1 /* 2 * Copyright (c) 2003-2010 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 /* 36 * Each cpu in a system has its own self-contained light weight kernel 37 * thread scheduler, which means that generally speaking we only need 38 * to use a critical section to avoid problems. Foreign thread 39 * scheduling is queued via (async) IPIs. 40 */ 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/kernel.h> 45 #include <sys/proc.h> 46 #include <sys/rtprio.h> 47 #include <sys/kinfo.h> 48 #include <sys/queue.h> 49 #include <sys/sysctl.h> 50 #include <sys/kthread.h> 51 #include <machine/cpu.h> 52 #include <sys/lock.h> 53 #include <sys/caps.h> 54 #include <sys/spinlock.h> 55 #include <sys/ktr.h> 56 57 #include <sys/thread2.h> 58 #include <sys/spinlock2.h> 59 #include <sys/mplock2.h> 60 61 #include <sys/dsched.h> 62 63 #include <vm/vm.h> 64 #include <vm/vm_param.h> 65 #include <vm/vm_kern.h> 66 #include <vm/vm_object.h> 67 #include <vm/vm_page.h> 68 #include <vm/vm_map.h> 69 #include <vm/vm_pager.h> 70 #include <vm/vm_extern.h> 71 72 #include <machine/stdarg.h> 73 #include <machine/smp.h> 74 75 #if !defined(KTR_CTXSW) 76 #define KTR_CTXSW KTR_ALL 77 #endif 78 KTR_INFO_MASTER(ctxsw); 79 KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "#cpu[%d].td = %p", 80 sizeof(int) + sizeof(struct thread *)); 81 KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "#cpu[%d].td = %p", 82 sizeof(int) + sizeof(struct thread *)); 83 KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "#threads[%p].name = %s", 84 sizeof (struct thread *) + sizeof(char *)); 85 KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "#threads[%p].name = <dead>", sizeof (struct thread *)); 86 87 static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads"); 88 89 #ifdef INVARIANTS 90 static int panic_on_cscount = 0; 91 #endif 92 static __int64_t switch_count = 0; 93 static __int64_t preempt_hit = 0; 94 static __int64_t preempt_miss = 0; 95 static __int64_t preempt_weird = 0; 96 static __int64_t token_contention_count __debugvar = 0; 97 static int lwkt_use_spin_port; 98 static struct objcache *thread_cache; 99 100 #ifdef SMP 101 static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame); 102 #endif 103 static void lwkt_fairq_accumulate(globaldata_t gd, thread_t td); 104 105 extern void cpu_heavy_restore(void); 106 extern void cpu_lwkt_restore(void); 107 extern void cpu_kthread_restore(void); 108 extern void cpu_idle_restore(void); 109 110 #ifdef __x86_64__ 111 112 static int 113 jg_tos_ok(struct thread *td) 114 { 115 void *tos; 116 int tos_ok; 117 118 if (td == NULL) { 119 return 1; 120 } 121 KKASSERT(td->td_sp != NULL); 122 tos = ((void **)td->td_sp)[0]; 123 tos_ok = 0; 124 if ((tos == cpu_heavy_restore) || (tos == cpu_lwkt_restore) || 125 (tos == cpu_kthread_restore) || (tos == cpu_idle_restore)) { 126 tos_ok = 1; 127 } 128 return tos_ok; 129 } 130 131 #endif 132 133 /* 134 * We can make all thread ports use the spin backend instead of the thread 135 * backend. This should only be set to debug the spin backend. 136 */ 137 TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port); 138 139 #ifdef INVARIANTS 140 SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, ""); 141 #endif 142 SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, ""); 143 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, 144 "Successful preemption events"); 145 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, 146 "Failed preemption events"); 147 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, ""); 148 #ifdef INVARIANTS 149 SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count, CTLFLAG_RW, 150 &token_contention_count, 0, "spinning due to token contention"); 151 #endif 152 static int fairq_enable = 1; 153 SYSCTL_INT(_lwkt, OID_AUTO, fairq_enable, CTLFLAG_RW, &fairq_enable, 0, ""); 154 155 /* 156 * These helper procedures handle the runq, they can only be called from 157 * within a critical section. 158 * 159 * WARNING! Prior to SMP being brought up it is possible to enqueue and 160 * dequeue threads belonging to other cpus, so be sure to use td->td_gd 161 * instead of 'mycpu' when referencing the globaldata structure. Once 162 * SMP live enqueuing and dequeueing only occurs on the current cpu. 163 */ 164 static __inline 165 void 166 _lwkt_dequeue(thread_t td) 167 { 168 if (td->td_flags & TDF_RUNQ) { 169 struct globaldata *gd = td->td_gd; 170 171 td->td_flags &= ~TDF_RUNQ; 172 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq); 173 gd->gd_fairq_total_pri -= td->td_pri; 174 if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL) 175 atomic_clear_int_nonlocked(&gd->gd_reqflags, RQF_RUNNING); 176 } 177 } 178 179 /* 180 * Priority enqueue. 181 * 182 * NOTE: There are a limited number of lwkt threads runnable since user 183 * processes only schedule one at a time per cpu. 184 */ 185 static __inline 186 void 187 _lwkt_enqueue(thread_t td) 188 { 189 thread_t xtd; 190 191 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) { 192 struct globaldata *gd = td->td_gd; 193 194 td->td_flags |= TDF_RUNQ; 195 xtd = TAILQ_FIRST(&gd->gd_tdrunq); 196 if (xtd == NULL) { 197 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq); 198 atomic_set_int_nonlocked(&gd->gd_reqflags, RQF_RUNNING); 199 } else { 200 while (xtd && xtd->td_pri > td->td_pri) 201 xtd = TAILQ_NEXT(xtd, td_threadq); 202 if (xtd) 203 TAILQ_INSERT_BEFORE(xtd, td, td_threadq); 204 else 205 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq); 206 } 207 gd->gd_fairq_total_pri += td->td_pri; 208 } 209 } 210 211 static __boolean_t 212 _lwkt_thread_ctor(void *obj, void *privdata, int ocflags) 213 { 214 struct thread *td = (struct thread *)obj; 215 216 td->td_kstack = NULL; 217 td->td_kstack_size = 0; 218 td->td_flags = TDF_ALLOCATED_THREAD; 219 return (1); 220 } 221 222 static void 223 _lwkt_thread_dtor(void *obj, void *privdata) 224 { 225 struct thread *td = (struct thread *)obj; 226 227 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD, 228 ("_lwkt_thread_dtor: not allocated from objcache")); 229 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack && 230 td->td_kstack_size > 0, 231 ("_lwkt_thread_dtor: corrupted stack")); 232 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); 233 } 234 235 /* 236 * Initialize the lwkt s/system. 