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sig_atomic_t在Linux信号屏蔽函数中的应用

async-safe signals linux c

2

Amir Zadeh · 技术社区 · 15 年前

我最近在研究一本叫做高级Linux编程的书,我遇到了一个问题:书上说你应该使用 sig_atomic_t 变量类型,以确保如果在信号处理程序函数中设置全局标志或计数器,则在算术运算(即 ++ )把它们存到登记簿里。

我的问题是:如果我们不使用 西格玛 只是使用另一种类型和上下文切换发生了吗?我的意思是程序稍后会返回并保存它。有人能给我一个让我们的代码不稳定或有缺陷的场景吗?

3 回复 | 直到 13 年前

1

2

Bart van Ingen Schenau 15 年前

main context:
  read i (=10) from memory to register R1
  add 5 to R1
    <interrupt. Switch to interrupt context>
    read i (=10) from memory to register R1
    add 10 to R1
    write R1 to i in memory (i = 20)
    <end of interrupt. Back to main context>
  write R1 to i in memory (i = 15)

main context:
  read first half of i (=10) from memory to register R1
  read second half of i (=10) from memory to register R2
  add 5 to R1/R2 pair
  write R1 to first half of i in memory
    <interrupt. Switch to interrupt context>
    read first half of i (= ??) from memory to register R1
    read second half of i (= ??) from memory to register R2
    add 10 to R1/R2 pair
    write R1 to first half of i in memory
    write R2 to second half of i in memory
    <end of interrupt. Back to main context>
  write R2 to second half of i in memory

sig_atomic_t

2

Peter G. 15 年前

int64_t a = 2^32-1;

void some_signal_handler()
{
   ++a;
}

void f()
{
  if( a == 0 )
    printf("a is zero");
}

3

1

R.. GitHub STOP HELPING ICE 15 年前