1 #include "stdinc.h"
2 #include "dat.h"
3 #include "fns.h"
4 #include "error.h"
5 
6 /*
7  * Lock watcher.  Check that locking of blocks is always down.
8  *
9  * This is REALLY slow, and it won't work when the blocks aren't
10  * arranged in a tree (e.g., after the first snapshot).  But it's great
11  * for debugging.
12  */
13 enum
14 {
15 	MaxLock = 16,
16 	HashSize = 1009,
17 };
18 
19 /*
20  * Thread-specific watch state.
21  */
22 typedef struct WThread WThread;
23 struct WThread
24 {
25 	Block *b[MaxLock];	/* blocks currently held */
26 	uint nb;
27 	uint pid;
28 };
29 
30 typedef struct WMap WMap;
31 typedef struct WEntry WEntry;
32 
33 struct WEntry
34 {
35 	uchar c[VtScoreSize];
36 	uchar p[VtScoreSize];
37 	int off;
38 
39 	WEntry *cprev;
40 	WEntry *cnext;
41 	WEntry *pprev;
42 	WEntry *pnext;
43 };
44 
45 struct WMap
46 {
47 	QLock lk;
48 
49 	WEntry *hchild[HashSize];
50 	WEntry *hparent[HashSize];
51 };
52 
53 static WMap map;
54 static void **wp;
55 static uint blockSize;
56 static WEntry *pool;
57 uint bwatchDisabled;
58 
59 static uint
60 hash(uchar score[VtScoreSize])
61 {
62 	uint i, h;
63 
64 	h = 0;
65 	for(i=0; i<VtScoreSize; i++)
66 		h = h*37 + score[i];
67 	return h%HashSize;
68 }
69 
70 #include <pool.h>
71 static void
72 freeWEntry(WEntry *e)
73 {
74 	memset(e, 0, sizeof(WEntry));
75 	e->pnext = pool;
76 	pool = e;
77 }
78 
79 static WEntry*
80 allocWEntry(void)
81 {
82 	int i;
83 	WEntry *w;
84 
85 	w = pool;
86 	if(w == nil){
87 		w = vtmallocz(1024*sizeof(WEntry));
88 		for(i=0; i<1024; i++)
89 			freeWEntry(&w[i]);
90 		w = pool;
91 	}
92 	pool = w->pnext;
93 	memset(w, 0, sizeof(WEntry));
94 	return w;
95 }
96 
97 /*
98  * remove all dependencies with score as a parent
99  */
100 static void
101 _bwatchResetParent(uchar *score)
102 {
103 	WEntry *w, *next;
104 	uint h;
105 
106 	h = hash(score);
107 	for(w=map.hparent[h]; w; w=next){
108 		next = w->pnext;
109 		if(memcmp(w->p, score, VtScoreSize) == 0){
110 			if(w->pnext)
111 				w->pnext->pprev = w->pprev;
112 			if(w->pprev)
113 				w->pprev->pnext = w->pnext;
114 			else
115 				map.hparent[h] = w->pnext;
116 			if(w->cnext)
117 				w->cnext->cprev = w->cprev;
118 			if(w->cprev)
119 				w->cprev->cnext = w->cnext;
120 			else
121 				map.hchild[hash(w->c)] = w->cnext;
122 			freeWEntry(w);
123 		}
124 	}
125 }
126 /*
127  * and child
128  */
129 static void
130 _bwatchResetChild(uchar *score)
131 {
132 	WEntry *w, *next;
133 	uint h;
134 
135 	h = hash(score);
136 	for(w=map.hchild[h]; w; w=next){
137 		next = w->cnext;
138 		if(memcmp(w->c, score, VtScoreSize) == 0){
139 			if(w->pnext)
140 				w->pnext->pprev = w->pprev;
141 			if(w->pprev)
142 				w->pprev->pnext = w->pnext;
143 			else
144 				map.hparent[hash(w->p)] = w->pnext;
145 			if(w->cnext)
146 				w->cnext->cprev = w->cprev;
147 			if(w->cprev)
148 				w->cprev->cnext = w->cnext;
149 			else
150 				map.hchild[h] = w->cnext;
151 			freeWEntry(w);
152 		}
153 	}
154 }
155 
156 static uchar*
157 parent(uchar c[VtScoreSize], int *off)
158 {
159 	WEntry *w;
160 	uint h;
161 
162 	h = hash(c);
163 	for(w=map.hchild[h]; w; w=w->cnext)
164 		if(memcmp(w->c, c, VtScoreSize) == 0){
165 			*off = w->off;
166 			return w->p;
167 		}
168 	return nil;
169 }
170 
171 static void
172 addChild(uchar p[VtEntrySize], uchar c[VtEntrySize], int off)
173 {
174 	uint h;
175 	WEntry *w;
176 
177 	w = allocWEntry();
178 	memmove(w->p, p, VtScoreSize);
179 	memmove(w->c, c, VtScoreSize);
180 	w->off = off;
181 
182 	h = hash(p);
183 	w->pnext = map.hparent[h];
184 	if(w->pnext)
185 		w->pnext->pprev = w;
186 	map.hparent[h] = w;
187 
188 	h = hash(c);
189 	w->cnext = map.hchild[h];
190 	if(w->cnext)
191 		w->cnext->cprev = w;
192 	map.hchild[h] = w;
193 }
194 
195 void
196 bwatchReset(uchar score[VtScoreSize])
197 {
198 	qlock(&map.lk);
199 	_bwatchResetParent(score);
200 	_bwatchResetChild(score);
201 	qunlock(&map.lk);
202 }
203 
204 void
205 bwatchInit(void)
206 {
207 	wp = privalloc();
208 	*wp = nil;
209 }
210 
211 void
212 bwatchSetBlockSize(uint bs)
213 {
214 	blockSize = bs;
215 }
216 
217 static WThread*
218 getWThread(void)
219 {
220 	WThread *w;
221 
222 	w = *wp;
223 	if(w == nil || w->pid != getpid()){
224 		w = vtmallocz(sizeof(WThread));
225 		*wp = w;
226 		w->pid = getpid();
227 	}
228 	return w;
229 }
230 
231 /*
232  * Derive dependencies from the contents of b.