237 */ 238 void 239 lwkt_init(void) 240 { 241 /* An objcache has 2 magazines per CPU so divide cache size by 2. */ 242 thread_cache = objcache_create_mbacked(M_THREAD, sizeof(struct thread), 243 NULL, CACHE_NTHREADS/2, 244 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL); 245 } 246 247 /* 248 * Schedule a thread to run. As the current thread we can always safely 249 * schedule ourselves, and a shortcut procedure is provided for that 250 * function. 251 * 252 * (non-blocking, self contained on a per cpu basis) 253 */ 254 void 255 lwkt_schedule_self(thread_t td) 256 { 257 crit_enter_quick(td); 258 KASSERT(td != &td->td_gd->gd_idlethread, 259 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!")); 260 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 261 _lwkt_enqueue(td); 262 crit_exit_quick(td); 263 } 264 265 /* 266 * Deschedule a thread. 267 * 268 * (non-blocking, self contained on a per cpu basis) 269 */ 270 void 271 lwkt_deschedule_self(thread_t td) 272 { 273 crit_enter_quick(td); 274 _lwkt_dequeue(td); 275 crit_exit_quick(td); 276 } 277 278 /* 279 * LWKTs operate on a per-cpu basis 280 * 281 * WARNING! Called from early boot, 'mycpu' may not work yet. 282 */ 283 void 284 lwkt_gdinit(struct globaldata *gd) 285 { 286 TAILQ_INIT(&gd->gd_tdrunq); 287 TAILQ_INIT(&gd->gd_tdallq); 288 } 289 290 /* 291 * Create a new thread. The thread must be associated with a process context 292 * or LWKT start address before it can be scheduled. If the target cpu is 293 * -1 the thread will be created on the current cpu. 294 * 295 * If you intend to create a thread without a process context this function 296 * does everything except load the startup and switcher function. 297 */ 298 thread_t 299 lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags) 300 { 301 globaldata_t gd = mycpu; 302 void *stack; 303 304 /* 305 * If static thread storage is not supplied allocate a thread. Reuse 306 * a cached free thread if possible. gd_freetd is used to keep an exiting 307 * thread intact through the exit. 308 */ 309 if (td == NULL) { 310 if ((td = gd->gd_freetd) != NULL) 311 gd->gd_freetd = NULL; 312 else 313 td = objcache_get(thread_cache, M_WAITOK); 314 KASSERT((td->td_flags & 315 (TDF_ALLOCATED_THREAD|TDF_RUNNING)) == TDF_ALLOCATED_THREAD, 316 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags)); 317 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK); 318 } 319 320 /* 321 * Try to reuse cached stack. 322 */ 323 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) { 324 if (flags & TDF_ALLOCATED_STACK) { 325 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size); 326 stack = NULL; 327 } 328 } 329 if (stack == NULL) { 330 stack = (void *)kmem_alloc(&kernel_map, stksize); 331 flags |= TDF_ALLOCATED_STACK; 332 } 333 if (cpu < 0) 334 lwkt_init_thread(td, stack, stksize, flags, gd); 335 else 336 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu)); 337 return(td); 338 } 339 340 /* 341 * Initialize a preexisting thread structure. This function is used by 342 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread. 343 * 344 * All threads start out in a critical section at a priority of 345 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as 346 * appropriate. This function may send an IPI message when the 347 * requested cpu is not the current cpu and consequently gd_tdallq may 348 * not be initialized synchronously from the point of view of the originating 349 * cpu. 350 * 351 * NOTE! we have to be careful in regards to creating threads for other cpus 352 * if SMP has not yet been activated. 353 */ 354 #ifdef SMP 355 356 static void 357 lwkt_init_thread_remote(void *arg) 358 { 359 thread_t td = arg; 360 361 /* 362 * Protected by critical section held by IPI dispatch 363 */ 364 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq); 365 } 366 367 #endif 368 369 void 370 lwkt_init_thread(thread_t td, void *stack, int stksize, int flags, 371 struct globaldata *gd) 372 { 373 globaldata_t mygd = mycpu; 374 375 bzero(td, sizeof(struct thread)); 376 td->td_kstack = stack; 377 td->td_kstack_size = stksize; 378 td->td_flags = flags; 379 td->td_gd = gd; 380 td->td_pri = TDPRI_KERN_DAEMON; 381 td->td_critcount = 1; 382 td->td_toks_stop = &td->td_toks_base; 383 #ifdef SMP 384 if ((flags & TDF_MPSAFE) == 0) 385 td->td_mpcount = 1; 386 #endif 387 if (lwkt_use_spin_port) 388 lwkt_initport_spin(&td->td_msgport); 389 else 390 lwkt_initport_thread(&td->td_msgport, td); 391 pmap_init_thread(td); 392 #ifdef SMP 393 /* 394 * Normally initializing a thread for a remote cpu requires sending an 395 * IPI. However, the idlethread is setup before the other cpus are 396 * activated so we have to treat it as a special case. XXX manipulation 397 * of gd_tdallq requires the BGL. 398 */ 399 if (gd == mygd || td == &gd->gd_idlethread) { 400 crit_enter_gd(mygd); 401 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 402 crit_exit_gd(mygd); 403 } else { 404 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td); 405 } 406 #else 407 crit_enter_gd(mygd); 408 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 409 crit_exit_gd(mygd); 410 #endif 411 412 dsched_new_thread(td); 413 } 414 415 void 416 lwkt_set_comm(thread_t td, const char *ctl, ...) 417 { 418 __va_list va; 419 420 __va_start(va, ctl); 421 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va); 422 __va_end(va); 423 KTR_LOG(ctxsw_newtd, td, &td->td_comm[0]); 424 } 425 426 void 427 lwkt_hold(thread_t td) 428 { 429 ++td->td_refs; 430 } 431 432 void 433 lwkt_rele(thread_t td) 434 { 435 KKASSERT(td->td_refs > 0); 436 --td->td_refs; 437 } 438 439 void 440 lwkt_wait_free(thread_t td) 441 { 442 while (td->td_refs) 443 tsleep(td, 0, "tdreap", hz); 444 } 445 446 void 447 lwkt_free_thread(thread_t td) 448 { 449 KASSERT((td->td_flags & TDF_RUNNING) == 0, 450 ("lwkt_free_thread: did not exit! %p", td)); 451 452 if (td->td_flags & TDF_ALLOCATED_THREAD) { 453 objcache_put(thread_cache, td); 454 } else if (td->td_flags & TDF_ALLOCATED_STACK) { 455 /* client-allocated struct with internally allocated stack */ 456 KASSERT(td->td_kstack && td->td_kstack_size > 0, 457 ("lwkt_free_thread: corrupted stack")); 458 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); 459 td->td_kstack = NULL; 460 td->td_kstack_size = 0; 461 } 462 KTR_LOG(ctxsw_deadtd, td); 463 } 464 465 466 /* 467 * Switch to the next runnable lwkt. If no LWKTs are runnable then 468 * switch to the idlethread. Switching must occur within a critical 469 * section to avoid races with the scheduling queue. 