1 /* 2 * linux/fs/lockd/svclock.c 3 * 4 * Handling of server-side locks, mostly of the blocked variety. 5 * This is the ugliest part of lockd because we tread on very thin ice. 6 * GRANT and CANCEL calls may get stuck, meet in mid-flight, etc. 7 * IMNSHO introducing the grant callback into the NLM protocol was one 8 * of the worst ideas Sun ever had. Except maybe for the idea of doing 9 * NFS file locking at all. 10 * 11 * I'm trying hard to avoid race conditions by protecting most accesses 12 * to a file's list of blocked locks through a semaphore. The global 13 * list of blocked locks is not protected in this fashion however. 14 * Therefore, some functions (such as the RPC callback for the async grant 15 * call) move blocked locks towards the head of the list *while some other 16 * process might be traversing it*. This should not be a problem in 17 * practice, because this will only cause functions traversing the list 18 * to visit some blocks twice. 19 * 20 * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de> 21 */ 22 23 #include <linux/config.h> 24 #include <linux/types.h> 25 #include <linux/errno.h> 26 #include <linux/kernel.h> 27 #include <linux/sched.h> 28 #include <linux/smp_lock.h> 29 #include <linux/sunrpc/clnt.h> 30 #include <linux/sunrpc/svc.h> 31 #include <linux/lockd/nlm.h> 32 #include <linux/lockd/lockd.h> 33 34 #define NLMDBG_FACILITY NLMDBG_SVCLOCK 35 36 #ifdef CONFIG_LOCKD_V4 37 #define nlm_deadlock nlm4_deadlock 38 #else 39 #define nlm_deadlock nlm_lck_denied 40 #endif 41 42 static void nlmsvc_insert_block(struct nlm_block *block, unsigned long); 43 static int nlmsvc_remove_block(struct nlm_block *block); 44 static void nlmsvc_grant_callback(struct rpc_task *task); 45 46 /* 47 * The list of blocked locks to retry 48 */ 49 static struct nlm_block * nlm_blocked; 50 51 /* 52 * Insert a blocked lock into the global list 53 */ 54 static void 55 nlmsvc_insert_block(struct nlm_block *block, unsigned long when) 56 { 57 struct nlm_block **bp, *b; 58 59 dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when); 60 if (block->b_queued) 61 nlmsvc_remove_block(block); 62 bp = &nlm_blocked; 63 if (when != NLM_NEVER) { 64 if ((when += jiffies) == NLM_NEVER) 65 when ++; 66 while ((b = *bp) && time_before_eq(b->b_when,when) && b->b_when != NLM_NEVER) 67 bp = &b->b_next; 68 } else 69 while ((b = *bp) != 0) 70 bp = &b->b_next; 71 72 block->b_queued = 1; 73 block->b_when = when; 74 block->b_next = b; 75 *bp = block; 76 } 77 78 /* 79 * Remove a block from the global list 80 */ 81 static int 82 nlmsvc_remove_block(struct nlm_block *block) 83 { 84 struct nlm_block **bp, *b; 85 86 if (!block->b_queued) 87 return 1; 88 for (bp = &nlm_blocked; (b = *bp) != 0; bp = &b->b_next) { 89 if (b == block) { 90 *bp = block->b_next; 91 block->b_queued = 0; 92 return 1; 93 } 94 } 95 96 return 0; 97 } 98 99 /* 100 * Find a block for a given lock and optionally remove it from 101 * the list. 102 */ 103 static struct nlm_block * 104 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock, int remove) 105 { 106 struct nlm_block **head, *block; 107 struct file_lock *fl; 108 109 dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n", 110 file, lock->fl.fl_pid, 111 (long long)lock->fl.fl_start, 112 (long long)lock->fl.fl_end, lock->fl.fl_type); 113 for (head = &nlm_blocked; (block = *head) != 0; head = &block->b_next) { 114 fl = &block->b_call.a_args.lock.fl; 115 dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n", 116 block->b_file, fl->fl_pid, 117 (long long)fl->fl_start, 118 (long long)fl->fl_end, fl->fl_type, 119 nlmdbg_cookie2a(&block->b_call.a_args.cookie)); 120 if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) { 121 if (remove) { 122 *head = block->b_next; 123 block->b_queued = 0; 124 } 125 return block; 126 } 127 } 128 129 return NULL; 130 } 131 132 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b) 133 { 134 if(a->len != b->len) 135 return 0; 136 if(memcmp(a->data,b->data,a->len)) 137 return 0; 138 return 1; 139 } 140 141 /* 142 * Find a block with a given NLM cookie. 143 */ 144 static inline struct nlm_block * 145 nlmsvc_find_block(struct nlm_cookie *cookie, struct sockaddr_in *sin) 146 { 147 struct nlm_block *block; 148 149 for (block = nlm_blocked; block; block = block->b_next) { 150 dprintk("cookie: head of blocked queue %p, block %p\n", 151 nlm_blocked, block); 152 if (nlm_cookie_match(&block->b_call.a_args.cookie,cookie) 153 && nlm_cmp_addr(sin, &block->b_host->h_addr)) 154 break; 155 } 156 157 return block; 158 } 159 160 /* 161 * Create a block and initialize it. 162 * 163 * Note: we explicitly set the cookie of the grant reply to that of 164 * the blocked lock request. The spec explicitly mentions that the client 165 * should _not_ rely on the callback containing the same cookie as the 166 * request, but (as I found out later) that's because some implementations 167 * do just this. Never mind the standards comittees, they support our 168 * logging industries. 169 */ 170 static inline struct nlm_block * 171 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file, 172 struct nlm_lock *lock, struct nlm_cookie *cookie) 173 { 174 struct nlm_block *block; 175 struct nlm_host *host; 176 struct nlm_rqst *call; 177 178 /* Create host handle for callback */ 179 host = nlmclnt_lookup_host(&rqstp->rq_addr, 180 rqstp->rq_prot, rqstp->rq_vers); 181 if (host == NULL) 182 return NULL; 183 184 /* Allocate memory for block, and initialize arguments */ 185 if (!(block = (struct nlm_block *) kmalloc(sizeof(*block), GFP_KERNEL))) 186 goto failed; 187 memset(block, 0, sizeof(*block)); 188 locks_init_lock(&block->b_call.a_args.lock.fl); 189 locks_init_lock(&block->b_call.a_res.lock.fl); 190 191 if (!nlmclnt_setgrantargs(&block->b_call, lock)) 192 goto failed_free; 193 194 /* Set notifier function for VFS, and init args */ 195 block->b_call.a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations; 196 block->b_call.a_args.cookie = *cookie; /* see above */ 197 198 dprintk("lockd: created block %p...\n", block); 199 200 /* Create and initialize the block */ 201 block->b_daemon = rqstp->rq_server; 202 block->b_host = host; 203 block->b_file = file; 204 205 /* Add to file's list of blocks */ 206 block->b_fnext = file->f_blocks; 207 file->f_blocks = block; 208 209 /* Set up RPC arguments for callback */ 210 call = &block->b_call; 211 call->a_host = host; 212 call->a_flags = RPC_TASK_ASYNC; 213 214 return block; 215 216 failed_free: 217 kfree(block); 218 failed: 219 nlm_release_host(host); 220 return NULL; 221 } 222 223 /* 224 * Delete a block. If the lock was cancelled or the grant callback 225 * failed, unlock is set to 1. 226 * It is the caller's responsibility to check whether the file 227 * can be closed hereafter. 