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	qlock.c - 9base - revived minimalist port of Plan 9 userland to Unix
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	---
	qlock.c (2268B)
	---
	1 #include <u.h>
	2 #include <libc.h>
	3
	4 /*
	5 * The function pointers are supplied by the thread
	6 * library during its initialization. If there is no thread
	7 * library, there is no multithreading.
	8 */
	9
	10 int (_lock)(Lock, int, ulong);
	11 void (_unlock)(Lock, ulong);
	12 int (_qlock)(QLock, int, ulong); /* do not use */
	13 void (_qunlock)(QLock, ulong);
	14 void (_rsleep)(Rendez, ulong); /* do not use */
	15 int (_rwakeup)(Rendez, int, ulong);
	16 int (_rlock)(RWLock, int, ulong); /* do not use */
	17 int (_wlock)(RWLock, int, ulong);
	18 void (_runlock)(RWLock, ulong);
	19 void (_wunlock)(RWLock, ulong);
	20
	21 void
	22 lock(Lock *l)
	23 {
	24 if(_lock)
	25 (*_lock)(l, 1, getcallerpc(&l));
	26 else
	27 l->held = 1;
	28 }
	29
	30 int
	31 canlock(Lock *l)
	32 {
	33 if(_lock)
	34 return (*_lock)(l, 0, getcallerpc(&l));
	35 else{
	36 if(l->held)
	37 return 0;
	38 l->held = 1;
	39 return 1;
	40 }
	41 }
	42
	43 void
	44 unlock(Lock *l)
	45 {
	46 if(_unlock)
	47 (*_unlock)(l, getcallerpc(&l));
	48 else
	49 l->held = 0;
	50 }
	51
	52 void
	53 qlock(QLock *l)
	54 {
	55 if(_qlock)
	56 (*_qlock)(l, 1, getcallerpc(&l));
	57 else
	58 l->l.held = 1;
	59 }
	60
	61 int
	62 canqlock(QLock *l)
	63 {
	64 if(_qlock)
	65 return (*_qlock)(l, 0, getcallerpc(&l));
	66 else{
	67 if(l->l.held)
	68 return 0;
	69 l->l.held = 1;
	70 return 1;
	71 }
	72 }
	73
	74 void
	75 qunlock(QLock *l)
	76 {
	77 if(_qunlock)
	78 (*_qunlock)(l, getcallerpc(&l));
	79 else
	80 l->l.held = 0;
	81 }
	82
	83 void
	84 rlock(RWLock *l)
	85 {
	86 if(_rlock)
	87 (*_rlock)(l, 1, getcallerpc(&l));
	88 else
	89 l->readers++;
	90 }
	91
	92 int
	93 canrlock(RWLock *l)
	94 {
	95 if(_rlock)
	96 return (*_rlock)(l, 0, getcallerpc(&l));
	97 else{
	98 if(l->writer)
	99 return 0;
	100 l->readers++;
	101 return 1;
	102 }
	103 }
	104
	105 void
	106 runlock(RWLock *l)
	107 {
	108 if(_runlock)
	109 (*_runlock)(l, getcallerpc(&l));
	110 else
	111 l->readers--;
	112 }
	113
	114 void
	115 wlock(RWLock *l)
	116 {
	117 if(_wlock)
	118 (*_wlock)(l, 1, getcallerpc(&l));
	119 else
	120 l->writer = (void*)1;
	121 }
	122
	123 int
	124 canwlock(RWLock *l)
	125 {
	126 if(_wlock)
	127 return (*_wlock)(l, 0, getcallerpc(&l));
	128 else{
	129 if(l->writer \|\| l->readers)
	130 return 0;
	131 l->writer = (void*)1;
	132 return 1;
	133 }
	134 }
	135
	136 void
	137 wunlock(RWLock *l)
	138 {
	139 if(_wunlock)
	140 (*_wunlock)(l, getcallerpc(&l));
	141 else
	142 l->writer = nil;
	143 }
	144
	145 void
	146 rsleep(Rendez *r)
	147 {
	148 if(_rsleep)
	149 (*_rsleep)(r, getcallerpc(&r));
	150 }
	151
	152 int
	153 rwakeup(Rendez *r)
	154 {
	155 if(_rwakeup)
	156 return (*_rwakeup)(r, 0, getcallerpc(&r));
	157 return 0;
	158 }
	159
	160 int
	161 rwakeupall(Rendez *r)
	162 {
	163 if(_rwakeup)
	164 return (*_rwakeup)(r, 1, getcallerpc(&r));
	165 return 0;
	166 }