drivers/staging/lustre/lnet/lnet/lib-eq.c

   1 /*
   2  * GPL HEADER START
   3  *
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 only,
   8  * as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License version 2 for more details (a copy is included
  14  * in the LICENSE file that accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * version 2 along with this program; If not, see
  18  * http://www.gnu.org/licenses/gpl-2.0.html
  19  *
  20  * GPL HEADER END
  21  */
  22 /*
  23  * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
  24  * Use is subject to license terms.
  25  *
  26  * Copyright (c) 2012, Intel Corporation.
  27  */
  28 /*
  29  * This file is part of Lustre, http://www.lustre.org/
  30  * Lustre is a trademark of Sun Microsystems, Inc.
  31  *
  32  * lnet/lnet/lib-eq.c
  33  *
  34  * Library level Event queue management routines
  35  */
  36
  37 #define DEBUG_SUBSYSTEM S_LNET
  38 #include "../../include/linux/lnet/lib-lnet.h"
  39
  40 /**
  41  * Create an event queue that has room for \a count number of events.
  42  *
  43  * The event queue is circular and older events will be overwritten by new
  44  * ones if they are not removed in time by the user using the functions
  45  * LNetEQGet(), LNetEQWait(), or LNetEQPoll(). It is up to the user to
  46  * determine the appropriate size of the event queue to prevent this loss
  47  * of events. Note that when EQ handler is specified in \a callback, no
  48  * event loss can happen, since the handler is run for each event deposited
  49  * into the EQ.
  50  *
  51  * \param count The number of events to be stored in the event queue. It
  52  * will be rounded up to the next power of two.
  53  * \param callback A handler function that runs when an event is deposited
  54  * into the EQ. The constant value LNET_EQ_HANDLER_NONE can be used to
  55  * indicate that no event handler is desired.
  56  * \param handle On successful return, this location will hold a handle for
  57  * the newly created EQ.
  58  *
  59  * \retval 0       On success.
  60  * \retval -EINVAL If an parameter is not valid.
  61  * \retval -ENOMEM If memory for the EQ can't be allocated.
  62  *
  63  * \see lnet_eq_handler_t for the discussion on EQ handler semantics.
  64  */
  65 int
  66 LNetEQAlloc(unsigned int count, lnet_eq_handler_t callback,
  67             struct lnet_handle_eq *handle)
  68 {
  69         struct lnet_eq *eq;
  70
  71         LASSERT(the_lnet.ln_refcount > 0);
  72
  73         /*
  74          * We need count to be a power of 2 so that when eq_{enq,deq}_seq
  75          * overflow, they don't skip entries, so the queue has the same
  76          * apparent capacity at all times
  77          */
  78         if (count)
  79                 count = roundup_pow_of_two(count);
  80
  81         if (callback != LNET_EQ_HANDLER_NONE && count)
  82                 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);
  83
  84         /*
  85          * count can be 0 if only need callback, we can eliminate
  86          * overhead of enqueue event
  87          */
  88         if (!count && callback == LNET_EQ_HANDLER_NONE)
  89                 return -EINVAL;
  90
  91         eq = lnet_eq_alloc();
  92         if (!eq)
  93                 return -ENOMEM;
  94
  95         if (count) {
  96                 LIBCFS_ALLOC(eq->eq_events, count * sizeof(struct lnet_event));
  97                 if (!eq->eq_events)
  98                         goto failed;
  99                 /*
 100                  * NB allocator has set all event sequence numbers to 0,
 101                  * so all them should be earlier than eq_deq_seq
 102                  */
 103         }
 104
 105         eq->eq_deq_seq = 1;
 106         eq->eq_enq_seq = 1;
 107         eq->eq_size = count;
 108         eq->eq_callback = callback;
 109
 110         eq->eq_refs = cfs_percpt_alloc(lnet_cpt_table(),
 111                                        sizeof(*eq->eq_refs[0]));
 112         if (!eq->eq_refs)
 113                 goto failed;
 114
 115         /* MUST hold both exclusive lnet_res_lock */
 116         lnet_res_lock(LNET_LOCK_EX);
 117         /*
 118          * NB: hold lnet_eq_wait_lock for EQ link/unlink, so we can do
 119          * both EQ lookup and poll event with only lnet_eq_wait_lock
 120          */
 121         lnet_eq_wait_lock();
 122
 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);
 125
 126         lnet_eq_wait_unlock();
 127         lnet_res_unlock(LNET_LOCK_EX);
 128
 129         lnet_eq2handle(handle, eq);
 130         return 0;
 131
 132 failed:
 133         if (eq->eq_events)
 134                 LIBCFS_FREE(eq->eq_events, count * sizeof(struct lnet_event));
 135
 136         if (eq->eq_refs)
 137                 cfs_percpt_free(eq->eq_refs);
 138
 139         lnet_eq_free(eq);
 140         return -ENOMEM;
 141 }
 142 EXPORT_SYMBOL(LNetEQAlloc);
 143
 144 /**
 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.
 147  *
 148  * \param eqh A handle for the event queue to be released.
 149  *
 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.
