[PATCH 3.16 262/306] parisc: Fix race in pci-dma.c

Ben Hutchings
2017-02-15T23:12:14Z

From: John David Anglin <dave.anglin@bell.net>

commit c0452fb9fb8f49c7d68ab9fa0ad092016be7b45f upstream.

We are still troubled by occasional random segmentation faults and
memory memory corruption on SMP machines. The causes quite a few
package builds to fail on the Debian buildd machines for parisc. When
gcc-6 failed to build three times in a row, I looked again at the TLB
related code. I found a couple of issues. This is the first.

In general, we need to ensure page table updates and corresponding TLB
purges are atomic. The attached patch fixes an instance in pci-dma.c
where the page table update was not guarded by the TLB lock.

Tested on rp3440 and c8000. So far, no further random segmentation
faults have been observed.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/parisc/kernel/pci-dma.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/parisc/kernel/pci-dma.c
+++ b/arch/parisc/kernel/pci-dma.c
@@ -95,8 +95,8 @@ static inline int map_pte_uncached(pte_t

if (!pte_none(*pte))
printk(KERN_ERR "map_pte_uncached: page already exists\n");
- set_pte(pte, __mk_pte(*paddr_ptr, PAGE_KERNEL_UNC));
purge_tlb_start(flags);
+ set_pte(pte, __mk_pte(*paddr_ptr, PAGE_KERNEL_UNC));
pdtlb_kernel(orig_vaddr);
purge_tlb_end(flags);
vaddr += PAGE_SIZE;