On Thu, Oct 12, 2017 at 12:24:19PM +0200, Petr Mladek wrote: > On Thu 2017-09-28 14:18:25, Peter Zijlstra wrote:
> > +#ifdef CONFIG_EARLY_PRINTK > > +struct console *early_console; > > + > > +static bool __read_mostly force_early_printk; > > + > > +static int __init force_early_printk_setup(char *str) > > +{ > > + force_early_printk = true; > > + return 0; > > +} > > +early_param("force_early_printk", force_early_printk_setup); > > The parameter is currently used only when CONFIG_PRINTK is enabled. > But CONFIG_EARLY_PRINTK is independent. What would be your preferred > behavior when CONFIG_PRINTK is disabled, please? Can we even have !PRINTK && EARLY_PRINTK? If so it seems to me continued usage of early_printk() is what makes most sense. > > @@ -1816,6 +1852,11 @@ asmlinkage int vprintk_emit(int facility > > return vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args); > > #endif > > > > +#ifdef CONFIG_EARLY_PRINTK > > + if (force_early_printk && early_console) > > + return early_vprintk(fmt, args); > > +#endif > > + > > if (level == LOGLEVEL_SCHED) { > > level = LOGLEVEL_DEFAULT; > > in_sched = true; > > @@ -1939,7 +1980,12 @@ asmlinkage __visible int printk(const ch > > int r; > > > > va_start(args, fmt); > > - r = vprintk_func(fmt, args); > > +#ifdef CONFIG_EARLY_PRINTK > > + if (force_early_printk && early_console) > > + r = vprintk_default(fmt, args); > > + else > > +#endif > > + r = vprintk_func(fmt, args); > > There is rather theoretical race. We skip vprintk_func() because > we believe that vprintk_default()/vprintk_emit() would choose > handle this by early_printk(). Do you mean if someone were to toggle force_early_printk at runtime? The reason I did it like this and not use that function pointer thing is that I didn't want to risk anybody hijacking my output ever.