228 */ 229 static void 230 nlmsvc_delete_block(struct nlm_block *block, int unlock) 231 { 232 struct file_lock *fl = &block->b_call.a_args.lock.fl; 233 struct nlm_file *file = block->b_file; 234 struct nlm_block **bp; 235 236 dprintk("lockd: deleting block %p...\n", block); 237 238 /* Remove block from list */ 239 nlmsvc_remove_block(block); 240 if (fl->fl_next) 241 posix_unblock_lock(file->f_file, fl); 242 if (unlock) { 243 fl->fl_type = F_UNLCK; 244 posix_lock_file(file->f_file, fl); 245 block->b_granted = 0; 246 } 247 248 /* If the block is in the middle of a GRANT callback, 249 * don't kill it yet. */ 250 if (block->b_incall) { 251 nlmsvc_insert_block(block, NLM_NEVER); 252 block->b_done = 1; 253 return; 254 } 255 256 /* Remove block from file's list of blocks */ 257 for (bp = &file->f_blocks; *bp; bp = &(*bp)->b_fnext) { 258 if (*bp == block) { 259 *bp = block->b_fnext; 260 break; 261 } 262 } 263 264 if (block->b_host) 265 nlm_release_host(block->b_host); 266 nlmclnt_freegrantargs(&block->b_call); 267 kfree(block); 268 } 269 270 /* 271 * Loop over all blocks and perform the action specified. 272 * (NLM_ACT_CHECK handled by nlmsvc_inspect_file). 273 */ 274 int 275 nlmsvc_traverse_blocks(struct nlm_host *host, struct nlm_file *file, int action) 276 { 277 struct nlm_block *block, *next; 278 279 down(&file->f_sema); 280 for (block = file->f_blocks; block; block = next) { 281 next = block->b_fnext; 282 if (action == NLM_ACT_MARK) 283 block->b_host->h_inuse = 1; 284 else if (action == NLM_ACT_UNLOCK) { 285 if (host == NULL || host == block->b_host) 286 nlmsvc_delete_block(block, 1); 287 } 288 } 289 up(&file->f_sema); 290 return 0; 291 } 292 293 /* 294 * Attempt to establish a lock, and if it can't be granted, block it 295 * if required. 296 */ 297 u32 298 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file, 299 struct nlm_lock *lock, int wait, struct nlm_cookie *cookie) 300 { 301 struct file_lock *conflock; 302 struct nlm_block *block; 303 int error; 304 305 dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n", 306 file->f_file->f_dentry->d_inode->i_sb->s_id, 307 file->f_file->f_dentry->d_inode->i_ino, 308 lock->fl.fl_type, lock->fl.fl_pid, 309 (long long)lock->fl.fl_start, 310 (long long)lock->fl.fl_end, 311 wait); 312 313 314 /* Get existing block (in case client is busy-waiting) */ 315 block = nlmsvc_lookup_block(file, lock, 0); 316 317 lock->fl.fl_flags |= FL_LOCKD; 318 319 again: 320 /* Lock file against concurrent access */ 321 down(&file->f_sema); 322 323 if (!(conflock = posix_test_lock(file->f_file, &lock->fl))) { 324 error = posix_lock_file(file->f_file, &lock->fl); 325 326 if (block) 327 nlmsvc_delete_block(block, 0); 328 up(&file->f_sema); 329 330 dprintk("lockd: posix_lock_file returned %d\n", -error); 331 switch(-error) { 332 case 0: 333 return nlm_granted; 334 case EDEADLK: 335 return nlm_deadlock; 336 case EAGAIN: 337 return nlm_lck_denied; 338 default: /* includes ENOLCK */ 339 return nlm_lck_denied_nolocks; 340 } 341 } 342 343 if (!wait) { 344 up(&file->f_sema); 345 return nlm_lck_denied; 346 } 347 348 if (posix_locks_deadlock(&lock->fl, conflock)) { 349 up(&file->f_sema); 350 return nlm_deadlock; 351 } 352 353 /* If we don't have a block, create and initialize it. Then 354 * retry because we may have slept in kmalloc. */ 355 /* We have to release f_sema as nlmsvc_create_block may try to 356 * to claim it while doing host garbage collection */ 357 if (block == NULL) { 358 up(&file->f_sema); 359 dprintk("lockd: blocking on this lock (allocating).\n"); 360 if (!