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