diff options
Diffstat (limited to 'src/lib9/qlock.c')
| -rw-r--r-- | src/lib9/qlock.c | 360 |
1 files changed, 360 insertions, 0 deletions
diff --git a/src/lib9/qlock.c b/src/lib9/qlock.c new file mode 100644 index 00000000..55a18466 --- /dev/null +++ b/src/lib9/qlock.c @@ -0,0 +1,360 @@ +#include <lib9.h> + +static struct { + QLp *p; + QLp x[1024]; +} ql = { + ql.x +}; + +enum +{ + Queuing, + QueuingR, + QueuingW, + Sleeping, +}; + +static ulong (*_rendezvousp)(ulong, ulong) = rendezvous; + +/* this gets called by the thread library ONLY to get us to use its rendezvous */ +void +_qlockinit(ulong (*r)(ulong, ulong)) +{ + _rendezvousp = r; +} + +/* find a free shared memory location to queue ourselves in */ +static QLp* +getqlp(void) +{ + QLp *p, *op; + + op = ql.p; + for(p = op+1; ; p++){ + if(p == &ql.x[nelem(ql.x)]) + p = ql.x; + if(p == op) + abort(); + if(_tas(&(p->inuse)) == 0){ + ql.p = p; + p->next = nil; + break; + } + } + return p; +} + +void +qlock(QLock *q) +{ + QLp *p, *mp; + + lock(&q->lock); + if(!q->locked){ + q->locked = 1; + unlock(&q->lock); + return; + } + + + /* chain into waiting list */ + mp = getqlp(); + p = q->tail; + if(p == nil) + q->head = mp; + else + p->next = mp; + q->tail = mp; + mp->state = Queuing; + unlock(&q->lock); + + /* wait */ + while((*_rendezvousp)((ulong)mp, 1) == ~0) + ; + mp->inuse = 0; +} + +void +qunlock(QLock *q) +{ + QLp *p; + + lock(&q->lock); + p = q->head; + if(p != nil){ + /* wakeup head waiting process */ + q->head = p->next; + if(q->head == nil) + q->tail = nil; + unlock(&q->lock); + while((*_rendezvousp)((ulong)p, 0x12345) == ~0) + ; + return; + } + q->locked = 0; + unlock(&q->lock); +} + +int +canqlock(QLock *q) +{ + if(!canlock(&q->lock)) + return 0; + if(!q->locked){ + q->locked = 1; + unlock(&q->lock); + return 1; + } + unlock(&q->lock); + return 0; +} + +void +rlock(RWLock *q) +{ + QLp *p, *mp; + + lock(&q->lock); + if(q->writer == 0 && q->head == nil){ + /* no writer, go for it */ + q->readers++; + unlock(&q->lock); + return; + } + + mp = getqlp(); + p = q->tail; + if(p == 0) + q->head = mp; + else + p->next = mp; + q->tail = mp; + mp->next = nil; + mp->state = QueuingR; + unlock(&q->lock); + + /* wait in kernel */ + while((*_rendezvousp)((ulong)mp, 1) == ~0) + ; + mp->inuse = 0; +} + +int +canrlock(RWLock *q) +{ + lock(&q->lock); + if (q->writer == 0 && q->head == nil) { + /* no writer; go for it */ + q->readers++; + unlock(&q->lock); + return 1; + } + unlock(&q->lock); + return 0; +} + +void +runlock(RWLock *q) +{ + QLp *p; + + lock(&q->lock); + if(q->readers <= 0) + abort(); + p = q->head; + if(--(q->readers) > 0 || p == nil){ + unlock(&q->lock); + return; + } + + /* start waiting writer */ + if(p->state != QueuingW) + abort(); + q->head = p->next; + if(q->head == 0) + q->tail = 0; + q->writer = 1; + unlock(&q->lock); + + /* wakeup waiter */ + while((*_rendezvousp)((ulong)p, 0) == ~0) + ; +} + +void +wlock(RWLock *q) +{ + QLp *p, *mp; + + lock(&q->lock); + if(q->readers == 0 && q->writer == 0){ + /* noone waiting, go for it */ + q->writer = 1; + unlock(&q->lock); + return; + } + + /* wait */ + p = q->tail; + mp = getqlp(); + if(p == nil) + q->head = mp; + else + p->next = mp; + q->tail = mp; + mp->next = nil; + mp->state = QueuingW; + unlock(&q->lock); + + /* wait in kernel */ + while((*_rendezvousp)((ulong)mp, 1) == ~0) + ; + mp->inuse = 0; +} + +int +canwlock(RWLock *q) +{ + lock(&q->lock); + if (q->readers == 0 && q->writer == 0) { + /* no one waiting; go for it */ + q->writer = 1; + unlock(&q->lock); + return 1; + } + unlock(&q->lock); + return 0; +} + +void +wunlock(RWLock *q) +{ + QLp *p; + + lock(&q->lock); + if(q->writer == 0) + abort(); + p = q->head; + if(p == nil){ + q->writer = 0; + unlock(&q->lock); + return; + } + if(p->state == QueuingW){ + /* start waiting writer */ + q->head = p->next; + if(q->head == nil) + q->tail = nil; + unlock(&q->lock); + while((*_rendezvousp)((ulong)p, 0) == ~0) + ; + return; + } + + if(p->state != QueuingR) + abort(); + + /* wake waiting readers */ + while(q->head != nil && q->head->state == QueuingR){ + p = q->head; + q->head = p->next; + q->readers++; + while((*_rendezvousp)((ulong)p, 0) == ~0) + ; + } + if(q->head == nil) + q->tail = nil; + q->writer = 0; + unlock(&q->lock); +} + +void +rsleep(Rendez *r) +{ + QLp *t, *me; + + if(!r->l) + abort(); + lock(&r->l->lock); + /* we should hold the qlock */ + if(!r->l->locked) + abort(); + + /* add ourselves to the wait list */ + me = getqlp(); + me->state = Sleeping; + if(r->head == nil) + r->head = me; + else + r->tail->next = me; + me->next = nil; + r->tail = me; + + /* pass the qlock to the next guy */ + t = r->l->head; + if(t){ + r->l->head = t->next; + if(r->l->head == nil) + r->l->tail = nil; + unlock(&r->l->lock); + while((*_rendezvousp)((ulong)t, 0x12345) == ~0) + ; + }else{ + r->l->locked = 0; + unlock(&r->l->lock); + } + + /* wait for a wakeup */ + while((*_rendezvousp)((ulong)me, 0x23456) == ~0) + ; + me->inuse = 0; + if(!r->l->locked) + abort(); +} + +int +rwakeup(Rendez *r) +{ + QLp *t; + + /* + * take off wait and put on front of queue + * put on front so guys that have been waiting will not get starved + */ + + if(!r->l) + abort(); + lock(&r->l->lock); + if(!r->l->locked) + abort(); + + t = r->head; + if(t == nil){ + unlock(&r->l->lock); + return 0; + } + + r->head = t->next; + if(r->head == nil) + r->tail = nil; + + t->next = r->l->head; + r->l->head = t; + if(r->l->tail == nil) + r->l->tail = t; + + t->state = Queuing; + unlock(&r->l->lock); + return 1; +} + +int +rwakeupall(Rendez *r) +{ + int i; + + for(i=0; rwakeup(r); i++) + ; + return i; +} |