Module Name: src
Committed By: pgoyette
Date: Fri May 19 00:01:34 UTC 2017
Modified Files:
src/distrib/sets/lists/comp: mi
src/doc: CHANGES
src/sys/kern: files.kern
src/sys/sys: Makefile param.h
Added Files:
src/share/man/man9: localcount.9
src/sys/kern: subr_localcount.c
src/sys/sys: localcount.h
Log Message:
Introduce new localcount(9) reference-count primitives.
To generate a diff of this commit:
cvs rdiff -u -r1.2132 -r1.2133 src/distrib/sets/lists/comp/mi
cvs rdiff -u -r1.2282 -r1.2283 src/doc/CHANGES
cvs rdiff -u -r0 -r1.2 src/share/man/man9/localcount.9
cvs rdiff -u -r1.14 -r1.15 src/sys/kern/files.kern
cvs rdiff -u -r0 -r1.2 src/sys/kern/subr_localcount.c
cvs rdiff -u -r1.160 -r1.161 src/sys/sys/Makefile
cvs rdiff -u -r0 -r1.2 src/sys/sys/localcount.h
cvs rdiff -u -r1.538 -r1.539 src/sys/sys/param.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/distrib/sets/lists/comp/mi
diff -u src/distrib/sets/lists/comp/mi:1.2132 src/distrib/sets/lists/comp/mi:1.2133
--- src/distrib/sets/lists/comp/mi:1.2132 Tue May 9 22:43:09 2017
+++ src/distrib/sets/lists/comp/mi Fri May 19 00:01:33 2017
@@ -1,4 +1,4 @@
-# $NetBSD: mi,v 1.2132 2017/05/09 22:43:09 kamil Exp $
+# $NetBSD: mi,v 1.2133 2017/05/19 00:01:33 pgoyette Exp $
#
# Note: don't delete entries from here - mark them as "obsolete" instead.
./etc/mtree/set.comp comp-sys-root
@@ -2873,6 +2873,7 @@
./usr/include/sys/ksyms.h comp-c-include
./usr/include/sys/ktrace.h comp-c-include
./usr/include/sys/lkm.h comp-obsolete obsolete
+./usr/include/sys/localcount.h comp-c-include
./usr/include/sys/localedef.h comp-c-include
./usr/include/sys/lock.h comp-c-include
./usr/include/sys/lockf.h comp-c-include
@@ -10745,6 +10746,7 @@
./usr/share/man/cat9/le64enc.0 comp-sys-catman .cat
./usr/share/man/cat9/le64toh.0 comp-sys-catman .cat
./usr/share/man/cat9/linedisc.0 comp-sys-catman .cat
+./usr/share/man/cat9/localcount.0 comp-sys-catman .cat
./usr/share/man/cat9/lock.0 comp-sys-catman .cat
./usr/share/man/cat9/locking.0 comp-sys-catman .cat
./usr/share/man/cat9/lockinit.0 comp-sys-catman .cat
@@ -18192,6 +18194,7 @@
./usr/share/man/html9/le64enc.html comp-sys-htmlman html
./usr/share/man/html9/le64toh.html comp-sys-htmlman html
./usr/share/man/html9/linedisc.html comp-sys-htmlman html
+./usr/share/man/html9/localcount.html comp-sys-htmlman html
./usr/share/man/html9/lock.html comp-sys-htmlman html
./usr/share/man/html9/locking.html comp-sys-htmlman html
./usr/share/man/html9/lockinit.html comp-sys-htmlman html
@@ -25793,6 +25796,7 @@
./usr/share/man/man9/le64enc.9 comp-sys-man .man
./usr/share/man/man9/le64toh.9 comp-sys-man .man
./usr/share/man/man9/linedisc.9 comp-sys-man .man
+./usr/share/man/man9/localcount.9 comp-sys-man .man
./usr/share/man/man9/lock.9 comp-sys-man .man
./usr/share/man/man9/locking.9 comp-sys-man .man
./usr/share/man/man9/lockinit.9 comp-sys-man .man
Index: src/doc/CHANGES
diff -u src/doc/CHANGES:1.2282 src/doc/CHANGES:1.2283
--- src/doc/CHANGES:1.2282 Tue May 16 23:00:42 2017
+++ src/doc/CHANGES Fri May 19 00:01:33 2017
@@ -1,4 +1,4 @@
-# LIST OF CHANGES FROM LAST RELEASE: <$Revision: 1.2282 $>
+# LIST OF CHANGES FROM LAST RELEASE: <$Revision: 1.2283 $>
#
#
# [Note: This file does not mention every change made to the NetBSD source tree.
@@ -513,3 +513,4 @@ Changes from NetBSD 7.0 to NetBSD 8.0:
openpam(3): update to 20170430 (resedacea) [christos 20170506]
dhcpcd: Import dhcpcd 7.0.0-rc1 [roy 20170510]
vioscsi(4): Stability fixes [jdolecek 20170515]
+ localcount(9): Add localcount ref-count primitives [pgoyette 20170519]
Index: src/sys/kern/files.kern
diff -u src/sys/kern/files.kern:1.14 src/sys/kern/files.kern:1.15
--- src/sys/kern/files.kern:1.14 Wed Apr 12 20:05:54 2017
+++ src/sys/kern/files.kern Fri May 19 00:01:33 2017
@@ -1,4 +1,4 @@
-# $NetBSD: files.kern,v 1.14 2017/04/12 20:05:54 christos Exp $
+# $NetBSD: files.kern,v 1.15 2017/05/19 00:01:33 pgoyette Exp $
#
# kernel sources
@@ -121,6 +121,7 @@ defparam opt_kmem.h KMEM_GUARD_DEPTH
file kern/subr_kmem.c kern
file kern/subr_kobj.c kern
file kern/subr_kobj_vfs.c kern
+file kern/subr_localcount.c kern
file kern/subr_lockdebug.c kern
file kern/subr_log.c kern
file kern/subr_lwp_specificdata.c kern
Index: src/sys/sys/Makefile
diff -u src/sys/sys/Makefile:1.160 src/sys/sys/Makefile:1.161
--- src/sys/sys/Makefile:1.160 Fri Dec 16 22:10:12 2016
+++ src/sys/sys/Makefile Fri May 19 00:01:34 2017
@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.160 2016/12/16 22:10:12 christos Exp $
+# $NetBSD: Makefile,v 1.161 2017/05/19 00:01:34 pgoyette Exp $
.include <bsd.own.mk>
@@ -25,7 +25,7 @@ INCS= acct.h agpio.h aio.h ansi.h aout_m
ioctl_compat.h iostat.h ipc.h \
joystick.h \
kcore.h kcpuset.h kgdb.h kmem.h ksem.h ksyms.h ktrace.h \
- localedef.h lock.h lockf.h lua.h lwp.h lwpctl.h \
+ localcount.h localedef.h lock.h lockf.h lua.h lwp.h lwpctl.h \
malloc.h mallocvar.h mbuf.h md4.h md5.h midiio.h \
mman.h module.h mount.h mqueue.h msg.h msgbuf.h mtio.h mutex.h \
namei.h null.h \
Index: src/sys/sys/param.h
diff -u src/sys/sys/param.h:1.538 src/sys/sys/param.h:1.539
--- src/sys/sys/param.h:1.538 Thu Apr 27 19:18:50 2017
+++ src/sys/sys/param.h Fri May 19 00:01:34 2017
@@ -1,4 +1,4 @@
-/* $NetBSD: param.h,v 1.538 2017/04/27 19:18:50 riastradh Exp $ */
+/* $NetBSD: param.h,v 1.539 2017/05/19 00:01:34 pgoyette Exp $ */
/*-
* Copyright (c) 1982, 1986, 1989, 1993
@@ -67,7 +67,7 @@
* 2.99.9 (299000900)
*/
-#define __NetBSD_Version__ 799007100 /* NetBSD 7.99.71 */
+#define __NetBSD_Version__ 799007200 /* NetBSD 7.99.72 */
#define __NetBSD_Prereq__(M,m,p) (((((M) * 100000000) + \
(m) * 1000000) + (p) * 100) <= __NetBSD_Version__)
Added files:
Index: src/share/man/man9/localcount.9
diff -u /dev/null src/share/man/man9/localcount.9:1.2
--- /dev/null Fri May 19 00:01:34 2017
+++ src/share/man/man9/localcount.9 Fri May 19 00:01:33 2017
@@ -0,0 +1,192 @@
+.\" $NetBSD: localcount.9,v 1.2 2017/05/19 00:01:33 pgoyette Exp $
+.\"
+.\" Copyright (c) 2016
+.\" All rights reserved.