470 * 471 * We always have full control over our cpu's run queue. Other cpus 472 * that wish to manipulate our queue must use the cpu_*msg() calls to 473 * talk to our cpu, so a critical section is all that is needed and 474 * the result is very, very fast thread switching. 475 * 476 * The LWKT scheduler uses a fixed priority model and round-robins at 477 * each priority level. User process scheduling is a totally 478 * different beast and LWKT priorities should not be confused with 479 * user process priorities. 480 * 481 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch() 482 * cleans it up. Note that the td_switch() function cannot do anything that 483 * requires the MP lock since the MP lock will have already been setup for 484 * the target thread (not the current thread). It's nice to have a scheduler 485 * that does not need the MP lock to work because it allows us to do some 486 * really cool high-performance MP lock optimizations. 487 * 488 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch() 489 * is not called by the current thread in the preemption case, only when 490 * the preempting thread blocks (in order to return to the original thread). 491 */ 492 void 493 lwkt_switch(void) 494 { 495 globaldata_t gd = mycpu; 496 thread_t td = gd->gd_curthread; 497 thread_t ntd; 498 thread_t xtd; 499 thread_t nlast; 500 int nquserok; 501 #ifdef SMP 502 int mpheld; 503 #endif 504 int didaccumulate; 505 const char *lmsg; /* diagnostic - 'systat -pv 1' */ 506 const void *laddr; 507 508 /* 509 * Switching from within a 'fast' (non thread switched) interrupt or IPI 510 * is illegal. However, we may have to do it anyway if we hit a fatal 511 * kernel trap or we have paniced. 512 * 513 * If this case occurs save and restore the interrupt nesting level. 514 */ 515 if (gd->gd_intr_nesting_level) { 516 int savegdnest; 517 int savegdtrap; 518 519 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) { 520 panic("lwkt_switch: cannot switch from within " 521 "a fast interrupt, yet, td %p\n", td); 522 } else { 523 savegdnest = gd->gd_intr_nesting_level; 524 savegdtrap = gd->gd_trap_nesting_level; 525 gd->gd_intr_nesting_level = 0; 526 gd->gd_trap_nesting_level = 0; 527 if ((td->td_flags & TDF_PANICWARN) == 0) { 528 td->td_flags |= TDF_PANICWARN; 529 kprintf("Warning: thread switch from interrupt or IPI, " 530 "thread %p (%s)\n", td, td->td_comm); 531 print_backtrace(-1); 532 } 533 lwkt_switch(); 534 gd->gd_intr_nesting_level = savegdnest; 535 gd->gd_trap_nesting_level = savegdtrap; 536 return; 537 } 538 } 539 540 /* 541 * Passive release (used to transition from user to kernel mode 542 * when we block or switch rather then when we enter the kernel). 543 * This function is NOT called if we are switching into a preemption 544 * or returning from a preemption. Typically this causes us to lose 545 * our current process designation (if we have one) and become a true 546 * LWKT thread, and may also hand the current process designation to 547 * another process and schedule thread. 548 */ 549 if (td->td_release) 550 td->td_release(td); 551 552 crit_enter_gd(gd); 553 if (TD_TOKS_HELD(td)) 554 lwkt_relalltokens(td); 555 556 /* 557 * We had better not be holding any spin locks, but don't get into an 558 * endless panic loop. 559 */ 560 KASSERT(gd->gd_spinlock_rd == NULL || panicstr != NULL, 561 ("lwkt_switch: still holding a shared spinlock %p!", 562 gd->gd_spinlock_rd)); 563 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL, 564 ("lwkt_switch: still holding %d exclusive spinlocks!", 565 gd->gd_spinlocks_wr)); 566 567 568 #ifdef SMP 569 /* 570 * td_mpcount cannot be used to determine if we currently hold the 571 * MP lock because get_mplock() will increment it prior to attempting 572 * to get the lock, and switch out if it can't. Our ownership of 573 * the actual lock will remain stable while we are in a critical section 574 * (but, of course, another cpu may own or release the lock so the 575 * actual value of mp_lock is not stable). 576 */ 577 mpheld = MP_LOCK_HELD(); 578 #ifdef INVARIANTS 579 if (td->td_cscount) { 580 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n", 581 td); 582 if (panic_on_cscount) 583 panic("switching while mastering cpusync"); 584 } 585 #endif 586 #endif 587 588 /* 589 * If we had preempted another thread on this cpu, resume the preempted 590 * thread. This occurs transparently, whether the preempted thread 591 * was scheduled or not (it may have been preempted after descheduling 592 * itself). 593 * 594 * We have to setup the MP lock for the original thread after backing 595 * out the adjustment that was made to curthread when the original 596 * was preempted. 597 */ 598 if ((ntd = td->td_preempted) != NULL) { 599 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK); 600 #ifdef SMP 601 if (ntd->td_mpcount && mpheld == 0) { 602 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d", 603 td, ntd, td->td_mpcount, ntd->td_mpcount); 604 } 605 if (ntd->td_mpcount) { 606 td->td_mpcount -= ntd->td_mpcount; 607 KKASSERT(td->td_mpcount >= 0); 608 } 609 #endif 610 ntd->td_flags |= TDF_PREEMPT_DONE; 611 612 /* 613 * The interrupt may have woken a thread up, we need to properly 614 * set the reschedule flag if the originally interrupted thread is 615 * at a lower priority. 