 153  */
 154 int
 155 LNetEQFree(struct lnet_handle_eq eqh)
 156 {
 157         struct lnet_eq *eq;
 158         struct lnet_event *events = NULL;
 159         int **refs = NULL;
 160         int *ref;
 161         int rc = 0;
 162         int size = 0;
 163         int i;
 164
 165         LASSERT(the_lnet.ln_refcount > 0);
 166
 167         lnet_res_lock(LNET_LOCK_EX);
 168         /*
 169          * NB: hold lnet_eq_wait_lock for EQ link/unlink, so we can do
 170          * both EQ lookup and poll event with only lnet_eq_wait_lock
 171          */
 172         lnet_eq_wait_lock();
 173
 174         eq = lnet_handle2eq(&eqh);
 175         if (!eq) {
 176                 rc = -ENOENT;
 177                 goto out;
 178         }
 179
 180         cfs_percpt_for_each(ref, i, eq->eq_refs) {
 181                 LASSERT(*ref >= 0);
 182                 if (!*ref)
 183                         continue;
 184
 185                 CDEBUG(D_NET, "Event equeue (%d: %d) busy on destroy.\n",
 186                        i, *ref);
 187                 rc = -EBUSY;
 188                 goto out;
 189         }
 190
 191         /* stash for free after lock dropped */
 192         events = eq->eq_events;
 193         size = eq->eq_size;
 194         refs = eq->eq_refs;
 195
 196         lnet_res_lh_invalidate(&eq->eq_lh);
 197         list_del(&eq->eq_list);
 198         lnet_eq_free(eq);
 199  out:
 200         lnet_eq_wait_unlock();
 201         lnet_res_unlock(LNET_LOCK_EX);
 202
 203         if (events)
 204                 LIBCFS_FREE(events, size * sizeof(struct lnet_event));
 205         if (refs)
 206                 cfs_percpt_free(refs);
 207
 208         return rc;
 209 }
 210 EXPORT_SYMBOL(LNetEQFree);
 211
 212 void
 213 lnet_eq_enqueue_event(struct lnet_eq *eq, struct lnet_event *ev)
 214 {
 215         /* MUST called with resource lock hold but w/o lnet_eq_wait_lock */
 216         int index;
 217
 218         if (!eq->eq_size) {
 219                 LASSERT(eq->eq_callback != LNET_EQ_HANDLER_NONE);
 220                 eq->eq_callback(ev);
 221                 return;
 222         }
 223
 224         lnet_eq_wait_lock();
 225         ev->sequence = eq->eq_enq_seq++;
 226
 227         LASSERT(eq->eq_size == LOWEST_BIT_SET(eq->eq_size));
 228         index = ev->sequence & (eq->eq_size - 1);
 229
 230         eq->eq_events[index] = *ev;
 231
 232         if (eq->eq_callback != LNET_EQ_HANDLER_NONE)
 233                 eq->eq_callback(ev);
 234
 235         /* Wake anyone waiting in LNetEQPoll() */
 236         if (waitqueue_active(&the_lnet.ln_eq_waitq))
 237                 wake_up_all(&the_lnet.ln_eq_waitq);
 238         lnet_eq_wait_unlock();
 239 }
 240
 241 static int
 242 lnet_eq_dequeue_event(struct lnet_eq *eq, struct lnet_event *ev)
 243 {
 244         int new_index = eq->eq_deq_seq & (eq->eq_size - 1);
 245         struct lnet_event *new_event = &eq->eq_events[new_index];
 246         int rc;
 247
 248         /* must called with lnet_eq_wait_lock hold */
 249         if (LNET_SEQ_GT(eq->eq_deq_seq, new_event->sequence))
 250                 return 0;
 251
 252         /* We've got a new event... */
 253         *ev = *new_event;
 254
 255         CDEBUG(D_INFO, "event: %p, sequence: %lu, eq->size: %u\n",
 256                new_event, eq->eq_deq_seq, eq->eq_size);
 257
 258         /* ...but did it overwrite an event we've not seen yet? */
 259         if (eq->eq_deq_seq == new_event->sequence) {
 260                 rc = 1;
 261         } else {
 262                 /*
 263                  * don't complain with CERROR: some EQs are sized small
 264                  * anyway; if it's important, the caller should complain
 265                  */
 266                 CDEBUG(D_NET, "Event Queue Overflow: eq seq %lu ev seq %lu\n",
 267                        eq->eq_deq_seq, new_event->sequence);
 268                 rc = -EOVERFLOW;
 269         }
 270
 271         eq->eq_deq_seq = new_event->sequence + 1;
 272         return rc;
 273 }
 274
 275 /**
 276  * A nonblocking function that can be used to get the next event in an EQ.
 277  * If an event handler is associated with the EQ, the handler will run before
 278  * this function returns successfully. The event is removed from the queue.
 279  *
 280  * \param eventq A handle for the event queue.
 281  * \param event On successful return (1 or -EOVERFLOW), this location will
 282  * hold the next event in the EQ.
 283  *
 284  * \retval 0      No pending event in the EQ.
 285  * \retval 1      Indicates success.
 286  * \retval -ENOENT    If \a eventq does not point to a valid EQ.