(block = nlmsvc_create_block(rqstp, file, lock, cookie))) 361 return nlm_lck_denied_nolocks; 362 goto again; 363 } 364 365 /* Append to list of blocked */ 366 nlmsvc_insert_block(block, NLM_NEVER); 367 368 if (list_empty(&block->b_call.a_args.lock.fl.fl_block)) { 369 /* Now add block to block list of the conflicting lock 370 if we haven't done so. */ 371 dprintk("lockd: blocking on this lock.\n"); 372 posix_block_lock(conflock, &block->b_call.a_args.lock.fl); 373 } 374 375 up(&file->f_sema); 376 return nlm_lck_blocked; 377 } 378 379 /* 380 * Test for presence of a conflicting lock. 381 */ 382 u32 383 nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock, 384 struct nlm_lock *conflock) 385 { 386 struct file_lock *fl; 387 388 dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n", 389 file->f_file->f_dentry->d_inode->i_sb->s_id, 390 file->f_file->f_dentry->d_inode->i_ino, 391 lock->fl.fl_type, 392 (long long)lock->fl.fl_start, 393 (long long)lock->fl.fl_end); 394 395 if ((fl = posix_test_lock(file->f_file, &lock->fl)) != NULL) { 396 dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n", 397 fl->fl_type, (long long)fl->fl_start, 398 (long long)fl->fl_end); 399 conflock->caller = "somehost"; /* FIXME */ 400 conflock->oh.len = 0; /* don't return OH info */ 401 conflock->fl = *fl; 402 return nlm_lck_denied; 403 } 404 405 return nlm_granted; 406 } 407 408 /* 409 * Remove a lock. 410 * This implies a CANCEL call: We send a GRANT_MSG, the client replies 411 * with a GRANT_RES call which gets lost, and calls UNLOCK immediately 412 * afterwards. In this case the block will still be there, and hence 413 * must be removed. 414 */ 415 u32 416 nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock) 417 { 418 int error; 419 420 dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n", 421 file->f_file->f_dentry->d_inode->i_sb->s_id, 422 file->f_file->f_dentry->d_inode->i_ino, 423 lock->fl.fl_pid, 424 (long long)lock->fl.fl_start, 425 (long long)lock->fl.fl_end); 426 427 /* First, cancel any lock that might be there */ 428 nlmsvc_cancel_blocked(file, lock); 429 430 lock->fl.fl_type = F_UNLCK; 431 error = posix_lock_file(file->f_file, &lock->fl); 432 433 return (error < 0)? nlm_lck_denied_nolocks : nlm_granted; 434 } 435 436 /* 437 * Cancel a previously blocked request. 438 * 439 * A cancel request always overrides any grant that may currently 440 * be in progress. 441 * The calling procedure must check whether the file can be closed. 442 */ 443 u32 444 nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock) 445 { 446 struct nlm_block *block; 447 448 dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n", 449 file->f_file->f_dentry->d_inode->i_sb->s_id, 450 file->f_file->f_dentry->d_inode->i_ino, 451 lock->fl.fl_pid, 452 (long long)lock->fl.fl_start, 453 (long long)lock->fl.fl_end); 454 455 down(&file->f_sema); 456 if ((block = nlmsvc_lookup_block(file, lock, 1)) != NULL) 457 nlmsvc_delete_block(block, 1); 458 up(&file->f_sema); 459 return nlm_granted; 460 } 461 462 /* 463 * Unblock a blocked lock request. This is a callback invoked from the 464 * VFS layer when a lock on which we blocked is removed. 465 * 466 * This function doesn't grant the blocked lock instantly, but rather moves 467 * the block to the head of nlm_blocked where it can be picked up by lockd. 