1 | /* |
2 | * Copyright (c) 2022 Apple Inc. All rights reserved. |
3 | * |
4 | * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ |
5 | * |
6 | * This file contains Original Code and/or Modifications of Original Code |
7 | * as defined in and that are subject to the Apple Public Source License |
8 | * Version 2.0 (the 'License'). You may not use this file except in |
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10 | * may not be used to create, or enable the creation or redistribution of, |
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13 | * terms of an Apple operating system software license agreement. |
14 | * |
15 | * Please obtain a copy of the License at |
16 | * http://www.opensource.apple.com/apsl/ and read it before using this file. |
17 | * |
18 | * The Original Code and all software distributed under the License are |
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23 | * Please see the License for the specific language governing rights and |
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26 | * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ |
27 | */ |
28 | /* |
29 | * @OSF_COPYRIGHT@ |
30 | */ |
31 | /* |
32 | * Mach Operating System |
33 | * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University |
34 | * All Rights Reserved. |
35 | * |
36 | * Permission to use, copy, modify and distribute this software and its |
37 | * documentation is hereby granted, provided that both the copyright |
38 | * notice and this permission notice appear in all copies of the |
39 | * software, derivative works or modified versions, and any portions |
40 | * thereof, and that both notices appear in supporting documentation. |
41 | * |
42 | * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" |
43 | * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR |
44 | * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. |
45 | * |
46 | * Carnegie Mellon requests users of this software to return to |
47 | * |
48 | * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU |
49 | * School of Computer Science |
50 | * Carnegie Mellon University |
51 | * Pittsburgh PA 15213-3890 |
52 | * |
53 | * any improvements or extensions that they make and grant Carnegie Mellon |
54 | * the rights to redistribute these changes. |
55 | */ |
56 | |
57 | #include <kern/kalloc.h> |
58 | #include <kern/thread.h> |
59 | #include <machine/atomic.h> |
60 | #include <kern/kern_apfs_reflock.h> |
61 | |
62 | KALLOC_TYPE_DEFINE(KT_KERN_APFSREFLOCK, struct kern_apfs_reflock, KT_PRIV_ACCT); |
63 | |
64 | static_assert(sizeof(struct kern_apfs_reflock) == sizeof(uint64_t)); |
65 | |
66 | void |
67 | kern_apfs_reflock_init(kern_apfs_reflock_t reflock) |
68 | { |
69 | reflock->kern_apfs_rl_data.cond64_data = 0; |
70 | } |
71 | |
72 | void |
73 | kern_apfs_reflock_destroy(kern_apfs_reflock_t reflock) |
74 | { |
75 | if (reflock->kern_apfs_rl_data.cond64_data == KERN_APFS_REFLOCK_DESTROYED) { |
76 | panic("kern_apfs_reflock_t %p was already destroyed" , reflock); |
77 | } |
78 | if (reflock->kern_apfs_rl_allocated == 1) { |
79 | panic("kern_apfs_reflock_t %p was allocated. kern_apfs_reflock_free should be called instead of kern_apfs_reflock_destroy" , reflock); |
80 | } |
81 | if (reflock->kern_apfs_rl_owner != 0) { |
