On Tue, 22 Feb 2011, Guy Martin wrote:
> I'm running into some python test failures which I believe is caused by
> the COW break issue and I'd like to test the patch out.
>
> I've been trying to look through all the mail threads but I can't find
> it.
You might try the attached change to see if it helps. SMP lightly tested.
Possibly, using flush_dcache_page is overkill and it might not do the
exactly the right thing, but it resolves changing the calling interface
for ptep_set_wrprotect. There also might be some race conditions.
Dave
--
J. David Anglin dave.anglin@xxxxxxxxxxxxxx
National Research Council of Canada (613) 990-0752 (FAX: 952-6602)
diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h
index 5d7b8ce..4924e23 100644
--- a/arch/parisc/include/asm/pgtable.h
+++ b/arch/parisc/include/asm/pgtable.h
@@ -450,20 +450,7 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
return old_pte;
}
-static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
-{
-#ifdef CONFIG_SMP
- unsigned long new, old;
-
- do {
- old = pte_val(*ptep);
- new = pte_val(pte_wrprotect(__pte (old)));
- } while (cmpxchg((unsigned long *) ptep, old, new) != old);
-#else
- pte_t old_pte = *ptep;
- set_pte_at(mm, addr, ptep, pte_wrprotect(old_pte));
-#endif
-}
+extern void ptep_set_wrprotect(struct mm_struct *, unsigned long, pte_t *);
#define pte_same(A,B) (pte_val(A) == pte_val(B))
diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 3f11331..a16430d 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -502,3 +531,22 @@ flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr, unsigned long
__flush_cache_page(vma, vmaddr, page_to_phys(pfn_to_page(pfn)));
}
+
+void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
+{
+#ifdef CONFIG_SMP
+ unsigned long new, old;
+
+ if (atomic_read(&mm->mm_users) > 1)
+ flush_dcache_page(pte_page(*ptep));
+ do {
+ old = pte_val(*ptep);
+ new = pte_val(pte_wrprotect(__pte (old)));
+ } while (cmpxchg((unsigned long *) ptep, old, new) != old);
+#else
+ pte_t old_pte = *ptep;
+ if (atomic_read(&mm->mm_users) > 1)
+ flush_dcache_page(pte_page(old_pte));
+ set_pte_at(mm, addr, ptep, pte_wrprotect(old_pte));
+#endif
+}
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