问题描述
我一直在试图了解如何POSIX线程和POSIX信号相互作用的复杂性。特别是我感兴趣的：
- 什么来控制线程的信号被传递到的最佳方式（假定它不是在首位是致命的）？
- 什么是告诉另一个线程（实际上可能是忙），该信号已经到来的最好方法？ （我已经知道这是一个坏主意，用从信号处理程序的pthread条件变量是。）
- 如何安全地处理传递一个信号发生了其他线程的信息？这是否需要在信号处理程序会发生什么？ （我做的不是一般的想杀死其他线程。我需要一个远微妙的方法）
有关为什么我要这样的参考，我研究如何将包来支持线程转换，或拆分它，至少做一些有用的部分支持线程。信号是特别感兴趣的那些部分中的一个。
As @zoli2k indicated, explicitly nominating a single thread to handle all signals you want handled (or a set of threads each with specific signal responsibilities), is a good technique.
I won't say "best," but here's my recommendation:
Block all desired signals in main, so that all threads are inherit that signal mask. Then, fashion the special signal receiving thread as a signal-driven event loop, dispatching newly arrived signals as some other intra-thread communication.
The simplest way to do this is to have the thread accept signals in a loop using sigwaitinfo or sigtimedwait. The thread then converts the signals somehow, perhaps broadcasting a pthread_cond_t, waking up other threads with more I/O, enqueuing a command in an application-specific thread-safe queue, whatever.
Alternatively, the special thread could allow signals to be delivered to a signal handler, unmasking for delivery only when ready to handle signals. (Signal delivery via handlers tends to be more error-prone than signal acceptance via the sigwait family, however.) In this case, the receiver's signal handler performs some simple and async-signal-safe action: setting sig_atomic_t flags, calling sigaddset(&signals_i_have_seen_recently, latest_sig), write() a byte to a non-blocking self-pipe, etc. Then, back in its masked main loop, the thread communicates receipt of the signal to other threads as above.
(UPDATED @caf rightly points out that sigwait approaches are superior.)
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