ref: 3f419d1cd08268c49a442a85d9286441b620fcb4
dir: /libc/lock.c/
#include <u.h> #include <libc.h> #ifdef PTHREAD static pthread_mutex_t initmutex = PTHREAD_MUTEX_INITIALIZER; static void lockinit(Lock *lk) { pthread_mutexattr_t attr; pthread_mutex_lock(&initmutex); if(lk->init == 0){ pthread_mutexattr_init(&attr); pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_NORMAL); pthread_mutex_init(&lk->mutex, &attr); pthread_mutexattr_destroy(&attr); lk->init = 1; } pthread_mutex_unlock(&initmutex); } void lock(Lock *lk) { if(!lk->init) lockinit(lk); if(pthread_mutex_lock(&lk->mutex) != 0) abort(); } int canlock(Lock *lk) { int r; if(!lk->init) lockinit(lk); r = pthread_mutex_trylock(&lk->mutex); if(r == 0) return 1; if(r == EBUSY) return 0; abort(); } void unlock(Lock *lk) { if(pthread_mutex_unlock(&lk->mutex) != 0) abort(); } #else /* old, non-pthread systems */ int canlock(Lock *lk) { return !tas(&lk->key); } void lock(Lock *lk) { int i; /* easy case */ if(canlock(lk)) return; /* for multi processor machines */ for(i=0; i<100; i++) if(canlock(lk)) return; for(i=0; i<100; i++) { osyield(); if(canlock(lk)) return; } /* looking bad - make sure it is not a priority problem */ for(i=0; i<12; i++) { osmsleep(1<<i); if(canlock(lk)) return; } /* we are in trouble */ for(;;) { if(canlock(lk)) return; iprint("lock loop %ld: val=%d &lock=%ux pc=%p\n", getpid(), lk->key, lk, getcallerpc(&lk)); osmsleep(1000); } } void unlock(Lock *lk) { assert(lk->key); lk->key = 0; } #endif void ilock(Lock *lk) { lock(lk); } void iunlock(Lock *lk) { unlock(lk); }