]>
Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * Generic pidhash and scalable, time-bounded PID allocator | |
3 | * | |
4 | * (C) 2002-2003 William Irwin, IBM | |
5 | * (C) 2004 William Irwin, Oracle | |
6 | * (C) 2002-2004 Ingo Molnar, Red Hat | |
7 | * | |
8 | * pid-structures are backing objects for tasks sharing a given ID to chain | |
9 | * against. There is very little to them aside from hashing them and | |
10 | * parking tasks using given ID's on a list. | |
11 | * | |
12 | * The hash is always changed with the tasklist_lock write-acquired, | |
13 | * and the hash is only accessed with the tasklist_lock at least | |
14 | * read-acquired, so there's no additional SMP locking needed here. | |
15 | * | |
16 | * We have a list of bitmap pages, which bitmaps represent the PID space. | |
17 | * Allocating and freeing PIDs is completely lockless. The worst-case | |
18 | * allocation scenario when all but one out of 1 million PIDs possible are | |
19 | * allocated already: the scanning of 32 list entries and at most PAGE_SIZE | |
20 | * bytes. The typical fastpath is a single successful setbit. Freeing is O(1). | |
21 | */ | |
22 | ||
23 | #include <linux/mm.h> | |
24 | #include <linux/module.h> | |
25 | #include <linux/slab.h> | |
26 | #include <linux/init.h> | |
27 | #include <linux/bootmem.h> | |
28 | #include <linux/hash.h> | |
61a58c6c | 29 | #include <linux/pid_namespace.h> |
820e45db | 30 | #include <linux/init_task.h> |
1da177e4 LT |
31 | |
32 | #define pid_hashfn(nr) hash_long((unsigned long)nr, pidhash_shift) | |
92476d7f | 33 | static struct hlist_head *pid_hash; |
1da177e4 | 34 | static int pidhash_shift; |
820e45db | 35 | struct pid init_struct_pid = INIT_STRUCT_PID; |
1da177e4 LT |
36 | |
37 | int pid_max = PID_MAX_DEFAULT; | |
1da177e4 LT |
38 | |
39 | #define RESERVED_PIDS 300 | |
40 | ||
41 | int pid_max_min = RESERVED_PIDS + 1; | |
42 | int pid_max_max = PID_MAX_LIMIT; | |
43 | ||
1da177e4 LT |
44 | #define BITS_PER_PAGE (PAGE_SIZE*8) |
45 | #define BITS_PER_PAGE_MASK (BITS_PER_PAGE-1) | |
3fbc9648 | 46 | |
61a58c6c SB |
47 | static inline int mk_pid(struct pid_namespace *pid_ns, |
48 | struct pidmap *map, int off) | |
3fbc9648 | 49 | { |
61a58c6c | 50 | return (map - pid_ns->pidmap)*BITS_PER_PAGE + off; |
3fbc9648 SB |
51 | } |
52 | ||
1da177e4 LT |
53 | #define find_next_offset(map, off) \ |
54 | find_next_zero_bit((map)->page, BITS_PER_PAGE, off) | |
55 | ||
56 | /* | |
57 | * PID-map pages start out as NULL, they get allocated upon | |
58 | * first use and are never deallocated. This way a low pid_max | |
59 | * value does not cause lots of bitmaps to be allocated, but | |
60 | * the scheme scales to up to 4 million PIDs, runtime. | |
61 | */ | |
61a58c6c | 62 | struct pid_namespace init_pid_ns = { |
9a575a92 CLG |
63 | .kref = { |
64 | .refcount = ATOMIC_INIT(2), | |
65 | }, | |
3fbc9648 SB |
66 | .pidmap = { |
67 | [ 0 ... PIDMAP_ENTRIES-1] = { ATOMIC_INIT(BITS_PER_PAGE), NULL } | |
68 | }, | |
84d73786 SB |
69 | .last_pid = 0, |
70 | .child_reaper = &init_task | |
3fbc9648 | 71 | }; |
1da177e4 | 72 | |
92476d7f EB |
73 | /* |
74 | * Note: disable interrupts while the pidmap_lock is held as an | |
75 | * interrupt might come in and do read_lock(&tasklist_lock). | |
76 | * | |
77 | * If we don't disable interrupts there is a nasty deadlock between | |
78 | * detach_pid()->free_pid() and another cpu that does | |
79 | * spin_lock(&pidmap_lock) followed by an interrupt routine that does | |
