POSIX Threads Programming - LLNL HPC Tutorials

type

date

slug

1. Pthread Overview

Why Threads?

CPU眼里的：进程、线程 | MMU系列 | 空间独立性 - 阿布的视频 - 知乎 https://www.zhihu.com/zvideo/1469706912229429248

从 MMU 的视角，重新认识线程和进程，了解“空间独立性”的基本硬件原理和使用场景

网络服务器更多使用多进程，很少使用多线程

@ Linux程序设计（第四版）

优点

在编辑文档的同时对文档中的单词个数进行实时统计 → 编辑时同时知道工作进度

一个多线程的数据库服务器，这是一种明显的单进程服务多用户的情况。→ 多进程满足加锁和数据一致性要求复杂，而多线程容易的多

一个混杂着输入、计算和输出的应用程序，可以将这几个部分分离为３个线程来执行，从而改善程序执行的性能。

处理多个网络连接的服务器应用程序(由于线程的不安全，实际网络服务器多用多进程来实现)

缺点

编写多线程程序需要非常仔细的实际，时许细微的偏差和变量共享而引发错误

多线程调试困难得多，线程之间交互难以控制

计算任务分为多线程，需要多个处理器核，且不同部分运行同时计算

What is Pthread？

Processes contain information about program resources and program execution state,

This independent flow of control is accomplished because a thread maintains its own

ㅤ	Thread contain info
• Process ID, process group ID, user ID, and group ID	ㅤ
• Environment	ㅤ
• Working directory	ㅤ
• Program instructions	ㅤ
• Registers	Registers
• Stack	Stack pointer, Scheduling properties (such as policy or priority)
• Heap	ㅤ
• File descriptors	Thread specific data.
• Signal actions	Set of pending and blocked signals
• Shared libraries	ㅤ
Inter-process communication tools (such as message queues, pipes, semaphores, or shared memory)	ㅤ

So, in summary, in the UNIX environment a thread:

Exists within a process and uses the process resources

Has its own independent flow of control as long as its parent process exists and the OS supports it

Duplicates only the essential resources it needs to be independently schedulable

May share the process resources with other threads that act equally independently (and dependently)

Dies if the parent process dies - or something similar

Is “lightweight” because most of the overhead has already been accomplished through the creation of its process.

other supplementation refer to this link.

What are Pthreads?

Historically, hardware vendors have implemented their own proprietary versions of threads. These implementations differed substantially from each other making it difficult for programmers to develop portable threaded applications.

In order to take full advantage of the capabilities provided by threads, a standardized programming interface was required.

For UNIX systems, this interface has been specified by the IEEE POSIX 1003.1c standard (1995).

Implementations adhering to this standard are referred to as POSIX threads, or Pthreads.

Most hardware vendors now offer Pthreads in addition to their proprietary API’s.

Pthreads are defined as a set of C language programming types and procedure calls, implemented with a pthread.h header/include file and a thread library - though this library may be part of another library, such as libc, in some implementations.

Why Pthread?

Light Weight

Managing threads requires fewer system resources than managing processes.

For example, the following table compares timing results for the fork() subroutine and the pthread_create() subroutine. Timings reflect 50,000 process/thread creations, were performed with the time utility, and units are in seconds, no optimization flags.

Platform	fork()	pthread_create()
real	user	sys
Intel 2.6 GHz Xeon E5-2670 (16 cores/node)	8.1	0.1
Intel 2.8 GHz Xeon 5660 (12 cores/node)	4.4	0.4
AMD 2.3 GHz Opteron (16 cores/node)	12.5	1.0
AMD 2.4 GHz Opteron (8 cores/node)	17.6	2.2
IBM 4.0 GHz POWER6 (8 cpus/node)	9.5	0.6
IBM 1.9 GHz POWER5 p5-575 (8 cpus/node)	64.2	30.7
IBM 1.5 GHz POWER4 (8 cpus/node)	104.5	48.6
INTEL 2.4 GHz Xeon (2 cpus/node)	54.9	1.5
INTEL 1.4 GHz Itanium2 (4 cpus/node)	54.5	1.1

Efficient Communications/Data Exchange

To achieve optimum computing performance by using pthread instead of MPI . For Pthreads there is no intermediate memory copy required because threads share the same address space within a single process. There is no data transfer, per se. It can be as efficient as simply passing a pointer.

