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[src/trunk]: src/sys Tidy rwlocks a bit, no functional change intended. Mainly:
details: https://anonhg.NetBSD.org/src/rev/6fc06065be59
branches: trunk
changeset: 1006576:6fc06065be59
user: ad <ad%NetBSD.org@localhost>
date: Sun Jan 19 18:34:24 2020 +0000
description:
Tidy rwlocks a bit, no functional change intended. Mainly:
- rw_downgrade(): do it in a for () loop like all the others.
- Explicitly carry around RW_NODEBUG - don't be lazy.
- Remove pointless macros.
- Don't make assertions conditional on LOCKDEBUG, there's no reason.
- Make space for a new flag bit (not added yet).
diffstat:
sys/kern/kern_rwlock.c | 262 ++++++++++++++++++++++++------------------------
sys/sys/rwlock.h | 17 +--
2 files changed, 138 insertions(+), 141 deletions(-)
diffs (truncated from 532 to 300 lines):
diff -r f8de795a2154 -r 6fc06065be59 sys/kern/kern_rwlock.c
--- a/sys/kern/kern_rwlock.c Sun Jan 19 17:54:19 2020 +0000
+++ b/sys/kern/kern_rwlock.c Sun Jan 19 18:34:24 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_rwlock.c,v 1.60 2020/01/12 18:37:10 ad Exp $ */
+/* $NetBSD: kern_rwlock.c,v 1.61 2020/01/19 18:34:24 ad Exp $ */
/*-
* Copyright (c) 2002, 2006, 2007, 2008, 2009, 2019, 2020
@@ -39,7 +39,9 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_rwlock.c,v 1.60 2020/01/12 18:37:10 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_rwlock.c,v 1.61 2020/01/19 18:34:24 ad Exp $");
+
+#include "opt_lockdebug.h"
#define __RWLOCK_PRIVATE
@@ -63,58 +65,32 @@
* LOCKDEBUG
*/
-#if defined(LOCKDEBUG)
+#define RW_DEBUG_P(rw) (((rw)->rw_owner & RW_NODEBUG) == 0)
-#define RW_WANTLOCK(rw, op) \
- LOCKDEBUG_WANTLOCK(RW_DEBUG_P(rw), (rw), \
- (uintptr_t)__builtin_return_address(0), op == RW_READER);
-#define RW_LOCKED(rw, op) \
- LOCKDEBUG_LOCKED(RW_DEBUG_P(rw), (rw), NULL, \
- (uintptr_t)__builtin_return_address(0), op == RW_READER);
-#define RW_UNLOCKED(rw, op) \
- LOCKDEBUG_UNLOCKED(RW_DEBUG_P(rw), (rw), \
- (uintptr_t)__builtin_return_address(0), op == RW_READER);
-#define RW_DASSERT(rw, cond) \
-do { \
- if (__predict_false(!(cond))) \
- rw_abort(__func__, __LINE__, rw, "assertion failed: " #cond);\
-} while (/* CONSTCOND */ 0);
-
-#else /* LOCKDEBUG */
-
-#define RW_WANTLOCK(rw, op) /* nothing */
-#define RW_LOCKED(rw, op) /* nothing */
-#define RW_UNLOCKED(rw, op) /* nothing */
-#define RW_DASSERT(rw, cond) /* nothing */
-
-#endif /* LOCKDEBUG */
+#define RW_WANTLOCK(rw, op) \
+ LOCKDEBUG_WANTLOCK(RW_DEBUG_P(rw), (rw), \
+ (uintptr_t)__builtin_return_address(0), op == RW_READER);
+#define RW_LOCKED(rw, op) \
+ LOCKDEBUG_LOCKED(RW_DEBUG_P(rw), (rw), NULL, \
+ (uintptr_t)__builtin_return_address(0), op == RW_READER);
+#define RW_UNLOCKED(rw, op) \
+ LOCKDEBUG_UNLOCKED(RW_DEBUG_P(rw), (rw), \
+ (uintptr_t)__builtin_return_address(0), op == RW_READER);
/*
* DIAGNOSTIC
*/
#if defined(DIAGNOSTIC)
-
-#define RW_ASSERT(rw, cond) \
-do { \
- if (__predict_false(!(cond))) \
+#define RW_ASSERT(rw, cond) \
+do { \
+ if (__predict_false(!(cond))) \
rw_abort(__func__, __LINE__, rw, "assertion failed: " #cond);\
} while (/* CONSTCOND */ 0)
-
#else
-
#define RW_ASSERT(rw, cond) /* nothing */
-
#endif /* DIAGNOSTIC */
-#define RW_SETDEBUG(rw, on) ((rw)->rw_owner |= (on) ? 0 : RW_NODEBUG)
-#define RW_DEBUG_P(rw) (((rw)->rw_owner & RW_NODEBUG) == 0)
-#if defined(LOCKDEBUG)
-#define RW_INHERITDEBUG(n, o) (n) |= (o) & RW_NODEBUG
-#else /* defined(LOCKDEBUG) */
-#define RW_INHERITDEBUG(n, o) /* nothing */
-#endif /* defined(LOCKDEBUG) */
-
/*
* Memory barriers.
