1 /****************************************************************************** 2 * xenbus_xs.c 3 * 4 * This is the kernel equivalent of the "xs" library. We don't need everything 5 * and we use xenbus_comms for communication. 6 * 7 * Copyright (C) 2005 Rusty Russell, IBM Corporation 8 * 9 * This program is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU General Public License version 2 11 * as published by the Free Software Foundation; or, when distributed 12 * separately from the Linux kernel or incorporated into other 13 * software packages, subject to the following license: 14 * 15 * Permission is hereby granted, free of charge, to any person obtaining a copy 16 * of this source file (the "Software"), to deal in the Software without 17 * restriction, including without limitation the rights to use, copy, modify, 18 * merge, publish, distribute, sublicense, and/or sell copies of the Software, 19 * and to permit persons to whom the Software is furnished to do so, subject to 20 * the following conditions: 21 * 22 * The above copyright notice and this permission notice shall be included in 23 * all copies or substantial portions of the Software. 24 * 25 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 26 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 27 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 28 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 29 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 30 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 31 * IN THE SOFTWARE. 32 */ 33 34 #include <linux/unistd.h> 35 #include <linux/errno.h> 36 #include <linux/types.h> 37 #include <linux/uio.h> 38 #include <linux/kernel.h> 39 #include <linux/string.h> 40 #include <linux/err.h> 41 #include <linux/slab.h> 42 #include <linux/fcntl.h> 43 #include <linux/kthread.h> 44 #include <linux/rwsem.h> 45 #include <linux/module.h> 46 #include <linux/mutex.h> 47 #include <xen/xenbus.h> 48 #include "xenbus_comms.h" 49 50 struct xs_stored_msg { 51 struct list_head list; 52 53 struct xsd_sockmsg hdr; 54 55 union { 56 /* Queued replies. */ 57 struct { 58 char *body; 59 } reply; 60 61 /* Queued watch events. */ 62 struct { 63 struct xenbus_watch *handle; 64 char **vec; 65 unsigned int vec_size; 66 } watch; 67 } u; 68 }; 69 70 struct xs_handle { 71 /* A list of replies. Currently only one will ever be outstanding. */ 72 struct list_head reply_list; 73 spinlock_t reply_lock; 74 wait_queue_head_t reply_waitq; 75 76 /* 77 * Mutex ordering: transaction_mutex -> watch_mutex -> request_mutex. 78 * response_mutex is never taken simultaneously with the other three. 79 * 80 * transaction_mutex must be held before incrementing 81 * transaction_count. The mutex is held when a suspend is in 82 * progress to prevent new transactions starting. 83 * 84 * When decrementing transaction_count to zero the wait queue 85 * should be woken up, the suspend code waits for count to 86 * reach zero. 87 */ 88 89 /* One request at a time. */ 90 struct mutex request_mutex; 91 92 /* Protect xenbus reader thread against save/restore. */ 93 struct mutex response_mutex; 94 95 /* Protect transactions against save/restore. */ 96 struct mutex transaction_mutex; 97 atomic_t transaction_count; 98 wait_queue_head_t transaction_wq; 99 100 /* Protect watch (de)register