On Wed, May 08, 2013 at 02:47:34AM +0800, Wang YanQing wrote: > I meet emacs hang in start if I do the operation below: > 1: echo 3 > /proc/sys/vm/drop_caches > 2: emacs BigFile > 3: Press CTRL-S follow 2 immediately > > Then emacs hang on, CTRL-Q can't resume, the terminal > hang on, you can do nothing with this terminal except > close it. > > The reason is before emacs takeover control the tty, > we use CTRL-S to XOFF it. Then when emacs takeover the > control, it may don't use the flow-control, so emacs hang. > But after search the emacs's startup codes, I find they use TCXONC > to workaround this situation: > > /* This code added to insure that, if flow-control is not to be used, > we have an unlocked terminal at the start. */ > if (!tty_out->flow_control) ioctl (fileno (tty_out->input), TCXONC, 1); > ioctl (fileno (tty_out->input), TCXONC, 1); > > But this workaround never work due the kernel's current code. > This patch fix it. > > Below is the ChangeLog introduce the tty->flow_stopped flag: > > Thu Nov 21 10:05:22 1996 Theodre Ts'o <ty...@localhost.mit.edu> > > * tty_ioctl.c (tty_wait_until_sent): Always check the driver > wait_until_ready routine, even if there are no characters > in the xmit buffer. (There may be charactes in the device > FIFO.) > (n_tty_ioctl): Add new flag tty->flow_stopped which > indicates whether the tty is stopped due to a request by > the TCXONC ioctl (used by tcflow). If so, don't let an > incoming XOFF character restart the tty. The tty can only > be restarted by another TCXONC request. > > So I think this patch make TCXONC can restart tty which stopped by > STOP_CHAR don't break the original meaning. > > This patch will fix some strange tty relation hang problem, > I believe I meet it with vim in ssh, and also see below bug report: > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=465823
So this has been a problem since 1996? Or is it newly introduced due to some changes in this area in a newer kernel? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
