2 Bacula(R) - The Network Backup Solution
4 Copyright (C) 2000-2017 Kern Sibbald
6 The original author of Bacula is Kern Sibbald, with contributions
7 from many others, a complete list can be found in the file AUTHORS.
9 You may use this file and others of this release according to the
10 license defined in the LICENSE file, which includes the Affero General
11 Public License, v3.0 ("AGPLv3") and some additional permissions and
12 terms pursuant to its AGPLv3 Section 7.
14 This notice must be preserved when any source code is
15 conveyed and/or propagated.
17 Bacula(R) is a registered trademark of Kern Sibbald.
20 * Collection of Bacula Storage daemon locking software
22 * Kern Sibbald, June 2007
26 #include "bacula.h" /* pull in global headers */
27 #include "stored.h" /* pull in Storage Deamon headers */
30 const int dbglvl = 300;
32 const int dbglvl = 500;
38 * The Storage daemon has three locking concepts that must be
41 * 1. dblock blocking the device, which means that the device
42 * is "marked" in use. When setting and removing the
43 block, the device is locked, but after dblock is
44 called the device is unlocked.
45 * 2. Lock() simple mutex that locks the device structure. A Lock
46 * can be acquired while a device is blocked if it is not
48 * 3. rLock(locked) "recursive" Lock, when means that a Lock (mutex)
49 * will be acquired on the device if it is not blocked
50 * by some other thread. If the device was blocked by
51 * the current thread, it will acquire the lock.
52 * If some other thread has set a block on the device,
53 * this call will wait until the device is unblocked.
54 * Can be called with locked true, which means the
57 * A lock is normally set when modifying the device structure.
58 * A rLock is normally acquired when you want to block the device
59 * i.e. it will wait until the device is not blocked.
60 * A block is normally set during long operations like writing to
62 * If you are writing the device, you will normally block and
64 * A lock cannot be violated. No other thread can touch the
65 * device while a lock is set.
66 * When a block is set, every thread accept the thread that set
67 * the block will block if rLock is called.
68 * A device can be blocked for multiple reasons, labeling, writing,
69 * acquiring (opening) the device, waiting for the operator, unmounted,
71 * Under certain conditions the block that is set on a device can be
72 * stolen and the device can be used by another thread. For example,
73 * a device is blocked because it is waiting for the operator to
74 * mount a tape. The operator can then unmount the device, and label
75 * a tape, re-mount it, give back the block, and the job will continue.
80 * DEVICE::Lock() does P(m_mutex) (in dev.h)
81 * DEVICE::Unlock() does V(m_mutex)
83 * DEVICE::rLock(locked) allows locking the device when this thread
84 * already has the device blocked.
87 * if blocked and not same thread that locked
89 * leaves device locked
91 * DEVICE::rUnlock() unlocks but does not unblock
94 * DEVICE::dblock(why) does
95 * rLock(); (recursive device lock)
96 * block_device(this, why)
99 * DEVICE::dunblock does
104 * block_device() does (must be locked and not blocked at entry)
108 * unblock_device() does (must be blocked at entry)
111 * set unblocked status
114 * pthread_cond_broadcast
116 * steal_device_lock() does (must be locked and blocked at entry)
118 * set new blocked status
122 * give_back_device_lock() does (must be blocked but not locked)
124 * reset blocked status
125 * save previous blocked
128 * pthread_cond_broadcast
132 void DEVICE::dblock(int why)
134 rLock(false); /* need recursive lock to block */
135 block_device(this, why);
139 void DEVICE::dunblock(bool locked)
144 unblock_device(this);
151 * Debug DEVICE locks N.B.
155 #ifdef DEV_DEBUG_LOCK
157 void DEVICE::dbg_Lock(const char *tfile, int line)
159 Dmsg3(sd_dbglvl, "Lock from %s:%d precnt=%d\n", tfile, line, m_count);
160 bthread_mutex_lock_p(&m_mutex, tfile, line);
161 m_pid = pthread_self();
165 void DEVICE::dbg_Unlock(const char *tfile, int line)
168 Dmsg3(sd_dbglvl, "Unlock from %s:%d postcnt=%d\n", tfile, line, m_count);
169 bthread_mutex_unlock_p(&m_mutex, tfile, line);
172 void DEVICE::dbg_rUnlock(const char *tfile, int line)
174 Dmsg2(sd_dbglvl, "rUnlock from %s:%d\n", tfile, line);
175 dbg_Unlock(tfile, line);
186 void DEVICE::rUnlock()
196 void DEVICE::Unlock()
201 #endif /* DEV_DEBUG_LOCK */
204 * This is a recursive lock that checks if the device is blocked.
