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ARM: 6464/2: fix spinlock recursion in adjust_pte()

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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>
This commit is contained in:
Mika Westerberg
2010-10-28 11:45:22 +01:00
committed by Russell King
parent 4e929d2bcf
commit 4e54d93d3c
1 changed files with 26 additions and 2 deletions
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28
arch/arm/mm/fault-armv.c
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@@ -66,6 +66,30 @@ static int do_adjust_pte(struct vm_area_struct *vma, unsigned long address,
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)
{
@@ -90,11 +114,11 @@ static int adjust_pte(struct vm_area_struct *vma, unsigned long address,
*/
ptl = pte_lockptr(vma->vm_mm, pmd);
pte = pte_offset_map(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(pte);
return ret;