Re: [PATCH] mm/pgtable/debug: Fix test validating architecture page table helpers

From: Christophe Leroy
Date: Fri Sep 13 2019 - 03:11:57 EST

Le 13/09/2019 Ã 09:03, Christophe Leroy a ÃcritÂ:

Le 13/09/2019 Ã 08:58, Anshuman Khandual a ÃcritÂ:
On 09/13/2019 11:53 AM, Christophe Leroy wrote:
Fix build failure on powerpc.

Fix preemption imbalance.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
 mm/arch_pgtable_test.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
index 8b4a92756ad8..f2b3c9ec35fa 100644
--- a/mm/arch_pgtable_test.c
+++ b/mm/arch_pgtable_test.c
@@ -24,6 +24,7 @@
 #include <linux/swap.h>
 #include <linux/swapops.h>
 #include <linux/sched/mm.h>
+#include <linux/highmem.h>

This is okay.

 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>
@@ -400,6 +401,8 @@ static int __init arch_pgtable_tests_init(void)
ÂÂÂÂÂ p4d_clear_tests(p4dp);
ÂÂÂÂÂ pgd_clear_tests(mm, pgdp);
+ÂÂÂ pte_unmap(ptep);

Now the preemption imbalance via pte_alloc_map() path i.e

pte_alloc_map() -> pte_offset_map() -> kmap_atomic()

Is not this very much powerpc 32 specific or this will be applicable
for all platform which uses kmap_XXX() to map high memory ?


I think it applies at least to all arches using the generic implementation.

Applies also to arm:

Applies also to mips:

Same on sparc:

Same on x86:

I have not checked others, but I guess it is like that for all.

Seems like I answered too quickly. All kmap_atomic() do preempt_disable(), but not all pte_alloc_map() call kmap_atomic().

However, for instance ARM does:

And X86 as well:

Microblaze also: