[POWERPC] Make high hugepage areas preempt safe

Checking source for other get_paca()->field preemption dangers found that
open_high_hpage_areas does a structure copy into its paca while preemption
is enabled: unsafe however gcc accomplishes it.  Just remove that copy:
it's done safely afterwards by on_each_cpu, as in open_low_hpage_areas.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 5615acc295279366e7ac448011cf41db92369ab4..fd68b74c07c3c4e5c457371c1dd54c52767cec8a 100644 (file)
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -480,9 +480,6 @@ static int open_high_hpage_areas(struct mm_struct *mm, u16 newareas)
 
        mm->context.high_htlb_areas |= newareas;
 
-       /* update the paca copy of the context struct */
-       get_paca()->context = mm->context;
-
        /* the context change must make it to memory before the flush,
         * so that further SLB misses do the right thing. */
        mb();