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Index: head/share/man/man9/Makefile
===================================================================
--- head/share/man/man9/Makefile
+++ head/share/man/man9/Makefile
@@ -1181,6 +1181,8 @@
mutex.9 MTX_SYSINIT.9 \
mutex.9 mtx_trylock.9 \
mutex.9 mtx_trylock_flags.9 \
+ mutex.9 mtx_trylock_spin.9 \
+ mutex.9 mtx_trylock_spin_flags.9 \
mutex.9 mtx_unlock.9 \
mutex.9 mtx_unlock_flags.9 \
mutex.9 mtx_unlock_spin.9 \
Index: head/share/man/man9/mutex.9
===================================================================
--- head/share/man/man9/mutex.9
+++ head/share/man/man9/mutex.9
@@ -28,7 +28,7 @@
.\" from BSDI $Id: mutex.4,v 1.1.2.3 1998/04/27 22:53:13 ewv Exp $
.\" $FreeBSD$
.\"
-.Dd December 13, 2014
+.Dd July 18, 2016
.Dt MUTEX 9
.Os
.Sh NAME
@@ -41,6 +41,8 @@
.Nm mtx_lock_spin_flags ,
.Nm mtx_trylock ,
.Nm mtx_trylock_flags ,
+.Nm mtx_trylock_spin ,
+.Nm mtx_trylock_spin_flags ,
.Nm mtx_unlock ,
.Nm mtx_unlock_spin ,
.Nm mtx_unlock_flags ,
@@ -73,6 +75,10 @@
.Ft int
.Fn mtx_trylock_flags "struct mtx *mutex" "int flags"
.Ft void
+.Fn mtx_trylock_spin "struct mtx *mutex"
+.Ft int
+.Fn mtx_trylock_spin_flags "struct mtx *mutex" "int flags"
+.Ft void
.Fn mtx_unlock "struct mtx *mutex"
.Ft void
.Fn mtx_unlock_spin "struct mtx *mutex"
@@ -249,26 +255,33 @@
.Pp
The
.Fn mtx_trylock
-attempts to acquire the
+and
+.Fn mtx_trylock_spin
+functions attempt to acquire a
.Dv MTX_DEF
-mutex pointed to by
+or
+.Dv MTX_SPIN
+mutex, respectively, pointed to by
.Fa mutex .
-If the mutex cannot be immediately acquired
-.Fn mtx_trylock
-will return 0,
-otherwise the mutex will be acquired
-and a non-zero value will be returned.
+If the mutex cannot be immediately acquired, the functions will return 0,
+otherwise the mutex will be acquired and a non-zero value will be returned.
.Pp
The
.Fn mtx_trylock_flags
-function has the same behavior as
+and
+.Fn mtx_trylock_spin_flags
+functions have the same behavior as
.Fn mtx_trylock
-but should be used when the caller desires to pass in a
+and
+.Fn mtx_trylock_spin
+respectively, but should be used when the caller desires to pass in a
.Fa flags
value.
Presently, the only valid value in the
.Fn mtx_trylock
-case is
+and
+.Fn mtx_trylock_spin
+cases is
.Dv MTX_QUIET ,
and its effects are identical to those described for
.Fn mtx_lock
@@ -447,6 +460,13 @@
.It Dv MTX_RECURSE
Specifies that the initialized mutex is allowed to recurse.
This bit must be present if the mutex is permitted to recurse.
+.Pp
+Note that neither
+.Fn mtx_trylock
+nor
+.Fn mtx_trylock_spin
+support recursion;
+that is, attempting to acquire an already-owned mutex fails.
.It Dv MTX_QUIET
Do not log any mutex operations for this lock.
.It Dv MTX_NOWITNESS
@@ -534,3 +554,7 @@
.Bsx 4.1
and
.Fx 5.0 .
+The
+.Fn mtx_trylock_spin
+function was added in
+.Fx 12.0 .
