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17437f31 JA |
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/io_uring.h> | |
14 | ||
15 | #include <uapi/linux/io_uring.h> | |
16 | ||
17437f31 JA |
17 | #include "io_uring.h" |
18 | #include "sqpoll.h" | |
19 | ||
20 | #define IORING_SQPOLL_CAP_ENTRIES_VALUE 8 | |
21 | ||
22 | enum { | |
23 | IO_SQ_THREAD_SHOULD_STOP = 0, | |
24 | IO_SQ_THREAD_SHOULD_PARK, | |
25 | }; | |
26 | ||
27 | void io_sq_thread_unpark(struct io_sq_data *sqd) | |
28 | __releases(&sqd->lock) | |
29 | { | |
30 | WARN_ON_ONCE(sqd->thread == current); | |
31 | ||
32 | /* | |
33 | * Do the dance but not conditional clear_bit() because it'd race with | |
34 | * other threads incrementing park_pending and setting the bit. | |
35 | */ | |
36 | clear_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state); | |
37 | if (atomic_dec_return(&sqd->park_pending)) | |
38 | set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state); | |
39 | mutex_unlock(&sqd->lock); | |
40 | } | |
41 | ||
42 | void io_sq_thread_park(struct io_sq_data *sqd) | |
43 | __acquires(&sqd->lock) | |
44 | { | |
45 | WARN_ON_ONCE(sqd->thread == current); | |
46 | ||
47 | atomic_inc(&sqd->park_pending); | |
48 | set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state); | |
49 | mutex_lock(&sqd->lock); | |
50 | if (sqd->thread) | |
51 | wake_up_process(sqd->thread); | |
52 | } | |
53 | ||
54 | void io_sq_thread_stop(struct io_sq_data *sqd) | |
55 | { | |
56 | WARN_ON_ONCE(sqd->thread == current); | |
57 | WARN_ON_ONCE(test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state)); | |
58 | ||
59 | set_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state); | |
60 | mutex_lock(&sqd->lock); | |
61 | if (sqd->thread) | |
62 | wake_up_process(sqd->thread); | |
63 | mutex_unlock(&sqd->lock); | |
64 | wait_for_completion(&sqd->exited); | |
65 | } | |
66 | ||
67 | void io_put_sq_data(struct io_sq_data *sqd) | |
68 | { | |
69 | if (refcount_dec_and_test(&sqd->refs)) { | |
70 | WARN_ON_ONCE(atomic_read(&sqd->park_pending)); | |
71 | ||
72 | io_sq_thread_stop(sqd); | |
73 | kfree(sqd); | |
74 | } | |
75 | } | |
76 | ||
77 | static __cold void io_sqd_update_thread_idle(struct io_sq_data *sqd) | |
78 | { | |
79 | struct io_ring_ctx *ctx; | |
80 | unsigned sq_thread_idle = 0; | |
81 | ||
82 | list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) | |
83 | sq_thread_idle = max(sq_thread_idle, ctx->sq_thread_idle); | |
84 | sqd->sq_thread_idle = sq_thread_idle; | |
85 | } | |
86 | ||
87 | void io_sq_thread_finish(struct io_ring_ctx *ctx) | |
88 | { | |
89 | struct io_sq_data *sqd = ctx->sq_data; | |
90 | ||
91 | if (sqd) { | |
92 | io_sq_thread_park(sqd); | |
93 | list_del_init(&ctx->sqd_list); | |
94 | io_sqd_update_thread_idle(sqd); | |
95 | io_sq_thread_unpark(sqd); | |
96 | ||
97 | io_put_sq_data(sqd); | |
98 | ctx->sq_data = NULL; | |
99 | } | |
100 | } | |
101 | ||
102 | static struct io_sq_data *io_attach_sq_data(struct io_uring_params *p) | |
103 | { | |
104 | struct io_ring_ctx *ctx_attach; | |
105 | struct io_sq_data *sqd; | |
106 | struct fd f; | |
107 | ||
108 | f = fdget(p->wq_fd); | |
109 | if (!f.file) | |
110 | return ERR_PTR(-ENXIO); | |
111 | if (!io_is_uring_fops(f.file)) { | |
112 | fdput(f); | |
