signal-handling

I would like to know exactly how the execution of asynchronous signal handlers works on Linux. First, I am unclear as to which thread executes the signal handler. Second, I would like to know the steps that are followed to make the thread execute the signal handler. On the first matter, I have read two different, seemingly conflicting, explanations: The Linux Kernel, by Andries Brouwer, §5.2 "Receiving signals" states : When a signal arrives, the process is interrupted, the current registers are saved, and the signal handler is invoked. When the signal handler returns, the interrupted activity

using select() with pipe - this is what I am doing and now I need to catch SIGTERM on that. how can I do it? Do I have to do it when select() returns error ( < 0 ) ? First, SIGTERM will kill your process if not caught, and select() will not return. Thus, you must install a signal handler for SIGTERM . Do that using sigaction() . However, the SIGTERM signal can arrive at a moment where your thread is not blocked at select() . It would be a rare condition, if your process is mostly sleeping on the file descriptors, but it can otherwise happen. This means that either your signal handler must do

Can I provide/pass any arguments to signal handler? /* Signal handling */ struct sigaction act; act.sa_handler = signal_handler; /* some more settings */ Now, handler looks like this: void signal_handler(int signo) { /* some code */ } If I want to do something special i.e. delete temp files, can I provide those files as an argument to this handler? Edit 0: Thanks for the answers. We generally avoid/discourage use of global variables. And in this case, If you have a huge program, things can go wrong at different places and you might need to do a lot of cleanup. Why was the API designed this way

On Linux/Unix there are signals. The Ctrl C one ( SIGINT ) is obvious to me. Now, in some other applications there are signals via Ctrl X ?! Is that even a signal or does it generate an escape sequence? Is there anything else I can use as something similar to Ctrl C ( Ctrl V , Ctrl X ...)? If anyone has a clue, im familiar with C more than bash, but answers in both languages are appreciated! jfg956 To get all the terminal control character assignments: stty -a Damon There is possibly a misunderstanding. Ctrl C does not generate a signal. It is perfectly possible to press Ctrl C anywhere, and

It is said that you should only call asynchronous-safe functions inside a signal handler. My question is, what constitutes asynchronous-safeness ? A function which is both reentrant and thread safe is asynchronous-safe I guess? Or No? Re-entrance and thread safety has a little or nothing to do with this. Side effects, state and interruption of those functions are facts that matter. asynchronous-safe function [GNU Pth] A function is asynchronous-safe, or asynchronous-signal safe, if it can be called safely and without side effects from within a signal handler context. That is, it must be able

In my multithreaded GUI application I have the following signal handling code. I want to improve this code so that it will be correct and threading safe but there are some things I don't fully understand in signal handling: is signal handled at the process or thread level (can I have thread-specific signal handlers) ? in which thread context is signal_handler function executed ? is it possible to send many SIGTERM signals in a short time ? does it make sense to use a mutex to prevent parallel execution of signal_handler ? void signal_handler(int sig) { switch (sig) { case SIGTERM: :

I am doing something like this: #include <signal.h> class myClass { public: void myFunction () { signal(SIGIO,myHandler); } void myHandler (int signum) { /** * Handling code */ } } I am working on Ubuntu, using gcc. But it won't compile. It is complaining with: error: the argument with type void (MyClass::)(int) doesn't agree with void (*) (int) Any clues? Or maybe it is just that I cannot use a signal inside classes? Are signals only allowed in C? The error message is an approximate translation because my compiler is not in English. The second parameter of signal should be a pointer to a