82 | panic("kern_apfs_reflock_t %p: destroying a reflock currently locked by ctid %d" , reflock, reflock->kern_apfs_rl_owner); |
83 | } |
84 | if (reflock->kern_apfs_rl_wake != 0) { |
85 | panic("kern_apfs_reflock_t %p: destroying a reflock with threads currently waiting or in the process of waiting" , reflock); |
86 | } |
87 | assert(reflock->kern_apfs_rl_allow_force == 0); |
88 | assert(reflock->kern_apfs_rl_waiters == 0); |
89 | assert(reflock->kern_apfs_rl_delayed_free == 0); |
90 | reflock->kern_apfs_rl_data.cond64_data = KERN_APFS_REFLOCK_DESTROYED; |
91 | } |
92 | |
93 | kern_apfs_reflock_t |
94 | kern_apfs_reflock_alloc_init(void) |
95 | { |
96 | kern_apfs_reflock_t reflock = zalloc_flags(KT_KERN_APFSREFLOCK, Z_WAITOK | Z_ZERO | Z_NOFAIL); |
97 | reflock->kern_apfs_rl_allocated = 1; |
98 | return reflock; |
99 | } |
100 | |
101 | static void |
102 | kern_apfs_reflock_free_internal(kern_apfs_reflock_t reflock) |
103 | { |
104 | assert(reflock->kern_apfs_rl_waiters == 0); |
105 | assert(reflock->kern_apfs_rl_owner == 0); |
106 | assert(reflock->kern_apfs_rl_allow_force == 0); |
107 | assert(reflock->kern_apfs_rl_wake == 0); |
108 | assert(reflock->kern_apfs_rl_allocated == 1); |
109 | assert(reflock->kern_apfs_rl_delayed_free == 1); |
110 | |
111 | zfree(KT_KERN_APFSREFLOCK, reflock); |
112 | } |
113 | |
114 | static void inline |
115 | kern_apfs_reflock_check_valid(kern_apfs_reflock_t reflock) |
116 | { |
117 | if (reflock->kern_apfs_rl_data.cond64_data == KERN_APFS_REFLOCK_DESTROYED) { |
118 | panic("reflock %p was destoryed" , reflock); |
119 | } |
120 | if (reflock->kern_apfs_rl_allocated == 1 && reflock->kern_apfs_rl_delayed_free == 1) { |
121 | panic("reflock %p used after request for free" , reflock); |
122 | } |
123 | } |
124 | |
125 | void |
126 | kern_apfs_reflock_free(kern_apfs_reflock_t reflock) |
127 | { |
128 | struct kern_apfs_reflock old_reflock, new_reflock; |
129 | |
130 | if (reflock->kern_apfs_rl_allocated == 0) { |
131 | panic("kern_apfs_reflock_t %p was not allocated. kern_apfs_reflock_destroy should be called instead of kern_apfs_reflock_free" , reflock); |
132 | } |
133 | |
134 | /* |
135 | * This could be concurrent with kern_apfs_reflock_wait_for_unlock |
136 | */ |
137 | os_atomic_rmw_loop(&reflock->kern_apfs_rl_data.cond64_data, old_reflock.kern_apfs_rl_data.cond64_data, new_reflock.kern_apfs_rl_data.cond64_data, release, { |
138 | new_reflock = old_reflock; |
139 | |
140 | if (reflock->kern_apfs_rl_delayed_free == 1) { |
141 | panic("kern_apfs_reflock_t %p is already in the process of being freed" , reflock); |
142 | } |
143 | if (reflock->kern_apfs_rl_owner != 0) { |
144 | panic("kern_apfs_reflock_t %p: freeing a reflock currently locked by ctid %d" , reflock, reflock->kern_apfs_rl_owner); |
145 | } |
146 | assert(reflock->kern_apfs_rl_wake == 0); |
147 | assert(reflock->kern_apfs_rl_allow_force == 0); |
148 | |
149 | new_reflock.kern_apfs_rl_delayed_free = 1; |
150 | }); |
151 | |
152 | if (new_reflock.kern_apfs_rl_waiters == 0) { |
153 | kern_apfs_reflock_free_internal(reflock); |
154 | } |
155 | } |
156 | |
157 | bool |
158 | kern_apfs_reflock_try_get_ref(struct kern_apfs_reflock *reflock, kern_apfs_reflock_in_flags_t in_flags, kern_apfs_reflock_out_flags_t *out_flags) |
