1 /* 2 * Copyright (c) 2003,2004 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 * $DragonFly: src/sys/kern/lwkt_thread.c,v 1.101 2006/06/04 21:09:50 dillon Exp $ 35 */ 36 37 /* 38 * Each cpu in a system has its own self-contained light weight kernel 39 * thread scheduler, which means that generally speaking we only need 40 * to use a critical section to avoid problems. Foreign thread 41 * scheduling is queued via (async) IPIs. 42 */ 43 44 #ifdef _KERNEL 45 46 #include <sys/param.h> 47 #include <sys/systm.h> 48 #include <sys/kernel.h> 49 #include <sys/proc.h> 50 #include <sys/rtprio.h> 51 #include <sys/queue.h> 52 #include <sys/sysctl.h> 53 #include <sys/kthread.h> 54 #include <machine/cpu.h> 55 #include <sys/lock.h> 56 #include <sys/caps.h> 57 #include <sys/spinlock.h> 58 #include <sys/ktr.h> 59 60 #include <sys/thread2.h> 61 #include <sys/spinlock2.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 #include <vm/vm_zone.h> 72 73 #include <machine/stdarg.h> 74 #include <machine/ipl.h> 75 #include <machine/smp.h> 76 77 #else 78 79 #include <sys/stdint.h> 80 #include <libcaps/thread.h> 81 #include <sys/thread.h> 82 #include <sys/msgport.h> 83 #include <sys/errno.h> 84 #include <libcaps/globaldata.h> 85 #include <machine/cpufunc.h> 86 #include <sys/thread2.h> 87 #include <sys/msgport2.h> 88 #include <stdio.h> 89 #include <stdlib.h> 90 #include <string.h> 91 #include <machine/lock.h> 92 #include <machine/atomic.h> 93 #include <machine/cpu.h> 94 95 #endif 96 97 static int untimely_switch = 0; 98 #ifdef INVARIANTS 99 static int panic_on_cscount = 0; 100 #endif 101 static __int64_t switch_count = 0; 102 static __int64_t preempt_hit = 0; 103 static __int64_t preempt_miss = 0; 104 static __int64_t preempt_weird = 0; 105 static __int64_t token_contention_count = 0; 106 static __int64_t mplock_contention_count = 0; 107 108 #ifdef _KERNEL 109 110 SYSCTL_INT(_lwkt, OID_AUTO, untimely_switch, CTLFLAG_RW, &untimely_switch, 0, ""); 111 #ifdef INVARIANTS 112 SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, ""); 113 #endif 114 SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, ""); 115 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, ""); 116 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, ""); 117 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, ""); 118 #ifdef INVARIANTS 119 SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count, CTLFLAG_RW, 120 &token_contention_count, 0, "spinning due to token contention"); 121 SYSCTL_QUAD(_lwkt, OID_AUTO, mplock_contention_count, CTLFLAG_RW, 122 &mplock_contention_count, 0, "spinning due to MPLOCK contention"); 123 #endif 124 #endif 125 126 /* 127 * Kernel Trace 128 */ 129 #ifdef _KERNEL 130 131 #if !defined(KTR_GIANT_CONTENTION) 132 #define KTR_GIANT_CONTENTION KTR_ALL 133 #endif 134 135 KTR_INFO_MASTER(giant); 136 KTR_INFO(KTR_GIANT_CONTENTION, giant, beg, 0, "thread=%p", sizeof(void *)); 137 KTR_INFO(KTR_GIANT_CONTENTION, giant, end, 1, "thread=%p", sizeof(void *)); 138 139 #define loggiant(name) KTR_LOG(giant_ ## name, curthread) 140 141 #endif 142 143 /* 144 * These helper procedures handle the runq, they can only be called from 145 * within a critical section. 