LLDB暂停线程，而其他线程继续进行

Question

以lldb作为调试器，您可以暂停一个线程，而其他线程继续？

一个简单的C多线程示例，在下面的pthreads。

#include <pthread.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <assert.h>
/*********************************************************************************
 Start two background threads.
 Both print a message to logs.
 Goal: pause a single thread why the other thread continues
 *********************************************************************************/
typedef struct{
    int count;
    char *message;
}Chomper;
void *hello_world(void *voidptr) {
    uint64_t tid;
    unsigned int microseconds = 10;
    assert(pthread_threadid_np(NULL, &tid)== 0);
    printf("Thread ID: dec:%llu hex: %#08xn", tid, (unsigned int) tid);
    Chomper *chomper = (Chomper *)voidptr;  // help the compiler map the void pointer to the actual data structure
    for (int i = 0; i < chomper->count; i++) {
        usleep(microseconds);
        printf("%s: %dn", chomper->message, i);
    }
    return NULL;
}
int main() {
        pthread_t myThread1 = NULL, myThread2 = NULL;
        Chomper *shark = malloc(sizeof(*shark));
        shark->count = 5;
        shark->message = "hello";
        Chomper *jellyfish = malloc(sizeof(*jellyfish));
        jellyfish->count = 20;
        jellyfish->message = "goodbye";
        assert(pthread_create(&myThread1, NULL, hello_world, (void *) shark) == 0);
        assert(pthread_create(&myThread2, NULL, hello_world, (void *) jellyfish) == 0);
        assert(pthread_join(myThread1, NULL) == 0);
        assert(pthread_join(myThread2, NULL) == 0);
        free(shark);
        free(jellyfish);
        return 0;
}

Answer 1

取决于您的要求。在其他线程运行时，您不能暂停并检查一个线程的状态。该过程运行后，您必须暂停它才能读取内存，变量等。

但是您可以恢复该过程，但只允许某些线程运行。一种方法是使用：

(lldb) thread continue <LIST OF THREADS TO CONTINUE>

另一个是使用Python的lldb.SBThread.Suspend() API来防止某些线程或线程运行，直到使用lldb.SBThread.Resume()恢复它们为止。我们之所需要经常这样做，很容易做出这样做的基于Python的命令。请参阅：

https://lldb.llvm.org/use/python-reference.html#create-a-a-new-new-lldb-command-command-using-a-a-python function

有关详细信息。