Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 4e54d93d authored by Mika Westerberg's avatar Mika Westerberg Committed by Russell King
Browse files

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



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: default avatarMika Westerberg <mika.westerberg@iki.fi>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 4e929d2b

arch/arm/mm/fault-armv.c

+26 −2
Original line number Diff line number Diff line
@@ -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;