pthread4w-delphi编程示例（一）

最新推荐文章于 2023-11-15 18:11:02 发布

sonadorje

最新推荐文章于 2023-11-15 18:11:02 发布

阅读量521

点赞数

分类专栏： Delphi Other 文章标签：开发语言

本文链接：https://blog.youkuaiyun.com/sonadorje/article/details/122600476

版权

Delphi Other 专栏收录该内容

45 篇文章

订阅专栏

线程基础：

线程操作包括线程的创建、终止、同步（连接、阻塞）、调度、数据管理和进程交互。
线程不维护已创建线程的列表，也不知道创建它的线程。
一个进程中的所有线程共享相同的地址空间。
同一进程中的线程共享：
- 进程说明
- 大多数数据
- 打开文件（描述符）
- 信号和信号捕捉程序
- 当前工作目录
- 用户和组 ID
每个线程都有一个独特的：
- 线程 ID
- 一组寄存器，堆栈指针
- 局部变量堆栈，返回地址
- 信号掩码
- 优先事项
- 返回值：errno
如果正常，pthread 函数将返回“0”。

program mutex_demo1;

{$IFDEF FPC}
  {$MODE Delphi}//MacPas}
  {$assertions on}
{$ENDIF}

{$APPTYPE CONSOLE}

{$R *.res}
{$DEFINE __PTW32_MUTEX_TYPES}
uses
  {$IFnDEF FPC}
  System.SysUtils,
  System.Win.Crtl,
  Winapi.Windows,
  {$ELSE}
  Sysutils,
  {$ENDIF}
  libc.Types in '..\libc.Types.pas',
  pthreads.win in '..\pthreads.win.pas',
  pthreads.sem in '..\pthreads.sem.pas',
  pthreads.sched in '..\pthreads.sched.pas',
  pthreads.barrier in '..\pthreads.barrier.pas',
  pthreads.mutex in '..\pthreads.mutex.pas',
  pthreads.mutexattr in '..\pthreads.mutexattr.pas',
  pthreads.spin in '..\pthreads.spin.pas',
  pthreads.attr in '..\pthreads.attr.pas',
  pthreads.cond in '..\pthreads.cond.pas',
  pthreads.condattr in '..\pthreads.condattr.pas',
  pthreads.rwlock in '..\pthreads.rwlock.pas',
  pthreads.ptw32 in '..\pthreads.ptw32.pas',
  pthreads.oldmutex in '..\pthreads.oldmutex.pas',
  pthreads.core in '..\pthreads.core.pas',
  pthreads.CPU in '..\pthreads.CPU.pas',
  QueueUser_APCEx in '..\QueueUser_APCEx.pas';


procedure DoMessage(Message, Filename: String; LineNumber: Integer; ErrorAddr: Pointer);
var
  S: String;
begin
  S := Format('%s (%s, line %d, address $%x)',
    [Message, Filename, LineNumber, Pred(Integer(ErrorAddr))]);
  //OutputDebugString(PChar(S));
  Writeln(S);
end;

procedure AssertErrorHandler(const Message, Filename: string;  LineNumber: Integer; ErrorAddr: Pointer);
{ No local variables. Not compiler generated temporary variables. }
{ Using the call stack here will cause Access Violation errors. }
begin
  DoMessage(Message, Filename, LineNumber, ErrorAddr);
  //raise EMyAssert.Create('Boom!');
end;

var
  mutex1 : pthread_mutex_t = PTHREAD_MUTEX_INITIALIZER;
  counter : integer = 0;


function functionC(arg: Pointer): Pointer;
begin
   pthread_mutex_lock( &mutex1 );
   Inc(counter);
   writeln(format('Counter value: %d',[counter]));
   pthread_mutex_unlock( &mutex1 );
end;


procedure main;
var
  rc1, rc2 : integer;

  thread1, thread2 : pthread_t;
begin
   { Create independent threads each of which will execute functionC }
   rc1 := pthread_create( &thread1, nil, &functionC, nil );
   if rc1 > 0 then
   begin
      writeln(format('Thread creation failed: %d',[rc1]));
   end;

   rc2 := pthread_create( &thread2, nil, &functionC, nil );
   if rc2 > 0  then
   begin
      writeln(format('Thread creation failed: %d',[rc2]));
   end;
   { Wait till threads are complete before main continues. Unless we  }
   { wait we run the risk of executing an exit which will terminate   }
   { the process and all threads before the threads have completed.   }
   pthread_join( thread1, nil);
   pthread_join( thread2, nil);
   halt(0);
end;


begin
  AssertErrorProc := AssertErrorHandler;
  try
    main;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.

线程同步：

线程库提供了三种同步机制：

mutexes - 互斥锁：阻止其他线程访问变量。这强制线程对变量或变量集的独占访问。
joins - 让一个线程等到其他线程完成（终止）。
condition 变量 - 数据类型pthread_cond_t

互斥锁：

互斥锁用于防止由于竞争条件导致的数据不一致。当两个或多个线程需要对同一内存区域执行操作时，通常会发生竞争条件，但计算结果取决于执行这些操作的顺序。互斥锁用于序列化共享资源。每当一个全局资源被多个线程访问时，该资源都应该有一个与之关联的互斥锁。可以应用互斥锁来保护一段内存（“关键区域”）免受其他线程的影响。互斥锁只能应用于单个进程中的线程，而不能像信号量那样在进程之间工作。

Without Mutex		With Mutex
int counter=0; /* Function C */ void functionC() { counter++ }		/* Note scope of variable and mutex are the same / pthread_mutex_t mutex1 = PTHREAD_MUTEX_INITIALIZER; int counter=0; / Function C */ void functionC() { pthread_mutex_lock( &mutex1 ); counter++ pthread_mutex_unlock( &mutex1 ); }
Possible execution sequence
Thread 1	Thread 2	Thread 1	Thread 2
counter = 0	counter = 0	counter = 0	counter = 0
counter = 1	counter = 1	counter = 1	Thread 2 locked out. Thread 1 has exclusive use of variable counter
			counter = 2