1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Contains the core associated with submission side polling of the SQ
4 * ring, offloading submissions from the application to a kernel thread.
5 */
6 #include <linux/kernel.h>
7 #include <linux/errno.h>
8 #include <linux/file.h>
9 #include <linux/mm.h>
10 #include <linux/slab.h>
11 #include <linux/audit.h>
12 #include <linux/security.h>
13 #include <linux/cpuset.h>
14 #include <linux/io_uring.h>
15
16 #include <uapi/linux/io_uring.h>
17
18 #include "io_uring.h"
19 #include "napi.h"
20 #include "sqpoll.h"
21
22 #define IORING_SQPOLL_CAP_ENTRIES_VALUE 8
23 #define IORING_TW_CAP_ENTRIES_VALUE 8
24
25 enum {
26 IO_SQ_THREAD_SHOULD_STOP = 0,
27 IO_SQ_THREAD_SHOULD_PARK,
28 };
29
30 void io_sq_thread_unpark(struct io_sq_data *sqd)
31 __releases(&sqd->lock)
32 {
33 WARN_ON_ONCE(sqd->thread == current);
34
35 /*
36 * Do the dance but not conditional clear_bit() because it'd race with
37 * other threads incrementing park_pending and setting the bit.
38 */
39 clear_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
40 if (atomic_dec_return(&sqd->park_pending))
41 set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
42 mutex_unlock(&sqd->lock);
43 }
44
45 void io_sq_thread_park(struct io_sq_data *sqd)
46 __acquires(&sqd->lock)
47 {
48 WARN_ON_ONCE(data_race(sqd->thread) == current);
49
50 atomic_inc(&sqd->park_pending);
51 set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
52 mutex_lock(&sqd->lock);
53 if (sqd->thread)
54 wake_up_process(sqd->thread);
55 }
56
57 void io_sq_thread_stop(struct io_sq_data *sqd)
58 {
59 WARN_ON_ONCE(sqd->thread == current);
60 WARN_ON_ONCE(test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state));
61
62 set_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
63 mutex_lock(&sqd->lock);
64 if (sqd->thread)
65 wake_up_process(sqd->thread);
66 mutex_unlock(&sqd->lock);
67 wait_for_completion(&sqd->exited);
68 }
69
70 void io_put_sq_data(struct io_sq_data *sqd)
71 {
72 if (refcount_dec_and_test(&sqd->refs)) {
73 WARN_ON_ONCE(atomic_read(&sqd->park_pending));
74
75 io_sq_thread_stop(sqd);
76 kfree(sqd);
77 }
78 }
79
80 static __cold void io_sqd_update_thread_idle(struct io_sq_data *sqd)
81 {
82 struct io_ring_ctx *ctx;
83 unsigned sq_thread_idle = 0;
84
85 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
86 sq_thread_idle = max(sq_thread_idle, ctx->sq_thread_idle);
87 sqd->sq_thread_idle = sq_thread_idle;
88 }
89
90 void io_sq_thread_finish(struct io_ring_ctx *ctx)
91 {
92 struct io_sq_data *sqd = ctx->sq_data;
93
94 if (sqd) {
95 io_sq_thread_park(sqd);
96 list_del_init(&ctx->sqd_list);
97 io_sqd_update_thread_idle(sqd);
98 io_sq_thread_unpark(sqd);
99
100 io_put_sq_data(sqd);
101 ctx->sq_data = NULL;
102 }
103 }
104
105 static struct io_sq_data *io_attach_sq_data(struct io_uring_params *p)
106 {
107 struct io_ring_ctx *ctx_attach;
108 struct io_sq_data *sqd;
109 struct fd f;
110
111 f = fdget(p->wq_fd);
112 if (!f.file)
113 return ERR_PTR(-ENXIO);
114 if (!io_is_uring_fops(f.file)) {
115 fdput(f);
116 return ERR_PTR(-EINVAL);
117 }
118
119 ctx_attach = f.file->private_data;
