[src/trunk]: src/sys comment

[yamt <yamt%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/adb8c35f3e16
branches:  trunk
changeset: 778879:adb8c35f3e16
user:      yamt <yamt%NetBSD.org@localhost>
date:      Wed Apr 18 13:42:11 2012 +0000

description:
comment

diffstat:

 sys/kern/kern_synch.c |   8 ++++++--
 sys/kern/subr_pcu.c   |  31 +++++++++++++++++++++++++------
 sys/sys/pcu.h         |  16 +++++++++++++++-
 3 files changed, 46 insertions(+), 9 deletions(-)

diffs (143 lines):

diff -r 28f668b1fb71 -r adb8c35f3e16 sys/kern/kern_synch.c
--- a/sys/kern/kern_synch.c     Wed Apr 18 13:31:10 2012 +0000
+++ b/sys/kern/kern_synch.c     Wed Apr 18 13:42:11 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_synch.c,v 1.299 2012/03/03 00:22:24 matt Exp $    */
+/*     $NetBSD: kern_synch.c,v 1.300 2012/04/18 13:44:19 yamt Exp $    */
 
 /*-
  * Copyright (c) 1999, 2000, 2004, 2006, 2007, 2008, 2009
@@ -69,7 +69,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_synch.c,v 1.299 2012/03/03 00:22:24 matt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_synch.c,v 1.300 2012/04/18 13:44:19 yamt Exp $");
 
 #include "opt_kstack.h"
 #include "opt_perfctrs.h"
@@ -755,6 +755,10 @@
 
                KASSERT(l->l_cpu == ci);
                splx(oldspl);
+               /*
+                * note that, unless the caller disabled preemption,
+                * we can be preempted at any time after the above splx() call.
+                */
                retval = 1;
        } else {
                /* Nothing to do - just unlock and return. */
diff -r 28f668b1fb71 -r adb8c35f3e16 sys/kern/subr_pcu.c
--- a/sys/kern/subr_pcu.c       Wed Apr 18 13:31:10 2012 +0000
+++ b/sys/kern/subr_pcu.c       Wed Apr 18 13:42:11 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_pcu.c,v 1.10 2011/09/27 01:02:39 jym Exp $        */
+/*     $NetBSD: subr_pcu.c,v 1.11 2012/04/18 13:43:13 yamt Exp $       */
 
 /*-
  * Copyright (c) 2011 The NetBSD Foundation, Inc.
@@ -57,7 +57,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_pcu.c,v 1.10 2011/09/27 01:02:39 jym Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_pcu.c,v 1.11 2012/04/18 13:43:13 yamt Exp $");
 
 #include <sys/param.h>
 #include <sys/cpu.h>
@@ -75,6 +75,13 @@
 /* XXX */
 extern const pcu_ops_t * const pcu_ops_md_defs[];
 
+/*
+ * pcu_switchpoint: release PCU state if the LWP is being run on another CPU.
+ *
+ * On each context switches, called by mi_switch() with IPL_SCHED.
+ * 'l' is an LWP which is just we switched to.  (the new curlwp)
+ */
+
 void
 pcu_switchpoint(lwp_t *l)
 {
@@ -88,6 +95,7 @@
                /* PCUs are not in use. */
                return;
        }
+       /* commented out as we know we are already at IPL_SCHED */
        /* s = splsoftclock(); */
        for (id = 0; id < PCU_UNIT_COUNT; id++) {
                if ((pcu_inuse & (1 << id)) == 0) {
@@ -103,6 +111,12 @@
        /* splx(s); */
 }
 
+/*
+ * pcu_discard_all: discard PCU state of the given LWP.
+ *
+ * Used by exec and LWP exit.
+ */
+
 void
 pcu_discard_all(lwp_t *l)
 {
@@ -133,10 +147,19 @@
        splx(s);
 }
 
+/*
+ * pcu_save_all: save PCU state of the given LWP so that eg. coredump can
+ * examine it.
+ */
+
 void
 pcu_save_all(lwp_t *l)
 {
        const uint32_t pcu_inuse = l->l_pcu_used;
+       /*
+        * Unless LW_WCORE, we aren't releasing since this LWP isn't giving
+        * up PCU, just saving it.
+        */
        const int flags = PCU_SAVE | (l->l_flag & LW_WCORE ? PCU_RELEASE : 0);
 
        /*
@@ -162,10 +185,6 @@
                        continue;
                }
                const pcu_ops_t * const pcu = pcu_ops_md_defs[id];
-               /*
-                * We aren't releasing since this LWP isn't giving up PCU,
-                * just saving it.
-                */
                pcu_lwp_op(pcu, l, flags);
        }
        splx(s);
diff -r 28f668b1fb71 -r adb8c35f3e16 sys/sys/pcu.h
--- a/sys/sys/pcu.h     Wed Apr 18 13:31:10 2012 +0000
+++ b/sys/sys/pcu.h     Wed Apr 18 13:42:11 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pcu.h,v 1.8 2011/06/06 22:04:34 matt Exp $     */
+/*     $NetBSD: pcu.h,v 1.9 2012/04/18 13:42:11 yamt Exp $     */
 
 /*-
  * Copyright (c) 2011 The NetBSD Foundation, Inc.
@@ -49,6 +49,20 @@
 
 #if PCU_UNIT_COUNT > 0
 
+/*
+ * pcu_state_save(lwp)
+ *     save the current CPU's state into the given LWP's MD storage.
+ *
+ * pcu_state_load(lwp, used)
+ *     load PCU state from the given LWP's MD storage to the current CPU.
+ *     the 'used' argument is true if it isn't the first time the LWP uses
+ *     the PCU.
+ *
+ * pcu_state_release(lwp)
+ *     tell MD code detect the next use of the PCU on the LWP, and call
+ *     pcu_load().
+ */
+
 typedef struct {
        u_int   pcu_id;
        void    (*pcu_state_save)(lwp_t *);