159 | { |
160 | struct kern_apfs_reflock old_reflock, new_reflock; |
161 | ctid_t my_ctid = thread_get_ctid(thread: current_thread()); |
162 | bool acquired = false; |
163 | bool locked = false; |
164 | bool will_wait = (in_flags & KERN_APFS_REFLOCK_IN_WILL_WAIT) != 0; |
165 | bool force = (in_flags & KERN_APFS_REFLOCK_IN_FORCE) != 0; |
166 | bool try_lock = (in_flags & KERN_APFS_REFLOCK_IN_LOCK_IF_FIRST) != 0; |
167 | |
168 | if (force && try_lock) { |
169 | panic("Cannot use KERN_APFS_REFLOCK_IN_FORCE and KERN_APFS_REFLOCK_IN_LOCK_IF_FIRST together" ); |
170 | } |
171 | |
172 | kern_apfs_reflock_check_valid(reflock); |
173 | *out_flags = KERN_APFS_REFLOCK_OUT_DEFAULT; |
174 | |
175 | os_atomic_rmw_loop(&reflock->kern_apfs_rl_data.cond64_data, old_reflock.kern_apfs_rl_data.cond64_data, new_reflock.kern_apfs_rl_data.cond64_data, acquire, { |
176 | new_reflock = old_reflock; |
177 | locked = false; |
178 | /* |
179 | * Check if refcount modifications are halted by |
180 | * a thread that is holding the lock. |
181 | */ |
182 | if (old_reflock.kern_apfs_rl_owner != 0 && |
183 | !(force && old_reflock.kern_apfs_rl_allow_force == 1)) { |
184 | acquired = false; |
185 | if (will_wait && reflock->kern_apfs_rl_allocated == 1) { |
186 | /* |
187 | * We need to remember how many threads |
188 | * will call wait_unlock so that |
189 | * in case a free happens the last waiter |
190 | * leaving the wait_unlock will free the reflock. |
191 | */ |
192 | if (old_reflock.kern_apfs_rl_waiters == KERN_APFS_REFLOCK_MAXWAITERS) { |
193 | panic("kern_apfs_reflock: too many waiters for %p thread %p" , reflock, current_thread()); |
194 | } |
195 | new_reflock.kern_apfs_rl_waiters = old_reflock.kern_apfs_rl_waiters + 1; |
196 | } else { |
197 | /* |
198 | * Caller does not want to wait or we do not need to remember how many waiters there are. |
199 | */ |
200 | os_atomic_rmw_loop_give_up(break); |
201 | } |
202 | } else { |
203 | acquired = true; |
204 | if (old_reflock.kern_apfs_rl_count == KERN_APFS_REFLOCK_MAXREFCOUNT) { |
205 | panic("kern_apfs_reflock: too many refs for %p thread %p" , reflock, current_thread()); |
206 | } |
207 | new_reflock.kern_apfs_rl_count = old_reflock.kern_apfs_rl_count + 1; |
208 | if (try_lock && new_reflock.kern_apfs_rl_count == 1) { |
209 | new_reflock.kern_apfs_rl_owner = my_ctid; |
210 | new_reflock.kern_apfs_rl_allow_force = 0; |
211 | locked = true; |
212 | } |
213 | } |
214 | }); |
215 | |
216 | if (locked) { |
217 | assert(acquired == true); |
218 | assert((in_flags & KERN_APFS_REFLOCK_IN_LOCK_IF_FIRST) != 0); |
219 | *out_flags |= KERN_APFS_REFLOCK_OUT_LOCKED; |
220 | } |
221 | |
222 | return acquired; |
223 | } |
224 | |
225 | bool |
226 | kern_apfs_reflock_try_put_ref(kern_apfs_reflock_t reflock, kern_apfs_reflock_in_flags_t in_flags, kern_apfs_reflock_out_flags_t *out_flags) |
227 | { |
228 | struct kern_apfs_reflock old_reflock, new_reflock; |
229 | ctid_t my_ctid = thread_get_ctid(thread: current_thread()); |
230 | bool released = false; |
231 | bool last_release = false; |
232 | bool locked = false; |
233 | bool will_wait = (in_flags & KERN_APFS_REFLOCK_IN_WILL_WAIT) != 0; |
234 | bool force = (in_flags & KERN_APFS_REFLOCK_IN_FORCE) != 0; |
