diff options
| author | Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> | 2013-06-20 14:30:23 +0530 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2013-06-21 16:01:56 +1000 |
| commit | 7888b4ddb44dccd68bc20d0dc4425707dff88c72 (patch) | |
| tree | 7d9b5d74f6f51255fe06649511bf39d1a0516356 | |
| parent | 0ac52dd7666d5c0d0147d73a8e4b1d1ffd81cdf3 (diff) | |
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>
| -rw-r--r-- | arch/powerpc/mm/gup.c | 8 | ||||
| -rw-r--r-- | arch/powerpc/mm/hugetlbpage.c | 2 |
2 files changed, 5 insertions, 5 deletions
diff --git a/arch/powerpc/mm/gup.c b/arch/powerpc/mm/gup.c index 223a255545f..49822d90ea9 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 e9e6882231d..f2f01fd3ec6 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; |