206 * When blocked is set, all threads EXCEPT thread with id no_wait_id
207 * must wait. The no_wait_id thread is out obtaining a new volume
208 * and preparing the label.
210 #ifdef DEV_DEBUG_LOCK
211 void DEVICE::dbg_rLock(const char *tfile, int line, bool locked)
213 Dmsg3(sd_dbglvl, "rLock blked=%s from %s:%d\n", print_blocked(),
217 /* lockmgr version of P(m_mutex) */
218 bthread_mutex_lock_p(&m_mutex, tfile, line);
222 if (blocked() && !pthread_equal(no_wait_id, pthread_self())) {
223 num_waiting++; /* indicate that I am waiting */
227 /* thread id on Win32 may be a struct */
228 Dmsg3(sd_dbglvl, "rLock blked=%s no_wait=%p me=%p\n", print_blocked(),
229 no_wait_id, pthread_self());
231 if ((stat = bthread_cond_wait_p(&this->wait, &m_mutex, tfile, line)) != 0) {
233 this->dbg_Unlock(tfile, line);
234 Emsg1(M_ABORT, 0, _("pthread_cond_wait failure. ERR=%s\n"),
238 num_waiting--; /* no longer waiting */
241 #else /* DEV_DEBUG_LOCK */
243 void DEVICE::rLock(bool locked)
251 if (blocked() && !pthread_equal(no_wait_id, pthread_self())) {
252 num_waiting++; /* indicate that I am waiting */
256 /* thread id on Win32 may be a struct */
257 Dmsg3(sd_dbglvl, "rLock blked=%s no_wait=%p me=%p\n", print_blocked(),
258 no_wait_id, pthread_self());
260 if ((stat = pthread_cond_wait(&this->wait, &m_mutex)) != 0) {
263 Emsg1(M_ABORT, 0, _("pthread_cond_wait failure. ERR=%s\n"),
267 num_waiting--; /* no longer waiting */
271 #endif /* DEV_DEBUG_LOCK */
275 void DEVICE::dbg_Lock_acquire(const char *tfile, int line)
277 Dmsg2(sd_dbglvl, "Lock_acquire from %s:%d\n", tfile, line);
278 bthread_mutex_lock_p(&acquire_mutex, tfile, line);
281 void DEVICE::dbg_Unlock_acquire(const char *tfile, int line)
283 Dmsg2(sd_dbglvl, "Unlock_acquire from %s:%d\n", tfile, line);
284 bthread_mutex_unlock_p(&acquire_mutex, tfile, line);
287 void DEVICE::dbg_Lock_read_acquire(const char *tfile, int line)
289 Dmsg2(sd_dbglvl, "Lock_read_acquire from %s:%d\n", tfile, line);
290 bthread_mutex_lock_p(&read_acquire_mutex, tfile, line);
293 void DEVICE::dbg_Unlock_read_acquire(const char *tfile, int line)
295 Dmsg2(sd_dbglvl, "Unlock_read_acquire from %s:%d\n", tfile, line);
296 bthread_mutex_unlock_p(&read_acquire_mutex, tfile, line);
299 void DEVICE::dbg_Lock_VolCatInfo(const char *tfile, int line)
301 bthread_mutex_lock_p(&volcat_mutex, tfile, line);
304 void DEVICE::dbg_Unlock_VolCatInfo(const char *tfile, int line)
306 bthread_mutex_unlock_p(&volcat_mutex, tfile, line);
311 void DEVICE::Lock_acquire()
316 void DEVICE::Unlock_acquire()
321 void DEVICE::Lock_read_acquire()
323 P(read_acquire_mutex);
326 void DEVICE::Unlock_read_acquire()
328 V(read_acquire_mutex);
331 void DEVICE::Lock_VolCatInfo()
336 void DEVICE::Unlock_VolCatInfo()
345 /* Main device access control */
346 int DEVICE::init_mutex()
348 return pthread_mutex_init(&m_mutex, NULL);
351 /* Mutex around the freespace command */
352 int DEVICE::init_freespace_mutex()
354 return pthread_mutex_init(&freespace_mutex, NULL);
357 /* Write device acquire mutex */
358 int DEVICE::init_acquire_mutex()
360 return pthread_mutex_init(&acquire_mutex, NULL);
363 /* Read device acquire mutex */
364 int DEVICE::init_read_acquire_mutex()
366 return pthread_mutex_init(&read_acquire_mutex, NULL);
369 /* VolCatInfo mutex */
370 int DEVICE::init_volcat_mutex()
372 return pthread_mutex_init(&volcat_mutex, NULL);
376 int DEVICE::init_dcrs_mutex()
378 return pthread_mutex_init(&dcrs_mutex, NULL);
381 /* Set order in which device locks must be acquired */
382 void DEVICE::set_mutex_priorities()
384 /* Ensure that we respect this order in P/V operations */
385 bthread_mutex_set_priority(&m_mutex, PRIO_SD_DEV_ACCESS);
386 bthread_mutex_set_priority(&spool_mutex, PRIO_SD_DEV_SPOOL);
387 bthread_mutex_set_priority(&acquire_mutex, PRIO_SD_DEV_ACQUIRE);
390 int DEVICE::next_vol_timedwait(const struct timespec *timeout)
392 return pthread_cond_timedwait(&wait_next_vol, &m_mutex, timeout);
397 * Block all other threads from using the device
398 * Device must already be locked. After this call,
399 * the device is blocked to any thread calling dev->rLock(),
400 * but the device is not locked (i.e. no P on device). Also,
401 * the current thread can do slip through the dev->rLock()
402 * calls without blocking.
