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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2009-09-11 10:28:57 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2009-09-11 10:29:53 +0200
commit50aa98bad056a17655864a4d71ebc32d95c629a7 (patch)
treebf8d22851d99583e2ea388766697bf64672d7926 /arch/s390/include
parentc4de0c1a18237c2727dde8ad392e333539b0af3c (diff)
[S390] fix recursive locking on page_table_lock
Suzuki Poulose reported the following recursive locking bug on s390: Here is the stack trace : (see Appendix I for more info) [<0000000000406ed6>] _spin_lock+0x52/0x94 [<0000000000103bde>] crst_table_free+0x14e/0x1a4 [<00000000001ba684>] __pmd_alloc+0x114/0x1ec [<00000000001be8d0>] handle_mm_fault+0x2cc/0xb80 [<0000000000407d62>] do_dat_exception+0x2b6/0x3a0 [<0000000000114f8c>] sysc_return+0x0/0x8 [<00000200001642b2>] 0x200001642b2 The page_table_lock is already acquired in __pmd_alloc (mm/memory.c) and it tries to populate the pud/pgd with a new pmd allocated. If another thread populates it before we get a chance, we free the pmd using pmd_free(). On s390x, pmd_free(even pud_free ) is #defined to crst_table_free(), which acquires the page_table_lock to protect the crst_table index updates. Hence this ends up in a recursive locking of the page_table_lock. The solution suggested by Dave Hansen is to use a new spin lock in the mmu context to protect the access to the crst_list and the pgtable_list. Reported-by: Suzuki Poulose <suzuki@in.ibm.com> Cc: Dave Hansen <dave@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/include')
-rw-r--r--arch/s390/include/asm/mmu.h1
-rw-r--r--arch/s390/include/asm/pgalloc.h1
2 files changed, 2 insertions, 0 deletions
diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
index 3b59216e628..03be99919d6 100644
--- a/arch/s390/include/asm/mmu.h
+++ b/arch/s390/include/asm/mmu.h
@@ -2,6 +2,7 @@
#define __MMU_H
typedef struct {
+ spinlock_t list_lock;
struct list_head crst_list;
struct list_head pgtable_list;
unsigned long asce_bits;
diff --git a/arch/s390/include/asm/pgalloc.h b/arch/s390/include/asm/pgalloc.h
index b2658b9220f..ddad5903341 100644
--- a/arch/s390/include/asm/pgalloc.h
+++ b/arch/s390/include/asm/pgalloc.h
@@ -140,6 +140,7 @@ static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
static inline pgd_t *pgd_alloc(struct mm_struct *mm)
{
+ spin_lock_init(&mm->context.list_lock);
INIT_LIST_HEAD(&mm->context.crst_list);
INIT_LIST_HEAD(&mm->context.pgtable_list);
return (pgd_t *) crst_table_alloc(mm, s390_noexec);