Overlapping CPU work with I/O

Priority/real-time scheduling

Asynchronous event handling

Other Common Reasons

Examples

A perfect example is the typical web browser, where many interleaved tasks can be happening at the same time, and where tasks can vary in priority.

Another good example is a modern operating system, which makes extensive use of threads. A screenshot of the MS Windows OS and applications using threads is shown below.

Designing Threaded Programs

Parallel program

interchanged, interleaved and/or overlapped in real time

Programs having the following characteristics may be well suited for pthreads

Several common models for threaded programs exist:

Manager/worker: a single thread, the manager assigns work to other threads, the workers. Typically, the manager handles all input and parcels out work to the other tasks. At least two forms of the manager/worker model are common: static worker pool and dynamic worker pool.

Pipeline: a task is broken into a series of suboperations, each of which is handled in series, but concurrently, by a different thread. An automobile assembly line best describes this model.

Peer: similar to the manager/worker model, but after the main thread creates other threads, it participates in the work.

Shared Memory Model

Thread-safeness

Thread-safeness: in a nutshell, refers to an application’s ability to execute multiple threads simultaneously without “clobbering” shared data or creating “race” conditions.

For example, suppose that your application creates several threads, each of which makes a call to the same library routine:

This library routine accesses/modifies a global structure or location in memory.

As each thread calls this routine it is possible that they may try to modify this global structure/memory location at the same time.

If the routine does not employ some sort of synchronization constructs to prevent data corruption, then it is not thread-safe.

2. The Pthreads API

The Pthreads API

he subroutines which comprise the Pthreads API can be informally grouped into four major groups:

Thread management: Routines that work directly on threads - creating, detaching, joining, etc. They also include functions to set/query thread attributes (joinable, scheduling etc.)

Mutexes: Routines that deal with synchronization, called a “mutex”, which is an abbreviation for “mutual exclusion”. Mutex functions provide for creating, destroying, locking and unlocking mutexes. These are supplemented by mutex attribute functions that set or modify attributes associated with mutexes.

Condition variables: Routines that address communications between threads that share a mutex. Based upon programmer specified conditions. This group includes functions to create, destroy, wait and signal based upon specified variable values. Functions to set/query condition variable attributes are also included.

Synchronization: Routines that manage read/write locks and barriers.

Naming conventions: All identifiers in the threads library begin with pthread_. Some examples are shown below.

Routine Prefix	Functional Group
pthread_	Threads themselves and miscellaneous subroutines
pthread_attr_	Thread attributes objects
pthread_mutex_	Mutexes
pthread_mutexattr_	Mutex attributes objects.
pthread_cond_	Condition variables
pthread_condattr_	Condition attributes objects
pthread_key_	Thread-specific data keys
pthread_rwlock_	Read/write locks
pthread_barrier_	Synchronization barriers

3. Compiling Threaded Programs

Compiling Threaded Programs

Several examples of compile commands used for pthreads codes are listed in the table below.

4. Thread Management

Creating and Terminating Threads

Routines:

pthread_create(thread,attr,start_routine,arg)

pthread_exit(status)

pthread_cancel(thread)

pthread_attr_init(attr)

pthread_attr_destroy(attr)

Creating Threads:

Initially, your main() program comprises a single, default thread. All other threads must be explicitly created by the programmer. pthread_create creates a new thread and makes it executable. This routine can be called any number of times from anywhere within your code.

pthread_create arguments:

🐞

pthread_create 调用成功返回值是0，但失败时并未遵循UNIX函数的管理返回-1。

thread: An opaque, unique identifier for the new thread returned by the subroutine.

attr: An opaque attribute object that may be used to set thread attributes. You can specify a thread attributes object, or NULL for the default values.

start_routine: the C routine that the thread will execute once it is created.

arg: A single argument that may be passed to start_routine. It must be passed by reference as a pointer cast of type void. NULL may be used if no argument is to be passed.

The maximum number of threads that may be created by a process is implementation dependent.

reference

Thread Attributes:

By default, a thread is created with certain attributes. Some of these attributes can be changed by the programmer via the thread attribute object.

pthread_attr_init and pthread_attr_destroy are used to initialize/destroy the thread attribute object.

Other routines are then used to query/set specific attributes in the thread attribute object. Attributes include:

Detached or joinable state

Scheduling inheritance

Scheduling policy

Scheduling parameters

Scheduling contention scope

Stack size

Stack address

Stack guard (overflow) size

Some of these attributes will be discussed later.

