[src/trunk]: src/sys/kern Just make the turnstile locks statics and avoid the...

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

details:   https://anonhg.NetBSD.org/src/rev/79edf8beeecb
branches:  trunk
changeset: 1005681:79edf8beeecb
user:      ad <ad%NetBSD.org@localhost>
date:      Mon Dec 16 19:22:15 2019 +0000

description:
Just make the turnstile locks statics and avoid the indirect reference
since COHERENCY_UNIT does the right thing in !MP.

diffstat:

 sys/kern/kern_turnstile.c |  23 +++++++++++++----------
 1 files changed, 13 insertions(+), 10 deletions(-)

diffs (90 lines):

diff -r 301b81921ee2 -r 79edf8beeecb sys/kern/kern_turnstile.c
--- a/sys/kern/kern_turnstile.c Mon Dec 16 19:20:45 2019 +0000
+++ b/sys/kern/kern_turnstile.c Mon Dec 16 19:22:15 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_turnstile.c,v 1.34 2019/11/24 13:14:23 ad Exp $   */
+/*     $NetBSD: kern_turnstile.c,v 1.35 2019/12/16 19:22:15 ad Exp $   */
 
 /*-
  * Copyright (c) 2002, 2006, 2007, 2009, 2019 The NetBSD Foundation, Inc.
@@ -60,7 +60,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_turnstile.c,v 1.34 2019/11/24 13:14:23 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_turnstile.c,v 1.35 2019/12/16 19:22:15 ad Exp $");
 
 #include <sys/param.h>
 #include <sys/lockdebug.h>
@@ -78,12 +78,15 @@
 #define        TS_HASH_MASK    (TS_HASH_SIZE - 1)
 #define        TS_HASH(obj)    (((uintptr_t)(obj) >> 6) & TS_HASH_MASK)
 
-/* Keep the chains and mutex pointers apart to prevent false sharing. */
 static tschain_t       turnstile_chains[TS_HASH_SIZE] __cacheline_aligned;
-static kmutex_t                *turnstile_locks[TS_HASH_SIZE] __read_mostly;
 pool_cache_t           turnstile_cache __read_mostly;
 extern turnstile_t     turnstile0;
 
+static union {
+       kmutex_t        lock;
+       uint8_t         pad[COHERENCY_UNIT];
+} turnstile_locks[TS_HASH_SIZE] __cacheline_aligned;
+
 static int             turnstile_ctor(void *, void *, int);
 
 /*
@@ -98,7 +101,7 @@
 
        for (i = 0; i < TS_HASH_SIZE; i++) {
                LIST_INIT(&turnstile_chains[i]);
-               turnstile_locks[i] = mutex_obj_alloc(MUTEX_DEFAULT, IPL_SCHED);
+               mutex_init(&turnstile_locks[i].lock, MUTEX_DEFAULT, IPL_SCHED);
        }
 
        turnstile_cache = pool_cache_init(sizeof(turnstile_t), coherency_unit,
@@ -173,7 +176,7 @@
 
        hash = TS_HASH(obj);
        tc = &turnstile_chains[hash];
-       mutex_spin_enter(turnstile_locks[hash]);
+       mutex_spin_enter(&turnstile_locks[hash].lock);
 
        LIST_FOREACH(ts, tc, ts_chain)
                if (ts->ts_obj == obj)
@@ -195,7 +198,7 @@
 turnstile_exit(wchan_t obj)
 {
 
-       mutex_spin_exit(turnstile_locks[TS_HASH(obj)]);
+       mutex_spin_exit(&turnstile_locks[TS_HASH(obj)].lock);
 }
 
 /*
@@ -381,7 +384,7 @@
 
        hash = TS_HASH(obj);
        tc = &turnstile_chains[hash];
-       lock = turnstile_locks[hash];
+       lock = &turnstile_locks[hash].lock;
 
        KASSERT(q == TS_READER_Q || q == TS_WRITER_Q);
        KASSERT(mutex_owned(lock));
@@ -455,7 +458,7 @@
        lwp_t *l;
 
        hash = TS_HASH(ts->ts_obj);
-       lock = turnstile_locks[hash];
+       lock = &turnstile_locks[hash].lock;
        sq = &ts->ts_sleepq[q];
 
        KASSERT(q == TS_READER_Q || q == TS_WRITER_Q);
@@ -539,7 +542,7 @@
 
        hash = TS_HASH(obj);
        tc = &turnstile_chains[hash];
-       lock = turnstile_locks[hash];
+       lock = &turnstile_locks[hash].lock;
 
        LIST_FOREACH(ts, tc, ts_chain)
                if (ts->ts_obj == obj)