146 * 147 * WARNING! Prior to SMP being brought up it is possible to enqueue and 148 * dequeue threads belonging to other cpus, so be sure to use td->td_gd 149 * instead of 'mycpu' when referencing the globaldata structure. Once 150 * SMP live enqueuing and dequeueing only occurs on the current cpu. 151 */ 152 static __inline 153 void 154 _lwkt_dequeue(thread_t td) 155 { 156 if (td->td_flags & TDF_RUNQ) { 157 int nq = td->td_pri & TDPRI_MASK; 158 struct globaldata *gd = td->td_gd; 159 160 td->td_flags &= ~TDF_RUNQ; 161 TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq); 162 /* runqmask is passively cleaned up by the switcher */ 163 } 164 } 165 166 static __inline 167 void 168 _lwkt_enqueue(thread_t td) 169 { 170 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_TSLEEPQ|TDF_BLOCKQ)) == 0) { 171 int nq = td->td_pri & TDPRI_MASK; 172 struct globaldata *gd = td->td_gd; 173 174 td->td_flags |= TDF_RUNQ; 175 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq); 176 gd->gd_runqmask |= 1 << nq; 177 } 178 } 179 180 /* 181 * Schedule a thread to run. As the current thread we can always safely 182 * schedule ourselves, and a shortcut procedure is provided for that 183 * function. 184 * 185 * (non-blocking, self contained on a per cpu basis) 186 */ 187 void 188 lwkt_schedule_self(thread_t td) 189 { 190 crit_enter_quick(td); 191 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!")); 192 KKASSERT(td->td_proc == NULL || (td->td_proc->p_flag & P_ONRUNQ) == 0); 193 _lwkt_enqueue(td); 194 crit_exit_quick(td); 195 } 196 197 /* 198 * Deschedule a thread. 199 * 200 * (non-blocking, self contained on a per cpu basis) 201 */ 202 void 203 lwkt_deschedule_self(thread_t td) 204 { 205 crit_enter_quick(td); 206 _lwkt_dequeue(td); 207 crit_exit_quick(td); 208 } 209 210 #ifdef _KERNEL 211 212 /* 213 * LWKTs operate on a per-cpu basis 214 * 215 * WARNING! Called from early boot, 'mycpu' may not work yet. 216 */ 217 void 218 lwkt_gdinit(struct globaldata *gd) 219 { 220 int i; 221 222 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i) 223 TAILQ_INIT(&gd->gd_tdrunq[i]); 224 gd->gd_runqmask = 0; 225 TAILQ_INIT(&gd->gd_tdallq); 226 } 227 228 #endif /* _KERNEL */ 229 230 /* 231 * Create a new thread. The thread must be associated with a process context 232 * or LWKT start address before it can be scheduled. If the target cpu is 233 * -1 the thread will be created on the current cpu. 234 * 235 * If you intend to create a thread without a process context this function 236 * does everything except load the startup and switcher function. 237 */ 238 thread_t 239 lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags) 240 { 241 void *stack; 242 globaldata_t gd = mycpu; 243 244 if (td == NULL) { 245 crit_enter_gd(gd); 246 if (gd->gd_tdfreecount > 0) { 247 --gd->gd_tdfreecount; 248 td = TAILQ_FIRST(&gd->gd_tdfreeq); 249 KASSERT(td != NULL && (td->td_flags & TDF_RUNNING) == 0, 250 ("lwkt_alloc_thread: unexpected NULL or corrupted td")); 251 TAILQ_REMOVE(&gd->gd_tdfreeq, td, td_threadq); 252 crit_exit_gd(gd); 253 flags |= td->td_flags & (TDF_ALLOCATED_STACK|TDF_ALLOCATED_THREAD); 254 } else { 255 crit_exit_gd(gd); 256 #ifdef _KERNEL 257 td = zalloc(thread_zone); 258 #else 259 td = malloc(sizeof(struct thread)); 260 #endif 261 td->td_kstack = NULL; 262 td->td_kstack_size = 0; 263 flags |= TDF_ALLOCATED_THREAD; 264 } 265 } 266 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) { 267 if (flags & TDF_ALLOCATED_STACK) { 268 #ifdef _KERNEL 269 kmem_free(kernel_map, (vm_offset_t)stack, td->td_kstack_size); 270 #else 271 libcaps_free_stack(stack, td->td_kstack_size); 272 #endif 273 stack = NULL; 274 } 275 } 276 if (stack == NULL) { 277 #ifdef _KERNEL 278 stack = (void *)kmem_alloc(kernel_map, stksize); 279 #else 280 stack = libcaps_alloc_stack(stksize); 281 #endif 282 flags |= TDF_ALLOCATED_STACK; 283 } 284 if (cpu < 0) 285 lwkt_init_thread(td, stack, stksize, flags, mycpu); 286 else 287 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu)); 288 return(td); 289 } 290 291 #ifdef _KERNEL 292 293 /* 