468 */ 469 static void 470 nlmsvc_notify_blocked(struct file_lock *fl) 471 { 472 struct nlm_block **bp, *block; 473 474 dprintk("lockd: VFS unblock notification for block %p\n", fl); 475 for (bp = &nlm_blocked; (block = *bp) != 0; bp = &block->b_next) { 476 if (nlm_compare_locks(&block->b_call.a_args.lock.fl, fl)) { 477 nlmsvc_insert_block(block, 0); 478 svc_wake_up(block->b_daemon); 479 return; 480 } 481 } 482 483 printk(KERN_WARNING "lockd: notification for unknown block!\n"); 484 } 485 486 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2) 487 { 488 return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid; 489 } 490 491 struct lock_manager_operations nlmsvc_lock_operations = { 492 .fl_compare_owner = nlmsvc_same_owner, 493 .fl_notify = nlmsvc_notify_blocked, 494 }; 495 496 /* 497 * Try to claim a lock that was previously blocked. 498 * 499 * Note that we use both the RPC_GRANTED_MSG call _and_ an async 500 * RPC thread when notifying the client. This seems like overkill... 501 * Here's why: 502 * - we don't want to use a synchronous RPC thread, otherwise 503 * we might find ourselves hanging on a dead portmapper. 504 * - Some lockd implementations (e.g. HP) don't react to 505 * RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls. 506 */ 507 static void 508 nlmsvc_grant_blocked(struct nlm_block *block) 509 { 510 struct nlm_file *file = block->b_file; 511 struct nlm_lock *lock = &block->b_call.a_args.lock; 512 struct file_lock *conflock; 513 int error; 514 515 dprintk("lockd: grant blocked lock %p\n", block); 516 517 /* First thing is lock the file */ 518 down(&file->f_sema); 519 520 /* Unlink block request from list */ 521 nlmsvc_remove_block(block); 522 523 /* If b_granted is true this means we've been here before. 524 * Just retry the grant callback, possibly refreshing the RPC 525 * binding */ 526 if (block->b_granted) { 527 nlm_rebind_host(block->b_host); 528 goto callback; 529 } 530 531 /* Try the lock operation again */ 532 if ((conflock = posix_test_lock(file->f_file, &lock->fl)) != NULL) { 533 /* Bummer, we blocked again */ 534 dprintk("lockd: lock still blocked\n"); 535 nlmsvc_insert_block(block, NLM_NEVER); 536 posix_block_lock(conflock, &lock->fl); 537 up(&file->f_sema); 538 return; 539 } 540 541 /* Alright, no conflicting lock. Now lock it for real. If the 542 * following yields an error, this is most probably due to low 543 * memory. Retry the lock in a few seconds. 544 */ 545 if ((error = posix_lock_file(file->f_file, &lock->fl)) < 0) { 546 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n", 547 -error, __FUNCTION__); 548 nlmsvc_insert_block(block, 10 * HZ); 549 up(&file->f_sema); 550 return; 551 } 552 553 callback: 554 /* Lock was granted by VFS. */ 555 dprintk("lockd: GRANTing blocked lock.\n"); 556 block->b_granted = 1; 557 block->b_incall = 1; 558 559 /* Schedule next grant callback in 30 seconds */ 560 nlmsvc_insert_block(block, 30 * HZ); 561 562 /* Call the client */ 563 nlm_get_host(block->b_call.a_host); 564 if (nlmsvc_async_call(&block->b_call, NLMPROC_GRANTED_MSG, 565 nlmsvc_grant_callback) < 0) 566 nlm_release_host(block->b_call.a_host); 567 up(&file->f_sema); 568 } 569 570 /* 571 * This is the callback from the RPC layer when the NLM_GRANTED_MSG 572 * RPC call has succeeded or timed out. 573 * Like all RPC callbacks, it is invoked by the rpciod process, so it 574 * better not sleep. Therefore, we put the blocked lock on the nlm_blocked 575 * chain once more in order to have it removed by lockd itself (which can 576 * then sleep on the file semaphore without disrupting e.g. the nfs client). 