Hello, Arnd Bergmann, on mer. 14 juin 2017 23:15:38 +0200, 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.
> --- 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); > } I'm surprised that this be able generate so much stack use: the tty_insert_flip_char inline only uses a pointer and an int. And I'm surprised that multiple inlines can accumulate stack usage. I however agree that it's a bad idea to inline it in functions where it's called so many times (and we're talking about the keyboard anyway). > -static void puts_queue(struct vc_data *vc, char *cp) > +static noinline_if_stackbloat void puts_queue(struct vc_data *vc, char *cp) I don't see why, it's only called once in the callers. k_fn, however, is called several times in k_pad, so that could be why, but then it's rather be the inlining of k_fn which is a bad idea. > -static void fn_send_intr(struct vc_data *vc) > +static noinline_if_stackbloat void fn_send_intr(struct vc_data *vc) This one is only referenced, not called, I don't see how that could pose problem. Samuel