signals

I had some Python code that needed to be able to handle SIGINT. For this purpose I used something like this: def mymethod(*params): obj = MyObj(params) try: obj.do_some_long_stuff() except KeyboardInterrupt: obj.cleanup() Awesome and really straightforward. Yay, Python is great! However, I now need to also handle other signals, namely SIGTSTP and SIGQUIT. What I'm trying to do is something similar. Here's some pseudocode demonstrating what I'm trying to do with SIGTSTP (I hope it's clear enough): def mymethod(*params): obj = MyObj(params) try: obj.do_some_long_stuff() catch SIGINT: obj.cleanup

I have the following simple python script: import os, subprocess,signal,sys import time out = None sub = None def handler(signum,frame): print("script.py: cached sig: %i " % signum) sys.stdout.flush() if sub is not None and not sub.poll(): print("render.py: sent signal to prman pid: ", sub.pid) sys.stdout.flush() sub.send_signal(signal.SIGTERM) sub.wait() # deadlocks....???? #os.kill(sub.pid, signal.SIGTERM) # this works #os.waitpid(sub.pid,0) # this works for i in range(0,5): time.sleep(0.1) print("script.py: cleanup %i" % i) sys.stdout.flush() sys.exit(128+signum) signal.signal(signal.SIGINT

Process A forks say 4 child processes. exec() is used to replace the code of the children. The children initialize and have to wait for the parent to create all of the 4 of them. Then the parent sends a sigusr1 to each child process in order for them to start processing. The parent waits for all the children to complete procesing. When a child finishes its work it sends a sigusr2 to the parent. When the parent receives all the sigusr2 signals it continues with execution, merging the calculations of the child processes. This is a university exercise, and it was stated in class that process A

It is not Ctrl+Z. That is for SIGTSTP . Also, stty -a shows ^S as the combination but it doesn't seem to work. There is no key combination to send SIGSTOP. Control-S tells the terminal driver to suspend output, but does not send a signal to the process. Control-Q resumes output. 来源： https://stackoverflow.com/questions/8513923/what-is-the-key-combination-to-send-a-sigstop-signal-on-terminal

When we write a signal handler that may change the errno, should we save errno at the beginning of the signal handler and restore the errno at the end of it? Just like below: void signal_handler(int signo){ int temp_errno = errno; *** //code here may change the errno errno = temp_errno; } The glibc documentation says : signal handlers that call functions that may set errno or modify the floating-point environment must save their original values, and restore them before returning. So go ahead and do that. To those reading this who can't rewrite their signal handlers, there may be a workaround.

This works as expected since Perl 5.10.1: SIGINTs are trapped. #!/usr/bin/perl use strict; use warnings; $SIG{INT} = sub { die "Caught a sigint $!" }; sleep(20); But here SIGINTs are not trapped. #!/usr/bin/perl use strict; use warnings; $SIG{INT} = sub { die "Caught a sigint $!" }; END { sleep(20); } This can be fixed by setting the handler again in the END block, like so: END { $SIG{INT} = sub { die "Caught a sigint $!" }; sleep(20); } But that won't work if you have more than one block: handlers must be set again for every block. I've tried to figure this out and I can't find an explanation