Thread Binding and Scheduling:

Question: After a thread has been created, how do you know a) when it will be scheduled to run by the operating system, and b) which processor/core it will run on?

Click for answer

The Pthreads API provides several routines that may be used to specify how threads are scheduled for execution. For example, threads can be scheduled to run FIFO (first-in first-out), RR (round-robin) or OTHER (operating system determines). It also provides the ability to set a thread’s scheduling priority value.

These topics are not covered here, however a good overview of “how things work” under Linux can be found in the sched_setscheduler man page.

The Pthreads API does not provide routines for binding threads to specific cpus/cores. However, local implementations may include this functionality - such as providing the non-standard pthread_setaffinity_np routine. Note that “_np” in the name stands for “non-portable”.

Also, the local operating system may provide a way to do this. For example, Linux provides the sched_setaffinity routine.

Terminating Threads & `pthread_exit()`

There are several ways in which a thread may be terminated:

The thread returns normally from its starting routine. Its work is done.

The thread makes a call to the pthread_exit subroutine - whether its work is done or not.

The thread is canceled by another thread via the pthread_cancel routine.

The entire process is terminated due to making a call to either the exec() or exit()

If main() finishes first, without calling pthread_exit explicitly itself

Usuage1: The pthread_exit() routine allows the programmer to specify an optional termination status parameter.

Usuage2: In subroutines that execute to completion normally, you can often dispense with calling pthread_exit() - unless, of course, you want to pass the optional status code back.

Discussion on calling pthread_exit() from main():

There is a definite problem if main() finishes before the threads it spawned if you don’t call pthread_exit() explicitly. All of the threads it created will terminate because main() is done and no longer exists to support the threads.

By having main() explicitly call pthread_exit() as the last thing it does, main() will block and be kept alive to support the threads it created until they are done.

Example: Pthread Creation and Termination

Passing Arguments to Threads

The pthread_create() routine permits the programmer to pass one argument to the thread start routine. For cases where multiple arguments must be passed, this limitation is easily overcome by creating a structure which contains all of the arguments, and then passing a pointer to that structure in the pthread_create() routine.

All arguments must be passed by reference and cast to (void *).

Question: How can you safely pass data to newly created threads, given their non-deterministic start-up and scheduling?

Answer (Click to view.)

Make sure that all passed data is thread safe - that it can not be changed by other threads. The three examples that follow demonstrate what not and what to do.*

Example 01 -Thread Argument Passing

根据谷歌代码命名规范，使用snake_case的命名方法，默认是驼峰命名方法。

C99下没有sleep()，因此通过在linux系统下，#include <unistd.h>，包括sleep方法

Example 02 -Thread Argument Passing

This example shows how to setup/pass multiple arguments via a structure. Each thread receives a unique instance of the structure.

Example 03 -error passing

his example performs argument passing incorrectly. It passes the address of variable t, which is shared memory space and visible to all threads. As the loop iterates, the value of this memory location changes, possibly before the created threads can access it.

Joining and Detaching Threads

Routines:

pthread_join (threadid,status)

pthread_detach (threadid)

pthread_attr_setdetachstate (attr,detachstate)

pthread_attr_getdetachstate (attr,detachstate)

Joining:

“Joining” is one way to accomplish synchronization between threads. For example:

The Pthread_join() subroutine blocks the calling threads until the specified threadid thread terminates.

The programmer is able to obtain the target thread’s termination return status if it was specified in the target thread’s call to pthread_exit(). — The programmer is able to obtain the target thread’s termination return `status` if it was specified in the target thread’s call to `pthread_exit()`.

Joinable or Not?

When a thread is created, one of its attributes defines whether it is joinable or detached. Only threads that are created as joinable can be joined. If a thread is created as detached, it can never be joined.

To explicitly create a thread as joinable or detached, the attr argument in the pthread_create() routine is used.

The typical 4 step process is:

Declare a pthread attribute variable of the pthread_attr_t data type

Initialize the attribute variable with pthread_attr_init()

Set the attribute detached status with pthread_attr_setdetachstate()

When done, free library resources used by the attribute with pthread_attr_destroy()

Detaching

The pthread_detach() routine can be used to explicitly detach a thread even though it was created as joinable.

There is no converse routine.

