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Re: Signals vs. Windows

by Anonymous Monk
on Oct 03, 2012 at 16:38 UTC ( #997096=note: print w/ replies, xml ) Need Help??


in reply to Signals vs. Windows

but the child thread doesn't appear to be acting immediately on the signals

By design, see safe signals in perlrun

Signals are not a good way to do IPC, see threads/forks, Re: controlling threads with Tk: while loop vs. signals


Comment on Re: Signals vs. Windows
Re^2: Signals vs. Windows
by DanEllison (Sexton) on Oct 03, 2012 at 17:33 UTC

    The pertinent text I missed was actually out of "threads" which was:

    Correspondingly, sending a signal to a thread does not disrupt the operation the thread is currently working on: The signal will be acted upon after the current operation has completed. For instance, if the thread is stuck on an I/O call, sending it a signal will not cause the I/O call to be interrupted such that the signal is acted up immediately.

    Nothing in the documentation suggests that signals are not the way to perform IPC, but simply threads don't react to signals as well as processes. Keep in mind, I don't want to simply suspend or terminate the thread, but interrupt it and send it off in another direction. So, the problem restated is, I guess, how do I interrupt a thread from an I/O operation?

      Nothing in the documentation suggests that signals are not the way to perform IPC

      Hmm, "unsafe" about says it all :)

      So, the problem restated is, I guess, how do I interrupt a thread from an I/O operation?

      stop using safe signals, use unsafe signals, use kill

      So, the problem restated is, I guess, how do I interrupt a thread from an I/O operation?

      1. dont use blocking I/O, use overlapped/async I/O

      2. use Native API, create an alertable *synchronous* file handle using NtCreateFile, post a timer APC to the blocked thread with SetWaitableTimer, the APC will call CancelIo from within the blocked thread, and the blocked I/O will unblock.
        I'm trying to avoid a Windows only solution.

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