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https://gitlab.nic.cz/labs/bird.git
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e91754f5b9
In multithreaded environment, we need to pass messages between workers. This is done by queuing events to their respective queues. The double-linked list is not really useful for that as it needs locking everywhere. This commit rewrites the event subsystem to use a single-linked list where events are enqueued by a single atomic instruction and the queue is processed after atomically moving the whole queue aside.
89 lines
2.1 KiB
C
89 lines
2.1 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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#ifndef _BIRD_EVENT_H_
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#define _BIRD_EVENT_H_
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#include "lib/resource.h"
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#include "lib/locking.h"
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#include <stdatomic.h>
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struct birdloop;
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typedef struct event {
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resource r;
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void (*hook)(void *);
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void *data;
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struct event * _Atomic next;
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} event;
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typedef union event_list {
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struct {
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event * _Atomic receiver; /* Event receive list */
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event * _Atomic _executor; /* Event execute list */
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const char *name;
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struct birdloop *loop; /* The executor loop */
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char _end[0];
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};
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event _sentinel; /* Sentinel node to actively detect list end */
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} event_list;
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extern event_list global_event_list;
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extern event_list global_work_list;
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event *ev_new(pool *);
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void ev_run(event *);
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void ev_init_list(event_list *, struct birdloop *loop, const char *name);
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void ev_enqueue(event_list *, event *);
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#define ev_send ev_enqueue
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#define ev_send_loop(l, e) ev_send(birdloop_event_list((l)), (e))
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#define ev_schedule(e) ({ ASSERT_THE_BIRD_LOCKED; if (!ev_active((e))) ev_send(&global_event_list, (e)); })
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#define ev_schedule_work(e) ({ ASSERT_THE_BIRD_LOCKED; if (!ev_active((e))) ev_send(&global_work_list, (e)); })
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void ev_postpone(event *);
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int ev_run_list_limited(event_list *, uint);
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#define ev_run_list(l) ev_run_list_limited((l), ~0)
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#define LEGACY_EVENT_LIST(l) (((l) == &global_event_list) || ((l) == &global_work_list))
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static inline int
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ev_active(event *e)
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{
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return atomic_load_explicit(&e->next, memory_order_relaxed) != NULL;
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}
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static inline event_list *
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ev_get_list(event *e)
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{
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/* We are looking for the sentinel node at the list end.
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* After this, we have s->next == NULL */
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event *s = e;
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for (event *sn; sn = atomic_load_explicit(&s->next, memory_order_acquire); s = sn)
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;
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/* No sentinel, no list. */
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if (s == e)
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return NULL;
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else
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return SKIP_BACK(event_list, _sentinel, s);
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}
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static inline event*
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ev_new_init(pool *p, void (*hook)(void *), void *data)
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{
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event *e = ev_new(p);
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e->hook = hook;
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e->data = data;
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return e;
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}
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#endif
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