svn commit: r223307 - head/sys/vm

[Alan Cox]

On 06/21/2011 16:09, Attilio Rao wrote:
> 2011/6/21 Bruce Evans<brde at optusnet.com.au>:
>> On Tue, 21 Jun 2011, Bjoern A. Zeeb wrote:
>>
>>> On Jun 19, 2011, at 7:13 PM, Alan Cox wrote:
>>>
>>> Hi Alan,
>>>
>>>> Author: alc
>>>> Date: Sun Jun 19 19:13:24 2011
>>>> New Revision: 223307
>>>> URL: http://svn.freebsd.org/changeset/base/223307
>>>>
>>>> Log:
>>>>   Precisely document the synchronization rules for the page's dirty field.
>>>>   (Saying that the lock on the object that the page belongs to must be
>>>> held
>>>>   only represents one aspect of the rules.)
>>>>
>>>>   Eliminate the use of the page queues lock for atomically performing
>>>> read-
>>>>   modify-write operations on the dirty field when the underlying
>>>> architecture
>>>>   supports atomic operations on char and short types.
>>>>
>>>>   Document the fact that 32KB pages aren't really supported.
>>> contrary to the tinderbox I'd like to point out that all mips kernels
>>> built by universe are broken with a SVN HEAD from earlier today.  Could you
>>> please check and see if you can fix it?  The errors I get are:
>>>
>>> vm_page.o: In function `vm_page_clear_dirty':
>>> /sys/vm/vm_page.c:(.text+0x18d0): undefined reference to `atomic_clear_8'
>>> /sys/vm/vm_page.c:(.text+0x18d0): relocation truncated to fit: R_MIPS_26
>>> against `atomic_clear_8'
>>> vm_page.o: In function `vm_page_set_validclean':
>>> /sys/vm/vm_page.c:(.text+0x38f0): undefined reference to `atomic_clear_8'
>>> /sys/vm/vm_page.c:(.text+0x38f0): relocation truncated to fit: R_MIPS_26
>>> against `atomic_clear_8'
>> Atomic types shorter than int cannot be used in MI code, since they might
>> not exist.  Apparently they don't exist on mips.  jake@ fixed all their
>> old uses for sparc4 in ~Y2K.
> I'm sure they do, they exist in support.S though and may not have the
> _8 form (they may just have the _char version). I may look at the code
> again to be sure.
>

It appears that while mips/include/atomic.h declares the existence of 
atomic_clear_8, mips/mips/support.S doesn't implement it.  In other 
words, only support for int's and short's is currently implemented, not 
char's:

# grep atomic_clear mips/mips/support.S
  * atomic_clear_32(u_int32_t *a, u_int32_t b)
LEAF(atomic_clear_32)
END(atomic_clear_32)
  * atomic_clear_16(u_int16_t *a, u_int16_t b)
LEAF(atomic_clear_16)
END(atomic_clear_16)