616 */ 617 if (TAILQ_FIRST(&gd->gd_tdrunq) && 618 TAILQ_FIRST(&gd->gd_tdrunq)->td_pri > ntd->td_pri) { 619 need_lwkt_resched(); 620 } 621 /* YYY release mp lock on switchback if original doesn't need it */ 622 goto havethread_preempted; 623 } 624 625 /* 626 * Implement round-robin fairq with priority insertion. The priority 627 * insertion is handled by _lwkt_enqueue() 628 * 629 * We have to adjust the MP lock for the target thread. If we 630 * need the MP lock and cannot obtain it we try to locate a 631 * thread that does not need the MP lock. If we cannot, we spin 632 * instead of HLT. 633 * 634 * A similar issue exists for the tokens held by the target thread. 635 * If we cannot obtain ownership of the tokens we cannot immediately 636 * schedule the thread. 637 */ 638 for (;;) { 639 clear_lwkt_resched(); 640 didaccumulate = 0; 641 ntd = TAILQ_FIRST(&gd->gd_tdrunq); 642 643 /* 644 * Hotpath if we can get all necessary resources. 645 * 646 * If nothing is runnable switch to the idle thread 647 */ 648 if (ntd == NULL) { 649 ntd = &gd->gd_idlethread; 650 if (gd->gd_reqflags & RQF_IDLECHECK_MASK) 651 ntd->td_flags |= TDF_IDLE_NOHLT; 652 #ifdef SMP 653 if (ntd->td_mpcount) { 654 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) 655 panic("Idle thread %p was holding the BGL!", ntd); 656 if (mpheld == 0) { 657 cpu_pause(); 658 continue; 659 } 660 } 661 #endif 662 cpu_time.cp_msg[0] = 0; 663 cpu_time.cp_stallpc = 0; 664 goto haveidle; 665 } 666 667 /* 668 * Hotpath schedule 669 * 670 * NOTE: For UP there is no mplock and lwkt_getalltokens() 671 * always succeeds. 672 */ 673 if (ntd->td_fairq_accum >= 0 && 674 #ifdef SMP 675 (ntd->td_mpcount == 0 || mpheld || cpu_try_mplock()) && 676 #endif 677 (!TD_TOKS_HELD(ntd) || lwkt_getalltokens(ntd, &lmsg, &laddr)) 678 ) { 679 #ifdef SMP 680 clr_mplock_contention_mask(gd); 681 #endif 682 goto havethread; 683 } 684 685 lmsg = NULL; 686 laddr = NULL; 687 688 #ifdef SMP 689 /* Reload mpheld (it become stale after mplock/token ops) */ 690 mpheld = MP_LOCK_HELD(); 691 if (ntd->td_mpcount && mpheld == 0) { 692 lmsg = "mplock"; 693 laddr = ntd->td_mplock_stallpc; 694 } 695 #endif 696 697 /* 698 * Coldpath - unable to schedule ntd, continue looking for threads 699 * to schedule. This is only allowed of the (presumably) kernel 700 * thread exhausted its fair share. A kernel thread stuck on 701 * resources does not currently allow a user thread to get in 702 * front of it. 703 */ 704 #ifdef SMP 705 nquserok = ((ntd->td_pri < TDPRI_KERN_LPSCHED) || 706 (ntd->td_fairq_accum < 0)); 707 #else 708 nquserok = 1; 709 #endif 710 nlast = NULL; 711 712 for (;;) { 713 /* 714 * If the fair-share scheduler ran out ntd gets moved to the 715 * end and its accumulator will be bumped, if it didn't we 716 * maintain the same queue position. 717 * 718 * nlast keeps track of the last element prior to any moves. 719 */ 720 if (ntd->td_fairq_accum < 0) { 721 xtd = TAILQ_NEXT(ntd, td_threadq); 722 lwkt_fairq_accumulate(gd, ntd); 723 didaccumulate = 1; 724 TAILQ_REMOVE(&gd->gd_tdrunq, ntd, td_threadq); 725 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, ntd, td_threadq); 726 if (nlast == NULL) { 727 nlast = ntd; 728 if (xtd == NULL) 729 xtd = ntd; 730 } 731 ntd = xtd; 732 } else { 733 ntd = TAILQ_NEXT(ntd, td_threadq); 734 } 735 736 /* 737 * If we exhausted the run list switch to the idle thread. 738 * Since one or more threads had resource acquisition issues 739 * we do not allow the idle thread to halt. 740 * 741 * NOTE: nlast can be NULL. 742 */ 743 if (ntd == nlast) { 744 cpu_pause(); 745 ntd = &gd->gd_idlethread; 746 ntd->td_flags |= TDF_IDLE_NOHLT; 747 #ifdef SMP 748 set_mplock_contention_mask(gd); 749 cpu_mplock_contested(); 750 if (ntd->td_mpcount) { 751 mpheld = MP_LOCK_HELD(); 752 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) 753 panic("Idle thread %p was holding the BGL!", ntd); 754 if (mpheld == 0) { 755 cpu_pause(); 756 break; /* try again from the top, almost */ 757 } 758 } 759 #endif 760 761 /* 762 * If fairq accumulations occured we do not schedule the 763 * idle thread. This will cause us to try again from 764 * the (almost) top. 765 */ 766 if (didaccumulate) 767 break; /* try again from the top, almost */ 768 if (lmsg) 769 strlcpy(cpu_time.cp_msg, lmsg, sizeof(cpu_time.cp_msg)); 770 cpu_time.cp_stallpc = (uintptr_t)laddr; 771 goto haveidle; 772 } 773 774 /* 775 * Try to switch to this thread. 776 * 777 * NOTE: For UP there is no mplock and lwkt_getalltokens() 778 * always succeeds. 779 */ 780 if ((ntd->td_pri >= TDPRI_KERN_LPSCHED || nquserok) && 781 ntd->td_fairq_accum >= 0 && 782 #ifdef SMP 783 (ntd->td_mpcount == 0 || mpheld || cpu_try_mplock()) && 784 #endif 785 (!TD_TOKS_HELD(ntd) || lwkt_getalltokens(ntd, &lmsg, &laddr)) 786 ) { 787 #ifdef SMP 788 clr_mplock_contention_mask(gd); 789 #endif 790 goto havethread; 791 } 792 #ifdef SMP 793 /* Reload mpheld (it become stale after mplock/token ops) */ 794 mpheld = MP_LOCK_HELD(); 795 if (ntd->td_mpcount && mpheld == 0) { 796 lmsg = "mplock"; 797 laddr = ntd->td_mplock_stallpc; 798 } 799 800 if (ntd->td_pri >= TDPRI_KERN_LPSCHED && ntd->td_fairq_accum >= 0) 801 nquserok = 0; 802 #endif 803 } 804 } 805 806 /* 807 * Do the actual switch. WARNING: mpheld is stale here. 808 * 809 * We must always decrement td_fairq_accum on non-idle threads just 810 * in case a thread never gets a tick due to being in a continuous 811 * critical section. The page-zeroing code does that. 812 * 813 * If the thread we came up with is a higher or equal priority verses 814 * the thread at the head of the queue we move our thread to the 815 * front. This way we can always check the front of the queue. 816 */ 817 havethread: 818 ++gd->gd_cnt.v_swtch; 819 --ntd->td_fairq_accum; 820 xtd = TAILQ_FIRST(&gd->gd_tdrunq); 821 if (ntd != xtd && ntd->td_pri >= xtd->td_pri) { 822 TAILQ_REMOVE(&gd->gd_tdrunq, ntd, td_threadq); 823 TAILQ_INSERT_HEAD(&gd->gd_tdrunq, ntd, td_threadq); 824 } 825 havethread_preempted: 826 ; 827 /* 828 * If the new target does not need the MP lock and we are holding it, 829 * release the MP lock. If the new target requires the MP lock we have 830 * already acquired it for the target. 