Stack Management

Miscellaneous Routines

pthread_self ()

pthread_equal (thread1,thread2)

pthread_self returns the unique, system assigned thread ID of the calling thread.

pthread_equal compares two thread IDs. If the two IDs are different 0 is returned, otherwise a non-zero value is returned.

Note that for both of these routines, the thread identifier objects are opaque and can not be easily inspected. Because thread IDs are opaque objects, the C language equivalence operator == should not be used to compare two thread IDs against each other, or to compare a single thread ID against another value.

pthread_once (once_control, init_routine)

pthread_once executes the init_routine exactly once in a process. The first call to this routine by any thread in the process executes the given init_routine, without parameters. Any subsequent call will have no effect.

The init_routine routine is typically an initialization routine.

The once_control parameter is a synchronization control structure that requires initialization prior to calling pthread_once. For example:

pthread_once_t once_control = PTHREAD_ONCE_INIT;

5. Mutex Variables

Overview

Function

Mutex variables are one of the primary means of implementing thread synchronization and for protecting shared data when multiple writes occur. (Very often the action performed by a thread owning a mutex is the updating of global variables.)

a safe way to ensure that when several threads update the same variable

Opr Steps

A typical sequence in the use of a mutex is as follows:

Create and initialize a mutex variable

Several threads attempt to lock the mutex

Only one succeeds and that thread owns the mutex

The owner thread performs some set of actions

The owner unlocks the mutex

Another thread acquires the mutex and repeats the process

Finally the mutex is destroyed

When several threads compete for a mutex, the losers block at that call - an unblocking call is available with “trylock” instead of the “lock” call.

Creating and Destroying Mutexes

Routines:

pthread_mutex_init (mutex,attr)

pthread_mutex_destroy (mutex)

pthread_mutexattr_init (attr)

pthread_mutexattr_destroy (attr)

Usage:

Mutex variables must be declared with type pthread_mutex_t, and must be initialized before they can be used. There are two ways to initialize a mutex variable:

Statically, when it is declared. For example: pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;

Dynamically, with the pthread_mutex_init() routine. This method permits setting mutex object attributes, attr.

The mutex is initially unlocked.

The attr object is used to establish properties for the mutex object, and must be of type pthread_mutexattr_t if used (may be specified as NULL to accept defaults). The Pthreads standard defines three optional mutex attributes:

Protocol: Specifies the protocol used to prevent priority inversions for a mutex.

Prioceiling: Specifies the priority ceiling of a mutex.

Process-shared: Specifies the process sharing of a mutex.

Note that not all implementations may provide the three optional mutex attributes.

The pthread_mutexattr_init() and pthread_mutexattr_destroy() routines are used to create and destroy mutex attribute objects respectively.

pthread_mutex_destroy() should be used to free a mutex object which is no longer needed.

Locking and Unlocking Mutexes

Routines:

pthread_mutex_lock (mutex)

pthread_mutex_trylock (mutex)

pthread_mutex_unlock (mutex)

Usage:

The pthread_mutex_lock() routine is used by a thread to acquire a lock on the specified mutex variable. If the mutex is already locked by another thread, this call will block the calling thread until the mutex is unlocked.

pthread_mutex_trylock() will attempt to lock a mutex. However, if the mutex is already locked, the routine will return immediately with a “busy” error code. This routine may be useful in preventing deadlock conditions, as in a priority-inversion situation.

pthread_mutex_unlock() will unlock a mutex if called by the owning thread. Calling this routine is required after a thread has completed its use of protected data if other threads are to acquire the mutex for their work with the protected data. An error will be returned if:

If the mutex was already unlocked

If the mutex is owned by another thread

There is nothing “magical” about mutexes…in fact they are akin to a “gentlemen’s agreement” between participating threads. It is up to the code writer to ensure that the necessary threads all make the the mutex lock and unlock calls correctly. The following scenario demonstrates a logical error:

Lock

A = 2

Unlock

Lock

A = A+1

Unlock

A = A*B

Question: When more than one thread is waiting for a locked mutex, which thread will be granted the lock first after it is released?

Click for answer.

Unless thread priority scheduling (not covered) is used, the assignment will be left to the native system scheduler and may appear to be more or less random.

Example: Using Mutexes

This example program illustrates the use of mutex variables in a threads program that performs a dot product.

The main data is made available to all threads through a globally accessible structure.

Each thread works on a different part of the data.

