On 5 April 2009 00:03, Christopher Faylor wrote: > On Sat, Apr 04, 2009 at 03:11:06PM -0700, Josh Stone wrote: >>I've discovered a deadlock in Cygwin which is pretty easy to >>reproduce.?? This seems to happen on all of the console windows I can >>find, except for running in a normal cmd.exe. All of these are >>affected though: xterm, rxvt, mintty, puttycyg+cthelper, and putty >>localhost -> cygwin sshd. >> >>To reproduce, run a command that produces a lot of output -- "man -P >>cat bash" works well. While it's thinking about formatting that, just >>start mashing the keyboard. When it starts writing out the manpage >>while you're still mashing keys, it will lock up (100% of the time for >>me). You can kill the (Schr??dinger???s) cat and life will be ok again. >> >>I did some debugging and found that the terminal was stuck on >>acquire_output_mutex in fhandler_pty_master::doecho. The cat process >>had fhandler_tty_slave::write in its backtrace, so it was holding the >>write mutex. The cat won't release the mutex until its data is read, >>but the terminal won't read until after it acquires the mutex and >>finishes doecho. >> >>This is on cygwin-1.7.0-45, but I can reproduce it on the 1.5 series >>too. And since it happens on so many terminals and even sshd, I don't >>think we can say it's the application's fault. I can't reproduce it >>with a command like "man bash | cat" though, probably because the >>difference in line buffering makes the race harder to hit. > > I can duplicate this. I'll look into fixing it ASAP.
On 12 April 2009 16:49, Christopher Faylor: > It took me a while to remember that this is a long standing bug. I > think it is possible to fix thanks to the changes in Cygwin 1.7 but it > isn't a trivial fix. I will still poke at this as I have time but > it may require a minor rewrite of the tty layer to get right. I just stumbled into this issue while investigating a hang reported against mintty 0.6-beta1. I found that a single keypress while catting a large file can trigger this, and like the OP I was able to reproduce it in all the pty-based terminals. Surprised this doesn't come up more frequently, but I guess hacking away at the keyboard while output is going on just isn't something one would normally do. Anyway, as long as there isn't a fix, is there anything I could do in mintty to work around this? Would it help to move the writing of keyboard input to the pty device into its own thread? Andy -- 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