against save/restore. */ 101 struct rw_semaphore watch_mutex; 102 }; 103 104 static struct xs_handle xs_state; 105 106 /* List of registered watches, and a lock to protect it. */ 107 static LIST_HEAD(watches); 108 static DEFINE_SPINLOCK(watches_lock); 109 110 /* List of pending watch callback events, and a lock to protect it. */ 111 static LIST_HEAD(watch_events); 112 static DEFINE_SPINLOCK(watch_events_lock); 113 114 /* 115 * Details of the xenwatch callback kernel thread. The thread waits on the 116 * watch_events_waitq for work to do (queued on watch_events list). When it 117 * wakes up it acquires the xenwatch_mutex before reading the list and 118 * carrying out work. 119 */ 120 static pid_t xenwatch_pid; 121 static DEFINE_MUTEX(xenwatch_mutex); 122 static DECLARE_WAIT_QUEUE_HEAD(watch_events_waitq); 123 124 static int get_error(const char *errorstring) 125 { 126 unsigned int i; 127 128 for (i = 0; strcmp(errorstring, xsd_errors[i].errstring) != 0; i++) { 129 if (i == ARRAY_SIZE(xsd_errors) - 1) { 130 printk(KERN_WARNING 131 "XENBUS xen store gave: unknown error %s", 132 errorstring); 133 return EINVAL; 134 } 135 } 136 return xsd_errors[i].errnum; 137 } 138 139 static void *read_reply(enum xsd_sockmsg_type *type, unsigned int *len) 140 { 141 struct xs_stored_msg *msg; 142 char *body; 143 144 spin_lock(&xs_state.reply_lock); 145 146 while (list_empty(&xs_state.reply_list)) { 147 spin_unlock(&xs_state.reply_lock); 148 /* XXX FIXME: Avoid synchronous wait for response here. */ 149 wait_event(xs_state.reply_waitq, 150 !list_empty(&xs_state.reply_list)); 151 spin_lock(&xs_state.reply_lock); 152 } 153 154 msg = list_entry(xs_state.reply_list.next, 155 struct xs_stored_msg, list); 156 list_del(&msg->list); 157 158 spin_unlock(&xs_state.reply_lock); 159 160 *type = msg->hdr.type; 161 if (len) 162 *len = msg->hdr.len; 163 body = msg->u.reply.body; 164 165 kfree(msg); 166 167 return body; 168 } 169 170 static void transaction_start(void) 171 { 172 mutex_lock(&xs_state.transaction_mutex); 173 atomic_inc(&xs_state.transaction_count); 174 mutex_unlock(&xs_state.transaction_mutex); 175 } 176 177 static void transaction_end(void) 178 { 179 if (atomic_dec_and_test(&xs_state.transaction_count)) 180 wake_up(&xs_state.transaction_wq); 181 } 182 183 static void transaction_suspend(void) 184 { 185 mutex_lock(&xs_state.transaction_mutex); 186 wait_event(xs_state.transaction_wq, 187 atomic_read(&xs_state.transaction_count) == 0); 188 } 189 190 static void transaction_resume(void) 191 { 192 mutex_unlock(&xs_state.transaction_mutex); 193 } 194 195 void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg) 196 { 197 void *ret; 198 struct xsd_sockmsg req_msg = *msg; 199 int err; 200 201 if (req_msg.type == XS_TRANSACTION_START) 202 transaction_start(); 203 204 mutex_lock(&xs_state.request_mutex); 205 206 err = xb_write(msg, sizeof(*msg) + msg->len); 207 if (err) { 208 msg->type = XS_ERROR; 209 ret = ERR_PTR(err); 210 } else 211 ret = read_reply(&msg->type, &msg->len); 212 213 mutex_unlock(&xs_state.request_mutex); 214 215 if ((msg->type == XS_TRANSACTION_END) || 216 ((req_msg.type == XS_TRANSACTION_START) && 217 (msg->type == XS_ERROR))) 218 transaction_end(); 219 220 return ret; 221 } 222 EXPORT_SYMBOL(xenbus_dev_request_and_reply); 223 224 /* Send message to xs, get