From 50aa98bad056a17655864a4d71ebc32d95c629a7 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Fri, 11 Sep 2009 10:28:57 +0200 Subject: [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 Cc: Dave Hansen Signed-off-by: Martin Schwidefsky --- arch/s390/include/asm/mmu.h | 1 + arch/s390/include/asm/pgalloc.h | 1 + 2 files changed, 2 insertions(+) (limited to 'arch/s390/include') 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); -- cgit v1.2.3