404 void _block_device(const char *file, int line, DEVICE *dev, int state)
406 ASSERT2(dev->blocked() == BST_NOT_BLOCKED, "Block request of device already blocked");
407 dev->set_blocked(state); /* make other threads wait */
408 dev->no_wait_id = pthread_self(); /* allow us to continue */
409 Dmsg3(sd_dbglvl, "set blocked=%s from %s:%d\n", dev->print_blocked(), file, line);
413 * Unblock the device, and wake up anyone who went to sleep.
414 * Enter: device locked
415 * Exit: device locked
417 void _unblock_device(const char *file, int line, DEVICE *dev)
419 Dmsg3(sd_dbglvl, "unblock %s from %s:%d\n", dev->print_blocked(), file, line);
420 ASSERT2(dev->blocked(), "Unblock request of device not blocked");
421 dev->set_blocked(BST_NOT_BLOCKED);
422 clear_thread_id(dev->no_wait_id);
423 if (dev->num_waiting > 0) {
424 pthread_cond_broadcast(&dev->wait); /* wake them up */
429 * Enter with device locked and blocked
430 * Exit with device unlocked and blocked by us.
432 void _steal_device_lock(const char *file, int line, DEVICE *dev, bsteal_lock_t *hold, int state)
434 Dmsg3(sd_dbglvl, "steal lock. old=%s from %s:%d\n", dev->print_blocked(),
436 hold->dev_blocked = dev->blocked();
437 hold->dev_prev_blocked = dev->dev_prev_blocked;
438 hold->no_wait_id = dev->no_wait_id;
439 dev->set_blocked(state);
440 Dmsg1(sd_dbglvl, "steal lock. new=%s\n", dev->print_blocked());
441 dev->no_wait_id = pthread_self();
446 * Enter with device blocked by us but not locked
447 * Exit with device locked, and blocked by previous owner
449 void _give_back_device_lock(const char *file, int line, DEVICE *dev, bsteal_lock_t *hold)
451 Dmsg3(sd_dbglvl, "return lock. old=%s from %s:%d\n",
452 dev->print_blocked(), file, line);
454 dev->set_blocked(hold->dev_blocked);
455 dev->dev_prev_blocked = hold->dev_prev_blocked;
456 dev->no_wait_id = hold->no_wait_id;
457 Dmsg1(sd_dbglvl, "return lock. new=%s\n", dev->print_blocked());
458 if (dev->num_waiting > 0) {
459 pthread_cond_broadcast(&dev->wait); /* wake them up */
463 const char *DEVICE::print_blocked() const
466 case BST_NOT_BLOCKED:
467 return "BST_NOT_BLOCKED";
469 return "BST_UNMOUNTED";
470 case BST_WAITING_FOR_SYSOP:
471 return "BST_WAITING_FOR_SYSOP";
472 case BST_DOING_ACQUIRE:
473 return "BST_DOING_ACQUIRE";
474 case BST_WRITING_LABEL:
475 return "BST_WRITING_LABEL";
476 case BST_UNMOUNTED_WAITING_FOR_SYSOP:
477 return "BST_UNMOUNTED_WAITING_FOR_SYSOP";
481 return "BST_DESPOOLING";
483 return "BST_RELEASING";
485 return _("unknown blocked code");
491 * Check if the device is blocked or not
493 bool DEVICE::is_device_unmounted()
498 stat = (blk == BST_UNMOUNTED) ||
499 (blk == BST_UNMOUNTED_WAITING_FOR_SYSOP);