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Diffstat (limited to '04_exercise/rwlock/rwlock.c')
| -rw-r--r-- | 04_exercise/rwlock/rwlock.c | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/04_exercise/rwlock/rwlock.c b/04_exercise/rwlock/rwlock.c new file mode 100644 index 0000000..3de5083 --- /dev/null +++ b/04_exercise/rwlock/rwlock.c @@ -0,0 +1,67 @@ +// +// Created by stefan on 11.06.20. +// + +#include "rwlock.h" +#include <stdbool.h> +#include <stdio.h> +#include <pthread.h> +#include <stdlib.h> + +static const bool DEBUG = false; + + +void rwLockWrite(atomic_char *lock) { + char status; + bool succeeded; + do { + status = RW_UNLOCKED; + succeeded = atomic_compare_exchange_weak(lock, &status, RW_WRITE_LOCKED); + } while (!succeeded); + if(DEBUG) { + fprintf(stderr, "Thread %lu: Aquired Write Lock \n", pthread_self() % 1000); + } + +} + +void rwUnlockWrite(atomic_char *lock) { + char expected = RW_WRITE_LOCKED; + if (!atomic_compare_exchange_strong(lock, &expected, RW_UNLOCKED)) { + fprintf(stderr, "Couldn't unlock from writelock. Lock was at %d", expected); + perror("Lock got into undefined state"); + exit(-1); + } + if(DEBUG) { + fprintf(stderr, "Thread %lu: Released Write Lock \n", pthread_self() % 1000); + } + if (sched_yield() < 0) { + perror("Couldn't sleep. This shouldn't happen."); + exit(-1); + } + +} +void rwLockRead(atomic_char *lock) { + while (atomic_load(lock) == RW_WRITE_LOCKED) { + + } + atomic_fetch_add(lock, 1); + if(DEBUG) { + fprintf(stderr, "Thread %lu: Aquired Read Lock \n", pthread_self() % 1000); + } +} +void rwUnlockRead(atomic_char *lock) { + char value = atomic_load(lock); + if (value < 1) { + fprintf(stderr, "Couldn't unlock from readlock. Lock was at %d", value); + perror("Lock got into undefined state"); + exit(-1); + } + atomic_fetch_sub(lock, 1); + if(DEBUG) { + fprintf(stderr, "Thread %lu: Released Read Lock \n", pthread_self() % 1000); + } + if (sched_yield() < 0) { + perror("Couldn't sleep. This shouldn't happen."); + exit(-1); + } +}
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