294 * Initialize a preexisting thread structure. This function is used by 295 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread. 296 * 297 * All threads start out in a critical section at a priority of 298 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as 299 * appropriate. This function may send an IPI message when the 300 * requested cpu is not the current cpu and consequently gd_tdallq may 301 * not be initialized synchronously from the point of view of the originating 302 * cpu. 303 * 304 * NOTE! we have to be careful in regards to creating threads for other cpus 305 * if SMP has not yet been activated. 306 */ 307 #ifdef SMP 308 309 static void 310 lwkt_init_thread_remote(void *arg) 311 { 312 thread_t td = arg; 313 314 /* 315 * Protected by critical section held by IPI dispatch 316 */ 317 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq); 318 } 319 320 #endif 321 322 void 323 lwkt_init_thread(thread_t td, void *stack, int stksize, int flags, 324 struct globaldata *gd) 325 { 326 globaldata_t mygd = mycpu; 327 328 bzero(td, sizeof(struct thread)); 329 td->td_kstack = stack; 330 td->td_kstack_size = stksize; 331 td->td_flags = flags; 332 td->td_gd = gd; 333 td->td_pri = TDPRI_KERN_DAEMON + TDPRI_CRIT; 334 #ifdef SMP 335 if ((flags & TDF_MPSAFE) == 0) 336 td->td_mpcount = 1; 337 #endif 338 lwkt_initport(&td->td_msgport, td); 339 pmap_init_thread(td); 340 #ifdef SMP 341 /* 342 * Normally initializing a thread for a remote cpu requires sending an 343 * IPI. However, the idlethread is setup before the other cpus are 344 * activated so we have to treat it as a special case. XXX manipulation 345 * of gd_tdallq requires the BGL. 346 */ 347 if (gd == mygd || td == &gd->gd_idlethread) { 348 crit_enter_gd(mygd); 349 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 350 crit_exit_gd(mygd); 351 } else { 352 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td); 353 } 354 #else 355 crit_enter_gd(mygd); 356 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 357 crit_exit_gd(mygd); 358 #endif 359 } 360 361 #endif /* _KERNEL */ 362 363 void 364 lwkt_set_comm(thread_t td, const char *ctl, ...) 365 { 366 __va_list va; 367 368 __va_start(va, ctl); 369 vsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va); 370 __va_end(va); 371 } 372 373 void 374 lwkt_hold(thread_t td) 375 { 376 ++td->td_refs; 377 } 378 379 void 380 lwkt_rele(thread_t td) 381 { 382 KKASSERT(td->td_refs > 0); 383 --td->td_refs; 384 } 385 386 #ifdef _KERNEL 387 388 void 389 lwkt_wait_free(thread_t td) 390 { 391 while (td->td_refs) 392 tsleep(td, 0, "tdreap", hz); 393 } 394 395 #endif 396 397 void 398 lwkt_free_thread(thread_t td) 399 { 400 struct globaldata *gd = mycpu; 401 402 KASSERT((td->td_flags & TDF_RUNNING) == 0, 403 ("lwkt_free_thread: did not exit! %p", td)); 404 405 crit_enter_gd(gd); 406 if (gd->gd_tdfreecount < CACHE_NTHREADS && 407 (td->td_flags & TDF_ALLOCATED_THREAD) 408 ) { 409 ++gd->gd_tdfreecount; 410 TAILQ_INSERT_HEAD(&gd->gd_tdfreeq, td, td_threadq); 411 crit_exit_gd(gd); 412 } else { 413 crit_exit_gd(gd); 414 if (td->td_kstack && (td->td_flags & TDF_ALLOCATED_STACK)) { 415 #ifdef _KERNEL 416 kmem_free(kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); 417 #else 418 libcaps_free_stack(td->td_kstack, td->td_kstack_size); 419 #endif 420 /* gd invalid */ 421 td->td_kstack = NULL; 422 td->td_kstack_size = 0; 423 } 424 if (td->td_flags & TDF_ALLOCATED_THREAD) { 425 #ifdef _KERNEL 426 zfree(thread_zone, td); 427 #else 428 free(td); 429 #endif 430 } 431 } 432 } 433 434 435 /* 436 * Switch to the next runnable lwkt. If no LWKTs are runnable then 437 * switch to the idlethread. Switching must occur within a critical 438 * section to avoid races with the scheduling queue. 