564,9 @@ static void forget_original_parent(struct task_struct *father)
exit_ptrace(father, &dead_children);
/* Can drop and reacquire tasklist_lock */
reaper = find_new_reaper(father);
reaper = find_child_reaper(father);
reaper = find_new_reaper(father, reaper);
list_for_each_entry(p, &father->children, sibling) {
for_each_thread(p, t) {
t->real_parent = reaper;