1 /* 2 Bacula(R) - The Network Backup Solution 3 4 Copyright (C) 2000-2020 Kern Sibbald 5 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. 8 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. 13 14 This notice must be preserved when any source code is 15 conveyed and/or propagated. 16 17 Bacula(R) is a registered trademark of Kern Sibbald. 18 */ 19 /* 20 * Bacula Thread Read/Write locking code. It permits 21 * multiple readers but only one writer. 22 * 23 * Kern Sibbald, January MMI 24 * 25 * This code adapted from "Programming with POSIX Threads", by 26 * David R. Butenhof 27 * 28 */ 29 30 #ifndef __DEVLOCK_H 31 #define __DEVLOCK_H 1 32 33 struct take_lock_t { 34 pthread_t writer_id; /* id of writer */ 35 int reason; /* save reason */ 36 int prev_reason; /* previous reason */ 37 }; 38 39 40 class devlock { 41 private: 42 pthread_mutex_t mutex; 43 pthread_cond_t read; /* wait for read */ 44 pthread_cond_t write; /* wait for write */ 45 pthread_t writer_id; /* writer's thread id */ 46 int priority; /* used in deadlock detection */ 47 int valid; /* set when valid */ 48 int r_active; /* readers active */ 49 int w_active; /* writers active */ 50 int r_wait; /* readers waiting */ 51 int w_wait; /* writers waiting */ 52 int reason; /* reason for lock */ 53 int prev_reason; /* previous reason */ 54 bool can_take; /* can the lock be taken? */ 55 56 57 public: 58 devlock(int reason, bool can_take=false); 59 ~devlock(); 60 int init(int init_priority); 61 int destroy(); 62 int take_lock(take_lock_t *hold, int reason); 63 int return_lock(take_lock_t *hold); new_reason(int nreason)64 void new_reason(int nreason) { prev_reason = reason; reason = nreason; }; restore_reason()65 void restore_reason() { reason = prev_reason; prev_reason = 0; }; 66 67 int writelock(int reason, bool can_take=false); 68 int writetrylock(); 69 int writeunlock(); 70 void write_release(); 71 72 int readunlock(); 73 int readlock(); 74 int readtrylock(); 75 void read_release(); 76 77 }; 78 79 80 #define DEVLOCK_VALID 0xfadbec 81 82 #define DEVLOCK_INIIALIZER \ 83 {PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER, \ 84 PTHREAD_COND_INITIALIZER, DEVOCK_VALID, 0, 0, 0, 0} 85 86 #endif /* __DEVLOCK_H */ 87