* Re: const __initdata?
2007-11-29 7:28 const __initdata? Robert P. J. Day
@ 2007-11-29 16:53 ` Randy Dunlap
2007-11-30 17:08 ` Robert P. J. Day
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Randy Dunlap @ 2007-11-29 16:53 UTC (permalink / raw)
To: kernel-janitors
On Thu, 29 Nov 2007 02:28:43 -0500 (EST) Robert P. J. Day wrote:
>
> from include/linux/init.h:
>
> * For initialized data:
> * You should insert __initdata between the variable name and equal
> * sign followed by value, e.g.:
> *
> * static int init_variable __initdata = 0;
> * static char linux_logo[] __initdata = { 0x32, 0x36, ... };
> *
> * Don't forget to initialize data not at file scope, i.e. within a function,
> * as gcc otherwise puts the data into the bss section and not into the init
> * section.
> *
> * Also note, that this data cannot be "const".
>
> you mean, like this in drivers/hwmon/w83627ehf.c:
>
> /* w83627ehf_find() looks for a '627 in the Super-I/O config space */
> static int __init w83627ehf_find(int sioaddr, unsigned short *addr,
> struct w83627ehf_sio_data *sio_data)
> {
> static const char __initdata sio_name_W83627EHF[] = "W83627EHF";
> static const char __initdata sio_name_W83627EHG[] = "W83627EHG";
> static const char __initdata sio_name_W83627DHG[] = "W83627DHG";
> ...
>
> or am i misreading that?
We have certainly seen problems with const __initdata being put
into a read-only section instead of the .init.data section, but
with gcc 4.2.1, I see these 3 __initdata items being placed into
the .init.data section no matter where I put "const" on the data
declaration line. Maybe the problem has been fixed (relatively
recently).
---
~Randy
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: const __initdata?
2007-11-29 7:28 const __initdata? Robert P. J. Day
2007-11-29 16:53 ` Randy Dunlap
@ 2007-11-30 17:08 ` Robert P. J. Day
2007-11-30 17:22 ` Randy Dunlap
2007-12-01 0:20 ` Adrian Bunk
3 siblings, 0 replies; 5+ messages in thread
From: Robert P. J. Day @ 2007-11-30 17:08 UTC (permalink / raw)
To: kernel-janitors
On Thu, 29 Nov 2007, Randy Dunlap wrote:
> On Thu, 29 Nov 2007 02:28:43 -0500 (EST) Robert P. J. Day wrote:
>
> >
> > from include/linux/init.h:
> >
> > * For initialized data:
> > * You should insert __initdata between the variable name and equal
> > * sign followed by value, e.g.:
> > *
> > * static int init_variable __initdata = 0;
> > * static char linux_logo[] __initdata = { 0x32, 0x36, ... };
> > *
> > * Don't forget to initialize data not at file scope, i.e. within a function,
> > * as gcc otherwise puts the data into the bss section and not into the init
> > * section.
> > *
> > * Also note, that this data cannot be "const".
> >
> > you mean, like this in drivers/hwmon/w83627ehf.c:
> >
> > /* w83627ehf_find() looks for a '627 in the Super-I/O config space */
> > static int __init w83627ehf_find(int sioaddr, unsigned short *addr,
> > struct w83627ehf_sio_data *sio_data)
> > {
> > static const char __initdata sio_name_W83627EHF[] = "W83627EHF";
> > static const char __initdata sio_name_W83627EHG[] = "W83627EHG";
> > static const char __initdata sio_name_W83627DHG[] = "W83627DHG";
> > ...
> >
> > or am i misreading that?
>
> We have certainly seen problems with const __initdata being put
> into a read-only section instead of the .init.data section, but
> with gcc 4.2.1, I see these 3 __initdata items being placed into
> the .init.data section no matter where I put "const" on the data
> declaration line. Maybe the problem has been fixed (relatively
> recently).
hmmmm ... not sure if i replied to this already but, in any event,
*something* should be updated, no? at the very least, that comment.
rday
====================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA
http://crashcourse.ca
====================================
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: const __initdata?
