/* Check if we can reap the given task. This has to be called with stable
* tsk->mm
*/
void try_oom_reaper(struct task_struct *tsk)
{
struct mm_struct *mm = tsk->mm;
struct task_struct *p;
if (!mm)
return;
/*
* There might be other threads/processes which are either not
* dying or even not killable.
*/
if (atomic_read(&mm->mm_users) > 1) {
rcu_read_lock();
for_each_process(p) {
if (!process_shares_mm(p, mm))
continue;
if (fatal_signal_pending(p))
continue;
/*
* If the task is exiting make sure the whole thread group
* is exiting and cannot acces mm anymore.
*/
if (signal_group_exit(p->signal))
continue;
/* Give up */
rcu_read_unlock();
return;
}
rcu_read_unlock();
}
static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
struct core_state *core_state, int exit_code)
{
struct task_struct *g, *p;
unsigned long flags;
int nr = -EAGAIN;
spin_lock_irq(&tsk->sighand->siglock);
if (!signal_group_exit(tsk->signal)) {
mm->core_state = core_state;
nr = zap_process(tsk, exit_code);
tsk->signal->group_exit_task = tsk;
/* ignore all signals except SIGKILL, see prepare_signal() */
tsk->signal->flags = SIGNAL_GROUP_COREDUMP;
clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
}
spin_unlock_irq(&tsk->sighand->siglock);
if (unlikely(nr < 0))
return nr;
tsk->flags = PF_DUMPCORE;
if (atomic_read(&mm->mm_users) == nr + 1)
goto done;
/*
* We should find and kill all tasks which use this mm, and we should
* count them correctly into ->nr_threads. We don't take tasklist
* lock, but this is safe wrt:
*
* fork:
* None of sub-threads can fork after zap_process(leader). All
* processes which were created before this point should be
* visible to zap_threads() because copy_process() adds the new
* process to the tail of init_task.tasks list, and lock/unlock
* of ->siglock provides a memory barrier.
*
* do_exit:
* The caller holds mm->mmap_sem. This means that the task which
* uses this mm can't pass exit_mm(), so it can't exit or clear
* its ->mm.
*
* de_thread:
* It does list_replace_rcu(&leader->tasks, ¤t->tasks),
* we must see either old or new leader, this does not matter.
* However, it can change p->sighand, so lock_task_sighand(p)
* must be used. Since p->mm != NULL and we hold ->mmap_sem
* it can't fail.
*
* Note also that "g" can be the old leader with ->mm == NULL
* and already unhashed and thus removed from ->thread_group.
* This is OK, __unhash_process()->list_del_rcu() does not
* clear the ->next pointer, we will find the new leader via
* next_thread().
*/
rcu_read_lock();
for_each_process(g) {
if (g == tsk->group_leader)
continue;
if (g->flags & PF_KTHREAD)
continue;
p = g;
do {
if (p->mm) {
if (unlikely(p->mm == mm)) {
lock_task_sighand(p, &flags);
nr += zap_process(p, exit_code);
p->signal->flags = SIGNAL_GROUP_EXIT;
unlock_task_sighand(p, &flags);
}
break;
}
} while_each_thread(g, p);
}
rcu_read_unlock();
done:
atomic_set(&core_state->nr_threads, nr);
return nr;
}