+.\"
+.\" This code is derived from software contributed to The NetBSD Foundation
+.\" by Taylor R. Campbell.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+.\" POSSIBILITY OF SUCH DAMAGE.
+.\"
+.Dd December 8, 2016
+.Dt LOCALCOUNT 9
+.Os
+.Sh NAME
+.Nm localcount ,
+.Nm localcount_init ,
+.Nm localcount_fini ,
+.Nm localcount_acquire ,
+.Nm localcount_release ,
+.Nm localcount_drain
+.Sh SYNOPSIS
+.In sys/localcount.h
+.Ft int
+.Fn localcount_init "struct localcount *lc"
+.Ft void
+.Fn localcount_fini "struct localcount *lc"
+.Ft void
+.Fn localcount_acquire "struct localcount *lc"
+.Ft void
+.Fn localcount_release "struct localcount *lc" "struct kcondvar *cv" \
+"struct kmutex *mtx"
+.Ft void
+.Fn localcount_drain "struct localcount *lc" "struct kcondvar *cv" \
+"struct kmutex *mtx"
+.Sh DESCRIPTION
+Localcounts are used in the kernel to implement a medium-weight reference
+counting mechanism.
+During normal operations, localcounts do not need the interprocessor
+synchronization associated with
+.Xr atomic_ops 3
+atomic memory operations, and (unlike
+.Xr psref 9 )
+.Nm
+references can be held across sleeps and can migrate between CPUs.
+Draining a
+.Nm
+requires more expensive interprocessor synchronization than
+.Xr atomic_ops 3
+(similar to
+.Xr psref 9 ) .
+And
+.Nm
+references require eight bytes of memory per object per-CPU, significantly
+more than
+.Xr atomic_ops 3
+and almost always more than
+.Xr psref 9 .
+.Pp
+As a rough heuristic,
+.Nm
+should be used for classes of objects of which there are perhaps a few dozen
+instances (such as
+.Xr autoconf 9
+devices) but not thousands of instances (such as
+network flows) and on which there may be a mixture of long-term I/O waits,
+such as xyzread for a device xyz(4), and short-term fast operations, such as
+.Dv xyzioctl(IOC_READ_A_CPU_REG) .
+.Sh FUNCTIONS
+.Bl -tag -width abcd
+.It Fn localcount_init "lc"
+.Pp
+Dynamically initialize localcount
+.Ar lc
+for use.
+.Pp
+No other operations can be performed on a localcount until it has been
+initialized.
+.It Fn localcount_fini "lc"
+.Pp
+Release resources used by localcount
+.Ar lc .
+The caller must have already called
+.Fn localcount_drain .
+The localcount may not be used after
+.Fn localcount_fini
+has been called until it has been re-initialized by
+.Fn localcount_init .
+.It Fn localcount_acquire "lc"
+.Pp
+Acquire a reference to the localcount
+.Ar lc .
+.It Fn localcount_release "lc" "cv" "mtx"
+.Pp
+Release a reference to the localcount
+.Ar lc .