2007-11-29 7:28 const __initdata? Robert P. J. Day
2007-11-29 16:53 ` Randy Dunlap
2007-11-30 17:08 ` Robert P. J. Day
@ 2007-11-30 17:22 ` Randy Dunlap
2007-12-01 0:20 ` Adrian Bunk
3 siblings, 0 replies; 5+ messages in thread
From: Randy Dunlap @ 2007-11-30 17:22 UTC (permalink / raw)
To: kernel-janitors
On Fri, 30 Nov 2007 12:08:46 -0500 (EST) Robert P. J. Day wrote:
> On Thu, 29 Nov 2007, Randy Dunlap wrote:
>
> > On Thu, 29 Nov 2007 02:28:43 -0500 (EST) Robert P. J. Day wrote:
> >
> > >
> > > from include/linux/init.h:
> > >
> > > * For initialized data:
> > > * You should insert __initdata between the variable name and equal
> > > * sign followed by value, e.g.:
> > > *
> > > * static int init_variable __initdata = 0;
> > > * static char linux_logo[] __initdata = { 0x32, 0x36, ... };
> > > *
> > > * Don't forget to initialize data not at file scope, i.e. within a function,
> > > * as gcc otherwise puts the data into the bss section and not into the init
> > > * section.
> > > *
> > > * Also note, that this data cannot be "const".
> > >
> > > you mean, like this in drivers/hwmon/w83627ehf.c:
> > >
> > > /* w83627ehf_find() looks for a '627 in the Super-I/O config space */
> > > static int __init w83627ehf_find(int sioaddr, unsigned short *addr,
> > > struct w83627ehf_sio_data *sio_data)
> > > {
> > > static const char __initdata sio_name_W83627EHF[] = "W83627EHF";
> > > static const char __initdata sio_name_W83627EHG[] = "W83627EHG";
> > > static const char __initdata sio_name_W83627DHG[] = "W83627DHG";
> > > ...
> > >
> > > or am i misreading that?
> >
> > We have certainly seen problems with const __initdata being put
> > into a read-only section instead of the .init.data section, but
> > with gcc 4.2.1, I see these 3 __initdata items being placed into
> > the .init.data section no matter where I put "const" on the data
> > declaration line. Maybe the problem has been fixed (relatively
> > recently).
>
> hmmmm ... not sure if i replied to this already but, in any event,
> *something* should be updated, no? at the very least, that comment.
Sure, when we are sure that all supported versions of gcc do the
right thing.
---
~Randy
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: const __initdata?
2007-11-29 7:28 const __initdata? Robert P. J. Day
` (2 preceding siblings ...)
2007-11-30 17:22 ` Randy Dunlap
@ 2007-12-01 0:20 ` Adrian Bunk
3 siblings, 0 replies; 5+ messages in thread
From: Adrian Bunk @ 2007-12-01 0:20 UTC (permalink / raw)
To: kernel-janitors
On Thu, Nov 29, 2007 at 08:53:03AM -0800, Randy Dunlap wrote:
> On Thu, 29 Nov 2007 02:28:43 -0500 (EST) Robert P. J. Day wrote:
>
> >
> > from include/linux/init.h:
> >
> > * For initialized data:
> > * You should insert __initdata between the variable name and equal
> > * sign followed by value, e.g.:
> > *
> > * static int init_variable __initdata = 0;
> > * static char linux_logo[] __initdata = { 0x32, 0x36, ... };
> > *
> > * Don't forget to initialize data not at file scope, i.e. within a function,
> > * as gcc otherwise puts the data into the bss section and not into the init
> > * section.
> > *
> > * Also note, that this data cannot be "const".
> >
> > you mean, like this in drivers/hwmon/w83627ehf.c:
> >
> > /* w83627ehf_find() looks for a '627 in the Super-I/O config space */
> > static int __init w83627ehf_find(int sioaddr, unsigned short *addr,
> > struct w83627ehf_sio_data *sio_data)
> > {
> > static const char __initdata sio_name_W83627EHF[] = "W83627EHF";
> > static const char __initdata sio_name_W83627EHG[] = "W83627EHG";
> > static const char __initdata sio_name_W83627DHG[] = "W83627DHG";
> > ...
> >
> > or am i misreading that?
>
> We have certainly seen problems with const __initdata being put
> into a read-only section instead of the .init.data section, but
> with gcc 4.2.1, I see these 3 __initdata items being placed into
> the .init.data section no matter where I put "const" on the data
> declaration line. Maybe the problem has been fixed (relatively
> recently).
No, the difference is most likely related to the fact that these
variables are inside a function, and "static" on variables inside a
function does something different from "static" on variables outside
any function...
> ~Randy
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
^ permalink raw reply [flat|nested] 5+ messages in thread