svn commit: r223307 - head/sys/vm

Warner Losh imp at
Wed Jun 22 02:30:08 UTC 2011

On Jun 21, 2011, at 5:27 PM, Alan Cox wrote:

> On 06/21/2011 16:09, Attilio Rao wrote:
>> 2011/6/21 Bruce Evans<brde at>:
>>> 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:
>>>>> 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)

The current crop of atomic*16 and atomic*8 functions have the restriction that the address must be 32-bit aligned (and it forces this by aligning to 32-bits silently and then operates on the low 8 or 16 bits in that word!)

I'm guessing that this is likely just wrong.  Comments?


More information about the svn-src-head mailing list