235 | bool try_lock = (in_flags & KERN_APFS_REFLOCK_IN_LOCK_IF_LAST) != 0; |
236 | |
237 | if (force && try_lock) { |
238 | panic("Cannot use KERN_APFS_REFLOCK_IN_FORCE and KERN_APFS_REFLOCK_IN_LOCK_IF_LAST together" ); |
239 | } |
240 | |
241 | kern_apfs_reflock_check_valid(reflock); |
242 | *out_flags = KERN_APFS_REFLOCK_OUT_DEFAULT; |
243 | |
244 | os_atomic_rmw_loop(&reflock->kern_apfs_rl_data.cond64_data, old_reflock.kern_apfs_rl_data.cond64_data, new_reflock.kern_apfs_rl_data.cond64_data, release, { |
245 | if (old_reflock.kern_apfs_rl_count == 0) { |
246 | panic("kern_apfs_reflock: over releasing reflock %p thread %p" , reflock, current_thread()); |
247 | } |
248 | |
249 | new_reflock = old_reflock; |
250 | locked = false; |
251 | last_release = false; |
252 | |
253 | /* |
254 | * Check if refcount modifications are halted by |
255 | * a thread that is holding the lock. |
256 | */ |
257 | if (old_reflock.kern_apfs_rl_owner != 0 && |
258 | !(force && old_reflock.kern_apfs_rl_allow_force == 1)) { |
259 | released = false; |
260 | if (will_wait && reflock->kern_apfs_rl_allocated == 1) { |
261 | /* |
262 | * We need to remember how many threads |
263 | * will call wait_unlock so that |
264 | * in case a free happens the last waiters |
265 | * leaving the wait_unlock will free the reflock. |
266 | */ |
267 | if (old_reflock.kern_apfs_rl_waiters == KERN_APFS_REFLOCK_MAXWAITERS) { |
268 | panic("kern_apfs_reflock: too many waiters for %p thread %p" , reflock, current_thread()); |
269 | } |
270 | new_reflock.kern_apfs_rl_waiters = old_reflock.kern_apfs_rl_waiters + 1; |
271 | } else { |
272 | /* |
273 | * Caller does not want to wait or we do not need to remember how many waiters there are. |
274 | */ |
275 | os_atomic_rmw_loop_give_up(break); |
276 | } |
277 | } else { |
278 | released = true; |
279 | new_reflock.kern_apfs_rl_count = old_reflock.kern_apfs_rl_count - 1; |
280 | if (new_reflock.kern_apfs_rl_count == 0) { |
281 | last_release = true; |
282 | if (try_lock) { |
283 | new_reflock.kern_apfs_rl_owner = my_ctid; |
284 | new_reflock.kern_apfs_rl_allow_force = 0; |
285 | locked = true; |
286 | } |
287 | } |
288 | } |
289 | }); |
290 | |
291 | if (locked) { |
292 | assert(released == true); |
293 | assert((in_flags & KERN_APFS_REFLOCK_IN_LOCK_IF_LAST) != 0); |
294 | *out_flags |= KERN_APFS_REFLOCK_OUT_LOCKED; |
295 | } |
296 | |
297 | if (locked || last_release) { |
298 | os_atomic_thread_fence(acquire); |
299 | } |
300 | |
301 | return released; |
302 | } |
303 | |
304 | bool |
305 | kern_apfs_reflock_try_lock(kern_apfs_reflock_t reflock, kern_apfs_reflock_in_flags_t in_flags, uint32_t *refcount_when_lock) |
306 | { |
307 | struct kern_apfs_reflock old_reflock, new_reflock; |
308 | ctid_t my_ctid = thread_get_ctid(thread: current_thread()); |
309 | bool acquired = false; |
310 | bool allow_force = (in_flags & KERN_APFS_REFLOCK_IN_ALLOW_FORCE) != 0; |
311 | bool will_wait = (in_flags & KERN_APFS_REFLOCK_IN_WILL_WAIT) != 0; |
312 | uint32_t refcount = 0; |
313 | |
314 | kern_apfs_reflock_check_valid(reflock); |
315 | |
316 | os_atomic_rmw_loop(&reflock->kern_apfs_rl_data.cond64_data, old_reflock.kern_apfs_rl_data.cond64_data, new_reflock.kern_apfs_rl_data.cond64_data, acquire, { |
317 | new_reflock = old_reflock; |