+If the localcount is currently being drained, the mutex
+.Ar mtx
+will be used to synchronize updates to the global reference count (i.e.
+the total across all CPUs).
+If the reference count goes to zero,
+.Fn localcount_release
+will broadcast availability of the condvar
+.Ar cv .
+.It Fn localcount_drain "lc" "cv" "mtx"
+.Pp
+Wait for all references to the localcount
+.Ar lc
+to be released.
+The caller must hold the mutex
+.Ar mtx ;
+the mutex will be released during inter-CPU cross-calls (see
+.Xr xcall 9 ) and while waiting on the condvar
+.Ar cv .
+The same
+.Ar cv
+and
+.Ar mtx
+must be used with
+.Fn localcount_release .
+.Pp
+The caller must guarantee that no new references can be acquired with
+localcount_acquire before calling
+.Fn localcount_drain .
+For example, any object that may be found in a list and acquired must be
+removed from the list before calling
+.Fn localcount_drain .
+Once the localcount object
+.Ar lc
+is passed to
+.Fn localcount_drain ,
+it must be passed to
+.Fn localcount_fini
+before any other re-use.
+.Sh CODE REFERENCES
+The core of the localcount implementation is in
+.Pa sys/kern/subr_localcount.c .
+.Pp
+The header file
+.Pa sys/sys/localcount.h
+describes the public interface, and interfaces that machine-dependent
+code must provide to support localcounts.
+.Sh SEE ALSO
+.Xr atomic_ops 3 ,
+.Xr condvar 9 ,
+.Xr mutex 9 ,
+and
+.Xr psref 9
+.Sh HISTORY
+The localcount primitives first appeared in
+.Nx 8.0 .
+.Sh AUTHORS
+.Nm
+was designed by
+.An -nosplit
+.An Taylor R. Campbell ,
+who also provided a draft implementation.
+The implementation was completed, tested, and integrated by
+.An Paul Goyette .
+.Sh CAVEATS
+The
+.Nm
+facility does not provide any way to examine the reference count without
+actually waiting for the count to reach zero.
+.Pp
+Waiting for a
+.Nm
+reference count to reach zero is a one-shot operation.
+Once the
+.Nm
+has been waited for, no further operations are allowed until the
+.Nm
+has been re-initialized.
+
Index: src/sys/kern/subr_localcount.c
diff -u /dev/null src/sys/kern/subr_localcount.c:1.2
--- /dev/null Fri May 19 00:01:35 2017
+++ src/sys/kern/subr_localcount.c Fri May 19 00:01:33 2017
@@ -0,0 +1,255 @@
+/* $NetBSD: subr_localcount.c,v 1.2 2017/05/19 00:01:33 pgoyette Exp $ */
+
+/*-
+ * Copyright (c) 2016 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Taylor R. Campbell.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * CPU-local reference counts
+ *
+ * localcount(9) is a reference-counting scheme that involves no
+ * interprocessor synchronization most of the time, at the cost of
+ * eight bytes of memory per CPU per object and at the cost of
+ * expensive interprocessor synchronization to drain references.
+ *
+ * localcount(9) references may be held across sleeps, may be
+ * transferred from CPU to CPU or thread to thread: they behave
+ * semantically like typical reference counts, with different
+ * pragmatic performance characteristics.
+ */
+
+#include <sys/cdefs.h>
+__KERNEL_RCSID(0, "$NetBSD: subr_localcount.c,v 1.2 2017/05/19 00:01:33 pgoyette Exp $");
+
+#include <sys/param.h>
+#include <sys/localcount.h>
+#include <sys/types.h>
+#include <sys/condvar.h>
+#include <sys/errno.h>
+#include <sys/mutex.h>
+#include <sys/percpu.h>
+#include <sys/xcall.h>
+
+/*
+ * localcount_init(lc)
+ *
+ * Initialize a localcount object. Returns 0 on success, error
+ * code on failure. May fail to allocate memory for percpu(9).