kmalloc'ed reply. ERR_PTR() on error. */ 225 static void *xs_talkv(struct xenbus_transaction t, 226 enum xsd_sockmsg_type type, 227 const struct kvec *iovec, 228 unsigned int num_vecs, 229 unsigned int *len) 230 { 231 struct xsd_sockmsg msg; 232 void *ret = NULL; 233 unsigned int i; 234 int err; 235 236 msg.tx_id = t.id; 237 msg.req_id = 0; 238 msg.type = type; 239 msg.len = 0; 240 for (i = 0; i < num_vecs; i++) 241 msg.len += iovec[i].iov_len; 242 243 mutex_lock(&xs_state.request_mutex); 244 245 err = xb_write(&msg, sizeof(msg)); 246 if (err) { 247 mutex_unlock(&xs_state.request_mutex); 248 return ERR_PTR(err); 249 } 250 251 for (i = 0; i < num_vecs; i++) { 252 err = xb_write(iovec[i].iov_base, iovec[i].iov_len); 253 if (err) { 254 mutex_unlock(&xs_state.request_mutex); 255 return ERR_PTR(err); 256 } 257 } 258 259 ret = read_reply(&msg.type, len); 260 261 mutex_unlock(&xs_state.request_mutex); 262 263 if (IS_ERR(ret)) 264 return ret; 265 266 if (msg.type == XS_ERROR) { 267 err = get_error(ret); 268 kfree(ret); 269 return ERR_PTR(-err); 270 } 271 272 if (msg.type != type) { 273 if (printk_ratelimit()) 274 printk(KERN_WARNING 275 "XENBUS unexpected type [%d], expected [%d]\n", 276 msg.type, type); 277 kfree(ret); 278 return ERR_PTR(-EINVAL); 279 } 280 return ret; 281 } 282 283 /* Simplified version of xs_talkv: single message. */ 284 static void *xs_single(struct xenbus_transaction t, 285 enum xsd_sockmsg_type type, 286 const char *string, 287 unsigned int *len) 288 { 289 struct kvec iovec; 290 291 iovec.iov_base = (void *)string; 292 iovec.iov_len = strlen(string) + 1; 293 return xs_talkv(t, type, &iovec, 1, len); 294 } 295 296 /* Many commands only need an ack, don't care what it says. */ 297 static int xs_error(char *reply) 298 { 299 if (IS_ERR(reply)) 300 return PTR_ERR(reply); 301 kfree(reply); 302 return 0; 303 } 304 305 static unsigned int count_strings(const char *strings, unsigned int len) 306 { 307 unsigned int num; 308 const char *p; 309 310 for (p = strings, num = 0; p < strings + len; p += strlen(p) + 1) 311 num++; 312 313 return num; 314 } 315 316 /* Return the path to dir with /name appended. Buffer must be kfree()'ed. */ 317 static char *join(const char *dir, const char *name) 318 { 319 char *buffer; 320 321 if (strlen(name) == 0) 322 buffer = kasprintf(GFP_NOIO | __GFP_HIGH, "%s", dir); 323 else 324 buffer = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/%s", dir, name); 325 return (!buffer) ? ERR_PTR(-ENOMEM) : buffer; 326 } 327 328 static char **split(char *strings, unsigned int len, unsigned int *num) 329 { 330 char *p, **ret; 331 332 /* Count the strings. */ 333 *num = count_strings(strings, len); 334 335 /* Transfer to one big alloc for easy freeing. */ 336 ret = kmalloc(*num * sizeof(char *) + len, GFP_NOIO | __GFP_HIGH); 337 if (!ret) { 338 kfree(strings); 339 return ERR_PTR(-ENOMEM); 340 } 341 memcpy(&ret[*num], strings, len); 342 kfree(strings); 343 344 strings = (char *)&ret[*num]; 345 for (p = strings, *num = 0; p < strings + len; p += strlen(p) + 1) 346 ret[(*num)++] = p; 347 348 return ret; 349 } 350 351 char **xenbus_directory(struct xenbus_transaction t, 352 const char *dir, const char *node, unsigned int *num) 353 { 354 char *strings, *path; 355 unsigned int len; 356 357 path = join(dir, node); 358 if (IS_ERR(path)) 