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 "tctx.h"
20#include "napi.h"
21#include "sqpoll.h"
22
23#define IORING_SQPOLL_CAP_ENTRIES_VALUE 8
24#define IORING_TW_CAP_ENTRIES_VALUE 32
25
26enum {
27 IO_SQ_THREAD_SHOULD_STOP = 0,
28 IO_SQ_THREAD_SHOULD_PARK,
29};
30
31void io_sq_thread_unpark(struct io_sq_data *sqd)
32 __releases(&sqd->lock)
33{
34 WARN_ON_ONCE(sqpoll_task_locked(sqd) == current);
35
36 /*
37 * Do the dance but not conditional clear_bit() because it'd race with
38 * other threads incrementing park_pending and setting the bit.
39 */
40 clear_bit(nr: IO_SQ_THREAD_SHOULD_PARK, addr: &sqd->state);
41 if (atomic_dec_return(v: &sqd->park_pending))
42 set_bit(nr: IO_SQ_THREAD_SHOULD_PARK, addr: &sqd->state);
43 mutex_unlock(lock: &sqd->lock);
44 wake_up(&sqd->wait);
45}
46
47void io_sq_thread_park(struct io_sq_data *sqd)
48 __acquires(&sqd->lock)
49{
50 struct task_struct *tsk;
51
52 atomic_inc(v: &sqd->park_pending);
53 set_bit(nr: IO_SQ_THREAD_SHOULD_PARK, addr: &sqd->state);
54 mutex_lock(lock: &sqd->lock);
55
56 tsk = sqpoll_task_locked(sqd);
57 if (tsk) {
58 WARN_ON_ONCE(tsk == current);
59 wake_up_process(tsk);
60 }
61}
62
63void io_sq_thread_stop(struct io_sq_data *sqd)
64{
65 struct task_struct *tsk;
66
67 WARN_ON_ONCE(test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state));
68
69 set_bit(nr: IO_SQ_THREAD_SHOULD_STOP, addr: &sqd->state);
70 mutex_lock(lock: &sqd->lock);
71 tsk = sqpoll_task_locked(sqd);
72 if (tsk) {
73 WARN_ON_ONCE(tsk == current);
74 wake_up_process(tsk);
75 }
76 mutex_unlock(lock: &sqd->lock);
77 wait_for_completion(&sqd->exited);
78}
79
80void io_put_sq_data(struct io_sq_data *sqd)
81{
82 if (refcount_dec_and_test(r: &sqd->refs)) {
83 WARN_ON_ONCE(atomic_read(&sqd->park_pending));
84
85 io_sq_thread_stop(sqd);
86 kfree(objp: sqd);
87 }
88}
89
90static __cold void io_sqd_update_thread_idle(struct io_sq_data *sqd)
91{
92 struct io_ring_ctx *ctx;
93 unsigned sq_thread_idle = 0;
94
95 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
96 sq_thread_idle = max(sq_thread_idle, ctx->sq_thread_idle);
97 sqd->sq_thread_idle = sq_thread_idle;
98}
99
100void io_sq_thread_finish(struct io_ring_ctx *ctx)
101{
102 struct io_sq_data *sqd = ctx->sq_data;
103
104 if (sqd) {
105 io_sq_thread_park(sqd);
106 list_del_init(entry: &ctx->sqd_list);
107 io_sqd_update_thread_idle(sqd);
108 io_sq_thread_unpark(sqd);
109
110 io_put_sq_data(sqd);
111 ctx->sq_data = NULL;
112 }
113}
114
115static struct io_sq_data *io_attach_sq_data(struct io_uring_params *p)
116{
117 struct io_ring_ctx *ctx_attach;
118 struct io_sq_data *sqd;
119 CLASS(fd, f)(fd: p->wq_fd);
120
121 if (fd_empty(f))
122 return ERR_PTR(error: -ENXIO);
123 if (!io_is_uring_fops(fd_file(f)))
124 return ERR_PTR(error: -EINVAL);
125
126 ctx_attach = fd_file(f)->private_data;
127 sqd = ctx_attach->sq_data;
128 if (!sqd)
129 return ERR_PTR(error: -EINVAL);
130 if (sqd->task_tgid != current->tgid)
131 return ERR_PTR(error: -EPERM);
132
133 refcount_inc(r: &sqd->refs);
134 return sqd;
135}
136
137static struct io_sq_data *io_get_sq_data(struct io_uring_params *p,
138 bool *attached)
139{
140 struct io_sq_data *sqd;
141
142 *attached = false;
143 if (p->flags & IORING_SETUP_ATTACH_WQ) {
144 sqd = io_attach_sq_data(p);
145 if (!IS_ERR(ptr: sqd)) {
146 *attached = true;
147 return sqd;
148 }
149 /* fall through for EPERM case, setup new sqd/task */
150 if (PTR_ERR(ptr: sqd) != -EPERM)
151 return sqd;
152 }
153
154 sqd = kzalloc(sizeof(*sqd), GFP_KERNEL);
155 if (!sqd)
156 return ERR_PTR(error: -ENOMEM);
157
158 atomic_set(v: &sqd->park_pending, i: 0);
159 refcount_set(r: &sqd->refs, n: 1);
160 INIT_LIST_HEAD(list: &sqd->ctx_list);
161 mutex_init(&sqd->lock);
162 init_waitqueue_head(&sqd->wait);
163 init_completion(x: &sqd->exited);
164 return sqd;
165}
166
167static inline bool io_sqd_events_pending(struct io_sq_data *sqd)
168{
169 return READ_ONCE(sqd->state);
170}
171
172static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
173{
174 unsigned int to_submit;
175 int ret = 0;
176
177 to_submit = io_sqring_entries(ctx);
