On Thu, Jun 15, 2017 at 06:52:21AM +0200, Greg Kroah-Hartman wrote:
> On Wed, Jun 14, 2017 at 11:15:38PM +0200, Arnd Bergmann wrote:
> > As reported by kernelci, some functions in the VT code use significant
> > amounts of kernel stack when local variables get inlined into the caller
> > multiple times:
> >
> > drivers/tty/vt/keyboard.c: In function 'kbd_keycode':
> > drivers/tty/vt/keyboard.c:1452:1: error: the frame size of 2240 bytes is
> > larger than 2048 bytes [-Werror=frame-larger-than=]
> >
> > Annotating those functions as noinline_if_stackbloat prevents the inlining
> > and reduces the overall stack usage in this driver.
> >
> > Signed-off-by: Arnd Bergmann <a...@arndb.de>
> > ---
> > drivers/tty/vt/keyboard.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
> > index f4166263bb3a..c0d111444a0e 100644
> > --- a/drivers/tty/vt/keyboard.c
> > +++ b/drivers/tty/vt/keyboard.c
> > @@ -301,13 +301,13 @@ int kbd_rate(struct kbd_repeat *rpt)
> > /*
> > * Helper Functions.
> > */
> > -static void put_queue(struct vc_data *vc, int ch)
> > +static noinline_if_stackbloat void put_queue(struct vc_data *vc, int ch)
> > {
> > tty_insert_flip_char(&vc->port, ch, 0);
> > tty_schedule_flip(&vc->port);
> > }
>
> Ugh, really? We have to start telling gcc not to be stupid here?
> That's not going to be easy, and will just entail us doing this all over
> the place, right?
>
> The code isn't asking to be inlined, so why is gcc allowing it to be
> done that way? Doesn't that imply gcc is the problem here?
Wait, you are now, in this patch, _asking_ for it to be inlined. How is
that solving anything?
greg k-h
