xref: /freebsd/usr.sbin/bhyve/mevent.c (revision 0782240958117692ab9861abb5483c9e64f6bc39)
1 /*-
2  * Copyright (c) 2011 NetApp, Inc.
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 NETAPP, INC ``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 NETAPP, INC 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  * $FreeBSD$
27  */
28 
29 /*
30  * Micro event library for FreeBSD, designed for a single i/o thread
31  * using kqueue, and having events be persistent by default.
32  */
33 
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
36 
37 #include <assert.h>
38 #include <errno.h>
39 #include <stdlib.h>
40 #include <stdio.h>
41 #include <string.h>
42 #include <unistd.h>
43 
44 #include <sys/types.h>
45 #include <sys/event.h>
46 #include <sys/time.h>
47 
48 #include <pthread.h>
49 #include <pthread_np.h>
50 
51 #include "mevent.h"
52 
53 #define	MEVENT_MAX	64
54 
55 #define MEV_ENABLE	1
56 #define MEV_DISABLE	2
57 #define MEV_DEL_PENDING	3
58 
59 extern char *vmname;
60 
61 static pthread_t mevent_tid;
62 static int mevent_timid = 43;
63 static int mevent_pipefd[2];
64 static pthread_mutex_t mevent_lmutex = PTHREAD_MUTEX_INITIALIZER;
65 
66 struct mevent {
67 	void	(*me_func)(int, enum ev_type, void *);
68 #define me_msecs me_fd
69 	int	me_fd;
70 	int	me_timid;
71 	enum ev_type me_type;
72 	void    *me_param;
73 	int	me_cq;
74 	int	me_state;
75 	int	me_closefd;
76 	LIST_ENTRY(mevent) me_list;
77 };
78 
79 static LIST_HEAD(listhead, mevent) global_head, change_head;
80 
81 static void
82 mevent_qlock(void)
83 {
84 	pthread_mutex_lock(&mevent_lmutex);
85 }
86 
87 static void
88 mevent_qunlock(void)
89 {
90 	pthread_mutex_unlock(&mevent_lmutex);
91 }
92 
93 static void
94 mevent_pipe_read(int fd, enum ev_type type, void *param)
95 {
96 	char buf[MEVENT_MAX];
97 	int status;
98 
99 	/*
100 	 * Drain the pipe read side. The fd is non-blocking so this is
101 	 * safe to do.
102 	 */
103 	do {
104 		status = read(fd, buf, sizeof(buf));
105 	} while (status == MEVENT_MAX);
106 }
107 
108 static void
109 mevent_notify(void)
110 {
111 	char c;
112 
113 	/*
114 	 * If calling from outside the i/o thread, write a byte on the
115 	 * pipe to force the i/o thread to exit the blocking kevent call.
116 	 */
117 	if (mevent_pipefd[1] != 0 && pthread_self() != mevent_tid) {
118 		write(mevent_pipefd[1], &c, 1);
119 	}
120 }
121 
122 static int
123 mevent_kq_filter(struct mevent *mevp)
124 {
125 	int retval;
126 
127 	retval = 0;
128 
129 	if (mevp->me_type == EVF_READ)
130 		retval = EVFILT_READ;
131 
132 	if (mevp->me_type == EVF_WRITE)
133 		retval = EVFILT_WRITE;
134 
135 	if (mevp->me_type == EVF_TIMER)
136 		retval = EVFILT_TIMER;
137 
138 	return (retval);
139 }
140 
141 static int
142 mevent_kq_flags(struct mevent *mevp)
143 {
144 	int ret;
145 
146 	switch (mevp->me_state) {
147 	case MEV_ENABLE:
148 		ret = EV_ADD;
149 		if (mevp->me_type == EVF_TIMER)
150 			ret |= EV_ENABLE;
151 		break;
152 	case MEV_DISABLE:
153 		ret = EV_DISABLE;
154 		break;
155 	case MEV_DEL_PENDING:
156 		ret = EV_DELETE;
157 		break;
158 	}
159 
160 	return (ret);
161 }
162 
163 static int
164 mevent_kq_fflags(struct mevent *mevp)
165 {
166 	/* XXX nothing yet, perhaps EV_EOF for reads ? */
167 	return (0);
168 }