439 * 440 * We always have full control over our cpu's run queue. Other cpus 441 * that wish to manipulate our queue must use the cpu_*msg() calls to 442 * talk to our cpu, so a critical section is all that is needed and 443 * the result is very, very fast thread switching. 444 * 445 * The LWKT scheduler uses a fixed priority model and round-robins at 446 * each priority level. User process scheduling is a totally 447 * different beast and LWKT priorities should not be confused with 448 * user process priorities. 449 * 450 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch() 451 * cleans it up. Note that the td_switch() function cannot do anything that 452 * requires the MP lock since the MP lock will have already been setup for 453 * the target thread (not the current thread). It's nice to have a scheduler 454 * that does not need the MP lock to work because it allows us to do some 455 * really cool high-performance MP lock optimizations. 456 * 457 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch() 458 * is not called by the current thread in the preemption case, only when 459 * the preempting thread blocks (in order to return to the original thread). 460 */ 461 void 462 lwkt_switch(void) 463 { 464 globaldata_t gd = mycpu; 465 thread_t td = gd->gd_curthread; 466 thread_t ntd; 467 #ifdef SMP 468 int mpheld; 469 #endif 470 471 /* 472 * Switching from within a 'fast' (non thread switched) interrupt or IPI 473 * is illegal. However, we may have to do it anyway if we hit a fatal 474 * kernel trap or we have paniced. 475 * 476 * If this case occurs save and restore the interrupt nesting level. 477 */ 478 if (gd->gd_intr_nesting_level) { 479 int savegdnest; 480 int savegdtrap; 481 482 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) { 483 panic("lwkt_switch: cannot switch from within " 484 "a fast interrupt, yet, td %p\n", td); 485 } else { 486 savegdnest = gd->gd_intr_nesting_level; 487 savegdtrap = gd->gd_trap_nesting_level; 488 gd->gd_intr_nesting_level = 0; 489 gd->gd_trap_nesting_level = 0; 490 if ((td->td_flags & TDF_PANICWARN) == 0) { 491 td->td_flags |= TDF_PANICWARN; 492 printf("Warning: thread switch from interrupt or IPI, " 493 "thread %p (%s)\n", td, td->td_comm); 494 #ifdef DDB 495 db_print_backtrace(); 496 #endif 497 } 498 lwkt_switch(); 499 gd->gd_intr_nesting_level = savegdnest; 500 gd->gd_trap_nesting_level = savegdtrap; 501 return; 502 } 503 } 504 505 /* 506 * Passive release (used to transition from user to kernel mode 507 * when we block or switch rather then when we enter the kernel). 508 * This function is NOT called if we are switching into a preemption 509 * or returning from a preemption. Typically this causes us to lose 510 * our current process designation (if we have one) and become a true 511 * LWKT thread, and may also hand the current process designation to 512 * another process and schedule thread. 513 */ 514 if (td->td_release) 515 td->td_release(td); 516 517 crit_enter_gd(gd); 518 #ifdef SMP 519 if (td->td_toks) 520 lwkt_relalltokens(td); 521 #endif 522 523 /* 524 * We had better not be holding any spin locks, but don't get into an 525 * endless panic loop. 526 */ 527 KASSERT(gd->gd_spinlock_rd == NULL || panicstr != NULL, 528 ("lwkt_switch: still holding a shared spinlock %p!", 529 gd->gd_spinlock_rd)); 530 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL, 531 ("lwkt_switch: still holding %d exclusive spinlocks!", 532 gd->gd_spinlocks_wr)); 533 534 535 #ifdef SMP 536 /* 537 * td_mpcount cannot be used to determine if we currently hold the 538 * MP lock because get_mplock() will increment it prior to attempting 539 * to get the lock, and switch out if it can't. Our ownership of 540 * the actual lock will remain stable while we are in a critical section 541 * (but, of course, another cpu may own or release the lock so the 542 * actual value of mp_lock is not stable). 