[src/trunk]: src/sys/kern - Add a mutex_owner_running() for the benefit of th...

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details:   https://anonhg.NetBSD.org/src/rev/176a470ed8e7
branches:  trunk
changeset: 967460:176a470ed8e7
user:      ad <ad%NetBSD.org@localhost>
date:      Mon Dec 09 21:05:23 2019 +0000

description:
- Add a mutex_owner_running() for the benefit of the pagedaemon, which
  needs help with locking things in reverse order.
- Expunge the panicstr checks.
- Make MUTEX_NODEBUG work for adaptive mutexes too.

diffstat:

 sys/kern/kern_mutex.c |  100 ++++++++++++++++---------------------------------
 1 files changed, 33 insertions(+), 67 deletions(-)

diffs (177 lines):

diff -r 98d037f9bbfa -r 176a470ed8e7 sys/kern/kern_mutex.c
--- a/sys/kern/kern_mutex.c     Mon Dec 09 21:02:10 2019 +0000
+++ b/sys/kern/kern_mutex.c     Mon Dec 09 21:05:23 2019 +0000
@@ -1,7 +1,7 @@
-/*     $NetBSD: kern_mutex.c,v 1.80 2019/11/29 19:44:59 ad Exp $       */
+/*     $NetBSD: kern_mutex.c,v 1.81 2019/12/09 21:05:23 ad Exp $       */
 
 /*-
- * Copyright (c) 2002, 2006, 2007, 2008 The NetBSD Foundation, Inc.
+ * Copyright (c) 2002, 2006, 2007, 2008, 2019 The NetBSD Foundation, Inc.
  * All rights reserved.
  *
  * This code is derived from software contributed to The NetBSD Foundation
@@ -40,7 +40,7 @@
 #define        __MUTEX_PRIVATE
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.80 2019/11/29 19:44:59 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.81 2019/12/09 21:05:23 ad Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -61,9 +61,6 @@
 
 #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.
@@ -348,46 +345,23 @@
 _mutex_init(kmutex_t *mtx, kmutex_type_t type, int ipl,
     uintptr_t return_address)
 {
+       lockops_t *lockops __unused;
        bool dodebug;
 
        memset(mtx, 0, sizeof(*mtx));
 
-       switch (type) {
-       case MUTEX_ADAPTIVE:
-               KASSERT(ipl == IPL_NONE);
-               break;
-       case MUTEX_DEFAULT:
-       case MUTEX_DRIVER:
-               if (ipl == IPL_NONE || ipl == IPL_SOFTCLOCK ||
-                   ipl == IPL_SOFTBIO || ipl == IPL_SOFTNET ||
-                   ipl == IPL_SOFTSERIAL) {
-                       type = MUTEX_ADAPTIVE;
-               } else {
-                       type = MUTEX_SPIN;
-               }
-               break;
-       default:
-               break;
-       }
-
-       switch (type) {
-       case MUTEX_NODEBUG:
-               dodebug = LOCKDEBUG_ALLOC(mtx, NULL, return_address);
+       if (ipl == IPL_NONE || ipl == IPL_SOFTCLOCK ||
+           ipl == IPL_SOFTBIO || ipl == IPL_SOFTNET ||
+           ipl == IPL_SOFTSERIAL) {
+               lockops = (type == MUTEX_NODEBUG ?
+                   NULL : &mutex_adaptive_lockops);
+               dodebug = LOCKDEBUG_ALLOC(mtx, lockops, return_address);
+               MUTEX_INITIALIZE_ADAPTIVE(mtx, dodebug);
+       } else {
+               lockops = (type == MUTEX_NODEBUG ?
+                   NULL : &mutex_spin_lockops);
+               dodebug = LOCKDEBUG_ALLOC(mtx, lockops, return_address);
                MUTEX_INITIALIZE_SPIN(mtx, dodebug, ipl);
-               break;
-       case MUTEX_ADAPTIVE:
-               dodebug = LOCKDEBUG_ALLOC(mtx, &mutex_adaptive_lockops,
-                   return_address);
-               MUTEX_INITIALIZE_ADAPTIVE(mtx, dodebug);
-               break;
-       case MUTEX_SPIN:
-               dodebug = LOCKDEBUG_ALLOC(mtx, &mutex_spin_lockops,
-                   return_address);
-               MUTEX_INITIALIZE_SPIN(mtx, dodebug, ipl);
-               break;
-       default:
-               panic("mutex_init: impossible type");
-               break;
        }
 }
 
@@ -504,10 +478,6 @@
                 * 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
@@ -565,12 +535,6 @@
                        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");
                }
@@ -746,10 +710,6 @@
        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);
@@ -759,14 +719,6 @@
                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);
        MUTEX_ASSERT(mtx, MUTEX_OWNER(mtx->mtx_owner) == curthread);
@@ -869,6 +821,24 @@
 }
 
 /*
+ * mutex_owner_running:
+ *
+ *     Return true if an adaptive mutex is held and the owner is running
+ *     on a CPU.  For the pagedaemon.
+ */
+bool
+mutex_owner_running(const kmutex_t *mtx)
+{
+       bool rv;
+
+       MUTEX_ASSERT(mtx, MUTEX_ADAPTIVE_P(mtx));
+       kpreempt_disable();
+       rv = mutex_oncpu(MUTEX_OWNER(mtx->mtx_owner));
+       kpreempt_enable();
+       return rv;
+}
+
+/*
  * mutex_ownable:
  *
  *     When compiled with DEBUG and LOCKDEBUG defined, ensure that
@@ -956,10 +926,6 @@
         * 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