1/*-
2 * Copyright (c) 2010 Giovanni Trematerra <giovanni.trematerra@gmail.com>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27/*
28 *	PURPOSE:
29 *
30 *	This kernel module helped to identify a deadlock in kthread
31 *	interface, also pointed out a race in kthread_exit function.
32 *
33 */
34
35#include <sys/param.h>
36#include <sys/kernel.h>
37#include <sys/kthread.h>
38#include <sys/lock.h>
39#include <sys/module.h>
40#include <sys/mutex.h>
41#include <sys/systm.h>
42#include <sys/time.h>
43
44#ifdef TESTPAUSE_DEBUG
45#define DPRINTF(x) do {							\
46	printf (x);							\
47} while (0)
48#else
49#define DPRINTF(x)
50#endif
51
52static struct mtx test_global_lock;
53static int global_condvar;
54static int test_thrcnt;
55volatile int QUIT;
56
57static void
58thr_suspender(void *arg)
59{
60	struct thread *td = (struct thread *) arg;
61	int error;
62
63	for (;;) {
64		if (QUIT == 1)
65			break;
66		error = kthread_suspend(td, 10*hz);
67		if (error != 0 && QUIT == 0) {
68			if (error == EWOULDBLOCK)
69				panic("Ooops: kthread deadlock\n");
70			else
71				panic("kthread_suspend error: %d\n", error);
72			break;
73		}
74	}
75
76	mtx_lock(&test_global_lock);
77	test_thrcnt--;
78	wakeup(&global_condvar);
79	mtx_unlock(&test_global_lock);
80
81	kthread_exit();
82}
83
84static void
85thr_resumer(void *arg)
86{
87	struct thread *td = (struct thread *) arg;
88	int error;
89
90	for (;;) {
91		/* must be the last thread to exit */
92		if (QUIT == 1 && test_thrcnt == 1)
93			break;
94		error = kthread_resume(td);
95		if (error != 0)
96			panic("%s: error on kthread_resume. error: %d\n",
97				   	__func__, error);
98	}
99
100	mtx_lock(&test_global_lock);
101	test_thrcnt--;
102	wakeup(&global_condvar);
103	mtx_unlock(&test_global_lock);
104
105	kthread_exit();
106}
107
108static void
109thr_getsuspended(void *arg)
110{
111	for (;;) {
112		if (QUIT == 1)
113			break;
114		kthread_suspend_check();
115	}
116
117	mtx_lock(&test_global_lock);
118	test_thrcnt--;
119	wakeup(&global_condvar);
120	mtx_unlock(&test_global_lock);
121
122	kthread_exit();
123}
124
125static void
126kthrdlk_init(void)
127{
128	struct proc *testproc;
129	struct thread *newthr;
130	int error;
131
132	QUIT = 0;
133	test_thrcnt = 3;
134	mtx_init(&test_global_lock, "kthrdlk_lock", NULL, MTX_DEF);
135	testproc = NULL;
136	error = kproc_kthread_add(thr_getsuspended, NULL, &testproc, &newthr,
137	    0, 0, "kthrdlk", "thr_getsuspended");
138	if (error != 0)
139		panic("cannot start thr_getsuspended error: %d\n", error);
140
141	error = kproc_kthread_add(thr_resumer, newthr, &testproc, NULL, 0, 0,
142	    "kthrdlk", "thr_resumer");
143	if (error != 0)
144		panic("cannot start thr_resumer error: %d\n", error);
145
146	error = kproc_kthread_add(thr_suspender, newthr, &testproc, NULL, 0, 0,
147	    "kthrdlk", "thr_suspender");
148	if (error != 0)
149		panic("cannot start thr_suspender error: %d\n", error);
150}
151
152static void
153kthrdlk_done(void)
154{
155	int ret;
156	DPRINTF(("sending QUIT signal to the thrdlk threads\n"));
157
158	/* wait kernel threads end */
159	mtx_lock(&test_global_lock);
160	QUIT = 1;
161	while (test_thrcnt != 0) {
162		ret = mtx_sleep(&global_condvar, &test_global_lock, 0, "waiting thrs end", 30 * hz);
163		if (ret == EWOULDBLOCK) {
164			panic("some threads not die! remaining: %d", test_thrcnt);
165			break;
166		}
167	}
168	if (test_thrcnt == 0)
169		DPRINTF(("All test_pause threads die\n"));
170
171	mtx_destroy(&test_global_lock);
172}
173
174static int
175kthrdlk_handler(module_t mod, int /*modeventtype_t*/ what,
176                            void *arg)
177{
178	switch (what) {
179		case MOD_LOAD:
180			kthrdlk_init();
181			uprintf("kthrdlk loaded!\n");
182			return (0);
183		case MOD_UNLOAD:
184			kthrdlk_done();
185			uprintf("Bye Bye! kthrdlk unloaded!\n");
186			return (0);
187	}
188
189	return (EOPNOTSUPP);
190}
191
192static moduledata_t mod_data= {
193             "kthrdlk",
194             kthrdlk_handler,
195             0
196     };
197
198MODULE_VERSION(kthrdlk, 1);
199
200DECLARE_MODULE(kthrdlk, mod_data, SI_SUB_EXEC, SI_ORDER_ANY);
201
202