Le 13/09/2019 à 09:03, Christophe Leroy a écrit :
Le 13/09/2019 à 08:58, Anshuman Khandual a écrit :
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)
p4d_clear_tests(p4dp);
pgd_clear_tests(mm, pgdp);
+ 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 ?
See
https://elixir.bootlin.com/linux/v5.3-rc8/source/include/linux/highmem.h#L91
I think it applies at least to all arches using the generic implementation.
Applies also to arm:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/mm/highmem.c#L52
Applies also to mips:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/mips/mm/highmem.c#L47
Same on sparc:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/sparc/mm/highmem.c#L52
Same on x86:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/mm/highmem_32.c#L34
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:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/include/asm/pgtable.h#L200
And X86 as well:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/include/asm/pgtable_32.h#L51
Microblaze also:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/microblaze/include/asm/pgtable.h#L495
Christophe
