Commit 158e1645 authored by Al Viro's avatar Al Viro
Browse files

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: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 41f9d29f

include/linux/sched.h

+1 −1
Original line number Diff line number Diff line
@@ -1405,7 +1405,7 @@ struct task_struct { 
	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

include/linux/task_work.h

+2 −2
Original line number Diff line number Diff line
@@ -8,7 +8,7 @@ struct task_work; 
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 @@ void task_work_run(void); 


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();

}

include/linux/tracehook.h

+1 −1
Original line number Diff line number Diff line
@@ -192,7 +192,7 @@ static inline void tracehook_notify_resume(struct pt_regs *regs) 
	 * hlist_add_head(task->task_works);

	 */

	smp_mb__after_clear_bit();

	if (unlikely(!hlist_empty(&current->task_works)))

	if (unlikely(current->task_works))

		task_work_run();

}

kernel/fork.c

+1 −1
Original line number Diff line number Diff line
@@ -1415,7 +1415,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
	 */

	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

kernel/task_work.c

+33 −31
Original line number Diff line number Diff line
@@ -19,7 +19,12 @@ task_work_add(struct task_struct *task, struct task_work *twork, bool notify) 
	 */

	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 @@ struct task_work * 
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;

	}

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE