openwrt

1 openwrt开发环境配置
http://forgotfun.org/2018/05/openwrt-lesson-03.html

2 查看当前系统所使用的的线程库：
getconf GNU_LIBPTHREAD_VERSION

3 多线程
https://www.cnblogs.com/thinkinglife/p/5153723.html
pthread_cond_wait用于等待某个特定的条件为真，pthread_cond_signal用于通知阻塞的线程某个特定的条件为真了。在调用者两个函数之前需要声明一个pthread_cond_t类型的变量，用于这两个函数的参数

pthread_join用于等待某个线程退出，成功返回0，否则返回Exxx（为正数）

./Documentation/scheduler/sched-deadline.txt: pthread_join(thread, NULL);
./tools/usb/ffs-test.c: int ret = pthread_join(t->id, NULL);
./tools/usb/testusb.c: if (pthread_join (entry->thread, &retval))
./tools/usb/testusb.c: perror (“pthread_join”);
./tools/perf/bench/numa.c: ret = pthread_join(pthreads[t], NULL);
./tools/perf/bench/futex-wake.c: ret = pthread_join(worker[i], NULL);
./tools/perf/bench/futex-wake.c: err(EXIT_FAILURE, “pthread_join”);
./tools/perf/bench/futex-lock-pi.c: ret = pthread_join(worker[i].thread, NULL);
./tools/perf/bench/futex-lock-pi.c: err(EXIT_FAILURE, “pthread_join”);
./tools/perf/bench/futex-wake-parallel.c: if (pthread_join(td[i].worker, NULL))
./tools/perf/bench/futex-wake-parallel.c: err(EXIT_FAILURE, “pthread_join”);
./tools/perf/bench/futex-wake-parallel.c: ret = pthread_join(blocked_worker[i], NULL);
./tools/perf/bench/futex-wake-parallel.c: err(EXIT_FAILURE, “pthread_join”);
./tools/perf/bench/sched-pipe.c: ret = pthread_join(td->pthread, NULL);
./tools/perf/bench/futex-hash.c: ret = pthread_join(worker[i].thread, NULL);
./tools/perf/bench/futex-hash.c: err(EXIT_FAILURE, “pthread_join”);
./tools/perf/bench/futex-requeue.c: ret = pthread_join(worker[i], NULL);
./tools/perf/bench/futex-requeue.c: err(EXIT_FAILURE, “pthread_join”);
./tools/perf/bench/sched-messaging.c: pthread_join(id, &thread_status);
./tools/perf/util/event.c: pthread_join(synthesize_threads[i], NULL);
./tools/perf/tests/mmap-thread-lookup.c: err = pthread_join(threads[i].pt, NULL);
./tools/perf/builtin-top.c: pthread_join(thread, NULL);
./tools/lib/lockdep/tests/ABBA_2threads.c: pthread_join(t, NULL);
./tools/virtio/ringtest/main.c: ret = pthread_join(guest, &tret);
./tools/virtio/ringtest/main.c: ret = pthread_join(host, &tret);
./tools/virtio/virtio-trace/trace-agent.c: ret = pthread_join(rw_thread_per_cpu[cpu], NULL);
./tools/virtio/virtio-trace/trace-agent.c: pr_err(“pthread_join() error:%d (cpu %d)\n”, ret, cpu);
./tools/testing/selftests/timers/threadtest.c: pthread_join(pth[i], &tret);
./tools/testing/selftests/futex/functional/futex_requeue_pi.c: pthread_join(waiter[i],
./tools/testing/selftests/futex/functional/futex_requeue_pi.c: pthread_join(blocker, NULL);
./tools/testing/selftests/futex/functional/futex_requeue_pi.c: pthread_join(waker, NULL);
./tools/testing/selftests/futex/functional/futex_requeue_pi_signal_restart.c: pthread_join(waiter, NULL);
./tools/testing/selftests/futex/functional/futex_requeue_pi_mismatched_ops.c: pthread_join(child, NULL);
./tools/testing/selftests/futex/functional/futex_wait_private_mapped_file.c: pthread_join(thr, NULL);
./tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/test.c: if (pthread_join(tu, NULL))
./tools/testing/selftests/rcutorture/formal/srcu-cbmc/tests/store_buffering/test.c: if (pthread_join(tpr, NULL))
./tools/testing/selftests/vm/userfaultfd.c: if (pthread_join(background_threads[cpu], NULL))
./tools/testing/selftests/vm/userfaultfd.c: if (pthread_join(uffd_threads[cpu], &_userfaults[cpu]))
./tools/testing/selftests/vm/userfaultfd.c: if (pthread_join(uffd_threads[cpu], NULL))
./tools/testing/selftests/vm/userfaultfd.c: if (pthread_join(locking_threads[cpu], NULL))
./tools/testing/selftests/vm/userfaultfd.c: if (pthread_join(uffd_mon, (void **)&userfaults))
./tools/testing/selftests/vm/userfaultfd.c: if (pthread_join(uffd_mon, (void **)&userfaults))
./tools/testing/selftests/powerpc/tm/tm-unavailable.c: rc = pthread_join(t0, &ret_value);
./tools/testing/selftests/powerpc/tm/tm-unavailable.c: pr_err(rc, “pthread_join”);
./tools/testing/selftests/powerpc/tm/tm-trap.c: rc = pthread_join(t0_ping, NULL);
./tools/testing/selftests/powerpc/tm/tm-trap.c: pr_error(rc, “pthread_join()”);
./tools/testing/selftests/powerpc/tm/tm-trap.c: rc = pthread_join(t1_pong, NULL);
./tools/testing/selftests/powerpc/tm/tm-trap.c: pr_error(rc, “pthread_join()”);
./tools/testing/selftests/powerpc/tm/tm-vmx-unavail.c: pthread_join(thread[i], NULL);
./tools/testing/selftests/powerpc/tm/tm-tmspr.c: if (pthread_join(thread, NULL) != 0)
./tools/testing/selftests/powerpc/tm/tm-tmspr.c: if (pthread_join(thread, NULL) != 0)
./tools/testing/selftests/powerpc/dscr/dscr_default_test.c: if (pthread_join(threads[i], (void **)&(status[i]))) {
./tools/testing/selftests/powerpc/dscr/dscr_default_test.c: perror(“pthread_join() failed”);
./tools/testing/selftests/powerpc/math/fpu_preempt.c: pthread_join(tids[i], &rc_p);
./tools/testing/selftests/powerpc/math/fpu_signal.c: pthread_join(tids[i], &rc_p);
./tools/testing/selftests/powerpc/math/vmx_signal.c: pthread_join(tids[i], &rc_p);
./tools/testing/selftests/powerpc/math/vsx_preempt.c: pthread_join(tids[i], &rc_p);
./tools/testing/selftests/powerpc/math/vmx_preempt.c: pthread_join(tids[i], &rc_p);
./tools/testing/selftests/powerpc/benchmarks/fork.c: rc = pthread_join(tid, NULL);
./tools/testing/selftests/powerpc/benchmarks/fork.c: perror(“pthread_join”);
./tools/testing/selftests/mqueue/mq_perf_tests.c: pthread_join(cpu_threads[i], NULL);
./tools/testing/selftests/mqueue/mq_perf_tests.c: pthread_join(cpu_threads[0], &retval);
./tools/testing/selftests/sync/sync_stress_consumer.c: pthread_join(threads[i], NULL);
./tools/testing/selftests/sync/sync_stress_parallelism.c: pthread_join(a, NULL);
./tools/testing/selftests/sync/sync_stress_parallelism.c: pthread_join(b, NULL);
./tools/testing/selftests/seccomp/seccomp_bpf.c: ASSERT_EQ(0, pthread_join(thread, &status));
./tools/testing/selftests/seccomp/seccomp_bpf.c: ASSERT_EQ(0, pthread_join(thread, &status));
./tools/testing/selftests/seccomp/seccomp_bpf.c: int _rc = pthread_join(tid, status); \
./tools/testing/selftests/seccomp/seccomp_bpf.c: TH_LOG(“pthread_join of tid %u failed: %d\n”, \
./tools/testing/selftests/seccomp/seccomp_bpf.c: /* Poll for actual task death. pthread_join doesn’t guarantee it. */
./tools/testing/selftests/seccomp/seccomp_bpf.c: /* Poll for actual task death. pthread_join doesn’t guarantee it. */
./tools/testing/selftests/x86/ldt_gdt.c: if (pthread_join(thread, NULL) != 0)
./tools/testing/selftests/x86/ldt_gdt.c: err(1, “pthread_join”);
./tools/testing/selftests/x86/fsgsbase.c: if (pthread_join(thread, NULL) != 0)
./tools/testing/selftests/x86/fsgsbase.c: err(1, “pthread_join”);
./tools/testing/selftests/bpf/test_lpm_map.c: assert(pthread_join(thread_id[i], &ret) == 0 && ret == (void *)&info[i]);
./tools/testing/radix-tree/iteration_check.c: if (pthread_join(threads[i], NULL)) {
./tools/testing/radix-tree/iteration_check.c: perror(“pthread_join”);
./tools/testing/radix-tree/multiorder.c: pthread_join(worker_thread[i], NULL);
./tools/testing/radix-tree/idr-test.c: pthread_join(threads[i], NULL);
./tools/testing/radix-tree/regression1.c: if (pthread_join(threads[i], NULL)) {
./tools/testing/radix-tree/regression1.c: perror(“pthread_join”);
guang@guang-net:~/develop/linux$