831 * 832 * WARNING: mpheld is stale here. 833 */ 834 haveidle: 835 KASSERT(ntd->td_critcount, 836 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri)); 837 #ifdef SMP 838 if (ntd->td_mpcount == 0 ) { 839 if (MP_LOCK_HELD()) 840 cpu_rel_mplock(); 841 } else { 842 ASSERT_MP_LOCK_HELD(ntd); 843 } 844 #endif 845 if (td != ntd) { 846 ++switch_count; 847 #ifdef __x86_64__ 848 { 849 int tos_ok __debugvar = jg_tos_ok(ntd); 850 KKASSERT(tos_ok); 851 } 852 #endif 853 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd); 854 td->td_switch(ntd); 855 } 856 /* NOTE: current cpu may have changed after switch */ 857 crit_exit_quick(td); 858 } 859 860 /* 861 * Request that the target thread preempt the current thread. Preemption 862 * only works under a specific set of conditions: 863 * 864 * - We are not preempting ourselves 865 * - The target thread is owned by the current cpu 866 * - We are not currently being preempted 867 * - The target is not currently being preempted 868 * - We are not holding any spin locks 869 * - The target thread is not holding any tokens 870 * - We are able to satisfy the target's MP lock requirements (if any). 871 * 872 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically 873 * this is called via lwkt_schedule() through the td_preemptable callback. 874 * critcount is the managed critical priority that we should ignore in order 875 * to determine whether preemption is possible (aka usually just the crit 876 * priority of lwkt_schedule() itself). 877 * 878 * XXX at the moment we run the target thread in a critical section during 879 * the preemption in order to prevent the target from taking interrupts 880 * that *WE* can't. Preemption is strictly limited to interrupt threads 881 * and interrupt-like threads, outside of a critical section, and the 882 * preempted source thread will be resumed the instant the target blocks 883 * whether or not the source is scheduled (i.e. preemption is supposed to 884 * be as transparent as possible). 885 * 886 * The target thread inherits our MP count (added to its own) for the 887 * duration of the preemption in order to preserve the atomicy of the 888 * MP lock during the preemption. Therefore, any preempting targets must be 889 * careful in regards to MP assertions. Note that the MP count may be 890 * out of sync with the physical mp_lock, but we do not have to preserve 891 * the original ownership of the lock if it was out of synch (that is, we 892 * can leave it synchronized on return). 893 */ 894 void 895 lwkt_preempt(thread_t ntd, int critcount) 896 { 897 struct globaldata *gd = mycpu; 898 thread_t td; 899 #ifdef SMP 900 int mpheld; 901 int savecnt; 902 #endif 903 904 /* 905 * The caller has put us in a critical section. We can only preempt 906 * if the caller of the caller was not in a critical section (basically 907 * a local interrupt), as determined by the 'critcount' parameter. We 908 * also can't preempt if the caller is holding any spinlocks (even if 909 * he isn't in a critical section). This also handles the tokens test. 910 * 911 * YYY The target thread must be in a critical section (else it must 912 * inherit our critical section? I dunno yet). 913 * 914 * Set need_lwkt_resched() unconditionally for now YYY. 915 */ 916 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri)); 917 918 td = gd->gd_curthread; 919 if (ntd->td_pri <= td->td_pri) { 920 ++preempt_miss; 921 return; 922 } 923 if (td->td_critcount > critcount) { 924 ++preempt_miss; 925 need_lwkt_resched(); 926 return; 927 } 928 #ifdef SMP 929 if (ntd->td_gd != gd) { 930 ++preempt_miss; 931 need_lwkt_resched(); 932 return; 933 } 934 #endif 935 /* 936 * Take the easy way out and do not preempt if we are holding 937 * any spinlocks. We could test whether the thread(s) being 938 * preempted interlock against the target thread's tokens and whether 939 * we can get all the target thread's tokens, but this situation 940 * should not occur very often so its easier to simply not preempt. 941 * Also, plain spinlocks are impossible to figure out at this point so 942 * just don't preempt. 943 * 944 * Do not try to preempt if the target thread is holding any tokens. 945 * We could try to acquire the tokens but this case is so rare there 946 * is no need to support it. 947 */ 948 if (gd->gd_spinlock_rd || gd->gd_spinlocks_wr) { 949 ++preempt_miss; 950 need_lwkt_resched(); 951 return; 952 } 953 if (TD_TOKS_HELD(ntd)) { 954 ++preempt_miss; 955 need_lwkt_resched(); 956 return; 957 } 958 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) { 959 ++preempt_weird; 960 need_lwkt_resched(); 961 return; 962 } 963 if (ntd->td_preempted) { 964 ++preempt_hit; 965 need_lwkt_resched(); 966 return; 967 } 968 #ifdef SMP 969 /* 970 * note: an interrupt might have occured just as we were transitioning 971 * to or from the MP lock. In this case td_mpcount will be pre-disposed 972 * (non-zero) but not actually synchronized with the actual state of the 973 * lock. We can use it to imply an MP lock requirement for the 974 * preemption but we cannot use it to test whether we hold the MP lock 975 * or not. 976 */ 977 savecnt = td->td_mpcount; 978 mpheld = MP_LOCK_HELD(); 979 ntd->td_mpcount += td->td_mpcount; 980 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) { 981 ntd->td_mpcount -= td->td_mpcount; 982 ++preempt_miss; 983 need_lwkt_resched(); 984 return; 985 } 986 #endif 987 988 /* 989 * Since we are able to preempt the current thread, there is no need to 990 * call need_lwkt_resched(). 991 */ 992 ++preempt_hit; 993 ntd->td_preempted = td; 994 td->td_flags |= TDF_PREEMPT_LOCK; 995 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd); 996 td->td_switch(ntd); 997 998 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE)); 999 #ifdef SMP 1000 KKASSERT(savecnt == td->td_mpcount); 1001 mpheld = MP_LOCK_HELD(); 1002 if (mpheld && td->td_mpcount == 0) 1003 cpu_rel_mplock(); 1004 else if (mpheld == 0 && td->td_mpcount) 1005 panic("lwkt_preempt(): MP lock was not held through"); 1006 #endif 1007 ntd->td_preempted = NULL; 1008 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE); 1009 } 1010 1011 /* 1012 * Conditionally call splz() if gd_reqflags indicates work is pending. 