yulsfish / lfqueue

Simple Lock-Free Queue implemented in C

lfqueue

Simple Lock-Free Queue implemented in C based on this paper.

Status

These features are almost finished and will be added soon along with new lock-free data structures:

1. Hazard pointers based on Maged Michael - Safe Memory Reclamation for Lock-Free Objects
2. Memory Pool for reusing objects

Example

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

#include "lfq.h"

#define CHAR_TYPE 0

volatile int cond = 0;

void *consumer(void *_queue){
  Queue *queue = (Queue *)_queue;

  int i=100;
  Value *value = NULL;

  for(;;) {
    value = qpop(queue,(unsigned int)pthread_self());

    if(value != NULL && value->data != NULL){
      if (value->type == CHAR_TYPE) {
    printf("\n %s, %u\n", (char *)value->data, (unsigned int)pthread_self());
      }
    }

    sched_yield();
    value = NULL;
    CHECK_COND(cond);
  }
}

int main(){
  int i = 0;

  Queue *queue = q_initialize();

  pthread_t _thread;
  pthread_t _thread2;

  pthread_create(&_thread,NULL,consumer,queue);
  pthread_create(&_thread2,NULL,consumer,queue);

  Value *value = malloc(100 * sizeof(Value));

  for(i = 0; i < 100; i++){
    value[i].type = CHAR_TYPE;
    value[i].data = (char *) malloc(8* sizeof(char *));
    sprintf(value[i].data,"test %d.",i);
    qpush(queue,&value[i]);
  }

  sleep(1);

  for (i=0; i < 100; i++){
    Value *t = &value[i];
    free(t->data);
  }

  free(value);
  queue_free(queue);

  __sync_bool_compare_and_swap(&cond,0,1);

  pthread_join(_thread,NULL);
  pthread_join(_thread2,NULL);

  return 0;
}

TODOs

1. Memory Pool.
2. Hazard Pointer.
3. Migrating to C11.
4. Lock Free Dynamic Memory Allocation