On Nov 3, 2010, at 10:23 PM, exar...@twistedmatrix.com wrote: > On 01:45 am, ndbeck...@gmail.com wrote: >> On modern linux, signalfd can be used to convert sigchld into an event >> on a >> file descriptor. Looks like just what is wanted for processProtocol. > > It does, indeed. I'm not sure it's really worth bothering though. Here > are the drawbacks of using signalfd(): > > - It only works on Linux > - It works differently on older versions of Linux than on newer > versions > - You still can't have another SIGCHLD handler installed that will > called (so it's not any more cooperative with other library code)
Another drawback is that spawned subprocesses will start with SIGCHLD blocked (because the sigprocmask is inherited across fork/exec, like SIG_IGN is, but unlike signal handlers), unless twisted adds a pthread_atfork handler (which there is no way to do from Python, so that'd have to be more custom C code). And even with that, system() would still remain broken, because system() inexplicably doesn't call atfork handlers on linux/glibc (notabug according to glibc maintainers). Of course, the Twisted process API could unblock SIGCHLD itself before calling exec, but this would leave spawning a process with any other API (subprocess/etc) broken. Many programs will not react well to starting with SIGCHLD blocked. Since Twisted just recently managed to make spawning subprocesses with non-Twisted APIs actually work right, it'd be quite poor to break that again. James _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
