我用C编写了一个多线程TCP服务器。当我对它运行多个测试客户端时崩溃了。我得到了两种类型的崩溃，它们似乎都有相同的根本原因。附加的崩溃发生在main。在另一种风格中，当它想要锁定以关闭套接字时，我在客户端部分中发生崩溃。 有人可以告诉我导致坠机的原因吗？
TCP服务器代码：
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <arpa/inet.h> //inet_addr
#include <pthread.h> //for threading , link with lpthread
#define BUFSIZE 2048 // TODO
#define MAXWORKERS 10
pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
const pthread_cond_t condInit = PTHREAD_COND_INITIALIZER;
pthread_cond_t idle = PTHREAD_COND_INITIALIZER;
typedef struct {
pthread_t tid;
int sd;
pthread_cond_t cond;
uint8_t num;
uint8_t state;
} worker_t;
worker_t workers[MAXWORKERS]; // reference to worker
void error(const char *msg)
{
perror(msg);
exit(1);
}
/* worker thread */
void *handle_client(void *arg)
{
worker_t* worker = (worker_t *) arg;
int n;
char buf[BUFSIZE];
/* By default a new thread is joinable, we don't
really want this (unless we do something special we
end up with the thread equivalent of zombies). So
we explicitly change the thread type to detached
*/
pthread_detach(pthread_self());
printf("Thread %ld started for client number %d (sd %d)\n", pthread_self(),
worker->num, worker->sd);
/* worker thread */
while (1)
{
/* wait for work to do */
while (worker->state == 0)
{
pthread_cond_wait(&worker->cond, &mtx);
}
int sd = worker->sd; /* get the updated socket fd */
pthread_mutex_unlock(&mtx);
n = read(sd, buf, BUFSIZE);
if (n < 0)
error("ERROR reading from socket");
n = write(sd, "I got your message",18);
if (n < 0)
error("ERROR writing to socket");
/* work done - set itself idle assumes that read returned EOF */
pthread_mutex_lock(&mtx);
close(sd);
worker->state = 0;
printf("Worker %d has completed work \n", worker->num);
pthread_cond_signal(&idle); /* notifies dispatcher*/
pthread_mutex_unlock(&mtx);
} /* end while */
}
int main() { /* Dispatcher */
int ld, sd;
struct sockaddr_in skaddr;
struct sockaddr_in from;
int addrlen, length;
int i;
if ((ld = socket( AF_INET, SOCK_STREAM, 0)) < 0) {
perror("Problem creating socket\n");
exit(1);
}
skaddr.sin_family = AF_INET;
skaddr.sin_addr.s_addr = htonl(INADDR_ANY);
//skaddr.sin_port = htons(0);
skaddr.sin_port = htons(41332);
if (bind(ld, (struct sockaddr *) &skaddr, sizeof(skaddr)) < 0) {
perror("Problem binding\n");
exit(0);
}
/* find out what port we were assigned and print it out */
length = sizeof(skaddr);
if (getsockname(ld, (struct sockaddr *) &skaddr, &length) < 0) {
perror("Error getsockname\n");
exit(1);
}
in_port_t pport = ntohs(skaddr.sin_port);
printf("%d\n", pport);
/* put the socket into passive mode (waiting for connections) */
if (listen(ld, 5) < 0) {
perror("Error calling listen\n");
exit(1);
}
/* do some initialization */
for (i = 0; i < MAXWORKERS; i++) {
workers[i].state = 0;
workers[i].num = i;
workers[i].sd = 0;
workers[i].cond = condInit;
pthread_create(&workers[i].tid, NULL, handle_client, (void *) &workers[i]);
}
/* Dispatcher now processes incoming connections forever ... */
while (1) {
printf("Ready for a connection...\n");
addrlen = sizeof(skaddr);
printf("trying to accept a new connection\n");
if ((sd = accept(ld, (struct sockaddr*) &from, &addrlen)) < 0) {
perror("Problem with accept call\n");
exit(1);
}
printf("Got a connection - processing...\n");
for (i = 0; i < MAXWORKERS; i++) {
pthread_mutex_lock(&mtx);
if (workers[i].state == 0) /* worker i is idle – dispatch him to work */
{
printf("dispatch to worker number: %d \n", i);
pthread_mutex_unlock(&mtx);
break;
}
printf("worker number: %d was busy\n", i);
pthread_mutex_unlock(&mtx);
}
if (i == MAXWORKERS) {
/* all workers busy */
pthread_mutex_lock(&mtx);
pthread_cond_wait(&idle, &mtx); /* wait for one idle; */
pthread_mutex_unlock(&mtx);
} else { /* dispatch worker */
pthread_mutex_lock(&mtx);
workers[i].state = 1;
workers[i].sd = sd;
pthread_cond_signal(&workers[i].cond); /* wake up worker */
pthread_mutex_unlock(&mtx);
}
}
}
碰撞：
Thread 11 (Thread 0x7fae90004700 (LWP 16318)):
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x0000000000401024 in handle_client (arg=0x602408 <workers+648>) at main.c:87
#2 0x00007fae94bdf6ba in start_thread (arg=0x7fae90004700) at pthread_create.c:333
#3 0x00007fae949153dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 10 (Thread 0x7fae90805700 (LWP 16317)):