120 sqd = ctx_attach->sq_data;
121 if (!sqd) {
122 fdput(f);
123 return ERR_PTR(-EINVAL);
124 }
125 if (sqd->task_tgid != current->tgid) {
126 fdput(f);
127 return ERR_PTR(-EPERM);
128 }
129
130 refcount_inc(&sqd->refs);
131 fdput(f);
132 return sqd;
133 }
134
135 static struct io_sq_data *io_get_sq_data(struct io_uring_params *p,
136 bool *attached)
137 {
138 struct io_sq_data *sqd;
139
140 *attached = false;
141 if (p->flags & IORING_SETUP_ATTACH_WQ) {
142 sqd = io_attach_sq_data(p);
143 if (!IS_ERR(sqd)) {
144 *attached = true;
145 return sqd;
146 }
147 /* fall through for EPERM case, setup new sqd/task */
148 if (PTR_ERR(sqd) != -EPERM)
149 return sqd;
150 }
151
152 sqd = kzalloc(sizeof(*sqd), GFP_KERNEL);
153 if (!sqd)
154 return ERR_PTR(-ENOMEM);
155
156 atomic_set(&sqd->park_pending, 0);
157 refcount_set(&sqd->refs, 1);
158 INIT_LIST_HEAD(&sqd->ctx_list);
159 mutex_init(&sqd->lock);
160 init_waitqueue_head(&sqd->wait);
161 init_completion(&sqd->exited);
162 return sqd;
163 }
164
165 static inline bool io_sqd_events_pending(struct io_sq_data *sqd)
166 {
167 return READ_ONCE(sqd->state);
168 }
169
170 static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
171 {
172 unsigned int to_submit;
173 int ret = 0;
174
175 to_submit = io_sqring_entries(ctx);
176 /* if we're handling multiple rings, cap submit size for fairness */
177 if (cap_entries && to_submit > IORING_SQPOLL_CAP_ENTRIES_VALUE)
178 to_submit = IORING_SQPOLL_CAP_ENTRIES_VALUE;
179
180 if (!wq_list_empty(&ctx->iopoll_list) || to_submit) {
181 const struct cred *creds = NULL;
182
183 if (ctx->sq_creds != current_cred())
184 creds = override_creds(ctx->sq_creds);
185
186 mutex_lock(&ctx->uring_lock);
187 if (!wq_list_empty(&ctx->iopoll_list))
188 io_do_iopoll(ctx, true);
189
190 /*
191 * Don't submit if refs are dying, good for io_uring_register(),
192 * but also it is relied upon by io_ring_exit_work()
193 */
194 if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)) &&
195 !(ctx->flags & IORING_SETUP_R_DISABLED))
196 ret = io_submit_sqes(ctx, to_submit);
197 mutex_unlock(&ctx->uring_lock);
198
199 if (io_napi(ctx))
200 ret += io_napi_sqpoll_busy_poll(ctx);
201
202 if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
203 wake_up(&ctx->sqo_sq_wait);
204 if (creds)
205 revert_creds(creds);
206 }
207
208 return ret;
209 }
210
211 static bool io_sqd_handle_event(struct io_sq_data *sqd)
212 {
213 bool did_sig = false;
214 struct ksignal ksig;
215
216 if (test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) ||
217 signal_pending(current)) {
218 mutex_unlock(&sqd->lock);
219 if (signal_pending(current))
220 did_sig = get_signal(&ksig);
221 cond_resched();
222 mutex_lock(&sqd->lock);
223 sqd->sq_cpu = raw_smp_processor_id();
224 }
225 return did_sig || test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
226 }
227
228 /*
229 * Run task_work, processing the retry_list first. The retry_list holds
230 * entries that we passed on in the previous run, if we had more task_work
231 * than we were asked to process. Newly queued task_work isn't run until the
232 * retry list has been fully processed.
