+ * The event queue is circular and older events will be overwritten by new
+ * ones if they are not removed in time by the user using the functions
+ * LNetEQGet(), LNetEQWait(), or LNetEQPoll(). It is up to the user to
+ * determine the appropriate size of the event queue to prevent this loss
+ * of events. Note that when EQ handler is specified in \a callback, no
+ * event loss can happen, since the handler is run for each event deposited
+ * into the EQ.
+ *
+ * \param count The number of events to be stored in the event queue. It
+ * will be rounded up to the next power of two.
+ * \param callback A handler function that runs when an event is deposited
+ * into the EQ. The constant value LNET_EQ_HANDLER_NONE can be used to
+ * indicate that no event handler is desired.
+ * \param handle On successful return, this location will hold a handle for
+ * the newly created EQ.
+ *
+ * \retval 0 On success.
+ * \retval -EINVAL If an parameter is not valid.
+ * \retval -ENOMEM If memory for the EQ can't be allocated.
+ *
+ * \see lnet_eq_handler_t for the discussion on EQ handler semantics.
+ */
+int
+LNetEQAlloc(unsigned int count, lnet_eq_handler_t callback,
+ struct lnet_handle_eq *handle)
+{
+ struct lnet_eq *eq;
+
+ LASSERT(the_lnet.ln_refcount > 0);
+
+ /* We need count to be a power of 2 so that when eq_{enq,deq}_seq
+ * overflow, they don't skip entries, so the queue has the same
+ * apparent capacity at all times */
+
+ if (count)
+ count = roundup_pow_of_two(count);
+
+ if (callback != LNET_EQ_HANDLER_NONE && count != 0) {
+ CWARN("EQ callback is guaranteed to get every event, "
+ "do you still want to set eqcount %d for polling "
+ "event which will have locking overhead? "
+ "Please contact with developer to confirm\n", count);
+ }
+
+ /* count can be 0 if only need callback, we can eliminate
+ * overhead of enqueue event */
+ if (count == 0 && callback == LNET_EQ_HANDLER_NONE)
+ return -EINVAL;
+
+ eq = lnet_eq_alloc();
+ if (eq == NULL)
+ return -ENOMEM;
+
+ if (count != 0) {
+ LIBCFS_ALLOC(eq->eq_events, count * sizeof(struct lnet_event));
+ if (eq->eq_events == NULL)
+ goto failed;
+ /* NB allocator has set all event sequence numbers to 0,
+ * so all them should be earlier than eq_deq_seq */
+ }
+
+ eq->eq_deq_seq = 1;
+ eq->eq_enq_seq = 1;
+ eq->eq_size = count;
+ eq->eq_callback = callback;
+
+ eq->eq_refs = cfs_percpt_alloc(lnet_cpt_table(),
+ sizeof(*eq->eq_refs[0]));
+ if (eq->eq_refs == NULL)
+ goto failed;
+
+ /* MUST hold both exclusive lnet_res_lock */
+ lnet_res_lock(LNET_LOCK_EX);
+ /* NB: hold lnet_eq_wait_lock for EQ link/unlink, so we can do
+ * both EQ lookup and poll event with only lnet_eq_wait_lock */
+ lnet_eq_wait_lock();
+
+ lnet_res_lh_initialize(&the_lnet.ln_eq_container, &eq->eq_lh);
+ list_add(&eq->eq_list, &the_lnet.ln_eq_container.rec_active);
+
+ lnet_eq_wait_unlock();
+ lnet_res_unlock(LNET_LOCK_EX);
+
+ lnet_eq2handle(handle, eq);
+ return 0;
+
+failed:
+ if (eq->eq_events != NULL)
+ LIBCFS_FREE(eq->eq_events, count * sizeof(struct lnet_event));
+
+ if (eq->eq_refs != NULL)
+ cfs_percpt_free(eq->eq_refs);
+
+ lnet_eq_free(eq);
+ return -ENOMEM;
+}
+EXPORT_SYMBOL(LNetEQAlloc);
+
+/**
+ * Release the resources associated with an event queue if it's idle;
+ * otherwise do nothing and it's up to the user to try again.
+ *
+ * \param eqh A handle for the event queue to be released.
+ *
+ * \retval 0 If the EQ is not in use and freed.
+ * \retval -ENOENT If \a eqh does not point to a valid EQ.
+ * \retval -EBUSY If the EQ is still in use by some MDs.
