diff -urN 2.4.0-test5/mm/filemap.c msync-smp-race/mm/filemap.c
--- 2.4.0-test5/mm/filemap.c	Fri Jul 28 07:24:15 2000
+++ msync-smp-race/mm/filemap.c	Tue Aug  1 21:20:24 2000
@@ -1557,12 +1557,14 @@
 	pte_t pte = *ptep;
 	struct page *page;
 	int error;
+	spinlock_t * page_table_lock = &vma->vm_mm->page_table_lock;
 
+	spin_lock(page_table_lock);
 	if (!(flags & MS_INVALIDATE)) {
 		if (!pte_present(pte))
-			return 0;
+			goto out_unlock;
 		if (!pte_dirty(pte))
-			return 0;
+			goto out_unlock;
 		flush_page_to_ram(pte_page(pte));
 		flush_cache_page(vma, address);
 		set_pte(ptep, pte_mkclean(pte));
@@ -1571,20 +1573,22 @@
 		page_cache_get(page);
 	} else {
 		if (pte_none(pte))
-			return 0;
+			goto out_unlock;
 		flush_cache_page(vma, address);
 		pte_clear(ptep);
 		flush_tlb_page(vma, address);
 		if (!pte_present(pte)) {
 			swap_free(pte_to_swp_entry(pte));
-			return 0;
+			goto out_unlock;
 		}
 		page = pte_page(pte);
 		if (!pte_dirty(pte) || flags == MS_INVALIDATE) {
+			spin_unlock(page_table_lock);
 			page_cache_free(page);
 			return 0;
 		}
 	}
+	spin_unlock(page_table_lock);
 	pgoff = (address - vma->vm_start) >> PAGE_CACHE_SHIFT;
 	pgoff += vma->vm_pgoff;
 	if (page->index != pgoff) {
@@ -1596,6 +1600,10 @@
 	UnlockPage(page);
 	page_cache_free(page);
 	return error;
+
+ out_unlock:
+	spin_unlock(page_table_lock);
+	return 0;
 }
 
 static inline int filemap_sync_pte_range(pmd_t * pmd,