[英]C - Pthreads Using a Controller Function
I am attempting to write a toy pthread controller function outside of main()
. 我试图在
main()
之外编写一个玩具pthread控制器函数。
I am having issue with passing the argument struct into the pthread_create
function. 将参数struct传递到
pthread_create
函数时遇到问题。 Essentially it outputs nothing (well let's call it "nothing"). 本质上,它什么也不输出(我们称其为“无”)。
I assume that I am doing something wrong with the pointers to the struct wr
in the pthread_create
, and rather than outputting the struct I am attempting to output the struct pointer. 我假设我在
pthread_create
指向struct wr
的指针做错了什么,而不是输出结构,而是尝试输出结构指针。 What am I doing wrong here? 我在这里做错了什么?
Every example that I see online has pthread implementation in main()
is this just a byproduct of "simple" explanations or is this how I should be doing it in the first place? 我在网上看到的每个示例在
main()
都有pthread实现,这仅仅是“简单”说明的副产品,还是这首先应该是怎么做的?
Note Yes I do realize that two threads pools are started synchronously. 注意:是的,我的确意识到两个线程池是同步启动的。 That's not the question here.
这不是这里的问题。
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
struct wr {
char str[100];
int count;
};
void writeline (struct wr writer) {
printf("out: %s\n", writer.str);
writer.count--; //this is left over, just ignore it for now.
pthread_exit(0);
return NULL;
}
void controller (void (*func)(struct wr), struct wr writer, int threads){
pthread_t *tid;
tid = malloc(sizeof(pthread_t) * threads);
int i;
for (i = threads; i > 0; i--){
// Right here is where the problem starts.
pthread_create(&tid[i], NULL, (void *) writeline, (void *) &writer);
}
for (i = threads; i > 0; i--) {
pthread_join(tid[i], NULL);
}
}
int main () {
struct wr writer1 = {.str = "Bop!", .count = 3};
struct wr writer2 = {.str = "Boop!", .count = 3};
controller(writeline, writer1, 10);
controller(writeline, writer2, 2);
return 0;
}
And my Makefile options: 和我的Makefile选项:
CC=gcc
CFLAGS=-g -Wall -pthread
1) Your cast for the function is wrong: 1)您对该函数的转换是错误的:
pthread_create(&tid[i], NULL, (void *) writeline, (void *) &writer);
You are casting the function pointer to a data pointer, which is meaningless. 您正在将函数指针转换为数据指针,这毫无意义。
2) Your indexing is for tid
is also wrong. 2)您为
tid
编制索引也是错误的。 When you allocate, for example, 2 pthread_t
elements, your valid indexes are 0 and 1. But your for loop access 1 and 2. 例如,当您分配2个
pthread_t
元素时,有效索引为0和1。但是您的for循环访问为1和2。
3) You are not using the function pointer. 3)您没有使用函数指针。 So you don't need to pass it at all.
因此,您根本不需要通过它。
4) The thread function takes a void *
as argument, not a struct
. 4)线程函数将
void *
作为参数,而不是struct
。 So you need to change it and retrieve the argument in the function by casting it back to struct wr*
. 因此,您需要对其进行更改,并通过将其强制转换回
struct wr*
来检索函数中的参数。
Code with above changes: 具有以上更改的代码:
5) You need either pthread_exit
or return
. 5)您需要
pthread_exit
或return
。 pthread_exit
doesn't return. pthread_exit
不返回。 Remove one of them. 删除其中之一。
void* writeline (void *arg) {
struct wr writer = *(struct wr*)arg;
printf("out: %s\n", writer.str);
return NULL;
}
void controller (struct wr writer, int threads){
pthread_t *tid;
tid = malloc(sizeof(pthread_t) * threads);
int i;
for (i = 0; i <threads; i++) {
pthread_create(&tid[i], NULL, writeline, &writer);
}
for (i = 0; i <threads; i++) {
pthread_join(tid[i], NULL);
}
}
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