summaryrefslogtreecommitdiffstats
path: root/threads.c
blob: 04eea8f155f9c0ec1b187045eda091b27bf5f1ae (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
/* TODO: we should guard the individual thread actions with a mutex. Else, we may
 * run into race conditions on thread termination.
 */

/* threads.c
 *
 * This file implements threading support helpers (and maybe the thread object)
 * for rsyslog.
 * 
 * File begun on 2007-12-14 by RGerhards
 *
 * Copyright 2007 Rainer Gerhards and Adiscon GmbH.
 *
 * This file is part of rsyslog.
 *
 * Rsyslog is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Rsyslog is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Rsyslog.  If not, see <http://www.gnu.org/licenses/>.
 *
 * A copy of the GPL can be found in the file "COPYING" in this distribution.
 */
#include "config.h"

#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <pthread.h>
#include <assert.h>

#include "rsyslog.h"
#include "syslogd.h"
#include "linkedlist.h"
#include "threads.h"

/* static data */
int iMainMsgQueueSize;
msgQueue *pMsgQueue = NULL;

/* linked list of currently-known threads */
static linkedList_t llThrds;

/* methods */

/* Construct a new thread object
 */
static rsRetVal thrdConstruct(thrdInfo_t **ppThis)
{
	thrdInfo_t *pThis;

	assert(ppThis != NULL);

	if((pThis = calloc(1, sizeof(thrdInfo_t))) == NULL)
		return RS_RET_OUT_OF_MEMORY;

	/* OK, we got the element, now initialize members that should
	 * not be zero-filled.
	 */
	pThis->mutTermOK = (pthread_mutex_t *) malloc (sizeof (pthread_mutex_t));
	pthread_mutex_init (pThis->mutTermOK, NULL);

	*ppThis = pThis;
	return RS_RET_OK;
}


/* Destructs a thread object. The object must not be linked to the
 * linked list of threads. Please note that the thread should have been
 * stopped before. If not, we try to do it.
 */
static rsRetVal thrdDestruct(thrdInfo_t *pThis)
{
	assert(pThis != NULL);
dbgprintf("thrdDestruct, pThis: %lx\n", pThis);

	if(pThis->bIsActive == 1) {
		thrdTerminate(pThis);
	}
	free(pThis->mutTermOK);
	free(pThis);

	return RS_RET_OK;
}


/* terminate a thread gracefully. It's termination sync state is taken into
 * account.
 */
rsRetVal thrdTerminate(thrdInfo_t *pThis)
{
	assert(pThis != NULL);
	
dbgprintf("Terminate thread %lx via method %d\n", pThis->thrdID, pThis->eTermTool);
	if(pThis->eTermTool == eTermSync_SIGNAL) {
		/* we first wait for the thread to reach a point in execution where it
		 * is safe to terminate it.
		 * TODO: TIMEOUT!
		 */
		pthread_mutex_lock(pThis->mutTermOK);
		pThis->bShallStop = 1;	/* request termination */
		pthread_kill(pThis->thrdID, SIGUSR2); /* get thread out ouf blocking calls */
		pthread_join(pThis->thrdID, NULL);
		pthread_mutex_unlock(pThis->mutTermOK);	 /* cleanup... */
		/* TODO: TIMEOUT! */
	} else if(pThis->eTermTool == eTermSync_NONE) {
		pthread_cancel(pThis->thrdID);
	}
	pThis->bIsActive = 0;

	/* call cleanup function, if any */
	if(pThis->pAfterRun != NULL)
		pThis->pAfterRun(pThis);
	
	return RS_RET_OK;
}


/* terminate all known threads gracefully.
 */
rsRetVal thrdTerminateAll(void)
{
	llDestroy(&llThrds);
	return RS_RET_OK;
}


/* This is an internal wrapper around the user thread function. Its
 * purpose is to handle all the necessary housekeeping stuff so that the
 * user function needs not to be aware of the threading calls. The user
 * function call has just "normal", non-threading semantics.
 * rgerhards, 2007-12-17
 */
static void* thrdStarter(void *arg)
{
	DEFiRet;
	thrdInfo_t *pThis = (thrdInfo_t*) arg;

	assert(pThis != NULL);
	assert(pThis->pUsrThrdMain != NULL);

	/* block all signals except the one we need for graceful termination */
	sigset_t sigSet;
	sigfillset(&sigSet);
	pthread_sigmask(SIG_BLOCK, &sigSet, NULL);
	sigemptyset(&sigSet);
	sigaddset(&sigSet, SIGUSR2);
	pthread_sigmask(SIG_UNBLOCK, &sigSet, NULL);

	/* setup complete, we are now ready to execute the user code. We will not
	 * regain control until the user code is finished, in which case we terminate
	 * the thread.
	 */
	iRet = pThis->pUsrThrdMain(pThis);

	dbgprintf("thrdStarter: usrThrdMain 0x%lx returned with iRet %d, exiting now.\n", (unsigned long) pThis->thrdID, iRet);
	pthread_exit(0);
}

/* Start a new thread and add it to the list of currently
 * executing threads. It is added at the end of the list.
 * rgerhards, 2007-12-14
 */
rsRetVal thrdCreate(rsRetVal (*thrdMain)(thrdInfo_t*), eTermSyncType_t eTermSyncType, rsRetVal(*afterRun)(thrdInfo_t *))
{
	DEFiRet;
	thrdInfo_t *pThis;
	int i;

	assert(thrdMain != NULL);