*/
@@ -128,29 +104,6 @@
#define RW_MEMBAR_PRODUCER() membar_producer()
#endif
-static void rw_abort(const char *, size_t, krwlock_t *, const char *);
-static void rw_dump(const volatile void *, lockop_printer_t);
-static lwp_t *rw_owner(wchan_t);
-
-static inline uintptr_t
-rw_cas(krwlock_t *rw, uintptr_t o, uintptr_t n)
-{
-
- RW_INHERITDEBUG(n, o);
- return (uintptr_t)atomic_cas_ptr((volatile void *)&rw->rw_owner,
- (void *)o, (void *)n);
-}
-
-static inline void
-rw_swap(krwlock_t *rw, uintptr_t o, uintptr_t n)
-{
-
- RW_INHERITDEBUG(n, o);
- n = (uintptr_t)atomic_swap_ptr((volatile void *)&rw->rw_owner,
- (void *)n);
- RW_DASSERT(rw, n == o);
-}
-
/*
* For platforms that do not provide stubs, or for the LOCKDEBUG case.
*/
@@ -164,6 +117,10 @@
__strong_alias(rw_tryenter,rw_vector_tryenter);
#endif
+static void rw_abort(const char *, size_t, krwlock_t *, const char *);
+static void rw_dump(const volatile void *, lockop_printer_t);
+static lwp_t *rw_owner(wchan_t);
+
lockops_t rwlock_lockops = {
.lo_name = "Reader / writer lock",
.lo_type = LOCKOPS_SLEEP,
@@ -179,6 +136,37 @@
};
/*
+ * rw_cas:
+ *
+ * Do an atomic compare-and-swap on the lock word.
+ */
+static inline uintptr_t
+rw_cas(krwlock_t *rw, uintptr_t o, uintptr_t n)
+{
+
+ return (uintptr_t)atomic_cas_ptr((volatile void *)&rw->rw_owner,
+ (void *)o, (void *)n);
+}
+
+/*
+ * rw_swap:
+ *
+ * Do an atomic swap of the lock word. This is used only when it's
+ * known that the lock word is set up such that it can't be changed
+ * behind us (assert this), so there's no point considering the result.
+ */
+static inline void
+rw_swap(krwlock_t *rw, uintptr_t o, uintptr_t n)
+{
+
+ n = (uintptr_t)atomic_swap_ptr((volatile void *)&rw->rw_owner,
+ (void *)n);
+
+ RW_ASSERT(rw, n == o);
+ RW_ASSERT(rw, (o & RW_HAS_WAITERS) != 0);
+}
+
+/*
* rw_dump:
*
* Dump the contents of a rwlock structure.
@@ -214,16 +202,14 @@
*
* Initialize a rwlock for use.