80 | * read_lock(&tasklist_lock); | |
81 | * | |
82 | * After we clean up the tasklist_lock and know there are no | |
83 | * irq handlers that take it we can leave the interrupts enabled. | |
84 | * For now it is easier to be safe than to prove it can't happen. | |
85 | */ | |
3fbc9648 | 86 | |
1da177e4 LT |
87 | static __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock); |
88 | ||
61a58c6c | 89 | static fastcall void free_pidmap(struct pid_namespace *pid_ns, int pid) |
1da177e4 | 90 | { |
61a58c6c | 91 | struct pidmap *map = pid_ns->pidmap + pid / BITS_PER_PAGE; |
1da177e4 LT |
92 | int offset = pid & BITS_PER_PAGE_MASK; |
93 | ||
94 | clear_bit(offset, map->page); | |
95 | atomic_inc(&map->nr_free); | |
96 | } | |
97 | ||
61a58c6c | 98 | static int alloc_pidmap(struct pid_namespace *pid_ns) |
1da177e4 | 99 | { |
61a58c6c | 100 | int i, offset, max_scan, pid, last = pid_ns->last_pid; |
6a1f3b84 | 101 | struct pidmap *map; |
1da177e4 LT |
102 | |
103 | pid = last + 1; | |
104 | if (pid >= pid_max) | |
105 | pid = RESERVED_PIDS; | |
106 | offset = pid & BITS_PER_PAGE_MASK; | |
61a58c6c | 107 | map = &pid_ns->pidmap[pid/BITS_PER_PAGE]; |
1da177e4 LT |
108 | max_scan = (pid_max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset; |
109 | for (i = 0; i <= max_scan; ++i) { | |
110 | if (unlikely(!map->page)) { | |
3fbc9648 | 111 | void *page = kzalloc(PAGE_SIZE, GFP_KERNEL); |
1da177e4 LT |
112 | /* |
113 | * Free the page if someone raced with us | |
114 | * installing it: | |
115 | */ | |
92476d7f | 116 | spin_lock_irq(&pidmap_lock); |
1da177e4 | 117 | if (map->page) |
3fbc9648 | 118 | kfree(page); |
1da177e4 | 119 | else |
3fbc9648 | 120 | map->page = page; |
92476d7f | 121 | spin_unlock_irq(&pidmap_lock); |
1da177e4 LT |
122 | if (unlikely(!map->page)) |
123 | break; | |
124 | } | |
125 | if (likely(atomic_read(&map->nr_free))) { | |
126 | do { | |
127 | if (!test_and_set_bit(offset, map->page)) { | |
128 | atomic_dec(&map->nr_free); | |
61a58c6c | 129 | pid_ns->last_pid = pid; |
1da177e4 LT |
130 | return pid; |
131 | } | |
132 | offset = find_next_offset(map, offset); | |
61a58c6c | 133 | pid = mk_pid(pid_ns, map, offset); |
1da177e4 LT |
134 | /* |
135 | * find_next_offset() found a bit, the pid from it | |
136 | * is in-bounds, and if we fell back to the last | |
137 | * bitmap block and the final block was the same | |
138 | * as the starting point, pid is before last_pid. | |
139 | */ | |
140 | } while (offset < BITS_PER_PAGE && pid < pid_max && | |
141 | (i != max_scan || pid < last || | |
142 | !((last+1) & BITS_PER_PAGE_MASK))); | |
143 | } | |
61a58c6c | 144 | if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) { |
1da177e4 LT |
145 | ++map; |
146 | offset = 0; | |
147 | } else { | |
61a58c6c | 148 | map = &pid_ns->pidmap[0]; |
1da177e4 LT |
149 | offset = RESERVED_PIDS; |
150 | if (unlikely(last == offset)) | |
151 | break; | |
152 | } | |
61a58c6c | 153 | pid = mk_pid(pid_ns, map, offset); |
1da177e4 LT |
154 | } |
155 | return -1; | |
156 | } | |
157 | ||
61a58c6c | 158 | static int next_pidmap(struct pid_namespace *pid_ns, int last) |
0804ef4b EB |
159 | { |
160 | int offset; | |
f40f50d3 | 161 | struct pidmap *map, *end; |
0804ef4b EB |
162 | |
163 | offset = (last + 1) & BITS_PER_PAGE_MASK; | |
61a58c6c SB |
164 | map = &pid_ns->pidmap[(last + 1)/BITS_PER_PAGE]; |
165 | end = &pid_ns->pidmap[PIDMAP_ENTRIES]; | |
f40f50d3 | 166 | for (; map < end; map++, offset = 0) { |
0804ef4b EB |
