/** * apr tutorial sample code * http://dev.ariel-networks.com/apr/ */#ifdef HAVE_CONFIG_H#include <config.h>#endif#include <stdio.h>#include <stdlib.h>#include <assert.h>#include <apr_general.h>#include <apr_thread_proc.h>#include <apr_thread_mutex.h>/** * The number of running threads concurrently */#define NUM_THREADS    64/** * Each threads makes this number of loop to increment the count * As a result, the final count should become NUM_THREADS x NUM_LOOPS_PER_THREAD */#define NUM_LOOPS_PER_THREAD        8192typedef struct {    int mutexed_count;    apr_thread_mutex_t *mutex;    /* for comparison */    int unmutexed_count;} shared_ctx_t;/* Use macros for readability */#define MUTEX_LOCK(ctx)		apr_thread_mutex_lock((ctx)->mutex)#define MUTEX_UNLOCK(ctx)	apr_thread_mutex_unlock((ctx)->mutex)static void* APR_THREAD_FUNC doit(apr_thread_t *thd, void *data);/** * Thread execution and mutex sample code * @remark Error checks almost omitted */int main(int argc, const char *argv[]){    apr_status_t rv;    apr_pool_t *mp;    apr_thread_t *thd_arr[NUM_THREADS];    shared_ctx_t shared_ctx = { 0, NULL, 0 };    int i;            apr_initialize();    apr_pool_create(&mp, NULL);    apr_thread_mutex_create(&shared_ctx.mutex, APR_THREAD_MUTEX_UNNESTED, mp);    for (i = 0; i < NUM_THREADS; i++) {        rv = apr_thread_create(&thd_arr[i], NULL, doit, &shared_ctx, mp);        assert(rv == APR_SUCCESS);    }    for (i = 0; i < NUM_THREADS; i++) {        rv = apr_thread_join(&rv, thd_arr[i]);        assert(rv == APR_SUCCESS);    }    printf("shared_ctx::mutexed_count = %d, shared_ctx::unmutexed_count = %d\n",           shared_ctx.mutexed_count, shared_ctx.unmutexed_count);    assert(shared_ctx.mutexed_count == NUM_THREADS * NUM_LOOPS_PER_THREAD);    apr_terminate();    return 0;}/** * Thread entry point */static void* APR_THREAD_FUNC doit(apr_thread_t *thd, void *data){    shared_ctx_t *ctx = data;    int i;    for (i = 0; i < NUM_LOOPS_PER_THREAD; i++) {        MUTEX_LOCK(ctx);        ctx->mutexed_count++;        MUTEX_UNLOCK(ctx);        /* XXX Since this is not protected by mutex lock, the value is undetermined. */        ctx->unmutexed_count++;    }    apr_thread_exit(thd, APR_SUCCESS);    return NULL;}