543 */ 544 mpheld = MP_LOCK_HELD(); 545 #ifdef INVARIANTS 546 if (td->td_cscount) { 547 printf("Diagnostic: attempt to switch while mastering cpusync: %p\n", 548 td); 549 if (panic_on_cscount) 550 panic("switching while mastering cpusync"); 551 } 552 #endif 553 #endif 554 if ((ntd = td->td_preempted) != NULL) { 555 /* 556 * We had preempted another thread on this cpu, resume the preempted 557 * thread. This occurs transparently, whether the preempted thread 558 * was scheduled or not (it may have been preempted after descheduling 559 * itself). 560 * 561 * We have to setup the MP lock for the original thread after backing 562 * out the adjustment that was made to curthread when the original 563 * was preempted. 564 */ 565 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK); 566 #ifdef SMP 567 if (ntd->td_mpcount && mpheld == 0) { 568 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d", 569 td, ntd, td->td_mpcount, ntd->td_mpcount); 570 } 571 if (ntd->td_mpcount) { 572 td->td_mpcount -= ntd->td_mpcount; 573 KKASSERT(td->td_mpcount >= 0); 574 } 575 #endif 576 ntd->td_flags |= TDF_PREEMPT_DONE; 577 578 /* 579 * XXX. The interrupt may have woken a thread up, we need to properly 580 * set the reschedule flag if the originally interrupted thread is at 581 * a lower priority. 582 */ 583 if (gd->gd_runqmask > (2 << (ntd->td_pri & TDPRI_MASK)) - 1) 584 need_lwkt_resched(); 585 /* YYY release mp lock on switchback if original doesn't need it */ 586 } else { 587 /* 588 * Priority queue / round-robin at each priority. Note that user 589 * processes run at a fixed, low priority and the user process 590 * scheduler deals with interactions between user processes 591 * by scheduling and descheduling them from the LWKT queue as 592 * necessary. 593 * 594 * We have to adjust the MP lock for the target thread. If we 595 * need the MP lock and cannot obtain it we try to locate a 596 * thread that does not need the MP lock. If we cannot, we spin 597 * instead of HLT. 598 * 599 * A similar issue exists for the tokens held by the target thread. 600 * If we cannot obtain ownership of the tokens we cannot immediately 601 * schedule the thread. 602 */ 603 604 /* 605 * If an LWKT reschedule was requested, well that is what we are 606 * doing now so clear it. 607 */ 608 clear_lwkt_resched(); 609 again: 610 if (gd->gd_runqmask) { 611 int nq = bsrl(gd->gd_runqmask); 612 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) { 613 gd->gd_runqmask &= ~(1 << nq); 614 goto again; 615 } 616 #ifdef SMP 617 /* 618 * THREAD SELECTION FOR AN SMP MACHINE BUILD 619 * 620 * If the target needs the MP lock and we couldn't get it, 621 * or if the target is holding tokens and we could not 622 * gain ownership of the tokens, continue looking for a 623 * thread to schedule and spin instead of HLT if we can't. 624 * 625 * NOTE: the mpheld variable invalid after this conditional, it 626 * can change due to both cpu_try_mplock() returning success 627 * AND interactions in lwkt_getalltokens() due to the fact that 628 * we are trying to check the mpcount of a thread other then 629 * the current thread. Because of this, if the current thread 630 * is not holding td_mpcount, an IPI indirectly run via 631 * lwkt_getalltokens() can obtain and release the MP lock and 632 * cause the core MP lock to be released. 