linux内核中的信号机制--从用户层到内核层

linux内核中的信号机制--从用户层到内核层

Kernel version：2.6.14

CPU architecture：ARM920T

Author：ce123(http://blog.csdn.net/ce123)

如果进程要处理某一信号，那么要在进程中注册该信号。注册信号主要用来确定信号值及进程针对该信号值的动作之间的映射关系，即进程将要处理哪个进程和该信号被传递给进程时，将执行何种操作。主要有两个函数实现信号的注册：signal()和sigaction()。

signal()的函数原型如下：

intdo_sigaction(int sig, const struct k_sigaction *act, struct k_sigaction *oact){struct k_sigaction *k;if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))return -EINVAL;k = &currentt->sighand->action[sig-1];spin_lock_irq(&currentt->sighand->siglock);if (signal_pending(current)) {/* * If there might be a fatal signal pending on multiple * threads, make sure we take it before changing the action. */spin_unlock_irq(&currentt->sighand->siglock);return -ERESTARTNOINTR;}if (oact)//把原来的k_sigaction保存到oact结构中，这里是对整个数据结构进行复制*oact = *k;if (act) {/* * POSIX 3.3.1.3: *  "Setting a signal action to SIG_IGN for a signal that is *   pending shall cause the pending signal to be discarded, *   whether or not it is blocked." * *  "Setting a signal action to SIG_DFL for a signal that is *   pending and whose default action is to ignore the signal *   (for example, SIGCHLD), shall cause the pending signal to *   be discarded, whether or not it is blocked" */if (act->sa.sa_handler == SIG_IGN ||    (act->sa.sa_handler == SIG_DFL &&     sig_kernel_ignore(sig))) {/* * This is a fairly rare case, so we only take the * tasklist_lock once we're sure we'll need it. * Now we must do this little unlock and relock * dance to maintain the lock hierarchy. */struct task_struct *t = current;spin_unlock_irq(&t->sighand->siglock);read_lock(&tasklist_lock);spin_lock_irq(&t->sighand->siglock);*k = *act; //把新的k_sigaction结构复制到进程的sighand->action中sigdelsetmask(&k->sa.sa_mask,      sigmask(SIGKILL) | sigmask(SIGSTOP));rm_from_queue(sigmask(sig), &t->signal->shared_pending);do {rm_from_queue(sigmask(sig), &t->pending);recalc_sigpending_tsk(t);t = next_thread(t);} while (t != current);spin_unlock_irq(&current->sighand->siglock);read_unlock(&tasklist_lock);return 0;}*k = *act; //把新的k_sigaction结构复制到进程的sighand->action中sigdelsetmask(&k->sa.sa_mask,      sigmask(SIGKILL) | sigmask(SIGSTOP));}spin_unlock_irq(&currentt->sighand->siglock);return 0;}

2楼fire_work昨天 13:07

顶一个

1楼TuTuWanZi昨天 08:54

顶