Module Name: src
Committed By: yamt
Date: Tue Oct 11 23:53:31 UTC 2011
Modified Files:
src/sys/arch/x86/x86: pmap.c
Log Message:
add comments
To generate a diff of this commit:
cvs rdiff -u -r1.134 -r1.135 src/sys/arch/x86/x86/pmap.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/x86/x86/pmap.c
diff -u src/sys/arch/x86/x86/pmap.c:1.134 src/sys/arch/x86/x86/pmap.c:1.135
--- src/sys/arch/x86/x86/pmap.c:1.134 Tue Oct 11 23:50:24 2011
+++ src/sys/arch/x86/x86/pmap.c Tue Oct 11 23:53:31 2011
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap.c,v 1.134 2011/10/11 23:50:24 yamt Exp $ */
+/* $NetBSD: pmap.c,v 1.135 2011/10/11 23:53:31 yamt Exp $ */
/*-
* Copyright (c) 2008, 2010 The NetBSD Foundation, Inc.
@@ -171,7 +171,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.134 2011/10/11 23:50:24 yamt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.135 2011/10/11 23:53:31 yamt Exp $");
#include "opt_user_ldt.h"
#include "opt_lockdebug.h"
@@ -721,6 +721,22 @@ pmap_reference(struct pmap *pmap)
/*
* pmap_map_ptes: map a pmap's PTEs into KVM and lock them in
*
+ * there are several pmaps involved. some or all of them might be same.
+ *
+ * - the pmap given by the first argument
+ * our caller wants to access this pmap's PTEs.
+ *
+ * - pmap_kernel()
+ * the kernel pmap. note that it only contains the kernel part
+ * of the address space which is shared by any pmap. ie. any
+ * pmap can be used instead of pmap_kernel() for our purpose.
+ *
+ * - ci->ci_pmap
+ * pmap currently loaded on the cpu.
+ *
+ * - vm_map_pmap(&curproc->p_vmspace->vm_map)
+ * current process' pmap.
+ *
* => we lock enough pmaps to keep things locked in
* => must be undone with pmap_unmap_ptes before returning
*/
@@ -769,7 +785,8 @@ pmap_map_ptes(struct pmap *pmap, struct
}
} else {
/*
- * Toss current pmap from CPU, but keep ref to it.
+ * Toss current pmap from CPU, but keep a reference to it.
+ * The reference will be dropped by pmap_unmap_ptes().
* Can happen if we block during exit().
*/
cpumask = ci->ci_cpumask;
@@ -2574,6 +2591,14 @@ pmap_reactivate(struct pmap *pmap)
/*
* pmap_load: actually switch pmap. (fill in %cr3 and LDT info)
+ *
+ * ensures that the current process' pmap is loaded on the current cpu's MMU
+ * and there's no stale TLB entries.
+ *
+ * the caller should disable preemption or do check-and-retry to prevent
+ * a preemption from undoing our efforts.
+ *
+ * this function can block.
*/
void
@@ -2743,6 +2768,11 @@ pmap_deactivate(struct lwp *l)
ci = curcpu();
if (ci->ci_want_pmapload) {
+ /*
+ * ci_want_pmapload means that our pmap is not loaded on
+ * the CPU or TLB might be stale. note that pmap_kernel()
+ * is always considered loaded.
+ */
KASSERT(vm_map_pmap(&l->l_proc->p_vmspace->vm_map)
!= pmap_kernel());
KASSERT(vm_map_pmap(&l->l_proc->p_vmspace->vm_map)