318 | /* |
319 | * Check if a thread is already holding the lock. |
320 | */ |
321 | if (old_reflock.kern_apfs_rl_owner != 0) { |
322 | if (old_reflock.kern_apfs_rl_owner == my_ctid) { |
323 | panic("Trying to lock a reflock owned by the same thread %p, reflock %p" , current_thread(), reflock); |
324 | } |
325 | acquired = false; |
326 | if (will_wait && reflock->kern_apfs_rl_allocated == 1) { |
327 | /* |
328 | * We need to remember how many threads |
329 | * will call wait_unlock so that |
330 | * in case a free happens the last waiter |
331 | * leaving the wait_unlock will free the reflock. |
332 | */ |
333 | if (old_reflock.kern_apfs_rl_waiters == KERN_APFS_REFLOCK_MAXWAITERS) { |
334 | panic("kern_apfs_reflock: too many waiters for %p thread %p" , reflock, current_thread()); |
335 | } |
336 | new_reflock.kern_apfs_rl_waiters = old_reflock.kern_apfs_rl_waiters + 1; |
337 | } else { |
338 | /* |
339 | * Caller does not want to wait or we do not need to remember how many waiters there are. |
340 | */ |
341 | os_atomic_rmw_loop_give_up(break); |
342 | } |
343 | } else { |
344 | acquired = true; |
345 | refcount = old_reflock.kern_apfs_rl_count; |
346 | new_reflock.kern_apfs_rl_owner = my_ctid; |
347 | if (allow_force) { |
348 | new_reflock.kern_apfs_rl_allow_force = 1; |
349 | } else { |
350 | new_reflock.kern_apfs_rl_allow_force = 0; |
351 | } |
352 | } |
353 | }); |
354 | |
355 | if (acquired && refcount_when_lock != NULL) { |
356 | *refcount_when_lock = refcount; |
357 | } |
358 | |
359 | return acquired; |
360 | } |
361 | |
362 | wait_result_t |
363 | kern_apfs_reflock_wait_for_unlock(kern_apfs_reflock_t reflock, wait_interrupt_t interruptible, uint64_t deadline) |
364 | { |
365 | struct kern_apfs_reflock old_reflock, new_reflock; |
366 | ctid_t my_ctid = thread_get_ctid(thread: current_thread()); |
367 | wait_result_t ret; |
368 | bool wait = false; |
369 | bool free = false; |
370 | |
371 | os_atomic_rmw_loop(&reflock->kern_apfs_rl_data.cond64_data, old_reflock.kern_apfs_rl_data.cond64_data, new_reflock.kern_apfs_rl_data.cond64_data, relaxed, { |
372 | new_reflock = old_reflock; |
373 | free = false; |
374 | |
375 | /* |
376 | * Be sure that kern_apfs_rl_waiters were incremented |
377 | * before waiting. |
378 | */ |
379 | if (old_reflock.kern_apfs_rl_allocated == 1 && old_reflock.kern_apfs_rl_waiters == 0) { |
380 | panic("kern_apfs_reflock: kern_apfs_rl_waiters are 0 when trying to wait reflock %p thread %p. Probably a try* function with a positive will_wait wasn't called before waiting." , reflock, current_thread()); |
381 | } |
382 | |
383 | /* |
384 | * Check if a thread is still holding the lock. |
385 | */ |
386 | if (old_reflock.kern_apfs_rl_owner != 0) { |
387 | if (old_reflock.kern_apfs_rl_owner == my_ctid) { |
388 | panic("Trying to wait on a reflock owned by the same thread %p, reflock %p" , current_thread(), reflock); |
389 | } |
390 | /* |
391 | * Somebody is holding the lock. |
392 | * Notify we have seen this, and we |
393 | * are intentioned to wait. |
394 | */ |
395 | new_reflock.kern_apfs_rl_wake = 1; |
396 | wait = true; |
397 | } else { |
398 | /* |
399 | * Lock not held, do not wait. |
400 | */ |
401 | wait = false; |
402 | if (old_reflock.kern_apfs_rl_allocated == 1) { |