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x0000000000401024 in handle_client (arg=0x6023c0 <workers+576>) at main.c:87
#2 0x00007fae94bdf6ba in start_thread (arg=0x7fae90805700) at pthread_create.c:333
#3 0x00007fae949153dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 9 (Thread 0x7fae9400c700 (LWP 16310)):
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x0000000000401024 in handle_client (arg=0x6021c8 <workers+72>) at main.c:87
#2 0x00007fae94bdf6ba in start_thread (arg=0x7fae9400c700) at pthread_create.c:333
#3 0x00007fae949153dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 8 (Thread 0x7fae91006700 (LWP 16316)):
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x0000000000401024 in handle_client (arg=0x602378 <workers+504>) at main.c:87
#2 0x00007fae94bdf6ba in start_thread (arg=0x7fae91006700) at pthread_create.c:333
#3 0x00007fae949153dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 7 (Thread 0x7fae91807700 (LWP 16315)):
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x0000000000401024 in handle_client (arg=0x602330 <workers+432>) at main.c:87
#2 0x00007fae94bdf6ba in start_thread (arg=0x7fae91807700) at pthread_create.c:333
#3 0x00007fae949153dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 6 (Thread 0x7fae9300a700 (LWP 16312)):
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x0000000000401024 in handle_client (arg=0x602258 <workers+216>) at main.c:87
#2 0x00007fae94bdf6ba in start_thread (arg=0x7fae9300a700) at pthread_create.c:333
#3 0x00007fae949153dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 5 (Thread 0x7fae92008700 (LWP 16314)):
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x0000000000401024 in handle_client (arg=0x6022e8 <workers+360>) at main.c:87
#2 0x00007fae94bdf6ba in start_thread (arg=0x7fae92008700) at pthread_create.c:333
#3 0x00007fae949153dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 4 (Thread 0x7fae92809700 (LWP 16313)):
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x0000000000401024 in handle_client (arg=0x6022a0 <workers+288>) at main.c:87
#2 0x00007fae94bdf6ba in start_thread (arg=0x7fae92809700) at pthread_create.c:333
#3 0x00007fae949153dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 3 (Thread 0x7fae9380b700 (LWP 16311)):
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x0000000000401024 in handle_client (arg=0x602210 <workers+144>) at main.c:87
#2 0x00007fae94bdf6ba in start_thread (arg=0x7fae9380b700) at pthread_create.c:333
#3 0x00007fae949153dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 2 (Thread 0x7fae9480d700 (LWP 16309)):
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x0000000000401024 in handle_client (arg=0x602180 <workers>) at main.c:87
#2 0x00007fae94bdf6ba in start_thread (arg=0x7fae9480d700) at pthread_create.c:333
#3 0x00007fae949153dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 1 (Thread 0x7fae94ff3700 (LWP 16308)):
#0 0x00007fae94843428 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54
---Type <return> to continue, or q <return> to quit---
#1 0x00007fae9484502a in __GI_abort () at abort.c:89
#2 0x00007fae9483bbd7 in __assert_fail_base (fmt=<optimized out>, assertion=assertion@entry=0x7fae94beb015 "mutex->__data.__owner == 0", file=file@entry=0x7fae94beaff8 "../nptl/pthread_mutex_lock.c", line=line@entry=81,
function=function@entry=0x7fae94beb180 <__PRETTY_FUNCTION__.8623> "__pthread_mutex_lock") at assert.c:92
#3 0x00007fae9483bc82 in __GI___assert_fail (assertion=assertion@entry=0x7fae94beb015 "mutex->__data.__owner == 0", file=file@entry=0x7fae94beaff8 "../nptl/pthread_mutex_lock.c", line=line@entry=81,
function=function@entry=0x7fae94beb180 <__PRETTY_FUNCTION__.8623> "__pthread_mutex_lock") at assert.c:101
#4 0x00007fae94be1f68 in __GI___pthread_mutex_lock (mutex=mutex@entry=0x602140 <mtx>) at ../nptl/pthread_mutex_lock.c:81
#5 0x0000000000400cfa in main () at main.c:173
答案 0 :(得分：2)
在你的工作线程中，首先发生的事情是pthread_cond_wait没有先锁定互斥锁，或pthread_mutex_unlock没有先锁定互斥锁。在这两种情况下，根据POSIX文档，这是未定义的行为。
您的工作人员功能应该从此开始：
/* worker thread */
while (1)
{
/* wait for work to do */
pthread_mutex_lock(&mtx);
while (worker->state == 0)
{
pthread_cond_wait(&worker->cond, &mtx);
}
int sd = worker->sd; /* get the updated socket fd */
pthread_mutex_unlock(&mtx);