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b933281ed5
WALK_LIST_DELSAFE (in ev_run_list) is not safe with regard to deletion of next node. When some events are rescheduled during event execution, it may lead to deletion of next node and some events are skipped. Such skipped nodes remain in temporary list on stack and the last of them contains 'next' pointer to stack area. When this event is later scheduled, it damages stack area trying to remove it from the list, which leads to random crashes with funny backtraces :-) .
141 lines
2.8 KiB
C
141 lines
2.8 KiB
C
/*
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* BIRD Library -- Event Processing
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*
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* (c) 1999 Martin Mares <mj@ucw.cz>
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*
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* Can be freely distributed and used under the terms of the GNU GPL.
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*/
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/**
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* DOC: Events
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*
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* Events are there to keep track of deferred execution.
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* Since BIRD is single-threaded, it requires long lasting tasks to be split to smaller
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* parts, so that no module can monopolize the CPU. To split such a task, just create
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* an &event resource, point it to the function you want to have called and call ev_schedule()
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* to ask the core to run the event when nothing more important requires attention.
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*
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* You can also define your own event lists (the &event_list structure), enqueue your
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* events in them and explicitly ask to run them.
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*/
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#include "nest/bird.h"
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#include "lib/event.h"
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event_list global_event_list;
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inline void
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ev_postpone(event *e)
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{
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if (e->n.next)
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{
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rem_node(&e->n);
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e->n.next = NULL;
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}
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}
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static void
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ev_dump(resource *r)
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{
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event *e = (event *) r;
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debug("(code %p, data %p, %s)\n",
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e->hook,
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e->data,
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e->n.next ? "scheduled" : "inactive");
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}
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static struct resclass ev_class = {
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"Event",
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sizeof(event),
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(void (*)(resource *)) ev_postpone,
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ev_dump
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};
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/**
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* ev_new - create a new event
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* @p: resource pool
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*
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* This function creates a new event resource. To use it,
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* you need to fill the structure fields and call ev_schedule().
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*/
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event *
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ev_new(pool *p)
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{
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event *e = ralloc(p, &ev_class);
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e->hook = NULL;
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e->data = NULL;
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e->n.next = NULL;
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return e;
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}
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/**
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* ev_run - run an event
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* @e: an event
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*
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* This function explicitly runs the event @e (calls its hook
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* function) and removes it from an event list if it's linked to any.
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*
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* From the hook function, you can call ev_enqueue() or ev_schedule()
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* to re-add the event.
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*/
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inline void
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ev_run(event *e)
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{
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ev_postpone(e);
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e->hook(e->data);
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}
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/**
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* ev_enqueue - enqueue an event
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* @l: an event list
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* @e: an event
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*
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* ev_enqueue() stores the event @e to the specified event
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* list @l which can be run by calling ev_run_list().
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*/
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inline void
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ev_enqueue(event_list *l, event *e)
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{
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ev_postpone(e);
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add_tail(l, &e->n);
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}
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/**
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* ev_schedule - schedule an event
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* @e: an event
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*
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* This function schedules an event by enqueueing it to a system-wide
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* event list which is run by the platform dependent code whenever
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* appropriate.
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*/
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void
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ev_schedule(event *e)
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{
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ev_enqueue(&global_event_list, e);
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}
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/**
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* ev_run_list - run an event list
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* @l: an event list
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*
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* This function calls ev_run() for all events enqueued in the list @l.
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*/
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int
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ev_run_list(event_list *l)
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{
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node *n;
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list tmp_list;
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init_list(&tmp_list);
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add_tail_list(&tmp_list, l);
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init_list(l);
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WALK_LIST_FIRST(n, tmp_list)
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{
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event *e = SKIP_BACK(event, n, n);
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ev_run(e);
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}
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return !EMPTY_LIST(*l);
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}
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