178 /* if we're handling multiple rings, cap submit size for fairness */
179 if (cap_entries && to_submit > IORING_SQPOLL_CAP_ENTRIES_VALUE)
180 to_submit = IORING_SQPOLL_CAP_ENTRIES_VALUE;
181
182 if (to_submit || !wq_list_empty(&ctx->iopoll_list)) {
183 const struct cred *creds = NULL;
184
185 if (ctx->sq_creds != current_cred())
186 creds = override_creds(override_cred: ctx->sq_creds);
187
188 mutex_lock(lock: &ctx->uring_lock);
189 if (!wq_list_empty(&ctx->iopoll_list))
190 io_do_iopoll(ctx, force_nonspin: true);
191
192 /*
193 * Don't submit if refs are dying, good for io_uring_register(),
194 * but also it is relied upon by io_ring_exit_work()
195 */
196 if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)) &&
197 !(ctx->flags & IORING_SETUP_R_DISABLED))
198 ret = io_submit_sqes(ctx, nr: to_submit);
199 mutex_unlock(lock: &ctx->uring_lock);
200
201 if (to_submit && wq_has_sleeper(wq_head: &ctx->sqo_sq_wait))
202 wake_up(&ctx->sqo_sq_wait);
203 if (creds)
204 revert_creds(revert_cred: creds);
205 }
206
207 return ret;
208}
209
210static bool io_sqd_handle_event(struct io_sq_data *sqd)
211{
212 bool did_sig = false;
213 struct ksignal ksig;
214
215 if (test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) ||
216 signal_pending(current)) {
217 mutex_unlock(lock: &sqd->lock);
218 if (signal_pending(current))
219 did_sig = get_signal(ksig: &ksig);
220 wait_event(sqd->wait, !atomic_read(&sqd->park_pending));
221 mutex_lock(lock: &sqd->lock);
222 sqd->sq_cpu = raw_smp_processor_id();
223 }
224 return did_sig || test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
225}
226
227/*
228 * Run task_work, processing the retry_list first. The retry_list holds
229 * entries that we passed on in the previous run, if we had more task_work
230 * than we were asked to process. Newly queued task_work isn't run until the
231 * retry list has been fully processed.
232 */
233static unsigned int io_sq_tw(struct llist_node **retry_list, int max_entries)
234{
235 struct io_uring_task *tctx = current->io_uring;
236 unsigned int count = 0;
237
238 if (*retry_list) {
239 *retry_list = io_handle_tw_list(node: *retry_list, count: &count, max_entries);
240 if (count >= max_entries)
241 goto out;
242 max_entries -= count;
243 }
244 *retry_list = tctx_task_work_run(tctx, max_entries, count: &count);
245out:
246 if (task_work_pending(current))
247 task_work_run();
248 return count;
249}
250
251static bool io_sq_tw_pending(struct llist_node *retry_list)
252{
253 struct io_uring_task *tctx = current->io_uring;
254
255 return retry_list || !llist_empty(head: &tctx->task_list);
256}
257
258static void io_sq_update_worktime(struct io_sq_data *sqd, struct rusage *start)
259{
260 struct rusage end;
261
262 getrusage(current, RUSAGE_SELF, ru: &end);
263 end.ru_stime.tv_sec -= start->ru_stime.tv_sec;
264 end.ru_stime.tv_usec -= start->ru_stime.tv_usec;
265
266 sqd->work_time += end.ru_stime.tv_usec + end.ru_stime.tv_sec * 1000000;
267}
268
269static int io_sq_thread(void *data)
270{
271 struct llist_node *retry_list = NULL;
272 struct io_sq_data *sqd = data;
273 struct io_ring_ctx *ctx;
274 struct rusage start;
275 unsigned long timeout = 0;
276 char buf[TASK_COMM_LEN] = {};
277 DEFINE_WAIT(wait);
278
279 /* offload context creation failed, just exit */
280 if (!current->io_uring) {
281 mutex_lock(lock: &sqd->lock);
282 rcu_assign_pointer(sqd->thread, NULL);
283 put_task_struct(current);
284 mutex_unlock(lock: &sqd->lock);
285 goto err_out;
286 }
287
288 snprintf(buf, size: sizeof(buf), fmt: "iou-sqp-%d", sqd->task_pid);
289 set_task_comm(current, buf);
290
291 /* reset to our pid after we've set task_comm, for fdinfo */
292 sqd->task_pid = current->pid;
293
294 if (sqd->sq_cpu != -1) {
295 set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu));
296 } else {
297 set_cpus_allowed_ptr(current, cpu_online_mask);
298 sqd->sq_cpu = raw_smp_processor_id();
299 }
300
301 /*
302 * Force audit context to get setup, in case we do prep side async
303 * operations that would trigger an audit call before any issue side
304 * audit has been done.