167 | if (unlikely(!map->page)) |
168 | continue; | |
169 | offset = find_next_bit((map)->page, BITS_PER_PAGE, offset); | |
170 | if (offset < BITS_PER_PAGE) | |
61a58c6c | 171 | return mk_pid(pid_ns, map, offset); |
0804ef4b EB |
172 | } |
173 | return -1; | |
174 | } | |
175 | ||
92476d7f EB |
176 | fastcall void put_pid(struct pid *pid) |
177 | { | |
baf8f0f8 PE |
178 | struct pid_namespace *ns; |
179 | ||
92476d7f EB |
180 | if (!pid) |
181 | return; | |
baf8f0f8 PE |
182 | |
183 | /* FIXME - this must be the namespace this pid lives in */ | |
184 | ns = &init_pid_ns; | |
92476d7f EB |
185 | if ((atomic_read(&pid->count) == 1) || |
186 | atomic_dec_and_test(&pid->count)) | |
baf8f0f8 | 187 | kmem_cache_free(ns->pid_cachep, pid); |
92476d7f | 188 | } |
bbf73147 | 189 | EXPORT_SYMBOL_GPL(put_pid); |
92476d7f EB |
190 | |
191 | static void delayed_put_pid(struct rcu_head *rhp) | |
192 | { | |
193 | struct pid *pid = container_of(rhp, struct pid, rcu); | |
194 | put_pid(pid); | |
195 | } | |
196 | ||
197 | fastcall void free_pid(struct pid *pid) | |
198 | { | |
199 | /* We can be called with write_lock_irq(&tasklist_lock) held */ | |
200 | unsigned long flags; | |
201 | ||
202 | spin_lock_irqsave(&pidmap_lock, flags); | |
203 | hlist_del_rcu(&pid->pid_chain); | |
204 | spin_unlock_irqrestore(&pidmap_lock, flags); | |
205 | ||
0f245285 | 206 | free_pidmap(&init_pid_ns, pid->nr); |
92476d7f EB |
207 | call_rcu(&pid->rcu, delayed_put_pid); |
208 | } | |
209 | ||
210 | struct pid *alloc_pid(void) | |
211 | { | |
212 | struct pid *pid; | |
213 | enum pid_type type; | |
214 | int nr = -1; | |
baf8f0f8 | 215 | struct pid_namespace *ns; |
92476d7f | 216 | |
2894d650 | 217 | ns = task_active_pid_ns(current); |
baf8f0f8 | 218 | pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL); |
92476d7f EB |
219 | if (!pid) |
220 | goto out; | |
221 | ||
baf8f0f8 | 222 | nr = alloc_pidmap(ns); |
92476d7f EB |
223 | if (nr < 0) |
224 | goto out_free; | |
225 | ||
226 | atomic_set(&pid->count, 1); | |
227 | pid->nr = nr; | |
228 | for (type = 0; type < PIDTYPE_MAX; ++type) | |
229 | INIT_HLIST_HEAD(&pid->tasks[type]); | |
230 | ||
231 | spin_lock_irq(&pidmap_lock); | |
232 | hlist_add_head_rcu(&pid->pid_chain, &pid_hash[pid_hashfn(pid->nr)]); | |
233 | spin_unlock_irq(&pidmap_lock); | |
234 | ||
235 | out: | |
236 | return pid; | |
237 | ||
238 | out_free: | |
baf8f0f8 | 239 | kmem_cache_free(ns->pid_cachep, pid); |
92476d7f EB |
240 | pid = NULL; |
241 | goto out; | |
242 | } | |
243 | ||
244 | struct pid * fastcall find_pid(int nr) | |
1da177e4 LT |
245 | { |
246 | struct hlist_node *elem; | |
247 | struct pid *pid; | |
248 | ||
e56d0903 | 249 | hlist_for_each_entry_rcu(pid, elem, |
92476d7f | 250 | &pid_hash[pid_hashfn(nr)], pid_chain) { |
1da177e4 LT |
251 | if (pid->nr == nr) |
252 | return pid; | |
253 | } | |
254 | return NULL; | |
255 | } | |
bbf73147 | 256 | EXPORT_SYMBOL_GPL(find_pid); |
1da177e4 | 257 | |
e713d0da SB |
258 | /* |
259 | * attach_pid() must be called with the tasklist_lock write-held. | |
260 | */ | |
261 | int fastcall attach_pid(struct task_struct *task, enum pid_type type, | |
262 | struct pid *pid) | |
1da177e4 | 263 | { |
92476d7f | 264 | struct pid_link *link; |
92476d7f | 265 | |
92476d7f | 266 | link = &task->pids[type]; |
e713d0da | 267 | link->pid = pid; |
92476d7f | 268 | hlist_add_head_rcu(&link->node, &pid->tasks[type]); |
1da177e4 LT |
269 | |
270 | return 0; | |
271 | } | |
272 | ||
