[S390] fix tlb flushing vs. concurrent /proc accesses
The tlb flushing code uses the mm_users field of the mm_struct to
decide if each page table entry needs to be flushed individually with
IPTE or if a global flush for the mm_struct is sufficient after all page
table updates have been done. The comment for mm_users says "How many
users with user space?" but the /proc code increases mm_users after it
found the process structure by pid without creating a new user process.
Which makes mm_users useless for the decision between the two tlb
flusing methods. The current code can be confused to not flush tlb
entries by a concurrent access to /proc files if e.g. a fork is in
progres. The solution for this problem is to make the tlb flushing
logic independent from the mm_users field.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/hugetlb.h b/arch/s390/include/asm/hugetlb.h
index 670a1d1..bb8343d 100644
--- a/arch/s390/include/asm/hugetlb.h
+++ b/arch/s390/include/asm/hugetlb.h
@@ -97,6 +97,7 @@
{
pte_t pte = huge_ptep_get(ptep);
+ mm->context.flush_mm = 1;
pmd_clear((pmd_t *) ptep);
return pte;
}
@@ -167,7 +168,8 @@
({ \
pte_t __pte = huge_ptep_get(__ptep); \
if (pte_write(__pte)) { \
- if (atomic_read(&(__mm)->mm_users) > 1 || \
+ (__mm)->context.flush_mm = 1; \
+ if (atomic_read(&(__mm)->context.attach_count) > 1 || \
(__mm) != current->active_mm) \
huge_ptep_invalidate(__mm, __addr, __ptep); \
set_huge_pte_at(__mm, __addr, __ptep, \