305 */
306 audit_uring_entry(op: IORING_OP_NOP);
307 audit_uring_exit(success: true, code: 0);
308
309 mutex_lock(lock: &sqd->lock);
310 while (1) {
311 bool cap_entries, sqt_spin = false;
312
313 if (io_sqd_events_pending(sqd) || signal_pending(current)) {
314 if (io_sqd_handle_event(sqd))
315 break;
316 timeout = jiffies + sqd->sq_thread_idle;
317 }
318
319 cap_entries = !list_is_singular(head: &sqd->ctx_list);
320 getrusage(current, RUSAGE_SELF, ru: &start);
321 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
322 int ret = __io_sq_thread(ctx, cap_entries);
323
324 if (!sqt_spin && (ret > 0 || !wq_list_empty(&ctx->iopoll_list)))
325 sqt_spin = true;
326 }
327 if (io_sq_tw(retry_list: &retry_list, IORING_TW_CAP_ENTRIES_VALUE))
328 sqt_spin = true;
329
330 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
331 if (io_napi(ctx))
332 io_napi_sqpoll_busy_poll(ctx);
333
334 if (sqt_spin || !time_after(jiffies, timeout)) {
335 if (sqt_spin) {
336 io_sq_update_worktime(sqd, start: &start);
337 timeout = jiffies + sqd->sq_thread_idle;
338 }
339 if (unlikely(need_resched())) {
340 mutex_unlock(lock: &sqd->lock);
341 cond_resched();
342 mutex_lock(lock: &sqd->lock);
343 sqd->sq_cpu = raw_smp_processor_id();
344 }
345 continue;
346 }
347
348 prepare_to_wait(wq_head: &sqd->wait, wq_entry: &wait, TASK_INTERRUPTIBLE);
349 if (!io_sqd_events_pending(sqd) && !io_sq_tw_pending(retry_list)) {
350 bool needs_sched = true;
351
352 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
353 atomic_or(IORING_SQ_NEED_WAKEUP,
354 v: &ctx->rings->sq_flags);
355 if ((ctx->flags & IORING_SETUP_IOPOLL) &&
356 !wq_list_empty(&ctx->iopoll_list)) {
357 needs_sched = false;
358 break;
359 }
360
361 /*
362 * Ensure the store of the wakeup flag is not
363 * reordered with the load of the SQ tail
364 */
365 smp_mb__after_atomic();
366
367 if (io_sqring_entries(ctx)) {
368 needs_sched = false;
369 break;
370 }
371 }
372
373 if (needs_sched) {
374 mutex_unlock(lock: &sqd->lock);
375 schedule();
376 mutex_lock(lock: &sqd->lock);
377 sqd->sq_cpu = raw_smp_processor_id();
378 }
379 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
380 atomic_andnot(IORING_SQ_NEED_WAKEUP,
381 v: &ctx->rings->sq_flags);
382 }
383
384 finish_wait(wq_head: &sqd->wait, wq_entry: &wait);
385 timeout = jiffies + sqd->sq_thread_idle;
386 }
387
388 if (retry_list)
389 io_sq_tw(retry_list: &retry_list, UINT_MAX);
390
391 io_uring_cancel_generic(cancel_all: true, sqd);
392 rcu_assign_pointer(sqd->thread, NULL);
393 put_task_struct(current);
394 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
395 atomic_or(IORING_SQ_NEED_WAKEUP, v: &ctx->rings->sq_flags);
396 io_run_task_work();
397 mutex_unlock(lock: &sqd->lock);
398err_out:
399 complete(&sqd->exited);
400 do_exit(error_code: 0);
401}
402
403void io_sqpoll_wait_sq(struct io_ring_ctx *ctx)
404{
405 DEFINE_WAIT(wait);
406
407 do {
408 if (!io_sqring_full(ctx))
409 break;
410 prepare_to_wait(wq_head: &ctx->sqo_sq_wait, wq_entry: &wait, TASK_INTERRUPTIBLE);
411
412 if (!io_sqring_full(ctx))
413 break;
414 schedule();
415 } while (!signal_pending(current));
416
