On Oct 19 12:26, Andy Koppe wrote: > On 13 October 2012 16:38, Christopher Faylor wrote: > > On Sat, Oct 06, 2012 at 05:48:44AM +0100, Andy Koppe wrote: > >>The issue isn't specific to any of mintty, cat or Ctrl+S; for example, > >>I've managed to reproduce it with xterm, hexdump, and just hitting > >>Enter. Any other key that sends a keycode will do too. Ctrl+Q isn't > >>needed for the freeze to happen. In xterm I've even managed it with > >>find, by hitting Enter repeatedly. > >> > >>If you then look at the situation in ps, you'll see something like this: > >> > >>O 3396 1 3396 1472 ? 1004 05:11:07 /usr/bin/xterm > >>O 3528 4460 3528 528 pty3 1004 05:25:01 /usr/bin/cat > >> > >>The interesting bit there is the two 'O's in the first column, which > >>means both processes are waiting to output. I think what's happening > >>is that both of them are trying to write to their side of the > >>underlying pty device, but that those writes are blocking until data > >>is read from the other side of the pty. Result: deadlock. If the cat > >>is killed (possibly with -9, because of its nine lives), the terminal > >>happily continues on its way. > >> > >>So why doesn't this happen more often? Not sure. The speed difference > >>between the client process output and the terminal seems to play a > >>role here. I can only guess that the issue occurs if a buffer in the > >>pty's slave->master pipe overflows and something is written to the > >>master->slave pipe at the same time (which is unbuffered?). > >> > >>I don't understand the pty implementation enough to verify any of > >>that, so cgf would need to comment further. Note besides: I couldn't > >>make this deadlock happen on Ubuntu. > > > > This should work in the latest snapshot. I added a polling kludge for > > 1.7.17 while I mull over the best way to handle this. > > Using snapshot 2012-10-16, I confirmed that Ctrl+S during a long cat > no longer freezes the terminal and that Ctrl+Q > > However, I still see the deadlock described above when hitting any > other key that sends something, e.g. just Enter.
Too bad. Are you sure? I tried really hard to get a deadlock and could not reproduce it anymore under W7. My Enter key is still on paracetamol. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Project Co-Leader cygwin AT cygwin DOT com Red Hat -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