The main thread waits for all the threads to complete their computations, and then it prints the resulting sum.

6. Condition Variables

Overview

Functions

Condition variables provide yet another way for threads to synchronize. While mutexes implement synchronization by controlling thread access to data, condition variables allow threads to synchronize based upon the actual value of data.

A condition variable is a way to achieve the same goal without polling.

How to Use

A condition variable is always used in conjunction with a mutex lock.

A representative sequence for using condition variables is shown below.

Main Thread Declare and initialize global data/variables which require synchronization (such as "count") Declare and initialize a condition variable object Declare and initialize an associated mutex Create threads A and B to do work
Thread A 1. Do work up to the point where a certain condition must occur (such as "count" must reach a specified value) 2. Lock associated mutex and check value of a global variable 3. Call pthread_cond_wait() to perform a blocking wait for signal from Thread-B. Note that call to pthread_cond_wait() automatically and atomically unlocks the associated mutex variable so that it can be used by Thread-B. 4. When signalled, wake up. Mutex is automatically and atomically locked. 5. Explicitly unlock mutex 6. Continue	Thread B 1. Do work 2. Lock associated mutex 3. Change the value of the global variable that Thread-A is waiting upon. 4. Check value of the global Thread-A wait variable. If it fulfills the desired condition, signal Thread-A. 5. Unlock mutex. 6. Continue
Main ThreadJoin / Continue	ㅤ

Creating and Destroying Condition Variables

Routines:

pthread_cond_init (condition,attr)

pthread_cond_destroy (condition)

pthread_condattr_init (attr)

pthread_condattr_destroy (attr)

Usage:

Condition variables must be declared with type pthread_cond_t, and must be initialized before they can be used. There are two ways to initialize a condition variable:

Statically, when it is declared. For example: pthread_cond_t myconvar = PTHREAD_COND_INITIALIZER;

Dynamically, with the pthread_cond_init() routine. The ID of the created condition variable is returned to the calling thread through the condition parameter. This method permits setting condition variable object attributes, attr.

The optional attr object is used to set condition variable attributes. There is only one attribute defined for condition variables: process-shared, which allows the condition variable to be seen by threads in other processes. The attribute object, if used, must be of type pthread_condattr_t (may be specified as NULL to accept defaults). Note that not all implementations may provide the process-shared attribute.

The pthread_condattr_init() and pthread_condattr_destroy() routines are used to create and destroy condition variable attribute objects.

pthread_cond_destroy() should be used to free a condition variable that is no longer needed.

Waiting and Signaling on Condition Variables

Routines:

pthread_cond_wait (condition,mutex)

pthread_cond_signal (condition)

pthread_cond_broadcast (condition)

Usage:

pthread_cond_wait() blocks the calling thread until the specified condition is signalled. This routine should be called while mutex is locked, and it will automatically release the mutex while it waits. After signal is received and thread is awakened, mutex will be automatically locked for use by the thread. The programmer is then responsible for unlocking mutex when the thread is finished with it.

Recommendation: Using a WHILE loop instead of an IF statement (see watch_count routine in example below) to check the waited for condition can help deal with several potential problems, such as:

If several threads are waiting for the same wake up signal, they will take turns acquiring the mutex, and any one of them can then modify the condition they all waited for.
If the thread received the signal in error due to a program bug
The Pthreads library is permitted to issue spurious wake ups to a waiting thread without violating the standard.

The pthread_cond_signal() routine is used to signal (or wake up) another thread which is waiting on the condition variable. It should be called after mutex is locked, and must unlock mutex in order for pthread_cond_wait() routine to complete.

The pthread_cond_broadcast() routine should be used instead of pthread_cond_signal() if more than one thread is in a blocking wait state.

It is a logical error to call pthread_cond_signal() before calling pthread_cond_wait().

Proper locking and unlocking of the associated mutex variable is essential when using these routines. For example:

Failing to lock the mutex before calling pthread_cond_wait() may cause it NOT to block.
Failing to unlock the mutex after calling pthread_cond_signal() may not allow a matching pthread_cond_wait() routine to complete (it will remain blocked).

Example: Using Condition Variables

7. Monitoring, Debugging, and Performance Analysis for Pthreads

Monitoring and Debugging Pthreads

Debuggers vary in their ability to handle Pthreads. The TotalView debugger is LC’s recommended debugger for parallel programs. It is well suited for both monitoring and debugging threaded programs.

