diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/locking.h | 1 | ||||
| -rw-r--r-- | lib/route.h | 101 |
2 files changed, 94 insertions, 8 deletions
diff --git a/lib/locking.h b/lib/locking.h index a9a8aa9b..1df30063 100644 --- a/lib/locking.h +++ b/lib/locking.h @@ -16,6 +16,7 @@ struct lock_order { struct domain_generic *the_bird; struct domain_generic *proto; struct domain_generic *rtable; + struct domain_generic *attrs; struct domain_generic *resource; }; diff --git a/lib/route.h b/lib/route.h index 2d691215..cf3c70ba 100644 --- a/lib/route.h +++ b/lib/route.h @@ -11,11 +11,14 @@ #define _BIRD_LIB_ROUTE_H_ #include "lib/type.h" +#include "lib/rcu.h" +#include "lib/hash.h" +#include "lib/event.h" struct network; struct proto; struct cli; - +struct rtable; typedef struct rte { struct ea_list *attrs; /* Attributes of this route */ @@ -43,19 +46,101 @@ static inline int rte_is_filtered(rte *r) { return !!(r->flags & REF_FILTERED); struct rte_src { struct rte_src *next; /* Hash chain */ - struct proto *proto; /* Protocol the source is based on */ + struct rte_owner *owner; /* Route source owner */ u32 private_id; /* Private ID, assigned by the protocol */ u32 global_id; /* Globally unique ID of the source */ - unsigned uc; /* Use count */ + _Atomic u64 uc; /* Use count */ +}; + +struct rte_owner_class { + void (*get_route_info)(struct rte *, byte *buf); /* Get route information (for `show route' command) */ + int (*rte_better)(struct rte *, struct rte *); + int (*rte_mergable)(struct rte *, struct rte *); + u32 (*rte_igp_metric)(const rte *); +}; + +struct rte_owner { + struct rte_owner_class *class; + int (*rte_recalculate)(struct rtable *, struct network *, struct rte *, struct rte *, struct rte *); + HASH(struct rte_src) hash; + const char *name; + u32 hash_key; + u32 uc; + event_list *list; + event *prune; + event *stop; }; +DEFINE_DOMAIN(attrs); +extern DOMAIN(attrs) attrs_domain; + +#define RTA_LOCK LOCK_DOMAIN(attrs, attrs_domain) +#define RTA_UNLOCK UNLOCK_DOMAIN(attrs, attrs_domain) + +#define RTE_SRC_PU_SHIFT 44 +#define RTE_SRC_IN_PROGRESS (1ULL << RTE_SRC_PU_SHIFT) + +/* Get a route source. This also locks the source, therefore the caller has to + * unlock the source after the route has been propagated. */ +struct rte_src *rt_get_source_o(struct rte_owner *o, u32 id); +#define rt_get_source(p, id) rt_get_source_o(&(p)->sources, (id)) -struct rte_src *rt_find_source(struct proto *p, u32 id); -struct rte_src *rt_get_source(struct proto *p, u32 id); struct rte_src *rt_find_source_global(u32 id); -static inline void rt_lock_source(struct rte_src *src) { src->uc++; } -static inline void rt_unlock_source(struct rte_src *src) { src->uc--; } -void rt_prune_sources(void); + +static inline void rt_lock_source(struct rte_src *src) +{ + /* Locking a source is trivial; somebody already holds it so we just increase + * the use count. Nothing can be freed underneath our hands. */ + u64 uc = atomic_fetch_add_explicit(&src->uc, 1, memory_order_acq_rel); + ASSERT_DIE(uc > 0); +} + +static inline void rt_unlock_source(struct rte_src *src) +{ + /* Unlocking is tricky. We do it lockless so at the same time, the prune + * event may be running, therefore if the unlock gets us to zero, it must be + * the last thing in this routine, otherwise the prune routine may find the + * source's usecount zeroed, freeing it prematurely. + * + * The usecount is split into two parts: + * the top 20 bits are an in-progress indicator + * the bottom 44 bits keep the actual usecount. + * + * Therefore at most 1 million of writers can simultaneously unlock the same + * source, while at most ~17T different routes can reference it. Both limits + * are insanely high from the 2022 point of view. Let's suppose that when 17T + * routes or 1M writers get real, we get also 128bit atomic variables in the + * C norm. */ + + /* First, we push the in-progress indicator */ + u64 uc = atomic_fetch_add_explicit(&src->uc, RTE_SRC_IN_PROGRESS, memory_order_acq_rel); + + /* Then we split the indicator to its parts. Remember, we got the value before the operation happened. */ + u64 pending = (uc >> RTE_SRC_PU_SHIFT) + 1; + uc &= RTE_SRC_IN_PROGRESS - 1; + + /* We per-use the RCU critical section indicator to make the prune event wait + * until we finish here in the rare case we get preempted. */ + rcu_read_lock(); + + /* Obviously, there can't be more pending unlocks than the usecount itself */ + if (uc == pending) + /* If we're the last unlocker, schedule the owner's prune event */ + ev_send(src->owner->list, src->owner->prune); + else + ASSERT_DIE(uc > pending); + + /* And now, finally, simultaneously pop the in-progress indicator and the + * usecount, possibly allowing the source pruning routine to free this structure */ + atomic_fetch_sub_explicit(&src->uc, RTE_SRC_IN_PROGRESS + 1, memory_order_acq_rel); + + /* ... and to reduce the load a bit, the source pruning routine will better wait for + * RCU synchronization instead of a busy loop. */ + rcu_read_unlock(); +} + +void rt_init_sources(struct rte_owner *, const char *name, event_list *list); +void rt_destroy_sources(struct rte_owner *, event *); /* * Route Attributes |