	CHKiRet(thrdConstruct(&pThis));
	pThis->eTermTool = eTermSync_NONE; // eTermSyncType; TODO: review
	pThis->bIsActive = 1;
	pThis->pUsrThrdMain = thrdMain;
	pThis->pAfterRun = afterRun;
	i = pthread_create(&pThis->thrdID, NULL, thrdStarter, pThis);
	CHKiRet(llAppend(&llThrds, NULL, pThis));

finalize_it:
	return iRet;
}


/* This is a dummy handler. We user SIGUSR2 to interrupt blocking system calls
 * if we are in termination mode 1.
 */
static void sigusr2Dummy(int __attribute__((unused)) sig)
{
	dbgprintf("sigusr2Dummy called!\n");
}


/* initialize the thread-support subsystem
 * must be called once at the start of the program
 */
rsRetVal thrdInit(void)
{
	DEFiRet;
	struct sigaction sigAct;

	iRet = llInit(&llThrds, thrdDestruct, NULL, NULL);

	/* set up our termination subsystem */
	memset(&sigAct, 0, sizeof (sigAct));
	sigemptyset(&sigAct.sa_mask);
	sigAct.sa_handler = sigusr2Dummy;
	sigaction(SIGUSR2, &sigAct, NULL);

	return iRet;
}


/* de-initialize the thread subsystem
 * must be called once at the end of the program
 */
rsRetVal thrdExit(void)
{
	DEFiRet;

	iRet = llDestroy(&llThrds);

	return iRet;
}


/* thrdSleep() - a fairly portable way to put a thread to sleep. It 
 * will wake up when
 * a) the wake-time is over
 * b) the thread shall be terminated
 * Returns RS_RET_OK if all went well, RS_RET_TERMINATE_NOW if the calling
 * thread shall be terminated and any other state if an error happened.
 * rgerhards, 2007-12-17
 */
rsRetVal
thrdSleep(thrdInfo_t *pThis, int iSeconds, int iuSeconds)
{
	DEFiRet;
	struct timeval tvSelectTimeout;

	assert(pThis != NULL);
	tvSelectTimeout.tv_sec = iSeconds;
	tvSelectTimeout.tv_usec = iuSeconds; /* micro seconds */
	thrdUnblockTermination(pThis);
	/* there may be a race condition if pthread_kill() is called after unblock but
	 * before the select() is setup. TODO: check and re-eval -- rgerhards, 2007-12-20
	 */
	select(0, NULL, NULL, NULL, &tvSelectTimeout);
	if(pThis->bShallStop)
		iRet = RS_RET_TERMINATE_NOW;
	else
		thrdBlockTermination(pThis);
	return iRet;
}


/* queue functions (may be migrated to some other file...)
 */


msgQueue *queueInit (void)
{
	msgQueue *q;

	q = (msgQueue *)malloc(sizeof(msgQueue));
	if (q == NULL) return (NULL);
	if((q->pbuf = malloc(sizeof(void *) * iMainMsgQueueSize)) == NULL) {
		free(q);
		return NULL;
	}

	q->empty = 1;
	q->full = 0;
	q->head = 0;
	q->tail = 0;
	q->mut = (pthread_mutex_t *) malloc (sizeof (pthread_mutex_t));
	pthread_mutex_init (q->mut, NULL);
	q->notFull = (pthread_cond_t *) malloc (sizeof (pthread_cond_t));
	pthread_cond_init (q->notFull, NULL);
	q->notEmpty = (pthread_cond_t *) malloc (sizeof (pthread_cond_t));
	pthread_cond_init (q->notEmpty, NULL);
	
	return (q);
}

void queueDelete (msgQueue *q)
{
	pthread_mutex_destroy (q->mut);
	free (q->mut);
	pthread_cond_destroy (q->notFull);
	free (q->notFull);
	pthread_cond_destroy (q->notEmpty);
	free (q->notEmpty);
	free(q->pbuf);
	free (q);
}


/* In queueAdd() and queueDel() we have a potential race condition. If a message
 * is dequeued and at the same time a message is enqueued and the queue is either
 * full or empty, the full (or empty) indicator may be invalidly updated. HOWEVER,
 * this does not cause any real problems. No queue pointers can be wrong. And even
 * if one of the flags is set invalidly, that does not pose a real problem. If
 * "full" is invalidly set, at mose one message might be lost, if we are already in
 * a timeout situation (this is quite acceptable). And if "empty" is accidently set,
 * the receiver will not continue the inner loop, but break out of the outer. So no
 * harm is done at all. For this reason, I do not yet use a mutex to guard the two
 * flags - there would be a notable performance hit with, IMHO, no gain in stability
 * or functionality. But anyhow, now it's documented...
 * rgerhards, 2007-09-20
 * NOTE: this comment does not really apply - the callers handle the mutex, so it
 * *is* guarded.
 */
void queueAdd (msgQueue *q, void* in)
{
	q->pbuf[q->tail] = in;
	q->tail++;
	if (q->tail == iMainMsgQueueSize)
		q->tail = 0;
	if (q->tail == q->head)
		q->full = 1;
	q->empty = 0;

	return;
}

void queueDel(msgQueue *q, void **out)
{
	*out = (void*) q->pbuf[q->head];

	q->head++;
	if (q->head == iMainMsgQueueSize)
		q->head = 0;
	if (q->head == q->tail)
		q->empty = 1;
	q->full = 0;

	return;
}

/*
 * vi:set ai:
 */