113 | return ERR_PTR(-EINVAL); | |
114 | } | |
115 | ||
116 | ctx_attach = f.file->private_data; | |
117 | sqd = ctx_attach->sq_data; | |
118 | if (!sqd) { | |
119 | fdput(f); | |
120 | return ERR_PTR(-EINVAL); | |
121 | } | |
122 | if (sqd->task_tgid != current->tgid) { | |
123 | fdput(f); | |
124 | return ERR_PTR(-EPERM); | |
125 | } | |
126 | ||
127 | refcount_inc(&sqd->refs); | |
128 | fdput(f); | |
129 | return sqd; | |
130 | } | |
131 | ||
132 | static struct io_sq_data *io_get_sq_data(struct io_uring_params *p, | |
133 | bool *attached) | |
134 | { | |
135 | struct io_sq_data *sqd; | |
136 | ||
137 | *attached = false; | |
138 | if (p->flags & IORING_SETUP_ATTACH_WQ) { | |
139 | sqd = io_attach_sq_data(p); | |
140 | if (!IS_ERR(sqd)) { | |
141 | *attached = true; | |
142 | return sqd; | |
143 | } | |
144 | /* fall through for EPERM case, setup new sqd/task */ | |
145 | if (PTR_ERR(sqd) != -EPERM) | |
146 | return sqd; | |
147 | } | |
148 | ||
149 | sqd = kzalloc(sizeof(*sqd), GFP_KERNEL); | |
150 | if (!sqd) | |
151 | return ERR_PTR(-ENOMEM); | |
152 | ||
153 | atomic_set(&sqd->park_pending, 0); | |
154 | refcount_set(&sqd->refs, 1); | |
155 | INIT_LIST_HEAD(&sqd->ctx_list); | |
156 | mutex_init(&sqd->lock); | |
157 | init_waitqueue_head(&sqd->wait); | |
158 | init_completion(&sqd->exited); | |
159 | return sqd; | |
160 | } | |
161 | ||
162 | static inline bool io_sqd_events_pending(struct io_sq_data *sqd) | |
163 | { | |
164 | return READ_ONCE(sqd->state); | |
165 | } | |
166 | ||
167 | static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries) | |
168 | { | |
169 | unsigned int to_submit; | |
170 | int ret = 0; | |
171 | ||
172 | to_submit = io_sqring_entries(ctx); | |
173 | /* if we're handling multiple rings, cap submit size for fairness */ | |
174 | if (cap_entries && to_submit > IORING_SQPOLL_CAP_ENTRIES_VALUE) | |
175 | to_submit = IORING_SQPOLL_CAP_ENTRIES_VALUE; | |
176 | ||
177 | if (!wq_list_empty(&ctx->iopoll_list) || to_submit) { | |
178 | const struct cred *creds = NULL; | |
179 | ||
180 | if (ctx->sq_creds != current_cred()) | |
181 | creds = override_creds(ctx->sq_creds); | |
182 | ||
183 | mutex_lock(&ctx->uring_lock); | |
184 | if (!wq_list_empty(&ctx->iopoll_list)) | |
185 | io_do_iopoll(ctx, true); | |
186 | ||
187 | /* | |
188 | * Don't submit if refs are dying, good for io_uring_register(), | |
189 | * but also it is relied upon by io_ring_exit_work() | |
190 | */ | |
191 | if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)) && | |
192 | !(ctx->flags & IORING_SETUP_R_DISABLED)) | |
193 | ret = io_submit_sqes(ctx, to_submit); | |
194 | mutex_unlock(&ctx->uring_lock); | |
195 | ||
196 | if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait)) | |
197 | wake_up(&ctx->sqo_sq_wait); | |
198 | if (creds) | |
199 | revert_creds(creds); | |
200 | } | |
201 | ||
202 | return ret; | |
203 | } | |
204 | ||
205 | static bool io_sqd_handle_event(struct io_sq_data *sqd) | |
206 | { | |
207 | bool did_sig = false; | |
208 | struct ksignal ksig; | |
209 | ||
210 | if (test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) || | |
211 | signal_pending(current)) { | |
212 | mutex_unlock(&sqd->lock); | |
213 | if (signal_pending(current)) | |
214 | did_sig = get_signal(&ksig); | |