233 */
234 static unsigned int io_sq_tw(struct llist_node **retry_list, int max_entries)
235 {
236 struct io_uring_task *tctx = current->io_uring;
237 unsigned int count = 0;
238
239 if (*retry_list) {
240 *retry_list = io_handle_tw_list(*retry_list, &count, max_entries);
241 if (count >= max_entries)
242 goto out;
243 max_entries -= count;
244 }
245 *retry_list = tctx_task_work_run(tctx, max_entries, &count);
246 out:
247 if (task_work_pending(current))
248 task_work_run();
249 return count;
250 }
251
252 static bool io_sq_tw_pending(struct llist_node *retry_list)
253 {
254 struct io_uring_task *tctx = current->io_uring;
255
256 return retry_list || !llist_empty(&tctx->task_list);
257 }
258
259 static void io_sq_update_worktime(struct io_sq_data *sqd, struct rusage *start)
260 {
261 struct rusage end;
262
263 getrusage(current, RUSAGE_SELF, &end);
264 end.ru_stime.tv_sec -= start->ru_stime.tv_sec;
265 end.ru_stime.tv_usec -= start->ru_stime.tv_usec;
266
267 sqd->work_time += end.ru_stime.tv_usec + end.ru_stime.tv_sec * 1000000;
268 }
269
270 static int io_sq_thread(void *data)
271 {
272 struct llist_node *retry_list = NULL;
273 struct io_sq_data *sqd = data;
274 struct io_ring_ctx *ctx;
275 struct rusage start;
276 unsigned long timeout = 0;
277 char buf[TASK_COMM_LEN];
278 DEFINE_WAIT(wait);
279
280 /* offload context creation failed, just exit */
281 if (!current->io_uring)
282 goto err_out;
283
284 snprintf(buf, sizeof(buf), "iou-sqp-%d", sqd->task_pid);
285 set_task_comm(current, buf);
286
287 /* reset to our pid after we've set task_comm, for fdinfo */
288 sqd->task_pid = current->pid;
289
290 if (sqd->sq_cpu != -1) {
291 set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu));
292 } else {
293 set_cpus_allowed_ptr(current, cpu_online_mask);
294 sqd->sq_cpu = raw_smp_processor_id();
295 }
296
297 /*
298 * Force audit context to get setup, in case we do prep side async
299 * operations that would trigger an audit call before any issue side
300 * audit has been done.
301 */
302 audit_uring_entry(IORING_OP_NOP);
303 audit_uring_exit(true, 0);
304
305 mutex_lock(&sqd->lock);
306 while (1) {
307 bool cap_entries, sqt_spin = false;
308
309 if (io_sqd_events_pending(sqd) || signal_pending(current)) {
310 if (io_sqd_handle_event(sqd))
311 break;
312 timeout = jiffies + sqd->sq_thread_idle;
313 }
314
315 cap_entries = !list_is_singular(&sqd->ctx_list);
316 getrusage(current, RUSAGE_SELF, &start);
317 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
318 int ret = __io_sq_thread(ctx, cap_entries);
319
320 if (!sqt_spin && (ret > 0 || !wq_list_empty(&ctx->iopoll_list)))
321 sqt_spin = true;
322 }
323 if (io_sq_tw(&retry_list, IORING_TW_CAP_ENTRIES_VALUE))
324 sqt_spin = true;
325
326 if (sqt_spin || !time_after(jiffies, timeout)) {
327 if (sqt_spin) {
328 io_sq_update_worktime(sqd, &start);
329 timeout = jiffies + sqd->sq_thread_idle;
330 }
331 if (unlikely(need_resched())) {
332 mutex_unlock(&sqd->lock);
333 cond_resched();
334 mutex_lock(&sqd->lock);
335 sqd->sq_cpu = raw_smp_processor_id();
336 }
337 continue;
338 }
339
340 prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
341 if (!io_sqd_events_pending(sqd) && !io_sq_tw_pending(retry_list)) {
342 bool needs_sched = true;
343
344 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
345 atomic_or(IORING_SQ_NEED_WAKEUP,
346 &ctx->rings->sq_flags);
347 if ((ctx->flags & IORING_SETUP_IOPOLL) &&
348 !wq_list_empty(&ctx->iopoll_list)) {
349 needs_sched = false;
350 break;
351 }
352
353 /*
354 * Ensure the store of the wakeup flag is not
355 * reordered with the load of the SQ tail
356 */
357 smp_mb__after_atomic();
358
359 if (io_sqring_entries(ctx)) {
360 needs_sched = false;
361 break;
362 }
363 }
364
365 if (needs_sched) {
366 mutex_unlock(&sqd->lock);
367 schedule();
368 mutex_lock(&sqd->lock);
369 sqd->sq_cpu = raw_smp_processor_id();
370 }
