kmalloc before kmem_cache_init

[Sukanto Ghosh]

Hi Dave,

If you look into start_kernel() the call to parse_early_param()
precedes mm_init().
parse_early_param() eventually calls do_early_param().
do_early_param() parses for "earlycon" in kernel commandline and then calls the
setup_function associated with earlycon.

I have in my commandline: earlycon=uart8250,mmio32,0x10000000,9600

Call flow starting from drivers/tty/serial/8250_early.c will lead to kmalloc

early_param("early_con", setup_early_serial8250_console)
   setup_early_serial8250_console()
       early_serial8250_setup()
           parse_options()
               ioremap_nocache()
                  ... arch-specific-ioremap
                        -- some form of arch specific __ioremap_caller
                            --- get_vm_area_caller()
                                  __get_vm_area_node
                                       kzalloc_node
                                           kmalloc_node
                                                kmalloc


Regards,
Sukanto


On Jan 29, 2012 12:28 PM, "Dave Hylands" <dhylands at gmail.com> wrote:
>
> Hi Sukanto
>
> On Sat, Jan 28, 2012 at 10:02 PM, Sukanto Ghosh
> <sukanto.cse.iitb at gmail.com> wrote:
> > I am kind of lost trying to figure out how can kmallocs work if they
> > are called before kmem_cache_init
> >
> > (e.g. such a case occurs when in start_kernel() we call
> > parse_early_param() (which in turn might call
> > early_serial8250_setup() if earlycon= is used in kernel command-line)
> > before mm_init()  (which later calls
> > kmem_cache_init() )
>
> I don't think that you're allowed to call kmalloc during early_setup.
> I don't see where early_serial8250_setup calls kmalloc.
>
> --
> Dave Hylands
> Shuswap, BC, Canada
> http://www.davehylands.com