215 | cond_resched(); | |
216 | mutex_lock(&sqd->lock); | |
217 | } | |
218 | return did_sig || test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state); | |
219 | } | |
220 | ||
221 | static int io_sq_thread(void *data) | |
222 | { | |
223 | struct io_sq_data *sqd = data; | |
224 | struct io_ring_ctx *ctx; | |
225 | unsigned long timeout = 0; | |
226 | char buf[TASK_COMM_LEN]; | |
227 | DEFINE_WAIT(wait); | |
228 | ||
229 | snprintf(buf, sizeof(buf), "iou-sqp-%d", sqd->task_pid); | |
230 | set_task_comm(current, buf); | |
231 | ||
232 | if (sqd->sq_cpu != -1) | |
233 | set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu)); | |
234 | else | |
235 | set_cpus_allowed_ptr(current, cpu_online_mask); | |
17437f31 | 236 | |
17437f31 JA |
237 | mutex_lock(&sqd->lock); |
238 | while (1) { | |
239 | bool cap_entries, sqt_spin = false; | |
240 | ||
241 | if (io_sqd_events_pending(sqd) || signal_pending(current)) { | |
242 | if (io_sqd_handle_event(sqd)) | |
243 | break; | |
244 | timeout = jiffies + sqd->sq_thread_idle; | |
245 | } | |
246 | ||
247 | cap_entries = !list_is_singular(&sqd->ctx_list); | |
248 | list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) { | |
249 | int ret = __io_sq_thread(ctx, cap_entries); | |
250 | ||
251 | if (!sqt_spin && (ret > 0 || !wq_list_empty(&ctx->iopoll_list))) | |
252 | sqt_spin = true; | |
253 | } | |
254 | if (io_run_task_work()) | |
255 | sqt_spin = true; | |
256 | ||
257 | if (sqt_spin || !time_after(jiffies, timeout)) { | |
17437f31 JA |
258 | if (sqt_spin) |
259 | timeout = jiffies + sqd->sq_thread_idle; | |
533ab73f WC |
260 | if (unlikely(need_resched())) { |
261 | mutex_unlock(&sqd->lock); | |
262 | cond_resched(); | |
263 | mutex_lock(&sqd->lock); | |
264 | } | |
17437f31 JA |
265 | continue; |
266 | } | |
267 | ||
268 | prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE); | |
269 | if (!io_sqd_events_pending(sqd) && !task_work_pending(current)) { | |
270 | bool needs_sched = true; | |
271 | ||
272 | list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) { | |
273 | atomic_or(IORING_SQ_NEED_WAKEUP, | |
274 | &ctx->rings->sq_flags); | |
275 | if ((ctx->flags & IORING_SETUP_IOPOLL) && | |
276 | !wq_list_empty(&ctx->iopoll_list)) { | |
277 | needs_sched = false; | |
278 | break; | |
279 | } | |
280 | ||
281 | /* | |
282 | * Ensure the store of the wakeup flag is not | |
283 | * reordered with the load of the SQ tail | |
284 | */ | |
285 | smp_mb__after_atomic(); | |
286 | ||
287 | if (io_sqring_entries(ctx)) { | |
288 | needs_sched = false; | |
289 | break; | |
290 | } | |
291 | } | |
292 | ||
293 | if (needs_sched) { | |
294 | mutex_unlock(&sqd->lock); | |
295 | schedule(); | |
296 | mutex_lock(&sqd->lock); | |
297 | } | |
298 | list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) | |
299 | atomic_andnot(IORING_SQ_NEED_WAKEUP, | |
300 | &ctx->rings->sq_flags); | |
301 | } | |
302 | ||
303 | finish_wait(&sqd->wait, &wait); | |
304 | timeout = jiffies + sqd->sq_thread_idle; | |
305 | } | |
306 | ||
307 | io_uring_cancel_generic(true, sqd); | |
308 | sqd->thread = NULL; | |
309 | list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) | |
310 | atomic_or(IORING_SQ_NEED_WAKEUP, &ctx->rings->sq_flags); | |
311 | io_run_task_work(); | |
