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>
This commit is contained in:
Al Viro 2012-06-27 09:24:13 +04:00
parent 41f9d29f09
commit 158e1645e0
5 changed files with 38 additions and 36 deletions

View File

@ -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

View File

@ -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();
}

View File

@ -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();
}

View File

@ -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

View File

@ -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;
}
}