signal机制疑问

[blossom007cn]

最近在看内核代码时，发现LINUX是在进程调度时执行signal关联的handler函数，这会不会导致程序数据不一致，如

struct data
{
int a;
int b;
}g_data;

int fun()
{
g_data.a = 1;
g_data.b = 2;
}

int main()
{
signal( XXX, fun );
g_data.a = 0;
g_data.b = 0;

...
}

如果程序在执行g_data.b = 0;之前执行信号处理函数fun()，执行后g_data.a = 1; g_data.b = 2;而main函数中还认为g_data.a和g_data.b都是0
会不会造成数据不一致的情况出现呀？

[bluejing0]

这个。。真不清楚。。MARK下。

[bluejing0]

The occurrence of a signal may be synchronous or asynchronous to the process or thread, depending on the source of the signal and the underlying reason or cause. Synchronous signals occur as a direct result of the executing instruction stream, where an unrecoverable error (such as an illegal instruction or illegal address reference) requires an immediate termination of the process. Such signals are directed to the thread which caused the error with its execution stream. As an error of this type causes a trap into a kernel trap handler, synchronous signals are sometimes referred to as traps.

Asynchronous signals are external to (and in some cases, unrelated to) the current execution context. One obvious example would be the sending of a signal to a process from another process or thread via a kill(2), _lwp_kill(2) or sigsend(2) system call, or a thr_kill(3T), pthread_kill(3T) or sigqueue(3R) library invocation. Asynchronous signals are also aptly referred to as interrupts.

[Caballeroo]

要看信号处理函数是在那个线程中执行，如果在多线程的编程中，当fun函数在其他线程中执行的话，可能出现数据不一致，此时可采用同步的方法解决不一致问题。

要是在main中执行的话，则不会出现不一致。