diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/memalloc.c | 34 |
1 files changed, 32 insertions, 2 deletions
diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c index 08e4dde66cd5..15684d0fc883 100644 --- a/kernel/bpf/memalloc.c +++ b/kernel/bpf/memalloc.c @@ -118,6 +118,11 @@ struct bpf_mem_cache { struct llist_head free_by_rcu_ttrace; struct llist_head waiting_for_gp_ttrace; struct rcu_head rcu_ttrace; + /* + * 0 - idle + * 1 - __free_rcu() is queued + * 2 - __free_rcu() is queued and free_by_rcu_ttrace got more objects since + */ atomic_t call_rcu_ttrace_in_progress; raw_spinlock_t lock; }; @@ -276,6 +281,8 @@ static int free_all(struct bpf_mem_cache *c, struct llist_node *llnode, bool per return cnt; } +static void __do_call_rcu_ttrace(struct bpf_mem_cache *c); + static void __free_rcu(struct rcu_head *head) { struct bpf_mem_cache *c = container_of(head, struct bpf_mem_cache, rcu_ttrace); @@ -285,7 +292,19 @@ static void __free_rcu(struct rcu_head *head) llnode = llist_del_all(&c->waiting_for_gp_ttrace); free_all(c, llnode, !!c->percpu_size); - atomic_set(&c->call_rcu_ttrace_in_progress, 0); + + /* + * do_call_rcu_ttrace() that ran while GP was in flight left its objects + * in free_by_rcu_ttrace. This cache may never free or alloc in bulk + * again, so start the next GP from here. + * 'c' can be freed as soon as call_rcu_ttrace_in_progress is zero. + */ + if (atomic_cmpxchg(&c->call_rcu_ttrace_in_progress, 1, 0) == 1) + return; + + /* Pairs with synchronize_rcu() in free_mem_alloc() */ + guard(rcu)(); + __do_call_rcu_ttrace(c); } static void enque_to_free(struct bpf_mem_cache *c, void *obj) @@ -302,6 +321,12 @@ static void __do_call_rcu_ttrace(struct bpf_mem_cache *c) { struct llist_node *llnode, *t; + /* + * Must be done before llist_del_all(). Objects that it misses were + * added by do_call_rcu_ttrace() that will set 2 after this store. + */ + atomic_set(&c->call_rcu_ttrace_in_progress, 1); + WARN_ON_ONCE(!llist_empty(&c->waiting_for_gp_ttrace)); llist_for_each_safe(llnode, t, llist_del_all(&c->free_by_rcu_ttrace)) llist_add(llnode, &c->waiting_for_gp_ttrace); @@ -323,7 +348,7 @@ static void do_call_rcu_ttrace(struct bpf_mem_cache *c) { struct llist_node *llnode; - if (atomic_xchg(&c->call_rcu_ttrace_in_progress, 1)) { + if (atomic_xchg(&c->call_rcu_ttrace_in_progress, 2)) { if (unlikely(READ_ONCE(c->draining))) { scoped_guard(raw_spinlock_irqsave, &c->lock) llnode = llist_del_all(&c->free_by_rcu_ttrace); @@ -707,7 +732,12 @@ static void free_mem_alloc(struct bpf_mem_alloc *ma) * to wait for the pending __free_by_rcu(), and __free_rcu(). RCU Tasks * Trace grace period implies RCU grace period, so all __free_rcu don't * need extra call_rcu() (and thus extra rcu_barrier() here). + * + * __free_rcu() queues itself again unless it sees 'draining'. After + * synchronize_rcu() it either did that already or will not do it, so + * rcu_barrier_tasks_trace() cannot miss it. */ + synchronize_rcu(); rcu_barrier(); /* wait for __free_by_rcu */ rcu_barrier_tasks_trace(); /* wait for __free_rcu */ free_mem_alloc_no_barrier(ma); |