[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>
diff --git a/arch/parisc/kernel/pci-dma.c b/arch/parisc/kernel/pci-dma.c
index ae6213d..f94a02e 100644
--- a/arch/parisc/kernel/pci-dma.c
+++ b/arch/parisc/kernel/pci-dma.c
@@ -114,7 +114,7 @@
if (end > PGDIR_SIZE)
end = PGDIR_SIZE;
do {
- pte_t * pte = pte_alloc_kernel(&init_mm, pmd, vaddr);
+ pte_t * pte = pte_alloc_kernel(pmd, vaddr);
if (!pte)
return -ENOMEM;
if (map_pte_uncached(pte, orig_vaddr, end - vaddr, paddr_ptr))
diff --git a/arch/parisc/mm/ioremap.c b/arch/parisc/mm/ioremap.c
index f2df502..5c7a1b3 100644
--- a/arch/parisc/mm/ioremap.c
+++ b/arch/parisc/mm/ioremap.c
@@ -52,7 +52,7 @@
if (address >= end)
BUG();
do {
- pte_t * pte = pte_alloc_kernel(NULL, pmd, address);
+ pte_t * pte = pte_alloc_kernel(pmd, address);
if (!pte)
return -ENOMEM;
remap_area_pte(pte, address, end - address, address + phys_addr, flags);
@@ -75,10 +75,9 @@
flush_cache_all();
if (address >= end)
BUG();
- spin_lock(&init_mm.page_table_lock);
do {
pmd_t *pmd;
- pmd = pmd_alloc(dir, address);
+ pmd = pmd_alloc(&init_mm, dir, address);
error = -ENOMEM;
if (!pmd)
break;
@@ -89,7 +88,6 @@
address = (address + PGDIR_SIZE) & PGDIR_MASK;
dir++;
} while (address && (address < end));
- spin_unlock(&init_mm.page_table_lock);
flush_tlb_all();
return error;
}
