On Fri, Jan 27, 2012 at 12:51 PM, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> wrote: >> UML's console driver (arch/um/drivers/line.c) implements tty_operations. >> The crash happens because the tty subsystem calls the driver's close() >> function and later >> write_room() or chars_in_buffer(). >> >> write_room() and chars_in_buffer() fail badly because close() already >> cleaned up the driver's private data... > > You don't want to do that. That's what i thought. >> Greg, is UML's assumption wrong that after closing the tty no call to >> write_room() or chars_in_buffer() can happen? >> I have no idea why systemd is able to trigger this, UML's console >> driver is old and has always worked quite well. > > It's always been untrue but it's even more untrue nowdays. The tty layer > objects are refcounted, and the code has had significant rewrites. line.c > hidden away in uml hasn't been updated. > > I added a comment about 3 years ago pointing out another older change > that was needed and that wasn't acted on either.. > > Take a look at how all the other tty drivers use tty_port, how the ioctls > have been supposed to work for the past few years and the callback > changes, then use them. Can you recommend a well-written driver? -- Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