1013 * 1014 * td_nest_count prevents deep nesting via splz() or doreti() which 1015 * might otherwise blow out the kernel stack. Note that except for 1016 * this special case, we MUST call splz() here to handle any 1017 * pending ints, particularly after we switch, or we might accidently 1018 * halt the cpu with interrupts pending. 1019 * 1020 * (self contained on a per cpu basis) 1021 */ 1022 void 1023 splz_check(void) 1024 { 1025 globaldata_t gd = mycpu; 1026 thread_t td = gd->gd_curthread; 1027 1028 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2) 1029 splz(); 1030 } 1031 1032 /* 1033 * This function is used to negotiate a passive release of the current 1034 * process/lwp designation with the user scheduler, allowing the user 1035 * scheduler to schedule another user thread. The related kernel thread 1036 * (curthread) continues running in the released state. 1037 */ 1038 void 1039 lwkt_passive_release(struct thread *td) 1040 { 1041 struct lwp *lp = td->td_lwp; 1042 1043 td->td_release = NULL; 1044 lwkt_setpri_self(TDPRI_KERN_USER); 1045 lp->lwp_proc->p_usched->release_curproc(lp); 1046 } 1047 1048 1049 /* 1050 * This implements a normal yield. This routine is virtually a nop if 1051 * there is nothing to yield to but it will always run any pending interrupts 1052 * if called from a critical section. 1053 * 1054 * This yield is designed for kernel threads without a user context. 1055 * 1056 * (self contained on a per cpu basis) 1057 */ 1058 void 1059 lwkt_yield(void) 1060 { 1061 globaldata_t gd = mycpu; 1062 thread_t td = gd->gd_curthread; 1063 thread_t xtd; 1064 1065 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2) 1066 splz(); 1067 if (td->td_fairq_accum < 0) { 1068 lwkt_schedule_self(curthread); 1069 lwkt_switch(); 1070 } else { 1071 xtd = TAILQ_FIRST(&gd->gd_tdrunq); 1072 if (xtd && xtd->td_pri > td->td_pri) { 1073 lwkt_schedule_self(curthread); 1074 lwkt_switch(); 1075 } 1076 } 1077 } 1078 1079 /* 1080 * This yield is designed for kernel threads with a user context. 1081 * 1082 * The kernel acting on behalf of the user is potentially cpu-bound, 1083 * this function will efficiently allow other threads to run and also 1084 * switch to other processes by releasing. 1085 * 1086 * The lwkt_user_yield() function is designed to have very low overhead 1087 * if no yield is determined to be needed. 1088 */ 1089 void 1090 lwkt_user_yield(void) 1091 { 1092 globaldata_t gd = mycpu; 1093 thread_t td = gd->gd_curthread; 1094 1095 /* 1096 * Always run any pending interrupts in case we are in a critical 1097 * section. 1098 */ 1099 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2) 1100 splz(); 1101 1102 #ifdef SMP 1103 /* 1104 * XXX SEVERE TEMPORARY HACK. A cpu-bound operation running in the 1105 * kernel can prevent other cpus from servicing interrupt threads 1106 * which still require the MP lock (which is a lot of them). This 1107 * has a chaining effect since if the interrupt is blocked, so is 1108 * the event, so normal scheduling will not pick up on the problem. 1109 */ 1110 if (mp_lock_contention_mask && td->td_mpcount) { 1111 yield_mplock(td); 1112 } 1113 #endif 1114 1115 /* 1116 * Switch (which forces a release) if another kernel thread needs 1117 * the cpu, if userland wants us to resched, or if our kernel 1118 * quantum has run out. 1119 */ 1120 if (lwkt_resched_wanted() || 1121 user_resched_wanted() || 1122 td->td_fairq_accum < 0) 1123 { 1124 lwkt_switch(); 1125 } 1126 1127 #if 0 1128 /* 1129 * Reacquire the current process if we are released. 1130 * 1131 * XXX not implemented atm. The kernel may be holding locks and such, 1132 * so we want the thread to continue to receive cpu. 1133 */ 1134 if (td->td_release == NULL && lp) { 1135 lp->lwp_proc->p_usched->acquire_curproc(lp); 1136 td->td_release = lwkt_passive_release; 1137 lwkt_setpri_self(TDPRI_USER_NORM); 1138 } 1139 #endif 1140 } 1141 1142 /* 1143 * Generic schedule. Possibly schedule threads belonging to other cpus and 1144 * deal with threads that might be blocked on a wait queue. 1145 * 1146 * We have a little helper inline function which does additional work after 1147 * the thread has been enqueued, including dealing with preemption and 1148 * setting need_lwkt_resched() (which prevents the kernel from returning 1149 * to userland until it has processed higher priority threads). 1150 * 1151 * It is possible for this routine to be called after a failed _enqueue 1152 * (due to the target thread migrating, sleeping, or otherwise blocked). 1153 * We have to check that the thread is actually on the run queue! 1154 * 1155 * reschedok is an optimized constant propagated from lwkt_schedule() or 1156 * lwkt_schedule_noresched(). By default it is non-zero, causing a 1157 * reschedule to be requested if the target thread has a higher priority. 1158 * The port messaging code will set MSG_NORESCHED and cause reschedok to 1159 * be 0, prevented undesired reschedules. 1160 */ 1161 static __inline 1162 void 1163 _lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount, int reschedok) 1164 { 1165 thread_t otd; 1166 1167 if (ntd->td_flags & TDF_RUNQ) { 1168 if (ntd->td_preemptable && reschedok) { 1169 ntd->td_preemptable(ntd, ccount); /* YYY +token */ 1170 } else if (reschedok) { 1171 otd = curthread; 1172 if (ntd->td_pri > otd->td_pri) 1173 need_lwkt_resched(); 1174 } 1175 1176 /* 1177 * Give the thread a little fair share scheduler bump if it 1178 * has been asleep for a while. This is primarily to avoid 1179 * a degenerate case for interrupt threads where accumulator 1180 * crosses into negative territory unnecessarily. 