pthreads | 易学教程

Does each thread have its own stack?

阅读更多关于 Does each thread have its own stack?

问题 When I create multiple threads from a process, then does each thread have its own stack, or is it that they share the stack of their parent process. What happens when a thread makes a system call? Do threads also maintain their own kernel stack like processes? 回答1: Yes threads have their own stacks and their own kernel stacks (e.g. linux). When a thread makes a system call, you trap into kernel mode (from user mode), you pass the arguments to the kernel, the arguments are checked, the kernel

void * typed function parameter

阅读更多关于 void * typed function parameter

问题 I have a function, void *Client(void *threaData){} Can you tell me some things about void *threadData parameter. When you use void * parameter and why? 回答1: void * is a generic pointer which can point to any object type. The above function can take a pointer to any type and can return a pointer to any type. A generic pointer can be used if it is not sure about the data type of data inputted by the user. Example: The following function will print any data type provided the user input about the

void * typed function parameter

阅读更多关于 void * typed function parameter

Linux socket using multiple threads to send

阅读更多关于 Linux socket using multiple threads to send

问题 I have a single non-blocking socket sending udp packets to multiple targets and receiving responses from all of them on the same socket. I'm reading in a dedicated thread but writes (sendto) can come from several different threads. Is this a safe without any additional synchronization? Do I need to write while holding a mutex? Or, do writes need to come from the same thread and I need a queue? 回答1: The kernel will synchronize access to underlying file descriptor for you, so you don't need a

Linux C编程之十四线程、线程控制、线程属性

阅读更多关于 Linux C编程之十四线程、线程控制、线程属性

一、整体大纲二、线程相关 1. 什么是线程 LWP：light weight process 轻量级的进程，本质仍是进程(在Linux环境下) 进程：独立地址空间，拥有PCB 线程：也有PCB，但没有独立的地址空间(共享) 区别：在于是否共享地址空间。独居(进程)；合租(线程)。 Linux下：线程：最小的执行单位进程：最小分配资源单位，可看成是只有一个线程的进程。 2. Linux内核线程实现原理（1）线程实现原理类Unix系统中，早期是没有“线程”概念的，80年代才引入，借助进程机制实现出了线程的概念。因此在这类系统中，进程和线程关系密切。 1）轻量级进程(light-weight process)，也有PCB，创建线程使用的底层函数和进程一样，都是clone 2）从内核里看进程和线程是一样的，都有各自不同的PCB，但是PCB中指向内存资源的三级页表是相同的 3）进程可以蜕变成线程 4）线程可看做寄存器和栈的集合 5）在linux下，线程最是小的执行单位；进程是最小的分配资源单位察看LWP号：ps -Lf pid 查看指定线程的lwp号。三级映射：进程PCB --> 页目录(可看成数组，首地址位于PCB中) --> 页表 --> 物理页面 --> 内存单元参考：《Linux内核源代码情景分析》 ----毛德操对于进程来说，相同的地址(同一个虚拟地址

Memory leaks in pthread even if the state is detached

阅读更多关于 Memory leaks in pthread even if the state is detached

问题 I am learning pthreads programming. I understood that there are two states of thread: 1. Joinable 2. Detachable In case of Joinable, we need to call pthread_join to free the resources(stack), whereas in case of detached there is no need to call pthread_join and the resources will be freed on thread exit. I wrote a sample program to observe the behavior #include <stdio.h> #include <pthread.h> #include <stdlib.h> void *threadFn(void *arg) { pthread_detach(pthread_self()); sleep(1); printf(

Printing the default thread's priority

阅读更多关于 Printing the default thread's priority

问题 I'd like to write a code which prints the default thread's priority, but I don't know if this is possible. So far I created a thread with default attributes, but I didn't find any statement which allows me to store and print its default priority. // main.c #include <stdlib.h> #include <stdio.h> #include <pthread.h> #include <sched.h> #include "task.h" int main() { pthread_attr_t attr; struct sched_param prio; pthread_t tid; int create = 1; // default attributes pthread_attr_init(&attr);

Why `pthread_rwlock_t`'s ABI differs a lot among versions?

阅读更多关于 Why `pthread_rwlock_t`'s ABI differs a lot among versions?

问题 I am looking into different versions of implementation of pthread_rwlock_t . GLIBC2.30 typedef union { struct __pthread_rwlock_arch_t __data; char __size[__SIZEOF_PTHREAD_RWLOCK_T]; long int __align; } pthread_rwlock_t; struct __pthread_rwlock_arch_t { unsigned int __readers; unsigned int __writers; unsigned int __wrphase_futex; unsigned int __writers_futex; unsigned int __pad3; unsigned int __pad4; ... GLIBC2.17 typedef union { # ifdef __x86_64__ struct { int __lock; unsigned int __nr

Pthreads compile not working

阅读更多关于 Pthreads compile not working

问题 I have written some code but it doesn't seem to work when I compile it. I am trying to run this in Ubuntu: #include <pthread.h> #include <ctype.h> #include <unistd.h> char buffer[128]; void *write_thread(void *args) { int count = *((int*)args); write(STDOUT_FILENO, buffer, count); pthread_exit(0); } void *toupper_thread(void *args) { int i; int count = *((int*)args); for(i = 0; i < count; i++) { buffer[i] = toupper(buffer[i]); } pthread_t writeId; pthread_create(&writeId, NULL, write_thread,

Undefined reference error _dl_stack_flags with gcc and pthreads

阅读更多关于 Undefined reference error _dl_stack_flags with gcc and pthreads

问题 I get the following error when trying to compile an application using pthreads on Ubuntu: /usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../lib/libpthread.a(pthread_create.o): In function `allocate_stack': /build/buildd/eglibc-2.11.1/nptl/allocatestack.c:444: undefined reference to `_dl_stack_flags' Ubuntu version is: wade@wadesworld:~$ uname -a Linux wadesworld 2.6.18-194.8.1.el5.028stab070.5ent #1 SMP Fri Sep 17 19:46:02 MSD 2010 i686 GNU/Linux gcc version is: wade@wadesworld:~$ gcc -v Using