+ *
+ * The caller must call localcount_drain and then localcount_fini
+ * when done with lc.
+ */
+static void localcount_xc(void *, void *);
+
+int
+localcount_init(struct localcount *lc)
+{
+
+ lc->lc_totalp = NULL;
+ lc->lc_percpu = percpu_alloc(sizeof(int64_t));
+ if (lc->lc_percpu == NULL)
+ return ENOMEM;
+
+ return 0;
+}
+
+/*
+ * localcount_drain(lc, cv, interlock)
+ *
+ * Wait for all acquired references to lc to drain. Caller must
+ * hold interlock; localcount_drain releases it during cross-calls
+ * and waits on cv. The cv and interlock passed here must be the
+ * same as are passed to localcount_release for this lc.
+ *
+ * Caller must guarantee that no new references can be acquired
+ * with localcount_acquire before calling localcount_drain. For
+ * example, any object that may be found in a list and acquired
+ * must be removed from the list before localcount_drain.
+ *
+ * The localcount object lc may be used only with localcount_fini
+ * after this, unless reinitialized after localcount_fini with
+ * localcount_init.
+ */
+void
+localcount_drain(struct localcount *lc, kcondvar_t *cv, kmutex_t *interlock)
+{
+ int64_t total = 0;
+
+ KASSERT(mutex_owned(interlock));
+ KASSERT(lc->lc_totalp == NULL);
+
+ /* Mark it draining. */
+ lc->lc_totalp = &total;
+
+ /*
+ * Count up all references on all CPUs.
+ *
+ * This serves as a global memory barrier: after xc_wait, all
+ * CPUs will have witnessed the nonnull value of lc->lc_totalp,
+ * so that it is safe to wait on the cv for them.
+ */
+ mutex_exit(interlock);
+ xc_wait(xc_broadcast(0, &localcount_xc, lc, interlock));
+ mutex_enter(interlock);
+
+ /* Wait for remaining references to drain. */
+ while (total != 0) {
+ /*
+ * At this point, now that we have added up all
+ * references on all CPUs, the total had better be
+ * nonnegative.
+ */
+ KASSERTMSG((0 < total),
+ "negatively referenced localcount: %p, %"PRId64,
+ lc, total);
+ cv_wait(cv, interlock);
+ }
+
+ /* Paranoia: Cause any further use of lc->lc_totalp to crash. */
+ lc->lc_totalp = (void *)(uintptr_t)1;
+}
+
+/*
+ * localcount_fini(lc)
+ *
+ * Finalize a localcount object, releasing any memory allocated
+ * for it. Caller must have already called localcount_drain.
+ */
+void
+localcount_fini(struct localcount *lc)
+{
+
+ KASSERT(lc->lc_totalp == (void *)(uintptr_t)1);
+ percpu_free(lc->lc_percpu, sizeof(uint64_t));
+}
+
+/*
+ * localcount_xc(cookie0, cookie1)
+ *
+ * Accumulate and transfer the per-CPU reference counts to a
+ * global total, resetting the per-CPU counter to zero. Once
+ * localcount_drain() has started, we only maintain the total
+ * count in localcount_release().
+ */
+static void
+localcount_xc(void *cookie0, void *cookie1)
+{
+ struct localcount *lc = cookie0;
+ kmutex_t *interlock = cookie1;
+ int64_t *localp;
+
+ mutex_enter(interlock);
+ localp = percpu_getref(lc->lc_percpu);
+ *lc->lc_totalp += *localp;
+ *localp -= *localp; /* ie, *localp = 0; */
+ percpu_putref(lc->lc_percpu);
+ mutex_exit(interlock);
+}
+
+static void
+localcount_adjust(struct localcount *lc, int delta)
+{
+ int64_t *localp;
+
+ localp = percpu_getref(lc->lc_percpu);
+ *localp += delta;
+ percpu_putref(lc->lc_percpu);
+}
+
+/*
+ * localcount_acquire(lc)
+ *
+ * Acquire a reference to lc.
