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33 * This file is part of Lustre, http://www.lustre.org/
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38 * Library level Event queue management routines
41 #define DEBUG_SUBSYSTEM S_LNET
42 #include <lnet/lib-lnet.h>
45 * Create an event queue that has room for \a count number of events.
47 * The event queue is circular and older events will be overwritten by new
48 * ones if they are not removed in time by the user using the functions
49 * LNetEQGet(), LNetEQWait(), or LNetEQPoll(). It is up to the user to
50 * determine the appropriate size of the event queue to prevent this loss
51 * of events. Note that when EQ handler is specified in \a callback, no
52 * event loss can happen, since the handler is run for each event deposited
55 * \param count The number of events to be stored in the event queue. It
56 * will be rounded up to the next power of two.
57 * \param callback A handler function that runs when an event is deposited
58 * into the EQ. The constant value LNET_EQ_HANDLER_NONE can be used to
59 * indicate that no event handler is desired.
60 * \param handle On successful return, this location will hold a handle for
61 * the newly created EQ.
63 * \retval 0 On success.
64 * \retval -EINVAL If an parameter is not valid.
65 * \retval -ENOMEM If memory for the EQ can't be allocated.
67 * \see lnet_eq_handler_t for the discussion on EQ handler semantics.
70 LNetEQAlloc(unsigned int count, lnet_eq_handler_t callback,
71 lnet_handle_eq_t *handle)
75 LASSERT (the_lnet.ln_refcount > 0);
77 /* We need count to be a power of 2 so that when eq_{enq,deq}_seq
78 * overflow, they don't skip entries, so the queue has the same
79 * apparent capacity at all times */
81 count = roundup_pow_of_two(count);
83 if (callback != LNET_EQ_HANDLER_NONE && count != 0) {
84 CWARN("EQ callback is guaranteed to get every event, "
85 "do you still want to set eqcount %d for polling "
86 "event which will have locking overhead? "
87 "Please contact with developer to confirm\n", count);
90 /* count can be 0 if only need callback, we can eliminate
91 * overhead of enqueue event */
92 if (count == 0 && callback == LNET_EQ_HANDLER_NONE)
100 LIBCFS_ALLOC(eq->eq_events, count * sizeof(lnet_event_t));
101 if (eq->eq_events == NULL)
103 /* NB allocator has set all event sequence numbers to 0,
104 * so all them should be earlier than eq_deq_seq */
110 eq->eq_callback = callback;
112 eq->eq_refs = cfs_percpt_alloc(lnet_cpt_table(),
113 sizeof(*eq->eq_refs[0]));
114 if (eq->eq_refs == NULL)
117 /* MUST hold both exclusive lnet_res_lock */
118 lnet_res_lock(LNET_LOCK_EX);
119 /* NB: hold lnet_eq_wait_lock for EQ link/unlink, so we can do
120 * both EQ lookup and poll event with only lnet_eq_wait_lock */
123 lnet_res_lh_initialize(&the_lnet.ln_eq_container, &eq->eq_lh);
124 list_add(&eq->eq_list, &the_lnet.ln_eq_container.rec_active);
126 lnet_eq_wait_unlock();
127 lnet_res_unlock(LNET_LOCK_EX);
129 lnet_eq2handle(handle, eq);
133 if (eq->eq_events != NULL)
134 LIBCFS_FREE(eq->eq_events, count * sizeof(lnet_event_t));
136 if (eq->eq_refs != NULL)
137 cfs_percpt_free(eq->eq_refs);
142 EXPORT_SYMBOL(LNetEQAlloc);
145 * Release the resources associated with an event queue if it's idle;
146 * otherwise do nothing and it's up to the user to try again.
148 * \param eqh A handle for the event queue to be released.
150 * \retval 0 If the EQ is not in use and freed.
151 * \retval -ENOENT If \a eqh does not point to a valid EQ.
152 * \retval -EBUSY If the EQ is still in use by some MDs.