 287  * \retval -EOVERFLOW Indicates success (i.e., an event is returned) and that
 288  * at least one event between this event and the last event obtained from the
 289  * EQ has been dropped due to limited space in the EQ.
 290  */
 291
 292 /**
 293  * Block the calling process until there is an event in the EQ.
 294  * If an event handler is associated with the EQ, the handler will run before
 295  * this function returns successfully. This function returns the next event
 296  * in the EQ and removes it from the EQ.
 297  *
 298  * \param eventq A handle for the event queue.
 299  * \param event On successful return (1 or -EOVERFLOW), this location will
 300  * hold the next event in the EQ.
 301  *
 302  * \retval 1      Indicates success.
 303  * \retval -ENOENT    If \a eventq does not point to a valid EQ.
 304  * \retval -EOVERFLOW Indicates success (i.e., an event is returned) and that
 305  * at least one event between this event and the last event obtained from the
 306  * EQ has been dropped due to limited space in the EQ.
 307  */
 308
 309 static int
 310 lnet_eq_wait_locked(int *timeout_ms)
 311 __must_hold(&the_lnet.ln_eq_wait_lock)
 312 {
 313         int tms = *timeout_ms;
 314         int wait;
 315         wait_queue_t wl;
 316         unsigned long now;
 317
 318         if (!tms)
 319                 return -ENXIO; /* don't want to wait and no new event */
 320
 321         init_waitqueue_entry(&wl, current);
 322         set_current_state(TASK_INTERRUPTIBLE);
 323         add_wait_queue(&the_lnet.ln_eq_waitq, &wl);
 324
 325         lnet_eq_wait_unlock();
 326
 327         if (tms < 0) {
 328                 schedule();
 329         } else {
 330                 now = jiffies;
 331                 schedule_timeout(msecs_to_jiffies(tms));
 332                 tms -= jiffies_to_msecs(jiffies - now);
 333                 if (tms < 0) /* no more wait but may have new event */
 334                         tms = 0;
 335         }
 336
 337         wait = tms; /* might need to call here again */
 338         *timeout_ms = tms;
 339
 340         lnet_eq_wait_lock();
 341         remove_wait_queue(&the_lnet.ln_eq_waitq, &wl);
 342
 343         return wait;
 344 }
 345
 346 /**
 347  * Block the calling process until there's an event from a set of EQs or
 348  * timeout happens.
 349  *
 350  * If an event handler is associated with the EQ, the handler will run before
 351  * this function returns successfully, in which case the corresponding event
 352  * is consumed.
 353  *
 354  * LNetEQPoll() provides a timeout to allow applications to poll, block for a
 355  * fixed period, or block indefinitely.
 356  *
 357  * \param eventqs,neq An array of EQ handles, and size of the array.
 358  * \param timeout_ms Time in milliseconds to wait for an event to occur on
 359  * one of the EQs. The constant LNET_TIME_FOREVER can be used to indicate an
 360  * infinite timeout.
 361  * \param event,which On successful return (1 or -EOVERFLOW), \a event will
 362  * hold the next event in the EQs, and \a which will contain the index of the
 363  * EQ from which the event was taken.
 364  *
 365  * \retval 0      No pending event in the EQs after timeout.
 366  * \retval 1      Indicates success.
 367  * \retval -EOVERFLOW Indicates success (i.e., an event is returned) and that
 368  * at least one event between this event and the last event obtained from the
 369  * EQ indicated by \a which has been dropped due to limited space in the EQ.
 370  * \retval -ENOENT    If there's an invalid handle in \a eventqs.
 371  */
 372 int
 373 LNetEQPoll(struct lnet_handle_eq *eventqs, int neq, int timeout_ms,
 374            struct lnet_event *event, int *which)
 375 {
 376         int wait = 1;
 377         int rc;
 378         int i;
 379
 380         LASSERT(the_lnet.ln_refcount > 0);
 381
 382         if (neq < 1)
 383                 return -ENOENT;
 384
 385         lnet_eq_wait_lock();
 386
 387         for (;;) {
 388                 for (i = 0; i < neq; i++) {
 389                         struct lnet_eq *eq = lnet_handle2eq(&eventqs[i]);
 390
 391                         if (!eq) {
 392                                 lnet_eq_wait_unlock();
 393                                 return -ENOENT;
 394                         }
 395
 396                         rc = lnet_eq_dequeue_event(eq, event);
 397                         if (rc) {
 398                                 lnet_eq_wait_unlock();
 399                                 *which = i;
 400                                 return rc;
 401                         }
 402                 }
 403
 404                 if (!wait)
 405                         break;
 406
 407                 /*
 408                  * return value of lnet_eq_wait_locked:
 409                  * -1 : did nothing and it's sure no new event
 410                  *  1 : sleep inside and wait until new event
 411                  *  0 : don't want to wait anymore, but might have new event
 412                  *      so need to call dequeue again
 413                  */
 414                 wait = lnet_eq_wait_locked(&timeout_ms);
 415                 if (wait < 0) /* no new event */
 416                         break;
 417         }
 418
 419         lnet_eq_wait_unlock();
 420         return 0;
 421 }