[src/trunk]: src/sys/kern add defines to control whether or not mutex operati...

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

details:   https://anonhg.NetBSD.org/src/rev/40cf285b51ed
branches:  trunk
changeset: 830095:40cf285b51ed
user:      chs <chs%NetBSD.org@localhost>
date:      Sun Feb 25 18:54:29 2018 +0000

description:
add defines to control whether or not mutex operations are skipped
after we have panic'd.  no functional change.

diffstat:

 sys/kern/kern_mutex.c |  17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)

diffs (88 lines):

diff -r 055d6b40fb4d -r 40cf285b51ed sys/kern/kern_mutex.c
--- a/sys/kern/kern_mutex.c     Sun Feb 25 18:53:23 2018 +0000
+++ b/sys/kern/kern_mutex.c     Sun Feb 25 18:54:29 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_mutex.c,v 1.72 2018/02/06 07:46:24 ozaki-r Exp $  */
+/*     $NetBSD: kern_mutex.c,v 1.73 2018/02/25 18:54:29 chs Exp $      */
 
 /*-
  * Copyright (c) 2002, 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -40,7 +40,7 @@
 #define        __MUTEX_PRIVATE
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.72 2018/02/06 07:46:24 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.73 2018/02/25 18:54:29 chs Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -60,6 +60,9 @@
 
 #include <machine/lock.h>
 
+#define MUTEX_PANIC_SKIP_SPIN 1
+#define MUTEX_PANIC_SKIP_ADAPTIVE 1
+
 /*
  * When not running a debug kernel, spin mutexes are not much
  * more than an splraiseipl() and splx() pair.
@@ -489,8 +492,10 @@
                 * to reduce cache line ping-ponging between CPUs.
                 */
                do {
+#if MUTEX_PANIC_SKIP_SPIN
                        if (panicstr != NULL)
                                break;
+#endif
                        while (MUTEX_SPINBIT_LOCKED_P(mtx)) {
                                SPINLOCK_BACKOFF(count);
 #ifdef LOCKDEBUG
@@ -547,10 +552,12 @@
                        owner = mtx->mtx_owner;
                        continue;
                }
+#if MUTEX_PANIC_SKIP_ADAPTIVE
                if (__predict_false(panicstr != NULL)) {
                        KPREEMPT_ENABLE(curlwp);
                        return;
                }
+#endif
                if (__predict_false(MUTEX_OWNER(owner) == curthread)) {
                        MUTEX_ABORT(mtx, "locking against myself");
                }
@@ -726,8 +733,10 @@
        if (MUTEX_SPIN_P(mtx)) {
 #ifdef FULL
                if (__predict_false(!MUTEX_SPINBIT_LOCKED_P(mtx))) {
+#if MUTEX_PANIC_SKIP_SPIN
                        if (panicstr != NULL)
                                return;
+#endif
                        MUTEX_ABORT(mtx, "exiting unheld spin mutex");
                }
                MUTEX_UNLOCKED(mtx);
@@ -737,11 +746,13 @@
                return;
        }
 
+#ifdef MUTEX_PANIC_SKIP_ADAPTIVE
        if (__predict_false((uintptr_t)panicstr | cold)) {
                MUTEX_UNLOCKED(mtx);
                MUTEX_RELEASE(mtx);
                return;
        }
+#endif
 
        curthread = (uintptr_t)curlwp;
        MUTEX_DASSERT(mtx, curthread != 0);
@@ -932,8 +943,10 @@
         * to reduce cache line ping-ponging between CPUs.
         */
        do {
+#if MUTEX_PANIC_SKIP_SPIN
                if (panicstr != NULL)
                        break;
+#endif
                while (MUTEX_SPINBIT_LOCKED_P(mtx)) {
                        SPINLOCK_BACKOFF(count);
 #ifdef LOCKDEBUG