diff options
| -rw-r--r-- | include/linux/rcutiny.h | 18 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 45 |
2 files changed, 60 insertions, 3 deletions
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index fb2eb39c484f..5cc9637cac16 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -34,9 +34,25 @@ static inline void synchronize_rcu_expedited(void) synchronize_rcu(); } +/* + * Add one more declaration of kvfree() here. It is + * not so straight forward to just include <linux/mm.h> + * where it is defined due to getting many compile + * errors caused by that include. + */ +extern void kvfree(const void *addr); + static inline void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) { - call_rcu(head, func); + if (head) { + call_rcu(head, func); + return; + } + + // kvfree_rcu(one_arg) call. + might_sleep(); + synchronize_rcu(); + kvfree((void *) func); } void rcu_qs(void); diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index f22c47e72287..01f29e4500ba 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3314,6 +3314,13 @@ kvfree_call_rcu_add_ptr_to_bulk(struct kfree_rcu_cpu *krcp, void *ptr) if (IS_ENABLED(CONFIG_PREEMPT_RT)) return false; + /* + * NOTE: For one argument of kvfree_rcu() we can + * drop the lock and get the page in sleepable + * context. That would allow to maintain an array + * for the CONFIG_PREEMPT_RT as well if no cached + * pages are available. + */ bnode = (struct kvfree_rcu_bulk_data *) __get_free_page(GFP_NOWAIT | __GFP_NOWARN); } @@ -3353,16 +3360,33 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) { unsigned long flags; struct kfree_rcu_cpu *krcp; + bool success; void *ptr; + if (head) { + ptr = (void *) head - (unsigned long) func; + } else { + /* + * Please note there is a limitation for the head-less + * variant, that is why there is a clear rule for such + * objects: it can be used from might_sleep() context + * only. For other places please embed an rcu_head to + * your data. + */ + might_sleep(); + ptr = (unsigned long *) func; + } + krcp = krc_this_cpu_lock(&flags); - ptr = (void *)head - (unsigned long)func; // Queue the object but don't yet schedule the batch. if (debug_rcu_head_queue(ptr)) { // Probable double kfree_rcu(), just leak. WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n", __func__, head); + + // Mark as success and leave. + success = true; goto unlock_return; } @@ -3370,10 +3394,16 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) * Under high memory pressure GFP_NOWAIT can fail, * in that case the emergency path is maintained. */ - if (unlikely(!kvfree_call_rcu_add_ptr_to_bulk(krcp, ptr))) { + success = kvfree_call_rcu_add_ptr_to_bulk(krcp, ptr); + if (!success) { + if (head == NULL) + // Inline if kvfree_rcu(one_arg) call. + goto unlock_return; + head->func = func; head->next = krcp->head; krcp->head = head; + success = true; } WRITE_ONCE(krcp->count, krcp->count + 1); @@ -3387,6 +3417,17 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) unlock_return: krc_this_cpu_unlock(krcp, flags); + + /* + * Inline kvfree() after synchronize_rcu(). We can do + * it from might_sleep() context only, so the current + * CPU can pass the QS state. + */ + if (!success) { + debug_rcu_head_unqueue((struct rcu_head *) ptr); + synchronize_rcu(); + kvfree(ptr); + } } EXPORT_SYMBOL_GPL(kvfree_call_rcu); |