36c8b586 | 273 | void fastcall detach_pid(struct task_struct *task, enum pid_type type) |
1da177e4 | 274 | { |
92476d7f EB |
275 | struct pid_link *link; |
276 | struct pid *pid; | |
277 | int tmp; | |
1da177e4 | 278 | |
92476d7f EB |
279 | link = &task->pids[type]; |
280 | pid = link->pid; | |
1da177e4 | 281 | |
92476d7f EB |
282 | hlist_del_rcu(&link->node); |
283 | link->pid = NULL; | |
1da177e4 | 284 | |
92476d7f EB |
285 | for (tmp = PIDTYPE_MAX; --tmp >= 0; ) |
286 | if (!hlist_empty(&pid->tasks[tmp])) | |
287 | return; | |
1da177e4 | 288 | |
92476d7f | 289 | free_pid(pid); |
1da177e4 LT |
290 | } |
291 | ||
c18258c6 EB |
292 | /* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */ |
293 | void fastcall transfer_pid(struct task_struct *old, struct task_struct *new, | |
294 | enum pid_type type) | |
295 | { | |
296 | new->pids[type].pid = old->pids[type].pid; | |
297 | hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node); | |
298 | old->pids[type].pid = NULL; | |
299 | } | |
300 | ||
92476d7f | 301 | struct task_struct * fastcall pid_task(struct pid *pid, enum pid_type type) |
1da177e4 | 302 | { |
92476d7f EB |
303 | struct task_struct *result = NULL; |
304 | if (pid) { | |
305 | struct hlist_node *first; | |
306 | first = rcu_dereference(pid->tasks[type].first); | |
307 | if (first) | |
308 | result = hlist_entry(first, struct task_struct, pids[(type)].node); | |
309 | } | |
310 | return result; | |
311 | } | |
1da177e4 | 312 | |
92476d7f EB |
313 | /* |
314 | * Must be called under rcu_read_lock() or with tasklist_lock read-held. | |
315 | */ | |
36c8b586 | 316 | struct task_struct *find_task_by_pid_type(int type, int nr) |
92476d7f EB |
317 | { |
318 | return pid_task(find_pid(nr), type); | |
319 | } | |
1da177e4 | 320 | |
92476d7f | 321 | EXPORT_SYMBOL(find_task_by_pid_type); |
1da177e4 | 322 | |
1a657f78 ON |
323 | struct pid *get_task_pid(struct task_struct *task, enum pid_type type) |
324 | { | |
325 | struct pid *pid; | |
326 | rcu_read_lock(); | |
327 | pid = get_pid(task->pids[type].pid); | |
328 | rcu_read_unlock(); | |
329 | return pid; | |
330 | } | |
331 | ||
92476d7f EB |
332 | struct task_struct *fastcall get_pid_task(struct pid *pid, enum pid_type type) |
333 | { | |
334 | struct task_struct *result; | |
335 | rcu_read_lock(); | |
336 | result = pid_task(pid, type); | |
337 | if (result) | |
338 | get_task_struct(result); | |
339 | rcu_read_unlock(); | |
340 | return result; | |
1da177e4 LT |
341 | } |
342 | ||
92476d7f | 343 | struct pid *find_get_pid(pid_t nr) |
1da177e4 LT |
344 | { |
345 | struct pid *pid; | |
346 | ||
92476d7f EB |
347 | rcu_read_lock(); |
348 | pid = get_pid(find_pid(nr)); | |
349 | rcu_read_unlock(); | |
1da177e4 | 350 | |
92476d7f | 351 | return pid; |
1da177e4 LT |
352 | } |
353 | ||
0804ef4b EB |
354 | /* |
355 | * Used by proc to find the first pid that is greater then or equal to nr. | |
356 | * | |
357 | * If there is a pid at nr this function is exactly the same as find_pid. | |
358 | */ | |
359 | struct pid *find_ge_pid(int nr) | |
360 | { | |
361 | struct pid *pid; | |
362 | ||
363 | do { | |
364 | pid = find_pid(nr); | |
365 | if (pid) | |
366 | break; | |
2894d650 | 367 | nr = next_pidmap(task_active_pid_ns(current), nr); |
0804ef4b EB |
368 | } while (nr > 0); |
369 | ||
370 | return pid; | |
371 | } | |
bbf73147 | 372 | EXPORT_SYMBOL_GPL(find_get_pid); |
0804ef4b | 373 | |
baf8f0f8 PE |
374 | struct pid_cache { |
375 | int nr_ids; | |
376 | char name[16]; | |
