死锁检测组件-设想死锁检测组件-设想死锁的构建pthread的hook图的构建

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我是靠谱客的博主仁爱彩虹，这篇文章主要介绍死锁检测组件-设想死锁检测组件-设想死锁的构建pthread的hook图的构建，现在分享给大家，希望可以做个参考。

死锁检测组件-设想

现在有三个临界资源和三把锁绑定了，三把锁又分别被三个线程占用。（不用关注临界资源，因为锁和临界资源是绑定的）

但现在出现这种情况：线程1去申请获取锁2，线程2申请获取锁3，线程3申请获取锁1，这样就会造成死锁：

死锁问题，可转换为有向图的环路检测

死锁的构建

有四个线程，4把锁，以下代码一定会产生死锁

复制代码

pthread_mutex_t mtx1 = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t mtx2 = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t mtx3 = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t mtx4 = PTHREAD_MUTEX_INITIALIZER;
void *thread_routine_a(void *arg) {
printf("thread_routine a n");
pthread_mutex_lock(&mtx1);
sleep(1);
pthread_mutex_lock(&mtx2);
pthread_mutex_unlock(&mtx2);
pthread_mutex_unlock(&mtx1);
printf("thread_routine a exitn");
}
void *thread_routine_b(void *arg) {
printf("thread_routine b n");
pthread_mutex_lock(&mtx2);
sleep(1);
pthread_mutex_lock(&mtx3);
pthread_mutex_unlock(&mtx3);
pthread_mutex_unlock(&mtx2);
printf("thread_routine b exit n");
// -----
pthread_mutex_lock(&mtx1);
}
void *thread_routine_c(void *arg) {
printf("thread_routine c n");
pthread_mutex_lock(&mtx3);
sleep(1);
pthread_mutex_lock(&mtx4);
pthread_mutex_unlock(&mtx4);
pthread_mutex_unlock(&mtx3);
printf("thread_routine c exit n");
}
void *thread_routine_d(void *arg) {
printf("thread_routine d n");
pthread_mutex_lock(&mtx4);
sleep(1);
pthread_mutex_lock(&mtx1);
pthread_mutex_unlock(&mtx1);
pthread_mutex_unlock(&mtx4);
printf("thread_routine d exit n");
}
int main() {
#if 1
init_hook();
pthread_t tid1, tid2, tid3, tid4;
pthread_create(&tid1, NULL, thread_routine_a, NULL);
pthread_create(&tid2, NULL, thread_routine_b, NULL);
pthread_create(&tid3, NULL, thread_routine_c, NULL);
pthread_create(&tid4, NULL, thread_routine_d, NULL);
pthread_join(tid1, NULL);
pthread_join(tid2, NULL);
pthread_join(tid3, NULL);
pthread_join(tid4, NULL);
}

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pthread_mutex_t mtx1 = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t mtx2 = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t mtx3 = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t mtx4 = PTHREAD_MUTEX_INITIALIZER;
void *thread_routine_a(void *arg) {
printf("thread_routine a n");
pthread_mutex_lock(&mtx1);
sleep(1);
pthread_mutex_lock(&mtx2);
pthread_mutex_unlock(&mtx2);
pthread_mutex_unlock(&mtx1);
printf("thread_routine a exitn");
}
void *thread_routine_b(void *arg) {
printf("thread_routine b n");
pthread_mutex_lock(&mtx2);
sleep(1);
pthread_mutex_lock(&mtx3);
pthread_mutex_unlock(&mtx3);
pthread_mutex_unlock(&mtx2);
printf("thread_routine b exit n");
// -----
pthread_mutex_lock(&mtx1);
}
void *thread_routine_c(void *arg) {
printf("thread_routine c n");
pthread_mutex_lock(&mtx3);
sleep(1);
pthread_mutex_lock(&mtx4);
pthread_mutex_unlock(&mtx4);
pthread_mutex_unlock(&mtx3);
printf("thread_routine c exit n");
}
void *thread_routine_d(void *arg) {
printf("thread_routine d n");
pthread_mutex_lock(&mtx4);
sleep(1);
pthread_mutex_lock(&mtx1);
pthread_mutex_unlock(&mtx1);
pthread_mutex_unlock(&mtx4);
printf("thread_routine d exit n");
}
int main() {
#if 1
init_hook();
pthread_t tid1, tid2, tid3, tid4;
pthread_create(&tid1, NULL, thread_routine_a, NULL);
pthread_create(&tid2, NULL, thread_routine_b, NULL);
pthread_create(&tid3, NULL, thread_routine_c, NULL);
pthread_create(&tid4, NULL, thread_routine_d, NULL);
pthread_join(tid1, NULL);
pthread_join(tid2, NULL);
pthread_join(tid3, NULL);
pthread_join(tid4, NULL);
}

这里产生了：线程a => 线程b => 线程c => 线程d =》线程a的这样一个环路

但是我们不知道哪把锁被哪个线程占用了，没法构建有向图，也就无法得知是否产生了这样一个环路

这时，可以用hook，调自己写的 pthread_mutex_lock，将线程和锁的映射关系保存起来

pthread的hook

有点像装饰器模式

复制代码

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// 函数指针
typedef int (*pthread_mutex_lock_t)(pthread_mutex_t *mutex);
pthread_mutex_lock_t pthread_mutex_lock_f;
typedef int (*pthread_mutex_unlock_t)(pthread_mutex_t *mutex);
pthread_mutex_unlock_t pthread_mutex_unlock_f;
static int init_hook() {
//
RTLD_NEXT可以理解为代码段，在这里面找pthread_mutex_lock函数名，把地址返回
// 所以pthread_mutex_lock_f就是静态或动态库里的pthread_mutex_lock锁函数
pthread_mutex_lock_f = dlsym(RTLD_NEXT, "pthread_mutex_lock");
pthread_mutex_unlock_f = dlsym(RTLD_NEXT, "pthread_mutex_unlock");
}
int pthread_mutex_lock(pthread_mutex_t *mutex) {
printf("pthread_mutex_lock selfid %ld, mutex: %pn", pthread_self(), mutex);
beforelock(pthread_self(), mutex);
pthread_mutex_lock_f(mutex);
// 用钩子的好处，给系统函数命一个别名
afterlock(pthread_self(), mutex);
}
int pthread_mutex_unlock(pthread_mutex_t *mutex) {
printf("pthread_mutex_unlockn");
pthread_mutex_unlock_f(mutex);
afterunlock(pthread_self(), mutex);
}