359 return (char **)path; 360 361 strings = xs_single(t, XS_DIRECTORY, path, &len); 362 kfree(path); 363 if (IS_ERR(strings)) 364 return (char **)strings; 365 366 return split(strings, len, num); 367 } 368 EXPORT_SYMBOL_GPL(xenbus_directory); 369 370 /* Check if a path exists. Return 1 if it does. */ 371 int xenbus_exists(struct xenbus_transaction t, 372 const char *dir, const char *node) 373 { 374 char **d; 375 int dir_n; 376 377 d = xenbus_directory(t, dir, node, &dir_n); 378 if (IS_ERR(d)) 379 return 0; 380 kfree(d); 381 return 1; 382 } 383 EXPORT_SYMBOL_GPL(xenbus_exists); 384 385 /* Get the value of a single file. 386 * Returns a kmalloced value: call free() on it after use. 387 * len indicates length in bytes. 388 */ 389 void *xenbus_read(struct xenbus_transaction t, 390 const char *dir, const char *node, unsigned int *len) 391 { 392 char *path; 393 void *ret; 394 395 path = join(dir, node); 396 if (IS_ERR(path)) 397 return (void *)path; 398 399 ret = xs_single(t, XS_READ, path, len); 400 kfree(path); 401 return ret; 402 } 403 EXPORT_SYMBOL_GPL(xenbus_read); 404 405 /* Write the value of a single file. 406 * Returns -err on failure. 407 */ 408 int xenbus_write(struct xenbus_transaction t, 409 const char *dir, const char *node, const char *string) 410 { 411 const char *path; 412 struct kvec iovec[2]; 413 int ret; 414 415 path = join(dir, node); 416 if (IS_ERR(path)) 417 return PTR_ERR(path); 418 419 iovec[0].iov_base = (void *)path; 420 iovec[0].iov_len = strlen(path) + 1; 421 iovec[1].iov_base = (void *)string; 422 iovec[1].iov_len = strlen(string); 423 424 ret = xs_error(xs_talkv(t, XS_WRITE, iovec, ARRAY_SIZE(iovec), NULL)); 425 kfree(path); 426 return ret; 427 } 428 EXPORT_SYMBOL_GPL(xenbus_write); 429 430 /* Create a new directory. */ 431 int xenbus_mkdir(struct xenbus_transaction t, 432 const char *dir, const char *node) 433 { 434 char *path; 435 int ret; 436 437 path = join(dir, node); 438 if (IS_ERR(path)) 439 return PTR_ERR(path); 440 441 ret = xs_error(xs_single(t, XS_MKDIR, path, NULL)); 442 kfree(path); 443 return ret; 444 } 445 EXPORT_SYMBOL_GPL(xenbus_mkdir); 446 447 /* Destroy a file or directory (directories must be empty). */ 448 int xenbus_rm(struct xenbus_transaction t, const char *dir, const char *node) 449 { 450 char *path; 451 int ret; 452 453 path = join(dir, node); 454 if (IS_ERR(path)) 455 return PTR_ERR(path); 456 457 ret = xs_error(xs_single(t, XS_RM, path, NULL)); 458 kfree(path); 459 return ret; 460 } 461 EXPORT_SYMBOL_GPL(xenbus_rm); 462 463 /* Start a transaction: changes by others will not be seen during this 464 * transaction, and changes will not be visible to others until end. 465 */ 466 int xenbus_transaction_start(struct xenbus_transaction *t) 467 { 468 char *id_str; 469 470 transaction_start(); 471 472 id_str = xs_single(XBT_NIL, XS_TRANSACTION_START, "", NULL); 473 if (IS_ERR(id_str)) { 474 transaction_end(); 475 return PTR_ERR(id_str); 476 } 477 478 t->id = simple_strtoul(id_str, NULL, 0); 479 kfree(id_str); 480 return 0; 481 } 482 EXPORT_SYMBOL_GPL(xenbus_transaction_start); 483 484 /* End a transaction. 485 * If abandon is true, transaction is discarded instead of committed. 