On Tue, 20 Mar 2007, Eric W. Biederman wrote: > Hugh Dickins <[EMAIL PROTECTED]> writes: > > > I get a hang at startup or shutdown: tiocsctty() holds tty_mutex, and > > now with Eric's tty-in-tiocsctty-when-we-steal-a-tty-hang-it-up.patch > > it can end up calling con_close(), which tries to take tty_mutex. > > So best revert that in hot-fixes, until Eric provides a better. > > Well I'm confused I know I tested this, and I even added a printk and > saw it trigger a couple of times. > > Hmm. Looking at the code it is clearly not safe to hold the tty_mutex > when calling tty_vhangup. I thought the other caller in tty_io.c was doing > that but on a second glance it is clearly not. And the hangup and close > methods do seem to take the tty_mutex. > > How this worked in my testing is beyond me..
I agree there's something weird about it, and wonder whether it's exposing some other, unrelated bug e.g. something uninitialized. What I omitted to mention is that I reliably had init hanging on startup with my KDB kernels (on i386 UP and i386 SMP and x86_64 SMP); but never saw my non-KDB kernels (nor my powerpc kernel) hanging there at startup - they would hang (in the same way) at shutdown (every time? I can't swear to that). But I can't imagine what KDB would have to do with it, other than shifting stuff around. Hugh - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