403 | new_reflock.kern_apfs_rl_waiters = old_reflock.kern_apfs_rl_waiters - 1; |
404 | if (old_reflock.kern_apfs_rl_delayed_free == 1 && new_reflock.kern_apfs_rl_waiters == 0) { |
405 | free = true; |
406 | } |
407 | } else { |
408 | os_atomic_rmw_loop_give_up(break); |
409 | } |
410 | } |
411 | }); |
412 | |
413 | if (free) { |
414 | assert(wait == false); |
415 | kern_apfs_reflock_free_internal(reflock); |
416 | return KERN_NOT_WAITING; |
417 | } |
418 | |
419 | if (!wait) { |
420 | return KERN_NOT_WAITING; |
421 | } |
422 | |
423 | /* |
424 | * We want to sleep only if we see an owner still set and if the wakeup flag is set. |
425 | * If the owner observed is different from the one saved we want to not sleep. |
426 | */ |
427 | ret = cond_sleep_with_inheritor64_mask(cond: (cond_swi_var_t) reflock, expected_cond: new_reflock.kern_apfs_rl_data, KERN_APFS_SLEEP_DEBOUNCE_MASK, interruptible, deadline); |
428 | |
429 | /* |
430 | * In case reflock was allocated we need to remove |
431 | * ourselves from the waiters |
432 | */ |
433 | if (new_reflock.kern_apfs_rl_allocated == 1) { |
434 | os_atomic_rmw_loop(&reflock->kern_apfs_rl_data.cond64_data, old_reflock.kern_apfs_rl_data.cond64_data, new_reflock.kern_apfs_rl_data.cond64_data, acquire, { |
435 | new_reflock = old_reflock; |
436 | assert(old_reflock.kern_apfs_rl_waiters > 0); |
437 | new_reflock.kern_apfs_rl_waiters = old_reflock.kern_apfs_rl_waiters - 1; |
438 | }); |
439 | } |
440 | |
441 | if (new_reflock.kern_apfs_rl_delayed_free == 1 && new_reflock.kern_apfs_rl_waiters == 0) { |
442 | kern_apfs_reflock_free_internal(reflock); |
443 | } |
444 | |
445 | return ret; |
446 | } |
447 | |
448 | void |
449 | kern_apfs_reflock_unlock(kern_apfs_reflock_t reflock) |
450 | { |
451 | struct kern_apfs_reflock old_reflock, new_reflock; |
452 | ctid_t my_ctid = thread_get_ctid(thread: current_thread()); |
453 | bool waiters = false; |
454 | |
455 | kern_apfs_reflock_check_valid(reflock); |
456 | |
457 | os_atomic_rmw_loop(&reflock->kern_apfs_rl_data.cond64_data, old_reflock.kern_apfs_rl_data.cond64_data, new_reflock.kern_apfs_rl_data.cond64_data, release, { |
458 | if (old_reflock.kern_apfs_rl_owner != my_ctid) { |
459 | panic("Unlocking swiref_t %p from thread ctid %u owned by ctid %u" , reflock, my_ctid, old_reflock.kern_apfs_rl_owner); |
460 | } |
461 | |
462 | new_reflock = old_reflock; |
463 | /* Check if anybody is waiting for the unlock */ |
464 | if (old_reflock.kern_apfs_rl_wake == 1) { |
465 | waiters = true; |
466 | new_reflock.kern_apfs_rl_wake = 0; |
467 | } else { |
468 | waiters = false; |
469 | } |
470 | new_reflock.kern_apfs_rl_owner = 0; |
471 | new_reflock.kern_apfs_rl_allow_force = 0; |
472 | }); |
473 | |
474 | if (waiters) { |
475 | cond_wakeup_all_with_inheritor(cond: (cond_swi_var_t) reflock, THREAD_AWAKENED); |
476 | } |
477 | } |
478 | |
479 | uint64_t |
480 | kern_apfs_reflock_read_ref(kern_apfs_reflock_t reflock) |
481 | { |
482 | struct kern_apfs_reflock reflock_value; |
483 | |
484 | kern_apfs_reflock_check_valid(reflock); |
485 | |
486 | reflock_value.kern_apfs_rl_data.cond64_data = os_atomic_load(&reflock->kern_apfs_rl_data.cond64_data, relaxed); |
487 | |
488 | return reflock_value.kern_apfs_rl_count; |
489 | } |
490 | |