[PATCH] mm: init_mm without ptlock
authorHugh Dickins <hugh@veritas.com>
Sun, 30 Oct 2005 01:16:21 +0000 (18:16 -0700)
committerLinus Torvalds <torvalds@g5.osdl.org>
Sun, 30 Oct 2005 04:40:40 +0000 (21:40 -0700)
commit872fec16d9a0ed3b75b8893aa217e49cca575ee5
tree1dfc8b9f2754bdfff645188e497865c00201d535
parent46dea3d092d23a58b42499cc8a21de0fad079f4a
[PATCH] mm: init_mm without ptlock

First step in pushing down the page_table_lock.  init_mm.page_table_lock has
been used throughout the architectures (usually for ioremap): not to serialize
kernel address space allocation (that's usually vmlist_lock), but because
pud_alloc,pmd_alloc,pte_alloc_kernel expect caller holds it.

Reverse that: don't lock or unlock init_mm.page_table_lock in any of the
architectures; instead rely on pud_alloc,pmd_alloc,pte_alloc_kernel to take
and drop it when allocating a new one, to check lest a racing task already
did.  Similarly no page_table_lock in vmalloc's map_vm_area.

Some temporary ugliness in __pud_alloc and __pmd_alloc: since they also handle
user mms, which are converted only by a later patch, for now they have to lock
differently according to whether or not it's init_mm.

If sources get muddled, there's a danger that an arch source taking
init_mm.page_table_lock will be mixed with common source also taking it (or
neither take it).  So break the rules and make another change, which should
break the build for such a mismatch: remove the redundant mm arg from
pte_alloc_kernel (ppc64 scrapped its distinct ioremap_mm in 2.6.13).

Exceptions: arm26 used pte_alloc_kernel on user mm, now pte_alloc_map; ia64
used pte_alloc_map on init_mm, now pte_alloc_kernel; parisc had bad args to
pmd_alloc and pte_alloc_kernel in unused USE_HPPA_IOREMAP code; ppc64
map_io_page forgot to unlock on failure; ppc mmu_mapin_ram and ppc64 im_free
took page_table_lock for no good reason.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
26 files changed:
arch/alpha/mm/remap.c
arch/arm/mm/consistent.c
arch/arm/mm/ioremap.c
arch/arm26/mm/memc.c
arch/cris/mm/ioremap.c
arch/frv/mm/dma-alloc.c
arch/i386/mm/ioremap.c
arch/ia64/mm/init.c
arch/m32r/mm/ioremap.c
arch/m68k/mm/kmap.c
arch/m68k/sun3x/dvma.c
arch/mips/mm/ioremap.c
arch/parisc/kernel/pci-dma.c
arch/parisc/mm/ioremap.c
arch/ppc/kernel/dma-mapping.c
arch/ppc/mm/4xx_mmu.c
arch/ppc/mm/pgtable.c
arch/ppc64/mm/imalloc.c
arch/ppc64/mm/init.c
arch/s390/mm/ioremap.c
arch/sh/mm/ioremap.c
arch/sh64/mm/ioremap.c
arch/x86_64/mm/ioremap.c
include/linux/mm.h
mm/memory.c
mm/vmalloc.c