Messages in this thread | | | Date | Fri, 2 Feb 2007 01:54:23 +0800 | From | "Aubrey Li" <> | Subject | Re: [BUG]: 2.6.19.2: Weird serial core issue |
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On 2/1/07, Russell King <rmk+lkml@arm.linux.org.uk> wrote: > On Thu, Feb 01, 2007 at 06:09:24PM +0800, Aubrey Li wrote: > > On 2/1/07, Russell King <rmk+lkml@arm.linux.org.uk> wrote: > > >On Thu, Feb 01, 2007 at 10:33:40AM +0800, Aubrey Li wrote: > > >> On 2/1/07, Alan <alan@lxorguk.ukuu.org.uk> wrote: > > >> >What code is running on that console at the time. Most likely that user > > >> >code is also saving/restoring terminal settings so overwrite yours > > >> > > > >> > > >> I implemented the serial driver by myself, :). See the attachment. > > >> I didn't save/restore terminal setting in the my_set_termios(). > > >> > > >> I trace this back till tty_tioctl(..., unsigned long arg), everytime I > > >> type "ENTER" key, > > >> the argument "arg" passed into tty_ioctl() is the address of a termios > > >> structure, which include wrong c_cflag. > > > > > >If userspace is issuing an ioctl to re-enable crtscts, and the kernel > > >is obliging, how can this be a kernel bug? > > > > But the fact is not. > > 1) kernel boot up and enable crtscts by default > > 2) issue an ioctl to disable crtscts. > > 3) not do anything but type "ENTER", kernel re-enable crtscts. > > > > That's wrong. Terminal setting seems not be recorded by the serial core. > > serial core does not and should not "record" the terminal settings. > That's the job of the tty layer.
OK, if tty layer save the new terminal settings to an old one properly, How could this happen?
> > > Is it clear? > > No. You haven't analysed the call path causing tty_ioctl() to be > invoked, so you have no basis to point the finger *anywhere* at the > moment. > > Find out from where tty_ioctl() is called - maybe by adding a call > to dump_stack(). I think you'll find it is coming from userspace. >
If I recall correctly, the call path is as follows:
sys_ioctl->vfs_ioctl->do_ioctl->tty_ioctl->n_tty_ioctl->set_termios,
In set_termios, tmp_termios will be pointed to the argument "arg", which includes the wrong c_cflag.
Yes, from the back trace stack, it appears to come from userspace. But I didn't startup any application. If there should be one, I think it's shell.
But why shell remembers the initial terminal settings correctly, other than last inital terminal settings? It must be passed from kernel space, from tty layer, right?
I can't believe it's caused by the userspace, I'll go further to find the root cause.
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