233  */
234 void
235 bwatchDependency(Block *b)
236 {
237 	int i, epb, ppb;
238 	Entry e;
239 
240 	if(bwatchDisabled)
241 		return;
242 
243 	qlock(&map.lk);
244 	_bwatchResetParent(b->score);
245 
246 	switch(b->l.type){
247 	case BtData:
248 		break;
249 
250 	case BtDir:
251 		epb = blockSize / VtEntrySize;
252 		for(i=0; i<epb; i++){
253 			entryUnpack(&e, b->data, i);
254 			if(!(e.flags & VtEntryActive))
255 				continue;
256 			addChild(b->score, e.score, i);
257 		}
258 		break;
259 
260 	default:
261 		ppb = blockSize / VtScoreSize;
262 		for(i=0; i<ppb; i++)
263 			addChild(b->score, b->data+i*VtScoreSize, i);
264 		break;
265 	}
266 	qunlock(&map.lk);
267 }
268 
269 static int
270 depth(uchar *s)
271 {
272 	int d, x;
273 
274 	d = -1;
275 	while(s){
276 		d++;
277 		s = parent(s, &x);
278 	}
279 	return d;
280 }
281 
282 static int
283 lockConflicts(uchar xhave[VtScoreSize], uchar xwant[VtScoreSize])
284 {
285 	uchar *have, *want;
286 	int havedepth, wantdepth, havepos, wantpos;
287 
288 	have = xhave;
289 	want = xwant;
290 
291 	havedepth = depth(have);
292 	wantdepth = depth(want);
293 
294 	/*
295 	 * walk one or the other up until they're both
296  	 * at the same level.
297 	 */
298 	havepos = -1;
299 	wantpos = -1;
300 	have = xhave;
301 	want = xwant;
302 	while(wantdepth > havedepth){
303 		wantdepth--;
304 		want = parent(want, &wantpos);
305 	}
306 	while(havedepth > wantdepth){
307 		havedepth--;
308 		have = parent(have, &havepos);
309 	}
310 
311 	/*
312 	 * walk them up simultaneously until we reach
313 	 * a common ancestor.
314 	 */
315 	while(have && want && memcmp(have, want, VtScoreSize) != 0){
316 		have = parent(have, &havepos);
317 		want = parent(want, &wantpos);
318 	}
319 
320 	/*
321 	 * not part of same tree.  happens mainly with
322 	 * newly allocated blocks.
323 	 */
324 	if(!have || !want)
325 		return 0;
326 
327 	/*
328 	 * never walked want: means we want to lock
329 	 * an ancestor of have.  no no.
330 	 */
331 	if(wantpos == -1)
332 		return 1;
333 
334 	/*
335 	 * never walked have: means we want to lock a
336 	 * child of have.  that's okay.
337 	 */
338 	if(havepos == -1)
339 		return 0;
340 
341 	/*
342 	 * walked both: they're from different places in the tree.
343 	 * require that the left one be locked before the right one.
344 	 * (this is questionable, but it puts a total order on the block tree).
345 	 */
346 	return havepos < wantpos;
347 }
348 
349 static void
350 stop(void)
351 {
352 	int fd;
353 	char buf[32];
354 
355 	snprint(buf, sizeof buf, "#p/%d/ctl", getpid());
356 	fd = open(buf, OWRITE);
357 	write(fd, "stop", 4);
358 	close(fd);
359 }
360 
361 /*
362  * Check whether the calling thread can validly lock b.
363  * That is, check that the calling thread doesn't hold
364  * locks for any of b's children.
365  */
366 void
367 bwatchLock(Block *b)
368 {
369 	int i;
370 	WThread *w;
371 
372 	if(bwatchDisabled)
373 		return;
374 
375 	if(b->part != PartData)
376 		return;
377 
378 	qlock(&map.lk);
379 	w = getWThread();
380 	for(i=0; i<w->nb; i++){
381 		if(lockConflicts(w->b[i]->score, b->score)){
382 			fprint(2, "%d: have block %V; shouldn't lock %V\n",
383 				w->pid, w->b[i]->score, b->score);
384 			stop();
385 		}
386 	}
387 	qunlock(&map.lk);
388 	if(w->nb >= MaxLock){
389 		fprint(2, "%d: too many blocks held\n", w->pid);
390 		stop();
391 	}else
392 		w->b[w->nb++] = b;
393 }
394 
395 /*
396  * Note that the calling thread is about to unlock b.
397  */
398 void
399 bwatchUnlock(Block *b)
400 {
401 	int i;
402 	WThread *w;
403 
404 	if(bwatchDisabled)
405 		return;
406 
407 	if(b->part != PartData)
408 		return;
409 
410 	w = getWThread();
411 	for(i=0; i<w->nb; i++)
412 		if(w->b[i] == b)
413 			break;
414 	if(i>=w->nb){
415 		fprint(2, "%d: unlock of unlocked block %V\n", w->pid, b->score);
416 		stop();
417 	}else
418 		w->b[i] = w->b[--w->nb];
419 }