577 */ 578 static void 579 nlmsvc_grant_callback(struct rpc_task *task) 580 { 581 struct nlm_rqst *call = (struct nlm_rqst *) task->tk_calldata; 582 struct nlm_block *block; 583 unsigned long timeout; 584 struct sockaddr_in *peer_addr = RPC_PEERADDR(task->tk_client); 585 586 dprintk("lockd: GRANT_MSG RPC callback\n"); 587 dprintk("callback: looking for cookie %s, host (%u.%u.%u.%u)\n", 588 nlmdbg_cookie2a(&call->a_args.cookie), 589 NIPQUAD(peer_addr->sin_addr.s_addr)); 590 if (!(block = nlmsvc_find_block(&call->a_args.cookie, peer_addr))) { 591 dprintk("lockd: no block for cookie %s, host (%u.%u.%u.%u)\n", 592 nlmdbg_cookie2a(&call->a_args.cookie), 593 NIPQUAD(peer_addr->sin_addr.s_addr)); 594 return; 595 } 596 597 /* Technically, we should down the file semaphore here. Since we 598 * move the block towards the head of the queue only, no harm 599 * can be done, though. */ 600 if (task->tk_status < 0) { 601 /* RPC error: Re-insert for retransmission */ 602 timeout = 10 * HZ; 603 } else if (block->b_done) { 604 /* Block already removed, kill it for real */ 605 timeout = 0; 606 } else { 607 /* Call was successful, now wait for client callback */ 608 timeout = 60 * HZ; 609 } 610 nlmsvc_insert_block(block, timeout); 611 svc_wake_up(block->b_daemon); 612 block->b_incall = 0; 613 614 nlm_release_host(call->a_host); 615 } 616 617 /* 618 * We received a GRANT_RES callback. Try to find the corresponding 619 * block. 620 */ 621 void 622 nlmsvc_grant_reply(struct svc_rqst *rqstp, struct nlm_cookie *cookie, u32 status) 623 { 624 struct nlm_block *block; 625 struct nlm_file *file; 626 627 dprintk("grant_reply: looking for cookie %x, host (%08x), s=%d \n", 628 *(unsigned int *)(cookie->data), 629 ntohl(rqstp->rq_addr.sin_addr.s_addr), status); 630 if (!(block = nlmsvc_find_block(cookie, &rqstp->rq_addr))) 631 return; 632 file = block->b_file; 633 634 file->f_count++; 635 down(&file->f_sema); 636 if ((block = nlmsvc_find_block(cookie,&rqstp->rq_addr)) != NULL) { 637 if (status == NLM_LCK_DENIED_GRACE_PERIOD) { 638 /* Try again in a couple of seconds */ 639 nlmsvc_insert_block(block, 10 * HZ); 640 block = NULL; 641 } else { 642 /* Lock is now held by client, or has been rejected. 643 * In both cases, the block should be removed. */ 644 up(&file->f_sema); 645 if (status == NLM_LCK_GRANTED) 646 nlmsvc_delete_block(block, 0); 647 else 648 nlmsvc_delete_block(block, 1); 649 } 650 } 651 if (!block) 652 up(&file->f_sema); 653 nlm_release_file(file); 654 } 655 656 /* 657 * Retry all blocked locks that have been notified. This is where lockd 658 * picks up locks that can be granted, or grant notifications that must 659 * be retransmitted. 660 */ 661 unsigned long 662 nlmsvc_retry_blocked(void) 663 { 664 struct nlm_block *block; 665 666 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n", 667 nlm_blocked, 668 nlm_blocked? nlm_blocked->b_when : 0); 669 while ((block = nlm_blocked) != 0) { 670 if (block->b_when == NLM_NEVER) 671 break; 672 if (time_after(block->b_when,jiffies)) 673 break; 674 dprintk("nlmsvc_retry_blocked(%p, when=%ld, done=%d)\n", 675 block, block->b_when, block->b_done); 676 if (block->b_done) 677 nlmsvc_delete_block(block, 0); 678 else 679 nlmsvc_grant_blocked(block); 680 } 681 682 if ((block = nlm_blocked) && block->b_when != NLM_NEVER) 683 return (block->b_when - jiffies); 684 685 return MAX_SCHEDULE_TIMEOUT; 686 } 687