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SubjectRe: [PATCH v3 4/5] console: Avoid positive return code from unregister_console()
On (20/01/28 11:22), Andy Shevchenko wrote:
> On Tue, Jan 28, 2020 at 01:43:32PM +0900, Sergey Senozhatsky wrote:
> > On (20/01/27 13:47), Andy Shevchenko wrote:
> > [..]
> > > res = _braille_unregister_console(console);
> > > - if (res)
> > > + if (res < 0)
> > > return res;
> > > + if (res > 0)
> > > + return 0;
> > >
> > > - res = 1;
> > > + res = -ENODEV;
> > > console_lock();
> > > if (console_drivers == console) {
> > > console_drivers=console->next;
> > > @@ -2838,6 +2840,9 @@ int unregister_console(struct console *console)
> > > if (!res && (console->flags & CON_EXTENDED))
> > > nr_ext_console_drivers--;
> > >
> > > + if (res && !(console->flags & CON_ENABLED))
> > > + res = 0;
> >
> > Console is not on the console_drivers list. Why does !ENABLED case
> > require extra handling?
>
> It's mirroring (to some extend) the register_console() abort conditions.

Could you please explain?

I see the "newcon->flags & CON_ENABLED" error out path. I'm guessing,
that the expectation is that this is how we filter out consoles which
were not matched (there is that "newcon->flags |= CON_ENABLED" several
lines earlier.) So this looks like the assumption is that consoles don't
have CON_ENABLED bit set prior to register_console(), as far as I understand.

Well, look at these
...
drivers/net/netconsole.c: .flags = CON_ENABLED,
drivers/tty/ehv_bytechan.c: .flags = CON_PRINTBUFFER | CON_ENABLED,
drivers/tty/serial/mux.c: .flags = CON_ENABLED | CON_PRINTBUFFER,
...

-ss

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