| From | Andi Kleen <> | Subject | [PATCH] [181/223] ARM: 6464/2: fix spinlock recursion in adjust_pte() | Date | Mon, 13 Dec 2010 00:48:06 +0100 (CET) |
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2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ From: Mika Westerberg <mika.westerberg@iki.fi>
commit 4e54d93d3c9846ba1c2644ad06463dafa690d1b7 upstream.
When running following code in a machine which has VIVT caches and USE_SPLIT_PTLOCKS is not defined:
fd = open("/etc/passwd", O_RDONLY); addr = mmap(NULL, 4096, PROT_READ, MAP_SHARED, fd, 0); addr2 = mmap(NULL, 4096, PROT_READ, MAP_SHARED, fd, 0);
v = *((int *)addr);
we will hang in spinlock recursion in the page fault handler:
BUG: spinlock recursion on CPU#0, mmap_test/717 lock: c5e295d8, .magic: dead4ead, .owner: mmap_test/717, .owner_cpu: 0 [<c0026604>] (unwind_backtrace+0x0/0xec) [<c014ee48>] (do_raw_spin_lock+0x40/0x140) [<c0027f68>] (update_mmu_cache+0x208/0x250) [<c0079db4>] (__do_fault+0x320/0x3ec) [<c007af7c>] (handle_mm_fault+0x2f0/0x6d8) [<c0027834>] (do_page_fault+0xdc/0x1cc) [<c00202d0>] (do_DataAbort+0x34/0x94)
This comes from the fact that when USE_SPLIT_PTLOCKS is not defined, the only lock protecting the page tables is mm->page_table_lock which is already locked before update_mmu_cache() is called.
Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Andi Kleen <ak@linux.intel.com>
--- arch/arm/mm/fault-armv.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-)
Index: linux/arch/arm/mm/fault-armv.c =================================================================== --- linux.orig/arch/arm/mm/fault-armv.c +++ linux/arch/arm/mm/fault-armv.c @@ -65,6 +65,30 @@ static int do_adjust_pte(struct vm_area_ return ret; } +#if USE_SPLIT_PTLOCKS +/* + * If we are using split PTE locks, then we need to take the page + * lock here. Otherwise we are using shared mm->page_table_lock + * which is already locked, thus cannot take it. + */ +static inline void do_pte_lock(spinlock_t *ptl) +{ + /* + * Use nested version here to indicate that we are already + * holding one similar spinlock. + */ + spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); +} + +static inline void do_pte_unlock(spinlock_t *ptl) +{ + spin_unlock(ptl); +} +#else /* !USE_SPLIT_PTLOCKS */ +static inline void do_pte_lock(spinlock_t *ptl) {} +static inline void do_pte_unlock(spinlock_t *ptl) {} +#endif /* USE_SPLIT_PTLOCKS */ + static int adjust_pte(struct vm_area_struct *vma, unsigned long address, unsigned long pfn) { @@ -89,11 +113,11 @@ static int adjust_pte(struct vm_area_str */ ptl = pte_lockptr(vma->vm_mm, pmd); pte = pte_offset_map_nested(pmd, address); - spin_lock(ptl); + do_pte_lock(ptl); ret = do_adjust_pte(vma, address, pfn, pte); - spin_unlock(ptl); + do_pte_unlock(ptl); pte_unmap_nested(pte); return ret;
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