#include #include #include enum { QueuingW, /* queuing for write lock */ QueuingR, /* queuing for read lock */ }; typedef struct Thread Thread; struct Thread { int pid; int ref; char *error; int state; Thread *next; }; struct VtLock { Lock lk; Thread *writer; /* thread writering write lock */ int readers; /* number writering read lock */ Thread *qfirst; Thread *qlast; }; struct VtRendez { VtLock *lk; Thread *wfirst; Thread *wlast; }; enum { ERROR = 0, }; static Thread **vtRock; static void vtThreadInit(void); static void threadSleep(Thread*); static void threadWakeup(Thread*); int vtThread(void (*f)(void*), void *rock) { int tid; tid = rfork(RFNOWAIT|RFMEM|RFPROC); switch(tid){ case -1: vtOSError(); return -1; case 0: break; default: return tid; } vtAttach(); (*f)(rock); vtDetach(); _exits(0); return 0; } static Thread * threadLookup(void) { return *vtRock; } void vtAttach(void) { int pid; Thread *p; static int init; static Lock lk; lock(&lk); if(!init) { rfork(RFREND); vtThreadInit(); init = 1; } unlock(&lk); pid = getpid(); p = *vtRock; if(p != nil && p->pid == pid) { p->ref++; return; } p = vtMemAllocZ(sizeof(Thread)); p->ref = 1; p->pid = pid; *vtRock = p; } void vtDetach(void) { Thread *p; p = *vtRock; assert(p != nil); p->ref--; if(p->ref == 0) { vtMemFree(p->error); vtMemFree(p); *vtRock = nil; } } char * vtGetError(void) { char *s; if(ERROR) fprint(2, "vtGetError: %s\n", threadLookup()->error); s = threadLookup()->error; if(s == nil) return "unknown error"; return s; } char* vtSetError(char* fmt, ...) { Thread *p; char *s; va_list args; p = threadLookup(); va_start(args, fmt); s = vsmprint(fmt, args); vtMemFree(p->error); p->error = s; va_end(args); if(ERROR) fprint(2, "vtSetError: %s\n", p->error); werrstr("%s", p->error); return p->error; } static void vtThreadInit(void) { static Lock lk; lock(&lk); if(vtRock != nil) { unlock(&lk); return; } vtRock = privalloc(); if(vtRock == nil) vtFatal("can't allocate thread-private storage"); unlock(&lk); } VtLock* vtLockAlloc(void) { return vtMemAllocZ(sizeof(VtLock)); } /* * RSC: I think the test is backward. Let's see who uses it. * void vtLockInit(VtLock **p) { static Lock lk; lock(&lk); if(*p != nil) *p = vtLockAlloc(); unlock(&lk); } */ void vtLockFree(VtLock *p) { if(p == nil) return; assert(p->writer == nil); assert(p->readers == 0); assert(p->qfirst == nil); vtMemFree(p); } VtRendez* vtRendezAlloc(VtLock *p) { VtRendez *q; q = vtMemAllocZ(sizeof(VtRendez)); q->lk = p; return q; } void vtRendezFree(VtRendez *q) { if(q == nil) return; assert(q->wfirst == nil); vtMemFree(q); } int vtCanLock(VtLock *p) { Thread *t; lock(&p->lk); t = *vtRock; if(p->writer == nil && p->readers == 0) { p->writer = t; unlock(&p->lk); return 1; } unlock(&p->lk); return 0; } void vtLock(VtLock *p) { Thread *t; lock(&p->lk); t = *vtRock; if(p->writer == nil && p->readers == 0) { p->writer = t; unlock(&p->lk); return; } /* * venti currently contains code that assume locks can be passed between threads :-( * assert(p->writer != t); */ if(p->qfirst == nil) p->qfirst = t; else p->qlast->next = t; p->qlast = t; t->next = nil; t->state = QueuingW; unlock(&p->lk); threadSleep(t); assert(p->writer == t && p->readers == 0); } int vtCanRLock(VtLock *p) { lock(&p->lk); if(p->writer == nil && p->qfirst == nil) { p->readers++; unlock(&p->lk); return 1; } unlock(&p->lk); return 0; } void vtRLock(VtLock *p) { Thread *t; lock(&p->lk); t = *vtRock; if(p->writer == nil && p->qfirst == nil) { p->readers++; unlock(&p->lk); return; } /* * venti currently contains code that assumes locks can be passed between threads * assert(p->writer != t); */ if(p->qfirst == nil) p->qfirst = t; else p->qlast->next = t; p->qlast = t; t->next = nil; t->state = QueuingR; unlock(&p->lk); threadSleep(t); assert(p->writer == nil && p->readers > 0); } void vtUnlock(VtLock *p) { Thread *t, *tt; lock(&p->lk); /* * venti currently has code that assumes lock can be passed between threads :-) * assert(p->writer == *vtRock); */ assert(p->writer != nil); assert(p->readers == 0); t = p->qfirst; if(t == nil) { p->writer = nil; unlock(&p->lk); return; } if(t->state == QueuingW) { p->qfirst = t->next; p->writer = t; unlock(&p->lk); threadWakeup(t); return; } p->writer = nil; while(t != nil && t->state == QueuingR) { tt = t; t = t->next; p->readers++; threadWakeup(tt); } p->qfirst = t; unlock(&p->lk); } void vtRUnlock(VtLock *p) { Thread *t; lock(&p->lk); assert(p->writer == nil && p->readers > 0); p->readers--; t = p->qfirst; if(p->readers > 0 || t == nil) { unlock(&p->lk); return; } assert(t->state == QueuingW); p->qfirst = t->next; p->writer = t; unlock(&p->lk); threadWakeup(t); } int vtSleep(VtRendez *q) { Thread *s, *t, *tt; VtLock *p; p = q->lk; lock(&p->lk); s = *vtRock; /* * venti currently contains code that assume locks can be passed between threads :-( * assert(p->writer != s); */ assert(p->writer != nil); assert(p->readers == 0); t = p->qfirst; if(t == nil) { p->writer = nil; } else if(t->state == QueuingW) { p->qfirst = t->next; p->writer = t; threadWakeup(t); } else { p->writer = nil; while(t != nil && t->state == QueuingR) { tt = t; t = t->next; p->readers++; threadWakeup(tt); } } if(q->wfirst == nil) q->wfirst = s; else q->wlast->next = s; q->wlast = s; s->next = nil; unlock(&p->lk); threadSleep(s); assert(p->writer == s); return 1; } int vtWakeup(VtRendez *q) { Thread *t; VtLock *p; /* * take off wait and put on front of queue * put on front so guys that have been waiting will not get starved */ p = q->lk; lock(&p->lk); /* * venti currently has code that assumes lock can be passed between threads :-) * assert(p->writer == *vtRock); */ assert(p->writer != nil); t = q->wfirst; if(t == nil) { unlock(&p->lk); return 0; } q->wfirst = t->next; if(p->qfirst == nil) p->qlast = t; t->next = p->qfirst; p->qfirst = t; t->state = QueuingW; unlock(&p->lk); return 1; } int vtWakeupAll(VtRendez *q) { int i; for(i=0; vtWakeup(q); i++) ; return i; } static void threadSleep(Thread *t) { if(rendezvous(t, (void*)0x22bbdfd6) != (void*)0x44391f14) sysfatal("threadSleep: rendezvous failed: %r"); } static void threadWakeup(Thread *t) { if(rendezvous(t, (void*)0x44391f14) != (void*)0x22bbdfd6) sysfatal("threadWakeup: rendezvous failed: %r"); }