377 | struct kmem_cache *cachep; | |
378 | struct list_head list; | |
379 | }; | |
380 | ||
381 | static LIST_HEAD(pid_caches_lh); | |
382 | static DEFINE_MUTEX(pid_caches_mutex); | |
383 | ||
384 | /* | |
385 | * creates the kmem cache to allocate pids from. | |
386 | * @nr_ids: the number of numerical ids this pid will have to carry | |
387 | */ | |
388 | ||
389 | static struct kmem_cache *create_pid_cachep(int nr_ids) | |
390 | { | |
391 | struct pid_cache *pcache; | |
392 | struct kmem_cache *cachep; | |
393 | ||
394 | mutex_lock(&pid_caches_mutex); | |
395 | list_for_each_entry (pcache, &pid_caches_lh, list) | |
396 | if (pcache->nr_ids == nr_ids) | |
397 | goto out; | |
398 | ||
399 | pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL); | |
400 | if (pcache == NULL) | |
401 | goto err_alloc; | |
402 | ||
403 | snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids); | |
404 | cachep = kmem_cache_create(pcache->name, | |
405 | /* FIXME add numerical ids here */ | |
406 | sizeof(struct pid), 0, SLAB_HWCACHE_ALIGN, NULL); | |
407 | if (cachep == NULL) | |
408 | goto err_cachep; | |
409 | ||
410 | pcache->nr_ids = nr_ids; | |
411 | pcache->cachep = cachep; | |
412 | list_add(&pcache->list, &pid_caches_lh); | |
413 | out: | |
414 | mutex_unlock(&pid_caches_mutex); | |
415 | return pcache->cachep; | |
416 | ||
417 | err_cachep: | |
418 | kfree(pcache); | |
419 | err_alloc: | |
420 | mutex_unlock(&pid_caches_mutex); | |
421 | return NULL; | |
422 | } | |
423 | ||
213dd266 | 424 | struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns) |
9a575a92 | 425 | { |
e3222c4e | 426 | BUG_ON(!old_ns); |
9a575a92 | 427 | get_pid_ns(old_ns); |
e3222c4e | 428 | return old_ns; |
9a575a92 CLG |
429 | } |
430 | ||
431 | void free_pid_ns(struct kref *kref) | |
432 | { | |
433 | struct pid_namespace *ns; | |
434 | ||
435 | ns = container_of(kref, struct pid_namespace, kref); | |
436 | kfree(ns); | |
437 | } | |
438 | ||
1da177e4 LT |
439 | /* |
440 | * The pid hash table is scaled according to the amount of memory in the | |
441 | * machine. From a minimum of 16 slots up to 4096 slots at one gigabyte or | |
442 | * more. | |
443 | */ | |
444 | void __init pidhash_init(void) | |
445 | { | |
92476d7f | 446 | int i, pidhash_size; |
1da177e4 LT |
447 | unsigned long megabytes = nr_kernel_pages >> (20 - PAGE_SHIFT); |
448 | ||
449 | pidhash_shift = max(4, fls(megabytes * 4)); | |
450 | pidhash_shift = min(12, pidhash_shift); | |
451 | pidhash_size = 1 << pidhash_shift; | |
452 | ||
453 | printk("PID hash table entries: %d (order: %d, %Zd bytes)\n", | |
454 | pidhash_size, pidhash_shift, | |
92476d7f EB |
455 | pidhash_size * sizeof(struct hlist_head)); |
456 | ||
457 | pid_hash = alloc_bootmem(pidhash_size * sizeof(*(pid_hash))); | |
458 | if (!pid_hash) | |
459 | panic("Could not alloc pidhash!\n"); | |
460 | for (i = 0; i < pidhash_size; i++) | |
461 | INIT_HLIST_HEAD(&pid_hash[i]); | |
1da177e4 LT |
462 | } |
463 | ||
464 | void __init pidmap_init(void) | |
465 | { | |
61a58c6c | 466 | init_pid_ns.pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL); |
73b9ebfe | 467 | /* Reserve PID 0. We never call free_pidmap(0) */ |
61a58c6c SB |
468 | set_bit(0, init_pid_ns.pidmap[0].page); |
469 | atomic_dec(&init_pid_ns.pidmap[0].nr_free); | |
92476d7f | 470 | |
baf8f0f8 PE |
471 | init_pid_ns.pid_cachep = create_pid_cachep(1); |
472 | if (init_pid_ns.pid_cachep == NULL) | |
473 | panic("Can't create pid_1 cachep\n"); | |
1da177e4 | 474 | } |