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Subject[PATCH 12/21] mm: arches skip ptlock
Convert those few architectures which are calling pud_alloc, pmd_alloc,
pte_alloc_map on a user mm, not to take the page_table_lock first, nor
drop it after. Each of these can continue to use pte_alloc_map, no need
to change over to pte_alloc_map_lock, they're neither racy nor swappable.

In the sparc64 io_remap_pfn_range, flush_tlb_range then falls outside of
the page_table_lock: that's okay, on sparc64 it's like flush_tlb_mm, and
that has always been called from outside of page_table_lock in dup_mmap.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---
arch/arm/mm/mm-armv.c | 14 --------------
arch/arm26/mm/memc.c | 15 ---------------
arch/sparc/mm/generic.c | 4 +---
arch/sparc64/mm/generic.c | 6 ++----
arch/um/kernel/skas/mmu.c | 3 ---
5 files changed, 3 insertions(+), 39 deletions(-)
--- mm11/arch/arm/mm/mm-armv.c 2005-09-21 12:16:12.000000000 +0100
+++ mm12/arch/arm/mm/mm-armv.c 2005-10-11 23:56:41.000000000 +0100
@@ -180,11 +180,6 @@ pgd_t *get_pgd_slow(struct mm_struct *mm

if (!vectors_high()) {
/*
- * This lock is here just to satisfy pmd_alloc and pte_lock
- */
- spin_lock(&mm->page_table_lock);
-
- /*
* On ARM, first page must always be allocated since it
* contains the machine vectors.
*/
@@ -201,23 +196,14 @@ pgd_t *get_pgd_slow(struct mm_struct *mm
set_pte(new_pte, *init_pte);
pte_unmap_nested(init_pte);
pte_unmap(new_pte);
-
- spin_unlock(&mm->page_table_lock);
}

return new_pgd;

no_pte:
- spin_unlock(&mm->page_table_lock);
pmd_free(new_pmd);
- free_pages((unsigned long)new_pgd, 2);
- return NULL;
-
no_pmd:
- spin_unlock(&mm->page_table_lock);
free_pages((unsigned long)new_pgd, 2);
- return NULL;
-
no_pgd:
return NULL;
}
--- mm11/arch/arm26/mm/memc.c 2005-10-11 23:55:53.000000000 +0100
+++ mm12/arch/arm26/mm/memc.c 2005-10-11 23:56:41.000000000 +0100
@@ -79,12 +79,6 @@ pgd_t *get_pgd_slow(struct mm_struct *mm
goto no_pgd;

/*
- * This lock is here just to satisfy pmd_alloc and pte_lock
- * FIXME: I bet we could avoid taking it pretty much altogether
- */
- spin_lock(&mm->page_table_lock);
-
- /*
* On ARM, first page must always be allocated since it contains
* the machine vectors.
*/
@@ -113,23 +107,14 @@ pgd_t *get_pgd_slow(struct mm_struct *mm
memcpy(new_pgd + FIRST_KERNEL_PGD_NR, init_pgd + FIRST_KERNEL_PGD_NR,
(PTRS_PER_PGD - FIRST_KERNEL_PGD_NR) * sizeof(pgd_t));

- spin_unlock(&mm->page_table_lock);
-
/* update MEMC tables */
cpu_memc_update_all(new_pgd);
return new_pgd;

no_pte:
- spin_unlock(&mm->page_table_lock);
pmd_free(new_pmd);
- free_pgd_slow(new_pgd);
- return NULL;
-
no_pmd:
- spin_unlock(&mm->page_table_lock);
free_pgd_slow(new_pgd);
- return NULL;
-
no_pgd:
return NULL;
}
--- mm11/arch/sparc/mm/generic.c 2005-09-21 12:16:20.000000000 +0100
+++ mm12/arch/sparc/mm/generic.c 2005-10-11 23:56:41.000000000 +0100
@@ -78,9 +78,8 @@ int io_remap_pfn_range(struct vm_area_st
dir = pgd_offset(mm, from);
flush_cache_range(vma, beg, end);

- spin_lock(&mm->page_table_lock);
while (from < end) {
- pmd_t *pmd = pmd_alloc(current->mm, dir, from);
+ pmd_t *pmd = pmd_alloc(mm, dir, from);
error = -ENOMEM;
if (!pmd)
break;
@@ -90,7 +89,6 @@ int io_remap_pfn_range(struct vm_area_st
from = (from + PGDIR_SIZE) & PGDIR_MASK;
dir++;
}
- spin_unlock(&mm->page_table_lock);

flush_tlb_range(vma, beg, end);
return error;
--- mm11/arch/sparc64/mm/generic.c 2005-09-21 12:16:20.000000000 +0100
+++ mm12/arch/sparc64/mm/generic.c 2005-10-11 23:56:41.000000000 +0100
@@ -132,9 +132,8 @@ int io_remap_pfn_range(struct vm_area_st
dir = pgd_offset(mm, from);
flush_cache_range(vma, beg, end);

- spin_lock(&mm->page_table_lock);
while (from < end) {
- pud_t *pud = pud_alloc(current->mm, dir, from);
+ pud_t *pud = pud_alloc(mm, dir, from);
error = -ENOMEM;
if (!pud)
break;
@@ -144,8 +143,7 @@ int io_remap_pfn_range(struct vm_area_st
from = (from + PGDIR_SIZE) & PGDIR_MASK;
dir++;
}
- flush_tlb_range(vma, beg, end);
- spin_unlock(&mm->page_table_lock);

+ flush_tlb_range(vma, beg, end);
return error;
}
--- mm11/arch/um/kernel/skas/mmu.c 2005-09-21 12:16:21.000000000 +0100
+++ mm12/arch/um/kernel/skas/mmu.c 2005-10-11 23:56:41.000000000 +0100
@@ -28,7 +28,6 @@ static int init_stub_pte(struct mm_struc
pmd_t *pmd;
pte_t *pte;

- spin_lock(&mm->page_table_lock);
pgd = pgd_offset(mm, proc);
pud = pud_alloc(mm, pgd, proc);
if (!pud)
@@ -63,7 +62,6 @@ static int init_stub_pte(struct mm_struc
*pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
*pte = pte_mkexec(*pte);
*pte = pte_wrprotect(*pte);
- spin_unlock(&mm->page_table_lock);
return(0);

out_pmd:
@@ -71,7 +69,6 @@ static int init_stub_pte(struct mm_struc
out_pte:
pmd_free(pmd);
out:
- spin_unlock(&mm->page_table_lock);
return(-ENOMEM);
}

-
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