486 */ 487 int xenbus_transaction_end(struct xenbus_transaction t, int abort) 488 { 489 char abortstr[2]; 490 int err; 491 492 if (abort) 493 strcpy(abortstr, "F"); 494 else 495 strcpy(abortstr, "T"); 496 497 err = xs_error(xs_single(t, XS_TRANSACTION_END, abortstr, NULL)); 498 499 transaction_end(); 500 501 return err; 502 } 503 EXPORT_SYMBOL_GPL(xenbus_transaction_end); 504 505 /* Single read and scanf: returns -errno or num scanned. */ 506 int xenbus_scanf(struct xenbus_transaction t, 507 const char *dir, const char *node, const char *fmt, ...) 508 { 509 va_list ap; 510 int ret; 511 char *val; 512 513 val = xenbus_read(t, dir, node, NULL); 514 if (IS_ERR(val)) 515 return PTR_ERR(val); 516 517 va_start(ap, fmt); 518 ret = vsscanf(val, fmt, ap); 519 va_end(ap); 520 kfree(val); 521 /* Distinctive errno. */ 522 if (ret == 0) 523 return -ERANGE; 524 return ret; 525 } 526 EXPORT_SYMBOL_GPL(xenbus_scanf); 527 528 /* Single printf and write: returns -errno or 0. */ 529 int xenbus_printf(struct xenbus_transaction t, 530 const char *dir, const char *node, const char *fmt, ...) 531 { 532 va_list ap; 533 int ret; 534 #define PRINTF_BUFFER_SIZE 4096 535 char *printf_buffer; 536 537 printf_buffer = kmalloc(PRINTF_BUFFER_SIZE, GFP_NOIO | __GFP_HIGH); 538 if (printf_buffer == NULL) 539 return -ENOMEM; 540 541 va_start(ap, fmt); 542 ret = vsnprintf(printf_buffer, PRINTF_BUFFER_SIZE, fmt, ap); 543 va_end(ap); 544 545 BUG_ON(ret > PRINTF_BUFFER_SIZE-1); 546 ret = xenbus_write(t, dir, node, printf_buffer); 547 548 kfree(printf_buffer); 549 550 return ret; 551 } 552 EXPORT_SYMBOL_GPL(xenbus_printf); 553 554 /* Takes tuples of names, scanf-style args, and void **, NULL terminated. */ 555 int xenbus_gather(struct xenbus_transaction t, const char *dir, ...) 556 { 557 va_list ap; 558 const char *name; 559 int ret = 0; 560 561 va_start(ap, dir); 562 while (ret == 0 && (name = va_arg(ap, char *)) != NULL) { 563 const char *fmt = va_arg(ap, char *); 564 void *result = va_arg(ap, void *); 565 char *p; 566 567 p = xenbus_read(t, dir, name, NULL); 568 if (IS_ERR(p)) { 569 ret = PTR_ERR(p); 570 break; 571 } 572 if (fmt) { 573 if (sscanf(p, fmt, result) == 0) 574 ret = -EINVAL; 575 kfree(p); 576 } else 577 *(char **)result = p; 578 } 579 va_end(ap); 580 return ret; 581 } 582 EXPORT_SYMBOL_GPL(xenbus_gather); 583 584 static int xs_watch(const char *path, const char *token) 585 { 586 struct kvec iov[2]; 587 588 iov[0].iov_base = (void *)path; 589 iov[0].iov_len = strlen(path) + 1; 590 iov[1].iov_base = (void *)token; 591 iov[1].iov_len = strlen(token) + 1; 592 593 return xs_error(xs_talkv(XBT_NIL, XS_WATCH, iov, 594 ARRAY_SIZE(iov), NULL)); 595 } 596 597 static int xs_unwatch(const char *path, const char *token) 598 { 599 struct kvec iov[2]; 600 601 iov[0].iov_base = (char *)path; 602 iov[0].iov_len = strlen(path) + 1; 603 iov[1].iov_base = (char *)token; 604 iov[1].iov_len = strlen(token) + 1; 605 606 return xs_error(xs_talkv(XBT_NIL, XS_UNWATCH, iov, 607 ARRAY_SIZE(iov), NULL)); 608 } 609 610 static struct xenbus_watch *find_watch(const char *token) 611 { 612 struct xenbus_watch *i, *cmp; 613 614 cmp = (void *)simple_strtoul(token, NULL, 16); 615 616 list_for_each_entry(i, &watches, list) 617 if (i == cmp) 618 return i; 619 620 return NULL; 621 } 622 623 /* Register callback to watch this node. */ 624 int register_xenbus_watch(struct xenbus_watch *watch) 625 { 626 /* Pointer in ascii is the token. */ 