解答
资源获取环可以采用图来存储， 使用有向图来存储。 线程 A 获取线程 B 已占用的锁，则为线程 A 指向线程 B。 如何为线程 B 已占用的锁？运行过程线程 B 获取成功的锁。
检测的原理采用另一个线程定时对图进程检测是否有环的存在。
数据结构定义:
图算法，检测成环
#define _GNU_SOURCE
#include <dlfcn.h>
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#define THREAD_NUM 10
typedef unsigned long int uint64;
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;
#if 1 // graph
#define MAX 100
enum Type {PROCESS, RESOURCE};
struct source_type {
uint64 id;
enum Type type;
uint64 lock_id;
int degress;
};
struct vertex {
struct source_type s;
struct vertex *next;
};
struct task_graph {
struct vertex list[MAX];
int num;
struct source_type locklist[MAX];
int lockidx;
pthread_mutex_t mutex;
};
struct task_graph *tg = NULL;
int path[MAX+1];
int visited[MAX];
int k = 0;
int deadlock = 0;
struct vertex *create_vertex(struct source_type type) {
struct vertex *tex = (struct vertex *)malloc(sizeof(struct vertex ));
tex->s = type;
tex->next = NULL;
return tex;
}
int search_vertex(struct source_type type) {
int i = 0;
for (i = 0;i < tg->num;i ++) {
if (tg->list[i].s.type == type.type && tg->list[i].s.id == type.id) {
return i;
}
}
return -1;
}
void add_vertex(struct source_type type) {
if (search_vertex(type) == -1) {
tg->list[tg->num].s = type;
tg->list[tg->num].next = NULL;
tg->num ++;
}
}
int add_edge(struct source_type from, struct source_type to) {
add_vertex(from);
add_vertex(to);
struct vertex *v = &(tg->list[search_vertex(from)]);
while (v->next != NULL) {
v = v->next;
}
v->next = create_vertex(to);
}
int verify_edge(struct source_type i, struct source_type j) {
if (tg->num == 0) return 0;
int idx = search_vertex(i);
if (idx == -1) {
return 0;
}
struct vertex *v = &(tg->list[idx]);
while (v != NULL) {
if (v->s.id == j.id) return 1;
v = v->next;
}
return 0;
}
int remove_edge(struct source_type from, struct source_type to) {
int idxi = search_vertex(from);
int idxj = search_vertex(to);
if (idxi != -1 && idxj != -1) {
struct vertex *v = &tg->list[idxi];
struct vertex *remove;
while (v->next != NULL) {
if (v->next->s.id == to.id) {
remove = v->next;
v->next = v->next->next;
free(remove);
break;
}
v = v->next;
}
}
}
void print_deadlock(void) {
int i = 0;
printf("deadlock : ");
for (i = 0;i < k-1;i ++) {
printf("%ld --> ", tg->list[path[i]].s.id);
}
printf("%ld\n", tg->list[path[i]].s.id);
}
int DFS(int idx) {
struct vertex *ver = &tg->list[idx];
if (visited[idx] == 1) {
path[k++] = idx;
print_deadlock();
deadlock = 1;
return 0;
}
visited[idx] = 1;
path[k++] = idx;
while (ver->next != NULL) {
DFS(search_vertex(ver->next->s));
k --;
ver = ver->next;
}
return 1;
}
int search_for_cycle(int idx) {
struct vertex *ver = &tg->list[idx];
visited[idx] = 1;
k = 0;
path[k++] = idx;
while (ver->next != NULL) {
int i = 0;
for (i = 0;i < tg->num;i ++) {
if (i == idx) continue;
visited[i] = 0;
}
for (i = 1;i <= MAX;i ++) {
path[i] = -1;
}
k = 1;
DFS(search_vertex(ver->next->s));
ver = ver->next;
}
}
#if 0
int main() {
tg = (struct task_graph*)malloc(sizeof(struct task_graph));
tg->num = 0;
struct source_type v1;
v1.id = 1;
v1.type = PROCESS;
add_vertex(v1);
struct source_type v2;
v2.id = 2;
v2.type = PROCESS;
add_vertex(v2);
struct source_type v3;
v3.id = 3;
v3.type = PROCESS;
add_vertex(v3);
struct source_type v4;
v4.id = 4;
v4.type = PROCESS;
add_vertex(v4);
struct source_type v5;
v5.id = 5;
v5.type = PROCESS;
add_vertex(v5);
add_edge(v1, v2);
add_edge(v2, v3);
add_edge(v3, v4);
add_edge(v4, v5);
add_edge(v3, v1);
search_for_cycle(search_vertex(v1));
}
#endif
#endif
void check_dead_lock(void) {
int i = 0;
deadlock = 0;
for (i = 0;i < tg->num;i ++) {
if (deadlock == 1) break;
search_for_cycle(i);
}
if (deadlock == 0) {
printf("no deadlock\n");
}
}
static void *thread_routine(void *args) {
while (1) {
sleep(5);
check_dead_lock();
}
}
void start_check(void) {
tg = (struct task_graph*)malloc(sizeof(struct task_graph));
tg->num = 0;
tg->lockidx = 0;
pthread_t tid;
pthread_create(&tid, NULL, thread_routine, NULL);
}
#if 1
int search_lock(uint64 lock) {
int i = 0;