312 | mutex_unlock(&sqd->lock); | |
313 | ||
17437f31 JA |
314 | complete(&sqd->exited); |
315 | do_exit(0); | |
316 | } | |
317 | ||
88b80534 | 318 | void io_sqpoll_wait_sq(struct io_ring_ctx *ctx) |
17437f31 JA |
319 | { |
320 | DEFINE_WAIT(wait); | |
321 | ||
322 | do { | |
323 | if (!io_sqring_full(ctx)) | |
324 | break; | |
325 | prepare_to_wait(&ctx->sqo_sq_wait, &wait, TASK_INTERRUPTIBLE); | |
326 | ||
327 | if (!io_sqring_full(ctx)) | |
328 | break; | |
329 | schedule(); | |
330 | } while (!signal_pending(current)); | |
331 | ||
332 | finish_wait(&ctx->sqo_sq_wait, &wait); | |
17437f31 JA |
333 | } |
334 | ||
335 | __cold int io_sq_offload_create(struct io_ring_ctx *ctx, | |
336 | struct io_uring_params *p) | |
337 | { | |
338 | int ret; | |
339 | ||
340 | /* Retain compatibility with failing for an invalid attach attempt */ | |
341 | if ((ctx->flags & (IORING_SETUP_ATTACH_WQ | IORING_SETUP_SQPOLL)) == | |
342 | IORING_SETUP_ATTACH_WQ) { | |
343 | struct fd f; | |
344 | ||
345 | f = fdget(p->wq_fd); | |
346 | if (!f.file) | |
347 | return -ENXIO; | |
348 | if (!io_is_uring_fops(f.file)) { | |
349 | fdput(f); | |
350 | return -EINVAL; | |
351 | } | |
352 | fdput(f); | |
353 | } | |
354 | if (ctx->flags & IORING_SETUP_SQPOLL) { | |
355 | struct task_struct *tsk; | |
356 | struct io_sq_data *sqd; | |
357 | bool attached; | |
358 | ||
359 | ret = security_uring_sqpoll(); | |
360 | if (ret) | |
361 | return ret; | |
362 | ||
363 | sqd = io_get_sq_data(p, &attached); | |
364 | if (IS_ERR(sqd)) { | |
365 | ret = PTR_ERR(sqd); | |
366 | goto err; | |
367 | } | |
368 | ||
369 | ctx->sq_creds = get_current_cred(); | |
370 | ctx->sq_data = sqd; | |
371 | ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle); | |
372 | if (!ctx->sq_thread_idle) | |
373 | ctx->sq_thread_idle = HZ; | |
374 | ||
375 | io_sq_thread_park(sqd); | |
376 | list_add(&ctx->sqd_list, &sqd->ctx_list); | |
377 | io_sqd_update_thread_idle(sqd); | |
378 | /* don't attach to a dying SQPOLL thread, would be racy */ | |
379 | ret = (attached && !sqd->thread) ? -ENXIO : 0; | |
380 | io_sq_thread_unpark(sqd); | |
381 | ||
382 | if (ret < 0) | |
383 | goto err; | |
384 | if (attached) | |
385 | return 0; | |
386 | ||
387 | if (p->flags & IORING_SETUP_SQ_AFF) { | |
388 | int cpu = p->sq_thread_cpu; | |
389 | ||
390 | ret = -EINVAL; | |
391 | if (cpu >= nr_cpu_ids || !cpu_online(cpu)) | |
392 | goto err_sqpoll; | |
393 | sqd->sq_cpu = cpu; | |
394 | } else { | |
395 | sqd->sq_cpu = -1; | |
396 | } | |
397 | ||
398 | sqd->task_pid = current->pid; | |
399 | sqd->task_tgid = current->tgid; | |
400 | tsk = create_io_thread(io_sq_thread, sqd, NUMA_NO_NODE); | |
401 | if (IS_ERR(tsk)) { | |
402 | ret = PTR_ERR(tsk); | |
403 | goto err_sqpoll; | |
404 | } | |
405 | ||
406 | sqd->thread = tsk; | |
407 | ret = io_uring_alloc_task_context(tsk, ctx); | |
408 | wake_up_new_task(tsk); | |
409 | if (ret) | |
410 | goto err; | |
411 | } else if (p->flags & IORING_SETUP_SQ_AFF) { | |
412 | /* Can't have SQ_AFF without SQPOLL */ | |
413 | ret = -EINVAL; | |
414 | goto err; | |
415 | } | |
416 | ||
417 | return 0; | |
418 | err_sqpoll: | |
419 | complete(&ctx->sq_data->exited); | |
420 | err: | |
421 | io_sq_thread_finish(ctx); | |
422 | return ret; | |
423 | } |