169 
170 static int
171 mevent_build(int mfd, struct kevent *kev)
172 {
173 	struct mevent *mevp, *tmpp;
174 	int i;
175 
176 	i = 0;
177 
178 	mevent_qlock();
179 
180 	LIST_FOREACH_SAFE(mevp, &change_head, me_list, tmpp) {
181 		if (mevp->me_closefd) {
182 			/*
183 			 * A close of the file descriptor will remove the
184 			 * event
185 			 */
186 			close(mevp->me_fd);
187 		} else {
188 			if (mevp->me_type == EVF_TIMER) {
189 				kev[i].ident = mevp->me_timid;
190 				kev[i].data = mevp->me_msecs;
191 			} else {
192 				kev[i].ident = mevp->me_fd;
193 				kev[i].data = 0;
194 			}
195 			kev[i].filter = mevent_kq_filter(mevp);
196 			kev[i].flags = mevent_kq_flags(mevp);
197 			kev[i].fflags = mevent_kq_fflags(mevp);
198 			kev[i].udata = mevp;
199 			i++;
200 		}
201 
202 		mevp->me_cq = 0;
203 		LIST_REMOVE(mevp, me_list);
204 
205 		if (mevp->me_state == MEV_DEL_PENDING) {
206 			free(mevp);
207 		} else {
208 			LIST_INSERT_HEAD(&global_head, mevp, me_list);
209 		}
210 
211 		assert(i < MEVENT_MAX);
212 	}
213 
214 	mevent_qunlock();
215 
216 	return (i);
217 }
218 
219 static void
220 mevent_handle(struct kevent *kev, int numev)
221 {
222 	struct mevent *mevp;
223 	int i;
224 
225 	for (i = 0; i < numev; i++) {
226 		mevp = kev[i].udata;
227 
228 		/* XXX check for EV_ERROR ? */
229 
230 		(*mevp->me_func)(mevp->me_fd, mevp->me_type, mevp->me_param);
231 	}
232 }
233 
234 struct mevent *
235 mevent_add(int tfd, enum ev_type type,
236 	   void (*func)(int, enum ev_type, void *), void *param)
237 {
238 	struct mevent *lp, *mevp;
239 
240 	if (tfd < 0 || func == NULL) {
241 		return (NULL);
242 	}
243 
244 	mevp = NULL;
245 
246 	mevent_qlock();
247 
248 	/*
249 	 * Verify that the fd/type tuple is not present in any list
250 	 */
251 	LIST_FOREACH(lp, &global_head, me_list) {
252 		if (type != EVF_TIMER && lp->me_fd == tfd &&
253 		    lp->me_type == type) {
254 			goto exit;
255 		}
256 	}
257 
258 	LIST_FOREACH(lp, &change_head, me_list) {
259 		if (type != EVF_TIMER && lp->me_fd == tfd &&
260 		    lp->me_type == type) {
261 			goto exit;
262 		}
263 	}
264 
265 	/*
266 	 * Allocate an entry, populate it, and add it to the change list.
267 	 */
268 	mevp = malloc(sizeof(struct mevent));
269 	if (mevp == NULL) {
270 		goto exit;
271 	}
272 
273 	memset(mevp, 0, sizeof(struct mevent));
274 	if (type == EVF_TIMER) {
275 		mevp->me_msecs = tfd;
276 		mevp->me_timid = mevent_timid++;
277 	} else
278 		mevp->me_fd = tfd;
279 	mevp->me_type = type;
280 	mevp->me_func = func;
281 	mevp->me_param = param;
282 
283 	LIST_INSERT_HEAD(&change_head, mevp, me_list);
284 	mevp->me_cq = 1;
285 	mevp->me_state = MEV_ENABLE;
286 	mevent_notify();
287 
288 exit:
289 	mevent_qunlock();
290 
291 	return (mevp);
292 }
293 
294 static int
295 mevent_update(struct mevent *evp, int newstate)
296 {
297 	/*
298 	 * It's not possible to enable/disable a deleted event
299 	 */
300 	if (evp->me_state == MEV_DEL_PENDING)
301 		return (EINVAL);
302 
303 	/*
304 	 * No update needed if state isn't changing
305 	 */
306 	if (evp->me_state == newstate)
307 		return (0);
308 
309 	mevent_qlock();
310 
311 	evp->me_state = newstate;
312 
313 	/*
314 	 * Place the entry onto the changed list if not already there.