Index: head/sys/kern/kern_mutex.c
===================================================================
--- head/sys/kern/kern_mutex.c
+++ head/sys/kern/kern_mutex.c
@@ -281,6 +281,34 @@
WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
}
+int
+__mtx_trylock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
+ int line)
+{
+ struct mtx *m;
+
+ if (SCHEDULER_STOPPED())
+ return (1);
+
+ m = mtxlock2mtx(c);
+
+ KASSERT(m->mtx_lock != MTX_DESTROYED,
+ ("mtx_trylock_spin() of destroyed mutex @ %s:%d", file, line));
+ KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
+ ("mtx_trylock_spin() of sleep mutex %s @ %s:%d",
+ m->lock_object.lo_name, file, line));
+ KASSERT((opts & MTX_RECURSE) == 0,
+ ("mtx_trylock_spin: unsupp. opt MTX_RECURSE on mutex %s @ %s:%d\n",
+ m->lock_object.lo_name, file, line));
+ if (__mtx_trylock_spin(m, curthread, opts, file, line)) {
+ LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 1, file, line);
+ WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
+ return (1);
+ }
+ LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 0, file, line);
+ return (0);
+}
+
void
__mtx_unlock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
int line)
Index: head/sys/sys/mutex.h
===================================================================
--- head/sys/sys/mutex.h
+++ head/sys/sys/mutex.h
@@ -112,6 +112,8 @@
int line);
void __mtx_lock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
int line);
+int __mtx_trylock_spin_flags(volatile uintptr_t *c, int opts,
+ const char *file, int line);
void __mtx_unlock_spin_flags(volatile uintptr_t *c, int opts,
const char *file, int line);
#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
@@ -152,6 +154,8 @@
__mtx_unlock_flags(&(m)->mtx_lock, o, f, l)
#define _mtx_lock_spin_flags(m, o, f, l) \
__mtx_lock_spin_flags(&(m)->mtx_lock, o, f, l)
+#define _mtx_trylock_spin_flags(m, o, f, l) \
+ __mtx_trylock_spin_flags(&(m)->mtx_lock, o, f, l)
#define _mtx_unlock_spin_flags(m, o, f, l) \
__mtx_unlock_spin_flags(&(m)->mtx_lock, o, f, l)
#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
@@ -212,6 +216,21 @@
LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, \
mp, 0, 0, file, line); \
} while (0)
+#define __mtx_trylock_spin(mp, tid, opts, file, line) __extension__ ({ \
+ uintptr_t _tid = (uintptr_t)(tid); \
+ int _ret; \
+ \
+ spinlock_enter(); \
+ if (((mp)->mtx_lock != MTX_UNOWNED || !_mtx_obtain_lock((mp), _tid))) {\
+ spinlock_exit(); \
+ _ret = 0; \
+ } else { \
+ LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, \
+ mp, 0, 0, file, line); \
+ _ret = 1; \
+ } \
+ _ret; \
+})
#else /* SMP */
#define __mtx_lock_spin(mp, tid, opts, file, line) do { \
uintptr_t _tid = (uintptr_t)(tid); \
@@ -224,6 +243,20 @@
(mp)->mtx_lock = _tid; \
} \
} while (0)
+#define __mtx_trylock_spin(mp, tid, opts, file, line) __extension__ ({ \
+ uintptr_t _tid = (uintptr_t)(tid); \
+ int _ret; \
+ \
+ spinlock_enter(); \
+ if ((mp)->mtx_lock != MTX_UNOWNED) { \
+ spinlock_exit(); \
+ _ret = 0; \
+ } else { \
+ (mp)->mtx_lock = _tid; \
+ _ret = 1; \
+ } \
+ _ret; \
+})
#endif /* SMP */
/* Unlock a normal mutex. */
@@ -293,6 +326,10 @@
* mtx_trylock_flags(m, opts) is used the same way as mtx_trylock() but accepts
* relevant option flags `opts.'
*
+ * mtx_trylock_spin(m) attempts to acquire MTX_SPIN mutex `m' but doesn't
+ * spin if it cannot. Rather, it returns 0 on failure and non-zero on
+ * success. It always returns failure for recursed lock attempts.
+ *
* mtx_initialized(m) returns non-zero if the lock `m' has been initialized.
*
* mtx_owned(m) returns non-zero if the current thread owns the lock `m'
@@ -302,6 +339,7 @@
#define mtx_lock(m) mtx_lock_flags((m), 0)
#define mtx_lock_spin(m) mtx_lock_spin_flags((m), 0)
#define mtx_trylock(m) mtx_trylock_flags((m), 0)
+#define mtx_trylock_spin(m) mtx_trylock_spin_flags((m), 0)
#define mtx_unlock(m) mtx_unlock_flags((m), 0)
#define mtx_unlock_spin(m) mtx_unlock_spin_flags((m), 0)
@@ -335,6 +373,8 @@
_mtx_unlock_flags((m), (opts), (file), (line))
#define mtx_lock_spin_flags_(m, opts, file, line) \
_mtx_lock_spin_flags((m), (opts), (file), (line))
+#define mtx_trylock_spin_flags_(m, opts, file, line) \
+ _mtx_trylock_spin_flags((m), (opts), (file), (line))
#define mtx_unlock_spin_flags_(m, opts, file, line) \
_mtx_unlock_spin_flags((m), (opts), (file), (line))
#else /* LOCK_DEBUG == 0 && !MUTEX_NOINLINE */
@@ -344,6 +384,8 @@
__mtx_unlock((m), curthread, (opts), (file), (line))
#define mtx_lock_spin_flags_(m, opts, file, line) \
__mtx_lock_spin((m), curthread, (opts), (file), (line))
+#define mtx_trylock_spin_flags_(m, opts, file, line) \
+ __mtx_trylock_spin((m), curthread, (opts), (file), (line))
#define mtx_unlock_spin_flags_(m, opts, file, line) \
__mtx_unlock_spin((m))
#endif /* LOCK_DEBUG > 0 || MUTEX_NOINLINE */
@@ -369,6 +411,8 @@
mtx_unlock_spin_flags_((m), (opts), LOCK_FILE, LOCK_LINE)
#define mtx_trylock_flags(m, opts) \
mtx_trylock_flags_((m), (opts), LOCK_FILE, LOCK_LINE)
+#define mtx_trylock_spin_flags(m, opts) \
+ mtx_trylock_spin_flags_((m), (opts), LOCK_FILE, LOCK_LINE)
#define mtx_assert(m, what) \
mtx_assert_((m), (what), __FILE__, __LINE__)

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