1 /* $NetBSD: linux_stop_machine.c,v 1.4 2022/04/09 23:38:33 riastradh Exp $ */
2
3 /*-
4 * Copyright (c) 2018 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Taylor R. Campbell.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 #include <sys/cdefs.h>
33 __KERNEL_RCSID(0, "$NetBSD: linux_stop_machine.c,v 1.4 2022/04/09 23:38:33 riastradh Exp $");
34
35 #include <sys/mutex.h> /* XXX work around cycle x86/mutex.h<->x86/intr.h */
36
37 #include <sys/atomic.h>
38 #include <sys/intr.h>
39 #include <sys/lock.h>
40 #include <sys/systm.h>
41 #include <sys/xcall.h>
42
43 #include <linux/stop_machine.h>
44
45 struct stop_machine {
46 int (*callback)(void *);
47 void *cookie;
48 volatile unsigned ncpu;
49 volatile bool done;
50 };
51
52 static void
stop_machine_xcall(void * a,void * b)53 stop_machine_xcall(void *a, void *b)
54 {
55 struct stop_machine *S = a;
56 int s;
57
58 /* Block all activity on this CPU. */
59 s = splhigh();
60
61 /* Note that we're ready, and see whether we're the chosen one. */
62 membar_release();
63 if (atomic_dec_uint_nv(&S->ncpu) != 0) {
64 while (!atomic_load_acquire(&S->done))
65 SPINLOCK_BACKOFF_HOOK;
66 goto out;
67 }
68 membar_acquire();
69
70 /* It's time. Call the callback. */
71 S->callback(S->cookie);
72
73 /* Notify everyone else that we're done. */
74 atomic_store_release(&S->done, true);
75
76 /* Allow activity again. */
77 out: splx(s);
78 }
79
80 void
stop_machine(int (* callback)(void *),void * cookie,const struct kcpuset * cpus)81 stop_machine(int (*callback)(void *), void *cookie, const struct kcpuset *cpus)
82 {
83 struct stop_machine stop, *S = &stop;
84
85 KASSERT(cpus == NULL); /* not implemented */
86
87 S->callback = callback;
88 S->cookie = cookie;
89 S->ncpu = ncpu; /* XXX cpu hotplug */
90 S->done = false;
91
92 xc_wait(xc_broadcast(0, stop_machine_xcall, &S, NULL));
93 }
94