155 LNetEQFree(lnet_handle_eq_t eqh)
158 lnet_event_t *events = NULL;
165 LASSERT(the_lnet.ln_refcount > 0);
167 lnet_res_lock(LNET_LOCK_EX);
168 /* NB: hold lnet_eq_wait_lock for EQ link/unlink, so we can do
169 * both EQ lookup and poll event with only lnet_eq_wait_lock */
172 eq = lnet_handle2eq(&eqh);
178 cfs_percpt_for_each(ref, i, eq->eq_refs) {
183 CDEBUG(D_NET, "Event equeue (%d: %d) busy on destroy.\n",
189 /* stash for free after lock dropped */
190 events = eq->eq_events;
194 lnet_res_lh_invalidate(&eq->eq_lh);
195 list_del(&eq->eq_list);
198 lnet_eq_wait_unlock();
199 lnet_res_unlock(LNET_LOCK_EX);
202 LIBCFS_FREE(events, size * sizeof(lnet_event_t));
204 cfs_percpt_free(refs);
208 EXPORT_SYMBOL(LNetEQFree);
211 lnet_eq_enqueue_event(lnet_eq_t *eq, lnet_event_t *ev)
213 /* MUST called with resource lock hold but w/o lnet_eq_wait_lock */
216 if (eq->eq_size == 0) {
217 LASSERT(eq->eq_callback != LNET_EQ_HANDLER_NONE);
223 ev->sequence = eq->eq_enq_seq++;
225 LASSERT(eq->eq_size == LOWEST_BIT_SET(eq->eq_size));
226 index = ev->sequence & (eq->eq_size - 1);
228 eq->eq_events[index] = *ev;
230 if (eq->eq_callback != LNET_EQ_HANDLER_NONE)
233 /* Wake anyone waiting in LNetEQPoll() */
234 if (waitqueue_active(&the_lnet.ln_eq_waitq))
235 wake_up_all(&the_lnet.ln_eq_waitq);
236 lnet_eq_wait_unlock();
240 lnet_eq_dequeue_event(lnet_eq_t *eq, lnet_event_t *ev)
242 int new_index = eq->eq_deq_seq & (eq->eq_size - 1);
243 lnet_event_t *new_event = &eq->eq_events[new_index];
247 /* must called with lnet_eq_wait_lock hold */
248 if (LNET_SEQ_GT(eq->eq_deq_seq, new_event->sequence))
251 /* We've got a new event... */
254 CDEBUG(D_INFO, "event: %p, sequence: %lu, eq->size: %u\n",
255 new_event, eq->eq_deq_seq, eq->eq_size);
257 /* ...but did it overwrite an event we've not seen yet? */
258 if (eq->eq_deq_seq == new_event->sequence) {
261 /* don't complain with CERROR: some EQs are sized small
262 * anyway; if it's important, the caller should complain */
263 CDEBUG(D_NET, "Event Queue Overflow: eq seq %lu ev seq %lu\n",
264 eq->eq_deq_seq, new_event->sequence);
268 eq->eq_deq_seq = new_event->sequence + 1;
273 * A nonblocking function that can be used to get the next event in an EQ.
274 * If an event handler is associated with the EQ, the handler will run before
275 * this function returns successfully. The event is removed from the queue.
277 * \param eventq A handle for the event queue.
278 * \param event On successful return (1 or -EOVERFLOW), this location will
279 * hold the next event in the EQ.
281 * \retval 0 No pending event in the EQ.
282 * \retval 1 Indicates success.
283 * \retval -ENOENT If \a eventq does not point to a valid EQ.
284 * \retval -EOVERFLOW Indicates success (i.e., an event is returned) and that
285 * at least one event between this event and the last event obtained from the
286 * EQ has been dropped due to limited space in the EQ.
289 LNetEQGet (lnet_handle_eq_t eventq, lnet_event_t *event)
293 return LNetEQPoll(&eventq, 1, 0,
296 EXPORT_SYMBOL(LNetEQGet);
299 * Block the calling process until there is an event in the EQ.
