Module Name: src
Committed By: mlelstv
Date: Wed Nov 28 19:46:23 UTC 2018
Modified Files:
src/sys/kern: kern_synch.c
src/sys/sys: lwp.h
Log Message:
Move counting involuntary switches into mi_switch. preempt() passes that
information by setting a new LWP flag.
While here, don't even try to switch when the scheduler has no other LWP
to run. This check is currently spread over all callers of preempt()
and will be removed there.
ok mrg@.
To generate a diff of this commit:
cvs rdiff -u -r1.320 -r1.321 src/sys/kern/kern_synch.c
cvs rdiff -u -r1.179 -r1.180 src/sys/sys/lwp.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/kern_synch.c
diff -u src/sys/kern/kern_synch.c:1.320 src/sys/kern/kern_synch.c:1.321
--- src/sys/kern/kern_synch.c:1.320 Wed Nov 28 19:36:43 2018
+++ src/sys/kern/kern_synch.c Wed Nov 28 19:46:22 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_synch.c,v 1.320 2018/11/28 19:36:43 mlelstv Exp $ */
+/* $NetBSD: kern_synch.c,v 1.321 2018/11/28 19:46:22 mlelstv 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 1.320 2018/11/28 19:36:43 mlelstv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_synch.c,v 1.321 2018/11/28 19:46:22 mlelstv Exp $");
#include "opt_kstack.h"
#include "opt_dtrace.h"
@@ -286,12 +286,16 @@ preempt(void)
{
struct lwp *l = curlwp;
+ /* check if the scheduler has another LWP to run */
+ if ((l->l_cpu->ci_schedstate.spc_flags & SPCF_SHOULDYIELD) == 0)
+ return;
+
KERNEL_UNLOCK_ALL(l, &l->l_biglocks);
lwp_lock(l);
KASSERT(lwp_locked(l, l->l_cpu->ci_schedstate.spc_lwplock));
KASSERT(l->l_stat == LSONPROC);
l->l_kpriority = false;
- l->l_nivcsw++;
+ l->l_pflag |= LP_PREEMPTING;
(void)mi_switch(l);
KERNEL_LOCK(l->l_biglocks, l);
}
@@ -649,6 +653,9 @@ mi_switch(lwp_t *l)
KASSERT(l->l_ctxswtch == 0);
l->l_ctxswtch = 1;
l->l_ncsw++;
+ if ((l->l_pflag & LP_PREEMPTING) != 0)
+ l->l_nivcsw++;
+ l->l_pflag &= ~LP_PREEMPTING;
KASSERT((l->l_pflag & LP_RUNNING) != 0);
l->l_pflag &= ~LP_RUNNING;
@@ -752,6 +759,7 @@ mi_switch(lwp_t *l)
/* Nothing to do - just unlock and return. */
pserialize_switchpoint();
mutex_spin_exit(spc->spc_mutex);
+ l->l_pflag &= ~LP_PREEMPTING;
lwp_unlock(l);
retval = 0;
}
Index: src/sys/sys/lwp.h
diff -u src/sys/sys/lwp.h:1.179 src/sys/sys/lwp.h:1.180
--- src/sys/sys/lwp.h:1.179 Thu Apr 19 21:19:07 2018
+++ src/sys/sys/lwp.h Wed Nov 28 19:46:22 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: lwp.h,v 1.179 2018/04/19 21:19:07 christos Exp $ */
+/* $NetBSD: lwp.h,v 1.180 2018/11/28 19:46:22 mlelstv Exp $ */
/*
* Copyright (c) 2001, 2006, 2007, 2008, 2009, 2010
@@ -258,6 +258,7 @@ extern int maxlwp __read_mostly; /* max
#define LP_VFORKWAIT 0x00000200 /* Waiting at vfork() for a child */
#define LP_SINGLESTEP 0x00000400 /* Single step thread in ptrace(2) */
#define LP_TIMEINTR 0x00010000 /* Time this soft interrupt */
+#define LP_PREEMPTING 0x00020000 /* mi_switch called involuntarily */
#define LP_RUNNING 0x20000000 /* Active on a CPU */
#define LP_BOUND 0x80000000 /* Bound to a CPU */