*/
-void _rw_init(krwlock_t *, uintptr_t);
void
_rw_init(krwlock_t *rw, uintptr_t return_address)
{
- bool dodebug;
- memset(rw, 0, sizeof(*rw));
-
- dodebug = LOCKDEBUG_ALLOC(rw, &rwlock_lockops, return_address);
- RW_SETDEBUG(rw, dodebug);
+ if (LOCKDEBUG_ALLOC(rw, &rwlock_lockops, return_address))
+ rw->rw_owner = 0;
+ else
+ rw->rw_owner = RW_NODEBUG;
}
void
@@ -243,7 +229,7 @@
{
RW_ASSERT(rw, (rw->rw_owner & ~RW_NODEBUG) == 0);
- LOCKDEBUG_FREE(RW_DEBUG_P(rw), rw);
+ LOCKDEBUG_FREE((rw->rw_owner & RW_NODEBUG) == 0, rw);
}
/*
@@ -327,7 +313,7 @@
need_wait = RW_WRITE_LOCKED | RW_WRITE_WANTED;
queue = TS_READER_Q;
} else {
- RW_DASSERT(rw, op == RW_WRITER);
+ RW_ASSERT(rw, op == RW_WRITER);
incr = curthread | RW_WRITE_LOCKED;
set_wait = RW_HAS_WAITERS | RW_WRITE_WANTED;
need_wait = RW_WRITE_LOCKED | RW_THREAD;
@@ -430,7 +416,7 @@
(uintptr_t)__builtin_return_address(0)));
LOCKSTAT_EXIT(lsflag);
- RW_DASSERT(rw, (op != RW_READER && RW_OWNER(rw) == curthread) ||
+ RW_ASSERT(rw, (op != RW_READER && RW_OWNER(rw) == curthread) ||
(op == RW_READER && RW_COUNT(rw) != 0));
RW_LOCKED(rw, op);
}
@@ -448,7 +434,8 @@
int rcnt, wcnt;
lwp_t *l;
- curthread = (uintptr_t)curlwp;
+ l = curlwp;
+ curthread = (uintptr_t)l;
RW_ASSERT(rw, curthread != 0);
/*
@@ -491,8 +478,8 @@
*/
ts = turnstile_lookup(rw);
owner = rw->rw_owner;
- RW_DASSERT(rw, ts != NULL);
- RW_DASSERT(rw, (owner & RW_HAS_WAITERS) != 0);
+ RW_ASSERT(rw, ts != NULL);
+ RW_ASSERT(rw, (owner & RW_HAS_WAITERS) != 0);
wcnt = TS_WAITERS(ts, TS_WRITER_Q);
rcnt = TS_WAITERS(ts, TS_READER_Q);
@@ -509,31 +496,35 @@
* do the work of acquiring the lock in rw_vector_enter().
*/
if (rcnt == 0 || decr == RW_READ_INCR) {
- RW_DASSERT(rw, wcnt != 0);
- RW_DASSERT(rw, (owner & RW_WRITE_WANTED) != 0);
+ RW_ASSERT(rw, wcnt != 0);
+ RW_ASSERT(rw, (owner & RW_WRITE_WANTED) != 0);
if (rcnt != 0) {
/* Give the lock to the longest waiting writer. */
l = TS_FIRST(ts, TS_WRITER_Q);
- newown = (uintptr_t)l | RW_WRITE_LOCKED | RW_HAS_WAITERS;
+ newown = (uintptr_t)l | (owner & RW_NODEBUG);
+ newown |= RW_WRITE_LOCKED | RW_HAS_WAITERS;
if (wcnt > 1)
newown |= RW_WRITE_WANTED;
rw_swap(rw, owner, newown);
turnstile_wakeup(ts, TS_WRITER_Q, 1, l);
} else {
/* Wake all writers and let them fight it out. */
- rw_swap(rw, owner, RW_WRITE_WANTED);
+ newown = owner & RW_NODEBUG;
+ newown |= RW_WRITE_WANTED;
+ rw_swap(rw, owner, newown);
turnstile_wakeup(ts, TS_WRITER_Q, wcnt, NULL);
}
} else {
- RW_DASSERT(rw, rcnt != 0);
+ RW_ASSERT(rw, rcnt != 0);
/*
* Give the lock to all blocked readers. If there
* is a writer waiting, new readers that arrive
* after the release will be blocked out.
*/
- newown = rcnt << RW_READ_COUNT_SHIFT;
+ newown = owner & RW_NODEBUG;
+ newown += rcnt << RW_READ_COUNT_SHIFT;
if (wcnt != 0)
newown |= RW_HAS_WAITERS | RW_WRITE_WANTED;
@@ -552,8 +543,10 @@
rw_vector_tryenter(krwlock_t *rw, const krw_t op)
{
uintptr_t curthread, owner, incr, need_wait, next;
+ lwp_t *l;
- curthread = (uintptr_t)curlwp;
+ l = curlwp;
+ curthread = (uintptr_t)l;
RW_ASSERT(rw, curthread != 0);
@@ -561,7 +554,7 @@
incr = RW_READ_INCR;
need_wait = RW_WRITE_LOCKED | RW_WRITE_WANTED;
} else {
- RW_DASSERT(rw, op == RW_WRITER);
+ RW_ASSERT(rw, op == RW_WRITER);
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