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    SubjectRe: [RFC] New Improved Stronger Whiter Timers (was: Kernel Janitor)
    Date
    On Tue, 30 Jan 2001, Manfred Spraul wrote:
    > This one is an UP and SMP race:
    >
    > spin_unlock_irq(&timerlist_lock);
    > + if (timer->event)
    > + {
    > + if ((requeue = timer->event(data)))
    > + {
    > + timer->expires += requeue;
    > + internal_add_timer(timer);
    > + }
    > + }
    > + else
    > + timer->function(data); /* bad old way */
    > spin_lock_irq(&timerlist_lock);
    >
    > internal_add_timer assumes that the timerlist_lock is acquired.

    Yes, oops, here is the fix.

    --- ../2.4.1.clean/include/linux/timer.h Tue Jan 30 08:24:55 2001
    +++ ./include/linux/timer.h Tue Jan 30 21:52:58 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 +50,9 @@
    static inline void init_timer(struct timer_list * timer)
    {
    timer->list.next = timer->list.prev = NULL;
    + timer->function = NULL;
    + timer->event = NULL;
    + timer->data = 0;
    }

    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 Tue Jan 30 22:09:09 2001
    @@ -301,19 +301,30 @@
    curr = head->next;
    if (curr != head) {
    struct timer_list *timer;
    - void (*fn)(unsigned long);
    - unsigned long data;
    + unsigned long data, requeue;

    timer = list_entry(curr, struct timer_list, list);
    - fn = timer->function;
    data= timer->data;

    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);
    + if (timer->event)
    + {
    + requeue = timer->event(data);
    + spin_lock_irq(&timerlist_lock);
    + if (requeue)
    + {
    + timer->expires += requeue;
    + internal_add_timer(timer);
    + }
    + }
    + else
    + {
    + timer->function(data); /* bad old way */
    + spin_lock_irq(&timerlist_lock);
    + }
    timer_exit();
    goto repeat;
    }
    --
    Daniel
    -
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