// mutex.c
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>

#define NUM_THREAD 100

void *thread_inc (void *arg);
void *thread_des (void *arg);

long long num = 0;
pthread_mutex_t mutex;

int main (int argc, char *argv)
{
    pthread_t thread_id[NUM_THREAD];
    int i;

    pthread_mutex_init (&mutex, NULL);

    for (i = 0; i < NUM_THREAD; i++)
    {
        if (i%2)
        {
            pthread_create (&(thread_id[i]), NULL, thread_inc, NULL);
        }
        else
        {
            pthread_create (&(thread_id[i]), NULL, thread_des, NULL);
        }
    }

    for (i = 0; i < NUM_THREAD; i++)
    {
        pthread_join (thread_id[i], NULL);
    }

    printf ("result: %lld \n", num);
    pthread_mutex_destroy (&mutex);
    return 0;
}

void *thread_inc (void *arg)
{
    int i;

    pthread_mutex_lock (&mutex);
    for (i = 0; i < 500; i++)
    {
        num += 1;
    }
    pthread_mutex_unlock (&mutex);
    return NULL;
}

void *thread_des (void *arg)
{
    int i;

    for (i = 0; i < 500; i++)
    {
        pthread_mutex_lock (&mutex);
        num -= 1;
        pthread_mutex_unlock (&mutex);
    }
    return NULL;
}

#include <stdio.h>

int main (void)
{
    int i;
    for (i = 0; i < 100; i ++)
    {
        printf ("%2d:%d ",i, i%2);
        if (!(i % 10))
        {
            printf ("\n");
        }

    }
    printf ("\n");

    return 0;
}