627 char token[sizeof(watch) * 2 + 1]; 628 int err; 629 630 sprintf(token, "%lX", (long)watch); 631 632 down_read(&xs_state.watch_mutex); 633 634 spin_lock(&watches_lock); 635 BUG_ON(find_watch(token)); 636 list_add(&watch->list, &watches); 637 spin_unlock(&watches_lock); 638 639 err = xs_watch(watch->node, token); 640 641 /* Ignore errors due to multiple registration. */ 642 if ((err != 0) && (err != -EEXIST)) { 643 spin_lock(&watches_lock); 644 list_del(&watch->list); 645 spin_unlock(&watches_lock); 646 } 647 648 up_read(&xs_state.watch_mutex); 649 650 return err; 651 } 652 EXPORT_SYMBOL_GPL(register_xenbus_watch); 653 654 void unregister_xenbus_watch(struct xenbus_watch *watch) 655 { 656 struct xs_stored_msg *msg, *tmp; 657 char token[sizeof(watch) * 2 + 1]; 658 int err; 659 660 sprintf(token, "%lX", (long)watch); 661 662 down_read(&xs_state.watch_mutex); 663 664 spin_lock(&watches_lock); 665 BUG_ON(!find_watch(token)); 666 list_del(&watch->list); 667 spin_unlock(&watches_lock); 668 669 err = xs_unwatch(watch->node, token); 670 if (err) 671 printk(KERN_WARNING 672 "XENBUS Failed to release watch %s: %i\n", 673 watch->node, err); 674 675 up_read(&xs_state.watch_mutex); 676 677 /* Make sure there are no callbacks running currently (unless 678 its us) */ 679 if (current->pid != xenwatch_pid) 680 mutex_lock(&xenwatch_mutex); 681 682 /* Cancel pending watch events. */ 683 spin_lock(&watch_events_lock); 684 list_for_each_entry_safe(msg, tmp, &watch_events, list) { 685 if (msg->u.watch.handle != watch) 686 continue; 687 list_del(&msg->list); 688 kfree(msg->u.watch.vec); 689 kfree(msg); 690 } 691 spin_unlock(&watch_events_lock); 692 693 if (current->pid != xenwatch_pid) 694 mutex_unlock(&xenwatch_mutex); 695 } 696 EXPORT_SYMBOL_GPL(unregister_xenbus_watch); 697 698 void xs_suspend(void) 699 { 700 transaction_suspend(); 701 down_write(&xs_state.watch_mutex); 702 mutex_lock(&xs_state.request_mutex); 703 mutex_lock(&xs_state.response_mutex); 704 } 705 706 void xs_resume(void) 707 { 708 struct xenbus_watch *watch; 709 char token[sizeof(watch) * 2 + 1]; 710 711 xb_init_comms(); 712 713 mutex_unlock(&xs_state.response_mutex); 714 mutex_unlock(&xs_state.request_mutex); 715 transaction_resume(); 716 717 /* No need for watches_lock: the watch_mutex is sufficient. */ 718 list_for_each_entry(watch, &watches, list) { 719 sprintf(token, "%lX", (long)watch); 720 xs_watch(watch->node, token); 721 } 722 723 up_write(&xs_state.watch_mutex); 724 } 725 726 void xs_suspend_cancel(void) 727 { 728 mutex_unlock(&xs_state.response_mutex); 729 mutex_unlock(&xs_state.request_mutex); 730 up_write(&xs_state.watch_mutex); 731 mutex_unlock(&xs_state.transaction_mutex); 732 } 733 734 static int xenwatch_thread(void *unused) 735 { 736 struct list_head *ent; 737 struct xs_stored_msg *msg; 738 739 for (;;) { 740 wait_event_interruptible(watch_events_waitq, 741 !list_empty(&watch_events)); 742 743 if (kthread_should_stop()) 744 break; 745 746 mutex_lock(&xenwatch_mutex); 747 748 spin_lock(&watch_events_lock); 749 ent = watch_events.next; 750 if (ent != &watch_events) 751 list_del(ent); 752 spin_unlock(&watch_events_lock); 753 754 if (ent != &watch_events) { 755 msg = list_entry(ent, struct xs_stored_msg, list); 756 msg->u.watch.handle->callback( 757 msg->u.watch.handle, 758 (const char **)msg->u.watch.vec, 759 msg->u.watch.vec_size); 760 kfree(msg->u.watch.vec); 761 kfree(msg); 762 } 763 764 mutex_unlock(&xenwatch_mutex); 765 } 766 767 return 0; 768 } 769 770 static int process_msg(void) 771 { 772 struct xs_stored_msg *msg; 773 char *body; 774 int err; 775 776 /* 777 * We must disallow save/restore while reading a xenstore message. 