With Alfred's permission, remove vm_mtx in favor of a fine-grained approach

(this commit is just the first stage).  Also add various GIANT_ macros to
formalize the removal of Giant, making it easy to test in a more piecemeal
fashion. These macros will allow us to test fine-grained locks to a degree
before removing Giant, and also after, and to remove Giant in a piecemeal
fashion via sysctl's on those subsystems which the authors believe can
operate without Giant.

2 files changed, 18 insertions, 24 deletions

diff --git a/sys/powerpc/aim/vm_machdep.c b/sys/powerpc/aim/vm_machdep.c
index c281ef1..4651cef 100644
--- a/sys/powerpc/aim/vm_machdep.c
+++ b/sys/powerpc/aim/vm_machdep.c
@@ -185,14 +185,13 @@ void
 cpu_wait(p)
 	struct proc *p;
 {
+	GIANT_REQUIRED;
 	
-	mtx_lock(&vm_mtx);
 	/* drop per-process resources */
 	pmap_dispose_proc(p);
 
 	/* and clean-out the vmspace */
 	vmspace_free(p->p_vmspace);
-	mtx_unlock(&vm_mtx);
 }
 
 /*
@@ -241,10 +240,11 @@ vmapbuf(bp)
 	register caddr_t addr, v, kva;
 	vm_offset_t pa;
 
+	GIANT_REQUIRED;
+
 	if ((bp->b_flags & B_PHYS) == 0)
 		panic("vmapbuf");
 
-	mtx_lock(&vm_mtx);
 	for (v = bp->b_saveaddr, addr = (caddr_t)trunc_page(bp->b_data);
 	    addr < bp->b_data + bp->b_bufsize;
 	    addr += PAGE_SIZE, v += PAGE_SIZE) {
@@ -260,7 +260,6 @@ vmapbuf(bp)
 		vm_page_hold(PHYS_TO_VM_PAGE(pa));
 		pmap_kenter((vm_offset_t) v, pa);
 	}
-	mtx_unlock(&vm_mtx);
 
 	kva = bp->b_saveaddr;
 	bp->b_saveaddr = bp->b_data;
@@ -278,10 +277,11 @@ vunmapbuf(bp)
 	register caddr_t addr;
 	vm_offset_t pa;
 
+	GIANT_REQUIRED;
+
 	if ((bp->b_flags & B_PHYS) == 0)
 		panic("vunmapbuf");
 
-	mtx_lock(&vm_mtx);
 	for (addr = (caddr_t)trunc_page(bp->b_data);
 	    addr < bp->b_data + bp->b_bufsize;
 	    addr += PAGE_SIZE) {
@@ -289,7 +289,6 @@ vunmapbuf(bp)
 		pmap_kremove((vm_offset_t) addr);
 		vm_page_unhold(PHYS_TO_VM_PAGE(pa));
 	}
-	mtx_unlock(&vm_mtx);
 
 	bp->b_data = bp->b_saveaddr;
 }
@@ -347,17 +346,13 @@ vm_page_zero_idle()
          * pages because doing so may flush our L1 and L2 caches too much.
 	 */
 
-	if (mtx_trylock(&vm_mtx) == 0)
-		return (0);
 	if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count)) {
-		mtx_unlock(&vm_mtx);
 		return(0);
 	}		
 	if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) {
-		mtx_unlock(&vm_mtx);
 		return(0);
 	}
-
+	if (mtx_trylock(&Giant)) {
 		s = splvm();
 		m = vm_page_list_find(PQ_FREE, free_rover, FALSE);
 		zero_state = 0;
@@ -386,8 +381,10 @@ vm_page_zero_idle()
 		}
 		free_rover = (free_rover + PQ_PRIME2) & PQ_L2_MASK;
 		splx(s);
-		mtx_unlock(&vm_mtx);
+		mtx_unlock(&Giant);
 		return (1);
+	}
+	return(0);
 }
 
 /*
diff --git a/sys/powerpc/powerpc/vm_machdep.c b/sys/powerpc/powerpc/vm_machdep.c
index c281ef1..4651cef 100644
--- a/sys/powerpc/powerpc/vm_machdep.c
+++ b/sys/powerpc/powerpc/vm_machdep.c
@@ -185,14 +185,13 @@ void
 cpu_wait(p)
 	struct proc *p;
 {
+	GIANT_REQUIRED;
 	
-	mtx_lock(&vm_mtx);
 	/* drop per-process resources */
 	pmap_dispose_proc(p);
 
 	/* and clean-out the vmspace */
 	vmspace_free(p->p_vmspace);
-	mtx_unlock(&vm_mtx);
 }
 
 /*
@@ -241,10 +240,11 @@ vmapbuf(bp)
 	register caddr_t addr, v, kva;
 	vm_offset_t pa;
 
+	GIANT_REQUIRED;
+
 	if ((bp->b_flags & B_PHYS) == 0)
 		panic("vmapbuf");
 
-	mtx_lock(&vm_mtx);
 	for (v = bp->b_saveaddr, addr = (caddr_t)trunc_page(bp->b_data);
 	    addr < bp->b_data + bp->b_bufsize;
 	    addr += PAGE_SIZE, v += PAGE_SIZE) {
@@ -260,7 +260,6 @@ vmapbuf(bp)
 		vm_page_hold(PHYS_TO_VM_PAGE(pa));
 		pmap_kenter((vm_offset_t) v, pa);
 	}
-	mtx_unlock(&vm_mtx);
 
 	kva = bp->b_saveaddr;
 	bp->b_saveaddr = bp->b_data;
@@ -278,10 +277,11 @@ vunmapbuf(bp)
 	register caddr_t addr;
 	vm_offset_t pa;
 
+	GIANT_REQUIRED;
+
 	if ((bp->b_flags & B_PHYS) == 0)
 		panic("vunmapbuf");
 
-	mtx_lock(&vm_mtx);
 	for (addr = (caddr_t)trunc_page(bp->b_data);
 	    addr < bp->b_data + bp->b_bufsize;
 	    addr += PAGE_SIZE) {
@@ -289,7 +289,6 @@ vunmapbuf(bp)
 		pmap_kremove((vm_offset_t) addr);
 		vm_page_unhold(PHYS_TO_VM_PAGE(pa));
 	}
-	mtx_unlock(&vm_mtx);
 
 	bp->b_data = bp->b_saveaddr;
 }
@@ -347,17 +346,13 @@ vm_page_zero_idle()
          * pages because doing so may flush our L1 and L2 caches too much.
 	 */
 
-	if (mtx_trylock(&vm_mtx) == 0)
-		return (0);
 	if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count)) {
-		mtx_unlock(&vm_mtx);
 		return(0);
 	}		
 	if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) {
-		mtx_unlock(&vm_mtx);
 		return(0);
 	}
-
+	if (mtx_trylock(&Giant)) {
 		s = splvm();
 		m = vm_page_list_find(PQ_FREE, free_rover, FALSE);
 		zero_state = 0;
@@ -386,8 +381,10 @@ vm_page_zero_idle()
 		}
 		free_rover = (free_rover + PQ_PRIME2) & PQ_L2_MASK;
 		splx(s);
-		mtx_unlock(&vm_mtx);
+		mtx_unlock(&Giant);
 		return (1);
+	}
+	return(0);
 }
 
 /*