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From: "Jayachandran C." <jchandra@FreeBSD.org>
Date: Fri, 6 Aug 2010 09:25:42 +0000 (UTC)
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Subject: svn commit: r210922 - head/sys/mips/mips
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Author: jchandra
Date: Fri Aug  6 09:25:42 2010
New Revision: 210922
URL: http://svn.freebsd.org/changeset/base/210922

Log:
  Fix issue reported by alc :
  
   MIPS doesn't really need to use atomic_cmpset_int() in situations like
   this because the software dirty bit emulation in trap.c acquires
   the pmap lock.  Atomics like this appear to be a carryover from i386
   where the hardware-managed TLB might concurrently set the modified bit.
  
  Reviewed by:	alc

Modified:
  head/sys/mips/mips/pmap.c

Modified: head/sys/mips/mips/pmap.c
==============================================================================
--- head/sys/mips/mips/pmap.c	Fri Aug  6 09:23:47 2010	(r210921)
+++ head/sys/mips/mips/pmap.c	Fri Aug  6 09:25:42 2010	(r210922)
@@ -1716,7 +1716,7 @@ pmap_protect(pmap_t pmap, vm_offset_t sv
 	vm_page_lock_queues();
 	PMAP_LOCK(pmap);
 	for (; sva < eva; sva = va_next) {
-		pt_entry_t pbits, obits;
+		pt_entry_t pbits;
 		vm_page_t m;
 		vm_paddr_t pa;
 
@@ -1745,8 +1745,7 @@ pmap_protect(pmap_t pmap, vm_offset_t sv
 			/* Skip invalid PTEs */
 			if (!pte_test(pte, PTE_V))
 				continue;
-retry:
-			obits = pbits = *pte;
+			pbits = *pte;
 			pa = TLBLO_PTE_TO_PA(pbits);
 			if (page_is_managed(pa) && pte_test(&pbits, PTE_D)) {
 				m = PHYS_TO_VM_PAGE(pa);
@@ -1757,8 +1756,7 @@ retry:
 			pte_set(&pbits, PTE_RO);
 			
 			if (pbits != *pte) {
-				if (!atomic_cmpset_int((u_int *)pte, obits, pbits))
-					goto retry;
+				*pte = pbits;
 				pmap_update_page(pmap, sva, pbits);
 			}
 		}