On 6/21/11 7:27 PM, Warner Losh wrote:
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<b...@optusnet.com.au
<mailto:b...@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)
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?
I'm guessing it depends on whether the hardware supports atomic
sub-wordline accesses.
(mind you it's getting really hard to work out what a wordline means
these days)
Warner
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