1181 */ 1182 if (ntd->td_fairq_lticks != ticks) { 1183 ntd->td_fairq_lticks = ticks; 1184 ntd->td_fairq_accum += gd->gd_fairq_total_pri; 1185 if (ntd->td_fairq_accum > TDFAIRQ_MAX(gd)) 1186 ntd->td_fairq_accum = TDFAIRQ_MAX(gd); 1187 } 1188 } 1189 } 1190 1191 static __inline 1192 void 1193 _lwkt_schedule(thread_t td, int reschedok) 1194 { 1195 globaldata_t mygd = mycpu; 1196 1197 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule(): scheduling gd_idlethread is illegal!")); 1198 crit_enter_gd(mygd); 1199 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 1200 if (td == mygd->gd_curthread) { 1201 _lwkt_enqueue(td); 1202 } else { 1203 /* 1204 * If we own the thread, there is no race (since we are in a 1205 * critical section). If we do not own the thread there might 1206 * be a race but the target cpu will deal with it. 1207 */ 1208 #ifdef SMP 1209 if (td->td_gd == mygd) { 1210 _lwkt_enqueue(td); 1211 _lwkt_schedule_post(mygd, td, 1, reschedok); 1212 } else { 1213 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0); 1214 } 1215 #else 1216 _lwkt_enqueue(td); 1217 _lwkt_schedule_post(mygd, td, 1, reschedok); 1218 #endif 1219 } 1220 crit_exit_gd(mygd); 1221 } 1222 1223 void 1224 lwkt_schedule(thread_t td) 1225 { 1226 _lwkt_schedule(td, 1); 1227 } 1228 1229 void 1230 lwkt_schedule_noresched(thread_t td) 1231 { 1232 _lwkt_schedule(td, 0); 1233 } 1234 1235 #ifdef SMP 1236 1237 /* 1238 * When scheduled remotely if frame != NULL the IPIQ is being 1239 * run via doreti or an interrupt then preemption can be allowed. 1240 * 1241 * To allow preemption we have to drop the critical section so only 1242 * one is present in _lwkt_schedule_post. 1243 */ 1244 static void 1245 lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame) 1246 { 1247 thread_t td = curthread; 1248 thread_t ntd = arg; 1249 1250 if (frame && ntd->td_preemptable) { 1251 crit_exit_noyield(td); 1252 _lwkt_schedule(ntd, 1); 1253 crit_enter_quick(td); 1254 } else { 1255 _lwkt_schedule(ntd, 1); 1256 } 1257 } 1258 1259 /* 1260 * Thread migration using a 'Pull' method. The thread may or may not be 1261 * the current thread. It MUST be descheduled and in a stable state. 1262 * lwkt_giveaway() must be called on the cpu owning the thread. 1263 * 1264 * At any point after lwkt_giveaway() is called, the target cpu may 1265 * 'pull' the thread by calling lwkt_acquire(). 1266 * 1267 * We have to make sure the thread is not sitting on a per-cpu tsleep 1268 * queue or it will blow up when it moves to another cpu. 1269 * 1270 * MPSAFE - must be called under very specific conditions. 1271 */ 1272 void 1273 lwkt_giveaway(thread_t td) 1274 { 1275 globaldata_t gd = mycpu; 1276 1277 crit_enter_gd(gd); 1278 if (td->td_flags & TDF_TSLEEPQ) 1279 tsleep_remove(td); 1280 KKASSERT(td->td_gd == gd); 1281 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); 1282 td->td_flags |= TDF_MIGRATING; 1283 crit_exit_gd(gd); 1284 } 1285 1286 void 1287 lwkt_acquire(thread_t td) 1288 { 1289 globaldata_t gd; 1290 globaldata_t mygd; 1291 1292 KKASSERT(td->td_flags & TDF_MIGRATING); 1293 gd = td->td_gd; 1294 mygd = mycpu; 1295 if (gd != mycpu) { 1296 cpu_lfence(); 1297 KKASSERT((td->td_flags & TDF_RUNQ) == 0); 1298 crit_enter_gd(mygd); 1299 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) { 1300 #ifdef SMP 1301 lwkt_process_ipiq(); 1302 #endif 1303 cpu_lfence(); 1304 } 1305 td->td_gd = mygd; 1306 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1307 td->td_flags &= ~TDF_MIGRATING; 1308 crit_exit_gd(mygd); 1309 } else { 1310 crit_enter_gd(mygd); 1311 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1312 td->td_flags &= ~TDF_MIGRATING; 1313 crit_exit_gd(mygd); 1314 } 1315 } 1316 1317 #endif 1318 1319 /* 1320 * Generic deschedule. Descheduling threads other then your own should be 1321 * done only in carefully controlled circumstances. Descheduling is 1322 * asynchronous. 1323 * 1324 * This function may block if the cpu has run out of messages. 1325 */ 1326 void 1327 lwkt_deschedule(thread_t td) 1328 { 1329 crit_enter(); 1330 #ifdef SMP 1331 if (td == curthread) { 1332 _lwkt_dequeue(td); 1333 } else { 1334 if (td->td_gd == mycpu) { 1335 _lwkt_dequeue(td); 1336 } else { 1337 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td); 1338 } 1339 } 1340 #else 1341 _lwkt_dequeue(td); 1342 #endif 1343 crit_exit(); 1344 } 1345 1346 /* 1347 * Set the target thread's priority. This routine does not automatically 1348 * switch to a higher priority thread, LWKT threads are not designed for 1349 * continuous priority changes. Yield if you want to switch. 1350 */ 1351 void 1352 lwkt_setpri(thread_t td, int pri) 1353 { 1354 KKASSERT(td->td_gd == mycpu); 1355 if (td->td_pri != pri) { 1356 KKASSERT(pri >= 0); 1357 crit_enter(); 1358 if (td->td_flags & TDF_RUNQ) { 1359 _lwkt_dequeue(td); 1360 td->td_pri = pri; 1361 _lwkt_enqueue(td); 1362 } else { 1363 td->td_pri = pri; 1364 } 1365 crit_exit(); 1366 } 1367 } 1368 1369 /* 1370 * Set the initial priority for a thread prior to it being scheduled for 1371 * the first time. The thread MUST NOT be scheduled before or during 1372 * this call. The thread may be assigned to a cpu other then the current 1373 * cpu. 1374 * 1375 * Typically used after a thread has been created with TDF_STOPPREQ, 1376 * and before the thread is initially scheduled. 1377 */ 1378 void 1379 lwkt_setpri_initial(thread_t td, int pri) 1380 { 1381 KKASSERT(pri >= 0); 1382 KKASSERT((td->td_flags & TDF_RUNQ) == 0); 1383 td->td_pri = pri; 1384 } 1385 1386 void 1387 lwkt_setpri_self(int pri) 1388 { 1389 thread_t td = curthread; 1390 1391 KKASSERT(pri >= 0 && pri <= TDPRI_MAX); 1392 crit_enter(); 1393 if (td->td_flags & TDF_RUNQ) { 1394 _lwkt_dequeue(td); 1395 td->td_pri = pri; 1396 _lwkt_enqueue(td); 1397 } else { 1398 td->td_pri = pri; 1399 } 1400 crit_exit(); 1401 } 1402 1403 /* 1404 * 1/hz tick (typically 10ms) x TDFAIRQ_SCALE (typ 8) = 80ms full cycle. 1405 * 1406 * Example: two competing threads, same priority N. decrement by (2*N) 1407 * increment by N*8, each thread will get 4 ticks. 1408 */ 1409 void 1410 lwkt_fairq_schedulerclock(thread_t td) 1411 { 1412 if (fairq_enable) { 1413 while (td) { 1414 if (td != &td->td_gd->gd_idlethread) { 1415 td->td_fairq_accum -= td->td_gd->gd_fairq_total_pri; 1416 if (td->td_fairq_accum < -TDFAIRQ_MAX(td->td_gd)) 1417 td->td_fairq_accum = -TDFAIRQ_MAX(td->td_gd); 1418 if (td->td_fairq_accum < 0) 1419 need_lwkt_resched(); 1420 td->td_fairq_lticks = ticks; 1421 } 1422 td = td->td_preempted; 1423 } 1424 } 1425 } 1426 1427 static void 1428 lwkt_fairq_accumulate(globaldata_t gd, thread_t td) 1429 { 1430 td->td_fairq_accum += td->td_pri * TDFAIRQ_SCALE; 1431 if (td->td_fairq_accum > TDFAIRQ_MAX(td->td_gd)) 1432 td->td_fairq_accum = TDFAIRQ_MAX(td->td_gd); 1433 } 1434 1435 /* 1436 * Migrate the current thread to the specified cpu. 1437 * 1438 * This is accomplished by descheduling ourselves from the current cpu, 1439 * moving our thread to the tdallq of the target cpu, IPI messaging the 1440 * target cpu, and switching out. TDF_MIGRATING prevents scheduling 1441 * races while the thread is being migrated. 