Since the ->event interface holds the timerlist_lock across the entire
->event call invocation there is no SMP timer add-back race and the
timer_enter/exit mechanism isn't needed, so more baggage can go. The
timer_enter/exit is therefore moved off the ->event patch to the legacy
path. Normal del_timer is all that's needed to delete an ->event style
timer.
The only problem with this is, with the timerlist_lock held all the way
through the ->event execution there is bound to be more contention.
This is only a temporary problem: run_timer_list is going to be per-cpu
anyway, with a per-cpu spinlock.
The (trivially) updated patch:
--- ../2.4.1.clean/include/linux/timer.h Tue Jan 30 08:24:55 2001
+++ ./include/linux/timer.h Fri Feb 2 01:02:02 2001
@@ -22,6 +22,7 @@
unsigned long expires;
unsigned long data;
void (*function)(unsigned long);
+ unsigned long (*event)(unsigned long data);
};
extern void add_timer(struct timer_list * timer);
@@ -49,6 +50,7 @@
static inline void init_timer(struct timer_list * timer)
{
timer->list.next = timer->list.prev = NULL;
+ timer->event = NULL; /* not needed if no ->function */
}
static inline int timer_pending (const struct timer_list * timer)
--- ../2.4.1.clean/kernel/timer.c Sun Dec 10 18:53:19 2000
+++ ./kernel/timer.c Fri Feb 2 01:02:02 2001
@@ -299,22 +299,27 @@
repeat:
head = tv1.vec + tv1.index;
curr = head->next;
- if (curr != head) {
- struct timer_list *timer;
- void (*fn)(unsigned long);
- unsigned long data;
-
- timer = list_entry(curr, struct timer_list, list);
- fn = timer->function;
- data= timer->data;
-
+ if (curr != head) {
+ struct timer_list *timer = list_entry(curr, struct timer_list,
list);
detach_timer(timer);
timer->list.next = timer->list.prev = NULL;
- timer_enter(timer);
- spin_unlock_irq(&timerlist_lock);
- fn(data);
- spin_lock_irq(&timerlist_lock);
- timer_exit();
+ if (timer->event)
+ {
+ unsigned long requeue = timer->event(timer);
+ if (requeue)
+ {
+ timer->expires = timer_jiffies + requeue;
+ internal_add_timer(timer);
+ }
+ }
+ else
+ {
+ timer_enter(timer);
+ spin_unlock_irq(&timerlist_lock);
+ timer->function(timer->data); /* this should die */
+ spin_lock_irq(&timerlist_lock);
+ timer_exit();
+ }
goto repeat;
}
++timer_jiffies;
--
Daniel
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