300 * If an event handler is associated with the EQ, the handler will run before
301 * this function returns successfully. This function returns the next event
302 * in the EQ and removes it from the EQ.
304 * \param eventq A handle for the event queue.
305 * \param event On successful return (1 or -EOVERFLOW), this location will
306 * hold the next event in the EQ.
308 * \retval 1 Indicates success.
309 * \retval -ENOENT If \a eventq does not point to a valid EQ.
310 * \retval -EOVERFLOW Indicates success (i.e., an event is returned) and that
311 * at least one event between this event and the last event obtained from the
312 * EQ has been dropped due to limited space in the EQ.
315 LNetEQWait (lnet_handle_eq_t eventq, lnet_event_t *event)
319 return LNetEQPoll(&eventq, 1, LNET_TIME_FOREVER,
322 EXPORT_SYMBOL(LNetEQWait);
325 lnet_eq_wait_locked(int *timeout_ms)
326 __must_hold(&the_lnet.ln_eq_wait_lock)
328 int tms = *timeout_ms;
334 return -ENXIO; /* don't want to wait and no new event */
336 init_waitqueue_entry(&wl, current);
337 set_current_state(TASK_INTERRUPTIBLE);
338 add_wait_queue(&the_lnet.ln_eq_waitq, &wl);
340 lnet_eq_wait_unlock();
347 now = cfs_time_current();
348 schedule_timeout(cfs_time_seconds(tms) / 1000);
349 cfs_duration_usec(cfs_time_sub(cfs_time_current(), now), &tv);
350 tms -= (int)(tv.tv_sec * 1000 + tv.tv_usec / 1000);
351 if (tms < 0) /* no more wait but may have new event */
355 wait = tms != 0; /* might need to call here again */
359 remove_wait_queue(&the_lnet.ln_eq_waitq, &wl);
365 * Block the calling process until there's an event from a set of EQs or
368 * If an event handler is associated with the EQ, the handler will run before
369 * this function returns successfully, in which case the corresponding event
372 * LNetEQPoll() provides a timeout to allow applications to poll, block for a
373 * fixed period, or block indefinitely.
375 * \param eventqs,neq An array of EQ handles, and size of the array.
376 * \param timeout_ms Time in milliseconds to wait for an event to occur on
377 * one of the EQs. The constant LNET_TIME_FOREVER can be used to indicate an
379 * \param event,which On successful return (1 or -EOVERFLOW), \a event will
380 * hold the next event in the EQs, and \a which will contain the index of the
381 * EQ from which the event was taken.
383 * \retval 0 No pending event in the EQs after timeout.
384 * \retval 1 Indicates success.
385 * \retval -EOVERFLOW Indicates success (i.e., an event is returned) and that
386 * at least one event between this event and the last event obtained from the
387 * EQ indicated by \a which has been dropped due to limited space in the EQ.
388 * \retval -ENOENT If there's an invalid handle in \a eventqs.
391 LNetEQPoll(lnet_handle_eq_t *eventqs, int neq, int timeout_ms,
392 lnet_event_t *event, int *which)
399 LASSERT (the_lnet.ln_refcount > 0);
407 for (i = 0; i < neq; i++) {
408 lnet_eq_t *eq = lnet_handle2eq(&eventqs[i]);
411 lnet_eq_wait_unlock();
415 rc = lnet_eq_dequeue_event(eq, event);
417 lnet_eq_wait_unlock();
427 * return value of lnet_eq_wait_locked:
428 * -1 : did nothing and it's sure no new event
429 * 1 : sleep inside and wait until new event
430 * 0 : don't want to wait anymore, but might have new event
431 * so need to call dequeue again
433 wait = lnet_eq_wait_locked(&timeout_ms);
434 if (wait < 0) /* no new event */
438 lnet_eq_wait_unlock();