From: Martin Schwidefsky Date: Fri, 11 Sep 2009 08:28:57 +0000 (+0200) Subject: [S390] fix recursive locking on page_table_lock X-Git-Tag: v2.6.32-rc1~734^2~10 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=50aa98bad056a17655864a4d71ebc32d95c629a7;p=pandora-kernel.git [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 --- Reading git-diff-tree failed