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authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>2013-06-20 14:30:23 +0530
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2013-06-21 16:01:56 +1000
commit7888b4ddb44dccd68bc20d0dc4425707dff88c72 (patch)
tree7d9b5d74f6f51255fe06649511bf39d1a0516356 /arch/powerpc/mm
parent0ac52dd7666d5c0d0147d73a8e4b1d1ffd81cdf3 (diff)
downloadop-kernel-dev-7888b4ddb44dccd68bc20d0dc4425707dff88c72.zip
op-kernel-dev-7888b4ddb44dccd68bc20d0dc4425707dff88c72.tar.gz
powerpc: Prevent gcc to re-read the pagetables
GCC is very likely to read the pagetables just once and cache them in the local stack or in a register, but it is can also decide to re-read the pagetables. The problem is that the pagetable in those places can change from under gcc. With THP/hugetlbfs the pmd (and pgd for hugetlbfs giga pages) can change under gup_fast. The pages won't be freed untill we finish gup fast because we have irq disabled and we free these pages via rcu callback. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/mm')
-rw-r--r--arch/powerpc/mm/gup.c8
-rw-r--r--arch/powerpc/mm/hugetlbpage.c2
2 files changed, 5 insertions, 5 deletions
diff --git a/arch/powerpc/mm/gup.c b/arch/powerpc/mm/gup.c
index 223a255..49822d9 100644
--- a/arch/powerpc/mm/gup.c
+++ b/arch/powerpc/mm/gup.c
@@ -34,7 +34,7 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
ptep = pte_offset_kernel(&pmd, addr);
do {
- pte_t pte = *ptep;
+ pte_t pte = ACCESS_ONCE(*ptep);
struct page *page;
if ((pte_val(pte) & mask) != result)
@@ -63,7 +63,7 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
pmdp = pmd_offset(&pud, addr);
do {
- pmd_t pmd = *pmdp;
+ pmd_t pmd = ACCESS_ONCE(*pmdp);
next = pmd_addr_end(addr, end);
/*
@@ -97,7 +97,7 @@ static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
pudp = pud_offset(&pgd, addr);
do {
- pud_t pud = *pudp;
+ pud_t pud = ACCESS_ONCE(*pudp);
next = pud_addr_end(addr, end);
if (pud_none(pud))
@@ -160,7 +160,7 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
pgdp = pgd_offset(mm, addr);
do {
- pgd_t pgd = *pgdp;
+ pgd_t pgd = ACCESS_ONCE(*pgdp);
pr_devel(" %016lx: normal pgd %p\n", addr,
(void *)pgd_val(pgd));
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index e9e6882..f2f01fd 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -1024,7 +1024,7 @@ int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
if (pte_end < end)
end = pte_end;
- pte = *ptep;
+ pte = ACCESS_ONCE(*ptep);
mask = _PAGE_PRESENT | _PAGE_USER;
if (write)
mask |= _PAGE_RW;
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