An example screenshot from a TotalView session using a threaded code is shown below.

Stack Trace Pane: Displays the call stack of routines that the selected thread is executing.

Status Bars: Show status information for the selected thread and its associated process.

Stack Frame Pane: Shows a selected thread’s stack variables, registers, etc.

Source Pane: Shows the source code for the selected thread.

Root Window showing all threads

Threads Pane: Shows threads associated with the selected process

Performance Analysis Tools

There are a variety of performance analysis tools that can be used with threaded programs. Searching the web will turn up a wealth of information.

At LC, the list of supported computing tools can be found at: hpc.llnl.gov/software.

These tools vary significantly in their complexity, functionality and learning curve. Covering them in detail is beyond the scope of this tutorial.

Some tools worth investigating, specifically for threaded codes, include:

OpenSpeedShop
TAU
HPCToolkit
PAPI
Intel VTune Amplifier ThreadSpotter

8. Topics Not Covered

Topics Not Covered

Several features of the Pthreads API are not covered in this tutorial. These are listed below. See the Pthread Library Routines Reference section for more information.

Thread Scheduling

Implementations will differ on how threads are scheduled to run. In most cases, the default mechanism is adequate.
The Pthreads API provides routines to explicitly set thread scheduling policies and priorities which may override the default mechanisms.
The API does not require implementations to support these features.

Keys: Thread-Specific Data

As threads call and return from different routines, the local data on a thread’s stack comes and goes.
To preserve stack data you can usually pass it as an argument from one routine to the next, or else store the data in a global variable associated with a thread.
Pthreads provides another, possibly more convenient and versatile, way of accomplishing this through keys.

Mutex Protocol Attributes and Mutex Priority Management for the handling of “priority inversion” problems.

Condition Variable Sharing—across processes
Thread Cancellation
Threads and Signals
Sychronization constructs—barriers and locks

9. References and More Information

Original Author: Blaise Barney; Contact: [email protected], Livermore Computing.

"Pthreads Programming". B. Nichols et al. O'Reilly and Associates.

"Threads Primer". B. Lewis and D. Berg. Prentice Hall

"Programming With POSIX Threads". D. Butenhof. Addison Wesley

"Programming With Threads". S. Kleiman et al. Prentice Hall

POSIX Threads Programming | LLNL HPC Tutorials

Pthread：POSIX 多线程程序设计（中文翻译）

Introduction to Parallel Computing Tutorial | High Performance Computing (llnl.gov)

pthread详解中文阅读笔记-详细

线程锁的基本概念与简单封装_一个人的旅行的博客-CSDN博客_线程锁怎么定义

🔖

Pthread 习题

1. Pthread Overview

Shared Memory Model

Thread-safeness

2. The Pthreads API

3. Compiling Threaded Programs

4. Thread Management

Routines:

Creating Threads:

Thread Attributes:

Thread Binding and Scheduling:

Terminating Threads & `pthread_exit()`

Example 01 -Thread Argument Passing

Example 02 -Thread Argument Passing

Example 03 -error passing

Routines:

Joining:

Joinable or Not?

Detaching

5. Mutex Variables

Function

Opr Steps

Routines:

Usage:

Routines:

Usage:

6. Condition Variables

Functions

How to Use

Routines:

Usage:

Routines:

Usage:

7. Monitoring, Debugging, and Performance Analysis for Pthreads

8. Topics Not Covered

9. References and More Information

felixfixit

交流频道

去知识星球参与更多讨论

1. Pthread Overview

Shared Memory Model

Thread-safeness

2. The Pthreads API

3. Compiling Threaded Programs

4. Thread Management

Routines:

Creating Threads:

Thread Attributes:

Thread Binding and Scheduling:

Terminating Threads & pthread_exit()

Example 01 -Thread Argument Passing

Example 02 -Thread Argument Passing

Example 03 -error passing

Routines:

Joining:

Joinable or Not?

Detaching

5. Mutex Variables

Function

Opr Steps

Routines:

Usage:

Routines:

Usage:

6. Condition Variables

Functions

How to Use

Routines:

Usage:

Routines:

Usage:

7. Monitoring, Debugging, and Performance Analysis for Pthreads

8. Topics Not Covered

9. References and More Information

felixfixit

交流频道

去知识星球参与更多讨论

Terminating Threads & `pthread_exit()`