315 	 */
316 	if (evp->me_cq == 0) {
317 		evp->me_cq = 1;
318 		LIST_REMOVE(evp, me_list);
319 		LIST_INSERT_HEAD(&change_head, evp, me_list);
320 		mevent_notify();
321 	}
322 
323 	mevent_qunlock();
324 
325 	return (0);
326 }
327 
328 int
329 mevent_enable(struct mevent *evp)
330 {
331 
332 	return (mevent_update(evp, MEV_ENABLE));
333 }
334 
335 int
336 mevent_disable(struct mevent *evp)
337 {
338 
339 	return (mevent_update(evp, MEV_DISABLE));
340 }
341 
342 static int
343 mevent_delete_event(struct mevent *evp, int closefd)
344 {
345 	mevent_qlock();
346 
347 	/*
348          * Place the entry onto the changed list if not already there, and
349 	 * mark as to be deleted.
350          */
351         if (evp->me_cq == 0) {
352 		evp->me_cq = 1;
353 		LIST_REMOVE(evp, me_list);
354 		LIST_INSERT_HEAD(&change_head, evp, me_list);
355 		mevent_notify();
356         }
357 	evp->me_state = MEV_DEL_PENDING;
358 
359 	if (closefd)
360 		evp->me_closefd = 1;
361 
362 	mevent_qunlock();
363 
364 	return (0);
365 }
366 
367 int
368 mevent_delete(struct mevent *evp)
369 {
370 
371 	return (mevent_delete_event(evp, 0));
372 }
373 
374 int
375 mevent_delete_close(struct mevent *evp)
376 {
377 
378 	return (mevent_delete_event(evp, 1));
379 }
380 
381 static void
382 mevent_set_name(void)
383 {
384 
385 	pthread_set_name_np(mevent_tid, "mevent");
386 }
387 
388 void
389 mevent_dispatch(void)
390 {
391 	struct kevent changelist[MEVENT_MAX];
392 	struct kevent eventlist[MEVENT_MAX];
393 	struct mevent *pipev;
394 	int mfd;
395 	int numev;
396 	int ret;
397 
398 	mevent_tid = pthread_self();
399 	mevent_set_name();
400 
401 	mfd = kqueue();
402 	assert(mfd > 0);
403 
404 	/*
405 	 * Open the pipe that will be used for other threads to force
406 	 * the blocking kqueue call to exit by writing to it. Set the
407 	 * descriptor to non-blocking.
408 	 */
409 	ret = pipe(mevent_pipefd);
410 	if (ret < 0) {
411 		perror("pipe");
412 		exit(0);
413 	}
414 
415 	/*
416 	 * Add internal event handler for the pipe write fd
417 	 */
418 	pipev = mevent_add(mevent_pipefd[0], EVF_READ, mevent_pipe_read, NULL);
419 	assert(pipev != NULL);
420 
421 	for (;;) {
422 		/*
423 		 * Build changelist if required.
424 		 * XXX the changelist can be put into the blocking call
425 		 * to eliminate the extra syscall. Currently better for
426 		 * debug.
427 		 */
428 		numev = mevent_build(mfd, changelist);
429 		if (numev) {
430 			ret = kevent(mfd, changelist, numev, NULL, 0, NULL);
431 			if (ret == -1) {
432 				perror("Error return from kevent change");
433 			}
434 		}
435 
436 		/*
437 		 * Block awaiting events
438 		 */
439 		ret = kevent(mfd, NULL, 0, eventlist, MEVENT_MAX, NULL);
440 		if (ret == -1) {
441 			perror("Error return from kevent monitor");
442 		}
443 
444 		/*
445 		 * Handle reported events
446 		 */
447 		mevent_handle(eventlist, ret);
448 	}
449 }
450