sched: Add a generic notifier when a task struct is about to be freed
This patch adds a notifier which can be used by subsystems that may
be interested in when a task has completely died and is about to
have it's last resource freed.
The Android lowmemory killer uses this to determine when a task
it has killed has finally given up its goods.
Signed-off-by: San Mehat <san@google.com>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a837b20..1bb6858 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1745,6 +1745,9 @@
extern void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st);
extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *st);
+extern int task_free_register(struct notifier_block *n);
+extern int task_free_unregister(struct notifier_block *n);
+
/*
* Per process flags
*/
diff --git a/kernel/fork.c b/kernel/fork.c
index 0276c30..0900f2f 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -154,6 +154,9 @@
/* SLAB cache for mm_struct structures (tsk->mm) */
static struct kmem_cache *mm_cachep;
+/* Notifier list called when a task struct is freed */
+static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
+
static void account_kernel_stack(struct thread_info *ti, int account)
{
struct zone *zone = page_zone(virt_to_page(ti));
@@ -185,6 +188,18 @@
free_signal_struct(sig);
}
+int task_free_register(struct notifier_block *n)
+{
+ return atomic_notifier_chain_register(&task_free_notifier, n);
+}
+EXPORT_SYMBOL(task_free_register);
+
+int task_free_unregister(struct notifier_block *n)
+{
+ return atomic_notifier_chain_unregister(&task_free_notifier, n);
+}
+EXPORT_SYMBOL(task_free_unregister);
+
void __put_task_struct(struct task_struct *tsk)
{
WARN_ON(!tsk->exit_state);
@@ -195,6 +210,7 @@
delayacct_tsk_free(tsk);
put_signal_struct(tsk->signal);
+ atomic_notifier_call_chain(&task_free_notifier, 0, tsk);
if (!profile_handoff_task(tsk))
free_task(tsk);
}