[src/trunk]: src/sys schedstate_percpu: add new flag SPCF_IDLE as a cheap and...

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

details:   https://anonhg.NetBSD.org/src/rev/b5a39fe612a7
branches:  trunk
changeset: 967760:b5a39fe612a7
user:      ad <ad%NetBSD.org@localhost>
date:      Sat Dec 21 11:54:04 2019 +0000

description:
schedstate_percpu: add new flag SPCF_IDLE as a cheap and easy way to
determine that a CPU is currently idle.

diffstat:

 sys/kern/kern_synch.c |  8 +++++---
 sys/sys/sched.h       |  3 ++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diffs (57 lines):

diff -r 6f78e7ab0269 -r b5a39fe612a7 sys/kern/kern_synch.c
--- a/sys/kern/kern_synch.c     Sat Dec 21 11:41:18 2019 +0000
+++ b/sys/kern/kern_synch.c     Sat Dec 21 11:54:04 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_synch.c,v 1.333 2019/12/20 21:52:51 ad Exp $      */
+/*     $NetBSD: kern_synch.c,v 1.334 2019/12/21 11:54:04 ad Exp $      */
 
 /*-
  * Copyright (c) 1999, 2000, 2004, 2006, 2007, 2008, 2009, 2019
@@ -69,7 +69,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_synch.c,v 1.333 2019/12/20 21:52:51 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_synch.c,v 1.334 2019/12/21 11:54:04 ad Exp $");
 
 #include "opt_kstack.h"
 #include "opt_dtrace.h"
@@ -487,10 +487,13 @@
                newl->l_stat = LSONPROC;
                newl->l_pflag |= LP_RUNNING;
                lwp_setlock(newl, spc->spc_lwplock);
+               spc->spc_flags &= ~(SPCF_SWITCHCLEAR | SPCF_IDLE);
        } else {
                newl = ci->ci_data.cpu_idlelwp;
                newl->l_stat = LSONPROC;
                newl->l_pflag |= LP_RUNNING;
+               spc->spc_flags = (spc->spc_flags & ~SPCF_SWITCHCLEAR) |
+                   SPCF_IDLE;
        }
 
        /*
@@ -501,7 +504,6 @@
         * the release of spc_mutex becomes globally visible.
         */
        ci->ci_want_resched = ci->ci_data.cpu_softints;
-       spc->spc_flags &= ~SPCF_SWITCHCLEAR;
        spc->spc_curpriority = lwp_eprio(newl);
 
        return newl;
diff -r 6f78e7ab0269 -r b5a39fe612a7 sys/sys/sched.h
--- a/sys/sys/sched.h   Sat Dec 21 11:41:18 2019 +0000
+++ b/sys/sys/sched.h   Sat Dec 21 11:54:04 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sched.h,v 1.81 2019/12/20 21:05:34 ad Exp $    */
+/*     $NetBSD: sched.h,v 1.82 2019/12/21 11:54:04 ad Exp $    */
 
 /*-
  * Copyright (c) 1999, 2000, 2001, 2002, 2007, 2008, 2019
@@ -187,6 +187,7 @@
 #define        SPCF_RUNNING            0x0008  /* CPU is running */
 #define        SPCF_NOINTR             0x0010  /* shielded from interrupts */
 #define        SPCF_SMTPRIMARY         0x0020  /* CPU is first thread in core */
+#define        SPCF_IDLE               0x0040  /* CPU is currently idle */
 
 #define        SPCF_SWITCHCLEAR        (SPCF_SEENRR|SPCF_SHOULDYIELD)