+ *
+ * The reference may be held across sleeps and may be migrated
+ * from CPU to CPU, or even thread to thread -- it is only
+ * counted, not associated with a particular concrete owner.
+ *
+ * Involves no interprocessor synchronization. May be used in any
+ * context: while a lock is held, within a pserialize(9) read
+ * section, in hard interrupt context (provided other users block
+ * hard interrupts), in soft interrupt context, in thread context,
+ * &c.
+ *
+ * Caller must guarantee that there is no concurrent
+ * localcount_drain. For example, any object that may be found in
+ * a list and acquired must be removed from the list before
+ * localcount_drain.
+ */
+void
+localcount_acquire(struct localcount *lc)
+{
+
+ KASSERT(lc->lc_totalp == NULL);
+ localcount_adjust(lc, +1);
+}
+
+/*
+ * localcount_release(lc, cv, interlock)
+ *
+ * Release a reference to lc. If there is a concurrent
+ * localcount_drain and this may be the last reference, notify
+ * localcount_drain by acquiring interlock, waking cv, and
+ * releasing interlock. The cv and interlock passed here must be
+ * the same as are passed to localcount_drain for this lc.
+ *
+ * Involves no interprocessor synchronization unless there is a
+ * concurrent localcount_drain in progress.
+ */
+void
+localcount_release(struct localcount *lc, kcondvar_t *cv, kmutex_t *interlock)
+{
+
+ /*
+ * Block xcall so that if someone begins draining after we see
+ * lc->lc_totalp as null, then they won't start cv_wait until
+ * after they have counted this CPU's contributions.
+ *
+ * Otherwise, localcount_drain may notice an extant reference
+ * from this CPU and cv_wait for it, but having seen
+ * lc->lc_totalp as null, this CPU will not wake
+ * localcount_drain.
+ */
+ kpreempt_disable();
+
+ KDASSERT(mutex_ownable(interlock));
+ if (__predict_false(lc->lc_totalp != NULL)) {
+ /*
+ * Slow path -- wake localcount_drain in case this is
+ * the last reference.
+ */
+ mutex_enter(interlock);
+ if (--*lc->lc_totalp == 0)
+ cv_broadcast(cv);
+ mutex_exit(interlock);
+ goto out;
+ }
+
+ localcount_adjust(lc, -1);
+ out: kpreempt_enable();
+}
Index: src/sys/sys/localcount.h
diff -u /dev/null src/sys/sys/localcount.h:1.2
--- /dev/null Fri May 19 00:01:35 2017
+++ src/sys/sys/localcount.h Fri May 19 00:01:34 2017
@@ -0,0 +1,65 @@
+/* $NetBSD: localcount.h,v 1.2 2017/05/19 00:01:34 pgoyette Exp $ */
+
+/*-
+ * Copyright (c) 2016 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Taylor R. Campbell.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _SYS_LOCALCOUNT_H
+#define _SYS_LOCALCOUNT_H
+
+#ifndef _KERNEL
+#error <sys/localcount.h> is for kernel consumers only.
+#endif
+
+#include <sys/types.h>
+
+struct kcondvar;
+struct kmutex;
+struct percpu;
+
+struct localcount {
+ int64_t *lc_totalp;
+ struct percpu *lc_percpu; /* int64_t */
+};
+
+int localcount_init(struct localcount *);
+void localcount_drain(struct localcount *, struct kcondvar *,
+ struct kmutex *);
+void localcount_fini(struct localcount *);
+void localcount_acquire(struct localcount *);
+void localcount_release(struct localcount *, struct kcondvar *,
+ struct kmutex *);
+
+#ifdef _MODULE
+#define DEVSW_MODULE_INIT \
+ .d_localcount = &(struct localcount){NULL, NULL},
+#else
+#define DEVSW_MODULE_INIT
+#endif
+
+#endif /* _SYS_LOCALCOUNT_H */