for (i = 0;i < tg->lockidx;i ++) {
if (tg->locklist[i].lock_id == lock) {
return i;
}
}
return -1;
}
int search_empty_lock(uint64 lock) {
int i = 0;
for (i = 0;i < tg->lockidx;i ++) {
if (tg->locklist[i].lock_id == 0) {
return i;
}
}
return tg->lockidx;
}
#endif
int inc(int *value, int add) {
int old;
__asm__ volatile(
"lock;xaddl %2, %1;"
: "=a"(old)
: "m"(*value), "a" (add)
: "cc", "memory"
);
return old;
}
void print_locklist(void) {
int i = 0;
printf("print_locklist: \n");
printf("---------------------\n");
for (i = 0;i < tg->lockidx;i ++) {
printf("threadid : %ld, lockid: %ld\n", tg->locklist[i].id, tg->locklist[i].lock_id);
}
printf("---------------------\n\n\n");
}
void lock_before(uint64 thread_id, uint64 lockaddr) {
int idx = 0;
// list<threadid, toThreadid>
for(idx = 0;idx < tg->lockidx;idx ++) {
if ((tg->locklist[idx].lock_id == lockaddr)) {
struct source_type from;
from.id = thread_id;
from.type = PROCESS;
add_vertex(from);
struct source_type to;
to.id = tg->locklist[idx].id;
tg->locklist[idx].degress++;
to.type = PROCESS;
add_vertex(to);
if (!verify_edge(from, to)) {
add_edge(from, to);
}
}
}
}
void lock_after(uint64 thread_id, uint64 lockaddr) {
int idx = 0;
if (-1 == (idx = search_lock(lockaddr))) { // lock list opera
int eidx = search_empty_lock(lockaddr);
tg->locklist[eidx].id = thread_id;
tg->locklist[eidx].lock_id = lockaddr;
inc(&tg->lockidx, 1);
} else {
struct source_type from;
from.id = thread_id;
from.type = PROCESS;
struct source_type to;
to.id = tg->locklist[idx].id;
tg->locklist[idx].degress --;
to.type = PROCESS;
if (verify_edge(from, to))
remove_edge(from, to);
tg->locklist[idx].id = thread_id;
}
}
void unlock_after(uint64 thread_id, uint64 lockaddr) {
int idx = search_lock(lockaddr);
if (tg->locklist[idx].degress == 0) {
tg->locklist[idx].id = 0;
tg->locklist[idx].lock_id = 0;
//inc(&tg->lockidx, -1);
}
}
int pthread_mutex_lock(pthread_mutex_t *mutex) {
pthread_t selfid = pthread_self(); //
lock_before(selfid, (uint64)mutex);
pthread_mutex_lock_f(mutex);
lock_after(selfid, (uint64)mutex);
}
int pthread_mutex_unlock(pthread_mutex_t *mutex) {
pthread_t selfid = pthread_self();
pthread_mutex_unlock_f(mutex);
unlock_after(selfid, (uint64)mutex);
}
static int init_hook() {
pthread_mutex_lock_f = dlsym(RTLD_NEXT, "pthread_mutex_lock");
pthread_mutex_unlock_f = dlsym(RTLD_NEXT, "pthread_mutex_unlock");
}
pthread_mutex_t mutex_1 = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t mutex_2 = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t mutex_3 = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t mutex_4 = PTHREAD_MUTEX_INITIALIZER;
void *thread_rountine_1(void *args)
{
pthread_t selfid = pthread_self(); //
pthread_mutex_lock(&mutex_1);
sleep(1);
pthread_mutex_lock(&mutex_2);
pthread_mutex_unlock(&mutex_2);
pthread_mutex_unlock(&mutex_1);
return (void *)(0);
}
void *thread_rountine_2(void *args)
{
pthread_t selfid = pthread_self(); //
pthread_mutex_lock(&mutex_2);
sleep(1);
pthread_mutex_lock(&mutex_3);
pthread_mutex_unlock(&mutex_3);
pthread_mutex_unlock(&mutex_2);
return (void *)(0);
}
void *thread_rountine_3(void *args)
{
pthread_t selfid = pthread_self(); //
pthread_mutex_lock(&mutex_3);
sleep(1);
pthread_mutex_lock(&mutex_4);
pthread_mutex_unlock(&mutex_4);
pthread_mutex_unlock(&mutex_3);
return (void *)(0);
}
void *thread_rountine_4(void *args)
{
pthread_t selfid = pthread_self(); //
pthread_mutex_lock(&mutex_4);
sleep(1);
pthread_mutex_lock(&mutex_3);
pthread_mutex_unlock(&mutex_3);
pthread_mutex_unlock(&mutex_4);
return (void *)(0);
}
int main()
{
init_hook();
start_check();
pthread_t tid1, tid2, tid3, tid4;
pthread_create(&tid1, NULL, thread_rountine_1, NULL);
pthread_create(&tid2, NULL, thread_rountine_2, NULL);
pthread_create(&tid3, NULL, thread_rountine_3, NULL);
pthread_create(&tid4, NULL, thread_rountine_4, NULL);
pthread_join(tid1, NULL);
pthread_join(tid2, NULL);
pthread_join(tid3, NULL);
pthread_join(tid4, NULL);
return 0;
}
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