371 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
372 atomic_andnot(IORING_SQ_NEED_WAKEUP,
373 &ctx->rings->sq_flags);
374 }
375
376 finish_wait(&sqd->wait, &wait);
377 timeout = jiffies + sqd->sq_thread_idle;
378 }
379
380 if (retry_list)
381 io_sq_tw(&retry_list, UINT_MAX);
382
383 io_uring_cancel_generic(true, sqd);
384 sqd->thread = NULL;
385 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
386 atomic_or(IORING_SQ_NEED_WAKEUP, &ctx->rings->sq_flags);
387 io_run_task_work();
388 mutex_unlock(&sqd->lock);
389 err_out:
390 complete(&sqd->exited);
391 do_exit(0);
392 }
393
394 void io_sqpoll_wait_sq(struct io_ring_ctx *ctx)
395 {
396 DEFINE_WAIT(wait);
397
398 do {
399 if (!io_sqring_full(ctx))
400 break;
401 prepare_to_wait(&ctx->sqo_sq_wait, &wait, TASK_INTERRUPTIBLE);
402
403 if (!io_sqring_full(ctx))
404 break;
405 schedule();
406 } while (!signal_pending(current));
407
408 finish_wait(&ctx->sqo_sq_wait, &wait);
409 }
410
411 __cold int io_sq_offload_create(struct io_ring_ctx *ctx,
412 struct io_uring_params *p)
413 {
414 int ret;
415
416 /* Retain compatibility with failing for an invalid attach attempt */
417 if ((ctx->flags & (IORING_SETUP_ATTACH_WQ | IORING_SETUP_SQPOLL)) ==
418 IORING_SETUP_ATTACH_WQ) {
419 struct fd f;
420
421 f = fdget(p->wq_fd);
422 if (!f.file)
423 return -ENXIO;
424 if (!io_is_uring_fops(f.file)) {
425 fdput(f);
426 return -EINVAL;
427 }
428 fdput(f);
429 }
430 if (ctx->flags & IORING_SETUP_SQPOLL) {
431 struct task_struct *tsk;
432 struct io_sq_data *sqd;
433 bool attached;
434
435 ret = security_uring_sqpoll();
436 if (ret)
437 return ret;
438
439 sqd = io_get_sq_data(p, &attached);
440 if (IS_ERR(sqd)) {
441 ret = PTR_ERR(sqd);
442 goto err;
443 }
444
445 ctx->sq_creds = get_current_cred();
446 ctx->sq_data = sqd;
447 ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
448 if (!ctx->sq_thread_idle)
449 ctx->sq_thread_idle = HZ;
450
451 io_sq_thread_park(sqd);
452 list_add(&ctx->sqd_list, &sqd->ctx_list);
453 io_sqd_update_thread_idle(sqd);
454 /* don't attach to a dying SQPOLL thread, would be racy */
455 ret = (attached && !sqd->thread) ? -ENXIO : 0;
456 io_sq_thread_unpark(sqd);
457
458 if (ret < 0)
459 goto err;
460 if (attached)
461 return 0;
462
463 if (p->flags & IORING_SETUP_SQ_AFF) {
464 cpumask_var_t allowed_mask;
465 int cpu = p->sq_thread_cpu;
466
467 ret = -EINVAL;
468 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
469 goto err_sqpoll;
470 ret = -ENOMEM;
471 if (!alloc_cpumask_var(&allowed_mask, GFP_KERNEL))
472 goto err_sqpoll;
473 ret = -EINVAL;
474 cpuset_cpus_allowed(current, allowed_mask);
475 if (!cpumask_test_cpu(cpu, allowed_mask)) {
476 free_cpumask_var(allowed_mask);
477 goto err_sqpoll;
478 }
479 free_cpumask_var(allowed_mask);
480 sqd->sq_cpu = cpu;
481 } else {
482 sqd->sq_cpu = -1;
483 }
484
485 sqd->task_pid = current->pid;
486 sqd->task_tgid = current->tgid;
487 tsk = create_io_thread(io_sq_thread, sqd, NUMA_NO_NODE);
488 if (IS_ERR(tsk)) {
489 ret = PTR_ERR(tsk);
490 goto err_sqpoll;
491 }
492
493 sqd->thread = tsk;
494 ret = io_uring_alloc_task_context(tsk, ctx);
495 wake_up_new_task(tsk);
496 if (ret)
497 goto err;
498 } else if (p->flags & IORING_SETUP_SQ_AFF) {
499 /* Can't have SQ_AFF without SQPOLL */
500 ret = -EINVAL;
501 goto err;
502 }
503
504 return 0;
505 err_sqpoll:
506 complete(&ctx->sq_data->exited);
507 err:
508 io_sq_thread_finish(ctx);
509 return ret;
510 }
511
512 __cold int io_sqpoll_wq_cpu_affinity(struct io_ring_ctx *ctx,
513 cpumask_var_t mask)
514 {
515 struct io_sq_data *sqd = ctx->sq_data;
516 int ret = -EINVAL;
517
518 if (sqd) {
519 io_sq_thread_park(sqd);
520 /* Don't set affinity for a dying thread */
521 if (sqd->thread)
522 ret = io_wq_cpu_affinity(sqd->thread->io_uring, mask);
523 io_sq_thread_unpark(sqd);
524 }
525
526 return ret;
527 }
528
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