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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/kernel
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>
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