+ */
+int
+LNetEQFree(struct lnet_handle_eq eqh)
+{
+ struct lnet_eq *eq;
+ struct lnet_event *events = NULL;
+ int **refs = NULL;
+ int *ref;
+ int rc = 0;
+ int size = 0;
+ int i;
+
+ LASSERT(the_lnet.ln_refcount > 0);
+
+ lnet_res_lock(LNET_LOCK_EX);
+ /* NB: hold lnet_eq_wait_lock for EQ link/unlink, so we can do
+ * both EQ lookup and poll event with only lnet_eq_wait_lock */
+ lnet_eq_wait_lock();
+
+ eq = lnet_handle2eq(&eqh);
+ if (eq == NULL) {
+ rc = -ENOENT;
+ goto out;
+ }
+
+ cfs_percpt_for_each(ref, i, eq->eq_refs) {
+ LASSERT(*ref >= 0);
+ if (*ref == 0)
+ continue;
+
+ CDEBUG(D_NET, "Event equeue (%d: %d) busy on destroy.\n",
+ i, *ref);
+ rc = -EBUSY;
+ goto out;
+ }
+
+ /* stash for free after lock dropped */
+ events = eq->eq_events;
+ size = eq->eq_size;
+ refs = eq->eq_refs;
+
+ lnet_res_lh_invalidate(&eq->eq_lh);
+ list_del(&eq->eq_list);
+ lnet_eq_free(eq);
+ out:
+ lnet_eq_wait_unlock();
+ lnet_res_unlock(LNET_LOCK_EX);
+
+ if (events != NULL)
+ LIBCFS_FREE(events, size * sizeof(struct lnet_event));
+ if (refs != NULL)
+ cfs_percpt_free(refs);
+
+ return rc;
+}
+EXPORT_SYMBOL(LNetEQFree);
+
+void
+lnet_eq_enqueue_event(struct lnet_eq *eq, struct lnet_event *ev)
+{
+ /* MUST called with resource lock hold but w/o lnet_eq_wait_lock */
+ int index;
+
+ if (eq->eq_size == 0) {
+ LASSERT(eq->eq_callback != LNET_EQ_HANDLER_NONE);
+ eq->eq_callback(ev);
+ return;
+ }
+
+ lnet_eq_wait_lock();
+ ev->sequence = eq->eq_enq_seq++;
+
+ LASSERT(eq->eq_size == LOWEST_BIT_SET(eq->eq_size));
+ index = ev->sequence & (eq->eq_size - 1);
+
+ eq->eq_events[index] = *ev;
+
+ if (eq->eq_callback != LNET_EQ_HANDLER_NONE)
+ eq->eq_callback(ev);
+
+ /* Wake anyone waiting in LNetEQPoll() */
+ if (waitqueue_active(&the_lnet.ln_eq_waitq))
+ wake_up_all(&the_lnet.ln_eq_waitq);
+ lnet_eq_wait_unlock();
+}
+
+static int
+lnet_eq_dequeue_event(struct lnet_eq *eq, struct lnet_event *ev)
+{
+ int new_index = eq->eq_deq_seq & (eq->eq_size - 1);
+ struct lnet_event *new_event = &eq->eq_events[new_index];
+ int rc;
+ ENTRY;
+
+ /* must called with lnet_eq_wait_lock hold */
+ if (LNET_SEQ_GT(eq->eq_deq_seq, new_event->sequence))
+ RETURN(0);
+
+ /* We've got a new event... */
+ *ev = *new_event;
+
+ CDEBUG(D_INFO, "event: %p, sequence: %lu, eq->size: %u\n",
+ new_event, eq->eq_deq_seq, eq->eq_size);
+
+ /* ...but did it overwrite an event we've not seen yet? */
+ if (eq->eq_deq_seq == new_event->sequence) {
+ rc = 1;
+ } else {
+ /* don't complain with CERROR: some EQs are sized small
+ * anyway; if it's important, the caller should complain */
+ CDEBUG(D_NET, "Event Queue Overflow: eq seq %lu ev seq %lu\n",
+ eq->eq_deq_seq, new_event->sequence);
+ rc = -EOVERFLOW;
+ }
+
+ eq->eq_deq_seq = new_event->sequence + 1;
+ RETURN(rc);
+}
+
+/**
+ * A nonblocking function that can be used to get the next event in an EQ.
+ * If an event handler is associated with the EQ, the handler will run before
+ * this function returns successfully. The event is removed from the queue.