417 finish_wait(wq_head: &ctx->sqo_sq_wait, wq_entry: &wait);
418}
419
420__cold int io_sq_offload_create(struct io_ring_ctx *ctx,
421 struct io_uring_params *p)
422{
423 int ret;
424
425 /* Retain compatibility with failing for an invalid attach attempt */
426 if ((ctx->flags & (IORING_SETUP_ATTACH_WQ | IORING_SETUP_SQPOLL)) ==
427 IORING_SETUP_ATTACH_WQ) {
428 CLASS(fd, f)(fd: p->wq_fd);
429 if (fd_empty(f))
430 return -ENXIO;
431 if (!io_is_uring_fops(fd_file(f)))
432 return -EINVAL;
433 }
434 if (ctx->flags & IORING_SETUP_SQPOLL) {
435 struct task_struct *tsk;
436 struct io_sq_data *sqd;
437 bool attached;
438
439 ret = security_uring_sqpoll();
440 if (ret)
441 return ret;
442
443 sqd = io_get_sq_data(p, attached: &attached);
444 if (IS_ERR(ptr: sqd)) {
445 ret = PTR_ERR(ptr: sqd);
446 goto err;
447 }
448
449 ctx->sq_creds = get_current_cred();
450 ctx->sq_data = sqd;
451 ctx->sq_thread_idle = msecs_to_jiffies(m: p->sq_thread_idle);
452 if (!ctx->sq_thread_idle)
453 ctx->sq_thread_idle = HZ;
454
455 io_sq_thread_park(sqd);
456 list_add(new: &ctx->sqd_list, head: &sqd->ctx_list);
457 io_sqd_update_thread_idle(sqd);
458 /* don't attach to a dying SQPOLL thread, would be racy */
459 ret = (attached && !sqd->thread) ? -ENXIO : 0;
460 io_sq_thread_unpark(sqd);
461
462 if (ret < 0)
463 goto err;
464 if (attached)
465 return 0;
466
467 if (p->flags & IORING_SETUP_SQ_AFF) {
468 cpumask_var_t allowed_mask;
469 int cpu = p->sq_thread_cpu;
470
471 ret = -EINVAL;
472 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
473 goto err_sqpoll;
474 ret = -ENOMEM;
475 if (!alloc_cpumask_var(mask: &allowed_mask, GFP_KERNEL))
476 goto err_sqpoll;
477 ret = -EINVAL;
478 cpuset_cpus_allowed(current, mask: allowed_mask);
479 if (!cpumask_test_cpu(cpu, cpumask: allowed_mask)) {
480 free_cpumask_var(mask: allowed_mask);
481 goto err_sqpoll;
482 }
483 free_cpumask_var(mask: allowed_mask);
484 sqd->sq_cpu = cpu;
485 } else {
486 sqd->sq_cpu = -1;
487 }
488
489 sqd->task_pid = current->pid;
490 sqd->task_tgid = current->tgid;
491 tsk = create_io_thread(fn: io_sq_thread, arg: sqd, NUMA_NO_NODE);
492 if (IS_ERR(ptr: tsk)) {
493 ret = PTR_ERR(ptr: tsk);
494 goto err_sqpoll;
495 }
496
497 mutex_lock(lock: &sqd->lock);
498 rcu_assign_pointer(sqd->thread, tsk);
499 mutex_unlock(lock: &sqd->lock);
500
501 get_task_struct(t: tsk);
502 ret = io_uring_alloc_task_context(task: tsk, ctx);
503 wake_up_new_task(tsk);
504 if (ret)
505 goto err;
506 } else if (p->flags & IORING_SETUP_SQ_AFF) {
507 /* Can't have SQ_AFF without SQPOLL */
508 ret = -EINVAL;
509 goto err;
510 }
511 return 0;
512err_sqpoll:
513 complete(&ctx->sq_data->exited);
514err:
515 io_sq_thread_finish(ctx);
516 return ret;
517}
518
519__cold int io_sqpoll_wq_cpu_affinity(struct io_ring_ctx *ctx,
520 cpumask_var_t mask)
521{
522 struct io_sq_data *sqd = ctx->sq_data;
523 int ret = -EINVAL;
524
525 if (sqd) {
526 struct task_struct *tsk;
527
528 io_sq_thread_park(sqd);
529 /* Don't set affinity for a dying thread */
530 tsk = sqpoll_task_locked(sqd);
531 if (tsk)
532 ret = io_wq_cpu_affinity(tctx: tsk->io_uring, mask);
533 io_sq_thread_unpark(sqd);
534 }
535
536 return ret;
537}
538