ARM: 6464/2: fix spinlock recursion in adjust_pte() (4e54d93d) · Commits · 戴 / test

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>

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;

Admin message