trim task_work: get rid of hlist
layout based on Oleg's suggestion; single-linked list,
task->task_works points to the last element, forward pointer
from said last element points to head. I'd still prefer
much more regular scheme with two pointers in task_work,
but...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4059c0f..b9216eb 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1405,7 +1405,7 @@
int (*notifier)(void *priv);
void *notifier_data;
sigset_t *notifier_mask;
- struct hlist_head task_works;
+ void *task_works;
struct audit_context *audit_context;
#ifdef CONFIG_AUDITSYSCALL
diff --git a/include/linux/task_work.h b/include/linux/task_work.h
index 627421c..3b3e2c8 100644
--- a/include/linux/task_work.h
+++ b/include/linux/task_work.h
@@ -8,7 +8,7 @@
typedef void (*task_work_func_t)(struct task_work *);
struct task_work {
- struct hlist_node hlist;
+ struct task_work *next;
task_work_func_t func;
};
@@ -24,7 +24,7 @@
static inline void exit_task_work(struct task_struct *task)
{
- if (unlikely(!hlist_empty(&task->task_works)))
+ if (unlikely(task->task_works))
task_work_run();
}
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 6a4d82b..1e98b55 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -192,7 +192,7 @@
* hlist_add_head(task->task_works);
*/
smp_mb__after_clear_bit();
- if (unlikely(!hlist_empty(¤t->task_works)))
+ if (unlikely(current->task_works))
task_work_run();
}
diff --git a/kernel/fork.c b/kernel/fork.c
index ab5211b..bebabad 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1415,7 +1415,7 @@
*/
p->group_leader = p;
INIT_LIST_HEAD(&p->thread_group);
- INIT_HLIST_HEAD(&p->task_works);
+ p->task_works = NULL;
/* Now that the task is set up, run cgroup callbacks if
* necessary. We need to run them before the task is visible
diff --git a/kernel/task_work.c b/kernel/task_work.c
index 82d1c79..9b8948d 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -19,7 +19,12 @@
*/
raw_spin_lock_irqsave(&task->pi_lock, flags);
if (likely(!(task->flags & PF_EXITING))) {
- hlist_add_head(&twork->hlist, &task->task_works);
+ struct task_work *last = task->task_works;
+ struct task_work *first = last ? last->next : twork;
+ twork->next = first;
+ if (last)
+ last->next = twork;
+ task->task_works = twork;
err = 0;
}
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
@@ -34,51 +39,48 @@
task_work_cancel(struct task_struct *task, task_work_func_t func)
{
unsigned long flags;
- struct task_work *twork;
- struct hlist_node *pos;
+ struct task_work *last, *res = NULL;
raw_spin_lock_irqsave(&task->pi_lock, flags);
- hlist_for_each_entry(twork, pos, &task->task_works, hlist) {
- if (twork->func == func) {
- hlist_del(&twork->hlist);
- goto found;
+ last = task->task_works;
+ if (last) {
+ struct task_work *q = last, *p = q->next;
+ while (1) {
+ if (p->func == func) {
+ q->next = p->next;
+ if (p == last)
+ task->task_works = q == p ? NULL : q;
+ res = p;
+ break;
+ }
+ if (p == last)
+ break;
+ q = p;
+ p = q->next;
}
}
- twork = NULL;
- found:
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
-
- return twork;
+ return res;
}
void task_work_run(void)
{
struct task_struct *task = current;
- struct hlist_head task_works;
- struct hlist_node *pos;
+ struct task_work *p, *q;
raw_spin_lock_irq(&task->pi_lock);
- hlist_move_list(&task->task_works, &task_works);
+ p = task->task_works;
+ task->task_works = NULL;
raw_spin_unlock_irq(&task->pi_lock);
- if (unlikely(hlist_empty(&task_works)))
+ if (unlikely(!p))
return;
- /*
- * We use hlist to save the space in task_struct, but we want fifo.
- * Find the last entry, the list should be short, then process them
- * in reverse order.
- */
- for (pos = task_works.first; pos->next; pos = pos->next)
- ;
- for (;;) {
- struct hlist_node **pprev = pos->pprev;
- struct task_work *twork = container_of(pos, struct task_work,
- hlist);
- twork->func(twork);
-
- if (pprev == &task_works.first)
- break;
- pos = container_of(pprev, struct hlist_node, next);
+ q = p->next; /* head */
+ p->next = NULL; /* cut it */
+ while (q) {
+ p = q->next;
+ q->func(q);
+ q = p;
}
}