778 * A partial read across s/r leaves us out of sync with xenstored. 779 */ 780 for (;;) { 781 err = xb_wait_for_data_to_read(); 782 if (err) 783 return err; 784 mutex_lock(&xs_state.response_mutex); 785 if (xb_data_to_read()) 786 break; 787 /* We raced with save/restore: pending data 'disappeared'. */ 788 mutex_unlock(&xs_state.response_mutex); 789 } 790 791 792 msg = kmalloc(sizeof(*msg), GFP_NOIO | __GFP_HIGH); 793 if (msg == NULL) { 794 err = -ENOMEM; 795 goto out; 796 } 797 798 err = xb_read(&msg->hdr, sizeof(msg->hdr)); 799 if (err) { 800 kfree(msg); 801 goto out; 802 } 803 804 body = kmalloc(msg->hdr.len + 1, GFP_NOIO | __GFP_HIGH); 805 if (body == NULL) { 806 kfree(msg); 807 err = -ENOMEM; 808 goto out; 809 } 810 811 err = xb_read(body, msg->hdr.len); 812 if (err) { 813 kfree(body); 814 kfree(msg); 815 goto out; 816 } 817 body[msg->hdr.len] = '\0'; 818 819 if (msg->hdr.type == XS_WATCH_EVENT) { 820 msg->u.watch.vec = split(body, msg->hdr.len, 821 &msg->u.watch.vec_size); 822 if (IS_ERR(msg->u.watch.vec)) { 823 err = PTR_ERR(msg->u.watch.vec); 824 kfree(msg); 825 goto out; 826 } 827 828 spin_lock(&watches_lock); 829 msg->u.watch.handle = find_watch( 830 msg->u.watch.vec[XS_WATCH_TOKEN]); 831 if (msg->u.watch.handle != NULL) { 832 spin_lock(&watch_events_lock); 833 list_add_tail(&msg->list, &watch_events); 834 wake_up(&watch_events_waitq); 835 spin_unlock(&watch_events_lock); 836 } else { 837 kfree(msg->u.watch.vec); 838 kfree(msg); 839 } 840 spin_unlock(&watches_lock); 841 } else { 842 msg->u.reply.body = body; 843 spin_lock(&xs_state.reply_lock); 844 list_add_tail(&msg->list, &xs_state.reply_list); 845 spin_unlock(&xs_state.reply_lock); 846 wake_up(&xs_state.reply_waitq); 847 } 848 849 out: 850 mutex_unlock(&xs_state.response_mutex); 851 return err; 852 } 853 854 static int xenbus_thread(void *unused) 855 { 856 int err; 857 858 for (;;) { 859 err = process_msg(); 860 if (err) 861 printk(KERN_WARNING "XENBUS error %d while reading " 862 "message\n", err); 863 if (kthread_should_stop()) 864 break; 865 } 866 867 return 0; 868 } 869 870 int xs_init(void) 871 { 872 int err; 873 struct task_struct *task; 874 875 INIT_LIST_HEAD(&xs_state.reply_list); 876 spin_lock_init(&xs_state.reply_lock); 877 init_waitqueue_head(&xs_state.reply_waitq); 878 879 mutex_init(&xs_state.request_mutex); 880 mutex_init(&xs_state.response_mutex); 881 mutex_init(&xs_state.transaction_mutex); 882 init_rwsem(&xs_state.watch_mutex); 883 atomic_set(&xs_state.transaction_count, 0); 884 init_waitqueue_head(&xs_state.transaction_wq); 885 886 /* Initialize the shared memory rings to talk to xenstored */ 887 err = xb_init_comms(); 888 if (err) 889 return err; 890 891 task = kthread_run(xenwatch_thread, NULL, "xenwatch"); 892 if (IS_ERR(task)) 893 return PTR_ERR(task); 894 xenwatch_pid = task->pid; 895 896 task = kthread_run(xenbus_thread, NULL, "xenbus"); 897 if (IS_ERR(task)) 898 return PTR_ERR(task); 899 900 return 0; 901 } 902