1442 * 1443 * We must be sure to remove ourselves from the current cpu's tsleepq 1444 * before potentially moving to another queue. The thread can be on 1445 * a tsleepq due to a left-over tsleep_interlock(). 1446 */ 1447 #ifdef SMP 1448 static void lwkt_setcpu_remote(void *arg); 1449 #endif 1450 1451 void 1452 lwkt_setcpu_self(globaldata_t rgd) 1453 { 1454 #ifdef SMP 1455 thread_t td = curthread; 1456 1457 if (td->td_gd != rgd) { 1458 crit_enter_quick(td); 1459 if (td->td_flags & TDF_TSLEEPQ) 1460 tsleep_remove(td); 1461 td->td_flags |= TDF_MIGRATING; 1462 lwkt_deschedule_self(td); 1463 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1464 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td); 1465 lwkt_switch(); 1466 /* we are now on the target cpu */ 1467 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq); 1468 crit_exit_quick(td); 1469 } 1470 #endif 1471 } 1472 1473 void 1474 lwkt_migratecpu(int cpuid) 1475 { 1476 #ifdef SMP 1477 globaldata_t rgd; 1478 1479 rgd = globaldata_find(cpuid); 1480 lwkt_setcpu_self(rgd); 1481 #endif 1482 } 1483 1484 /* 1485 * Remote IPI for cpu migration (called while in a critical section so we 1486 * do not have to enter another one). The thread has already been moved to 1487 * our cpu's allq, but we must wait for the thread to be completely switched 1488 * out on the originating cpu before we schedule it on ours or the stack 1489 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD 1490 * change to main memory. 1491 * 1492 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races 1493 * against wakeups. It is best if this interface is used only when there 1494 * are no pending events that might try to schedule the thread. 1495 */ 1496 #ifdef SMP 1497 static void 1498 lwkt_setcpu_remote(void *arg) 1499 { 1500 thread_t td = arg; 1501 globaldata_t gd = mycpu; 1502 1503 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) { 1504 #ifdef SMP 1505 lwkt_process_ipiq(); 1506 #endif 1507 cpu_lfence(); 1508 } 1509 td->td_gd = gd; 1510 cpu_sfence(); 1511 td->td_flags &= ~TDF_MIGRATING; 1512 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 1513 _lwkt_enqueue(td); 1514 } 1515 #endif 1516 1517 struct lwp * 1518 lwkt_preempted_proc(void) 1519 { 1520 thread_t td = curthread; 1521 while (td->td_preempted) 1522 td = td->td_preempted; 1523 return(td->td_lwp); 1524 } 1525 1526 /* 1527 * Create a kernel process/thread/whatever. It shares it's address space 1528 * with proc0 - ie: kernel only. 1529 * 1530 * NOTE! By default new threads are created with the MP lock held. A 1531 * thread which does not require the MP lock should release it by calling 1532 * rel_mplock() at the start of the new thread. 1533 */ 1534 int 1535 lwkt_create(void (*func)(void *), void *arg, 1536 struct thread **tdp, thread_t template, int tdflags, int cpu, 1537 const char *fmt, ...) 1538 { 1539 thread_t td; 1540 __va_list ap; 1541 1542 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu, 1543 tdflags); 1544 if (tdp) 1545 *tdp = td; 1546 cpu_set_thread_handler(td, lwkt_exit, func, arg); 1547 1548 /* 1549 * Set up arg0 for 'ps' etc 1550 */ 1551 __va_start(ap, fmt); 1552 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap); 1553 __va_end(ap); 1554 1555 /* 1556 * Schedule the thread to run 1557 */ 1558 if ((td->td_flags & TDF_STOPREQ) == 0) 1559 lwkt_schedule(td); 1560 else 1561 td->td_flags &= ~TDF_STOPREQ; 1562 return 0; 1563 } 1564 1565 /* 1566 * Destroy an LWKT thread. Warning! This function is not called when 1567 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and 1568 * uses a different reaping mechanism. 1569 */ 1570 void 1571 lwkt_exit(void) 1572 { 1573 thread_t td = curthread; 1574 thread_t std; 1575 globaldata_t gd; 1576 1577 if (td->td_flags & TDF_VERBOSE) 1578 kprintf("kthread %p %s has exited\n", td, td->td_comm); 1579 caps_exit(td); 1580 1581 /* 1582 * Get us into a critical section to interlock gd_freetd and loop 1583 * until we can get it freed. 1584 * 1585 * We have to cache the current td in gd_freetd because objcache_put()ing 1586 * it would rip it out from under us while our thread is still active. 1587 */ 1588 gd = mycpu; 1589 crit_enter_quick(td); 1590 while ((std = gd->gd_freetd) != NULL) { 1591 gd->gd_freetd = NULL; 1592 objcache_put(thread_cache, std); 1593 } 1594 1595 /* 1596 * Remove thread resources from kernel lists and deschedule us for 1597 * the last time. 1598 */ 1599 if (td->td_flags & TDF_TSLEEPQ) 1600 tsleep_remove(td); 1601 biosched_done(td); 1602 dsched_exit_thread(td); 1603 lwkt_deschedule_self(td); 1604 lwkt_remove_tdallq(td); 1605 if (td->td_flags & TDF_ALLOCATED_THREAD) 1606 gd->gd_freetd = td; 1607 cpu_thread_exit(); 1608 } 1609 1610 void 1611 lwkt_remove_tdallq(thread_t td) 1612 { 1613 KKASSERT(td->td_gd == mycpu); 1614 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1615 } 1616 1617 void 1618 crit_panic(void) 1619 { 1620 thread_t td = curthread; 1621 int lcrit = td->td_critcount; 1622 1623 td->td_critcount = 0; 1624 panic("td_critcount is/would-go negative! %p %d", td, lcrit); 1625 } 1626 1627 #ifdef SMP 1628 1629 /* 1630 * Called from debugger/panic on cpus which have been stopped. We must still 1631 * process the IPIQ while stopped, even if we were stopped while in a critical 1632 * section (XXX). 1633 * 1634 * If we are dumping also try to process any pending interrupts. This may 1635 * or may not work depending on the state of the cpu at the point it was 1636 * stopped. 1637 */ 1638 void 1639 lwkt_smp_stopped(void) 1640 { 1641 globaldata_t gd = mycpu; 1642 1643 crit_enter_gd(gd); 1644 if (dumping) { 1645 lwkt_process_ipiq(); 1646 splz(); 1647 } else { 1648 lwkt_process_ipiq(); 1649 } 1650 crit_exit_gd(gd); 1651 } 1652 1653 #endif 1654