633 */ 634 if ((ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) || 635 (ntd->td_toks && lwkt_getalltokens(ntd) == 0) 636 ) { 637 u_int32_t rqmask = gd->gd_runqmask; 638 639 mpheld = MP_LOCK_HELD(); 640 ntd = NULL; 641 while (rqmask) { 642 TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) { 643 if (ntd->td_mpcount && !mpheld && !cpu_try_mplock()) { 644 /* spinning due to MP lock being held */ 645 #ifdef INVARIANTS 646 ++mplock_contention_count; 647 #endif 648 /* mplock still not held, 'mpheld' still valid */ 649 continue; 650 } 651 652 /* 653 * mpheld state invalid after getalltokens call returns 654 * failure, but the variable is only needed for 655 * the loop. 656 */ 657 if (ntd->td_toks && !lwkt_getalltokens(ntd)) { 658 /* spinning due to token contention */ 659 #ifdef INVARIANTS 660 ++token_contention_count; 661 #endif 662 mpheld = MP_LOCK_HELD(); 663 continue; 664 } 665 break; 666 } 667 if (ntd) 668 break; 669 rqmask &= ~(1 << nq); 670 nq = bsrl(rqmask); 671 } 672 if (ntd == NULL) { 673 ntd = &gd->gd_idlethread; 674 ntd->td_flags |= TDF_IDLE_NOHLT; 675 goto using_idle_thread; 676 } else { 677 ++gd->gd_cnt.v_swtch; 678 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 679 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 680 } 681 } else { 682 ++gd->gd_cnt.v_swtch; 683 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 684 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 685 } 686 #else 687 /* 688 * THREAD SELECTION FOR A UP MACHINE BUILD. We don't have to 689 * worry about tokens or the BGL. 690 */ 691 ++gd->gd_cnt.v_swtch; 692 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 693 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 694 #endif 695 } else { 696 /* 697 * We have nothing to run but only let the idle loop halt 698 * the cpu if there are no pending interrupts. 699 */ 700 ntd = &gd->gd_idlethread; 701 if (gd->gd_reqflags & RQF_IDLECHECK_MASK) 702 ntd->td_flags |= TDF_IDLE_NOHLT; 703 #ifdef SMP 704 using_idle_thread: 705 /* 706 * The idle thread should not be holding the MP lock unless we 707 * are trapping in the kernel or in a panic. Since we select the 708 * idle thread unconditionally when no other thread is available, 709 * if the MP lock is desired during a panic or kernel trap, we 710 * have to loop in the scheduler until we get it. 711 */ 712 if (ntd->td_mpcount) { 713 mpheld = MP_LOCK_HELD(); 714 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) 715 panic("Idle thread %p was holding the BGL!", ntd); 716 else if (mpheld == 0) 717 goto again; 718 } 719 #endif 720 } 721 } 722 KASSERT(ntd->td_pri >= TDPRI_CRIT, 723 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri)); 724 725 /* 726 * Do the actual switch. If the new target does not need the MP lock 727 * and we are holding it, release the MP lock. If the new target requires 728 * the MP lock we have already acquired it for the target. 729 */ 730 #ifdef SMP 731 if (ntd->td_mpcount == 0 ) { 732 if (MP_LOCK_HELD()) 733 cpu_rel_mplock(); 734 } else { 735 ASSERT_MP_LOCK_HELD(ntd); 736 } 737 #endif 738 if (td != ntd) { 739 ++switch_count; 740 td->td_switch(ntd); 741 } 742 /* NOTE: current cpu may have changed after switch */ 743 crit_exit_quick(td); 744 } 745 746 /* 747 * Request that the target thread preempt the current thread. Preemption 748 * only works under a specific set of conditions: 749 * 750 * - We are not preempting ourselves 751 * - The target thread is owned by the current cpu 752 * - We are not currently being preempted 753 * - The target is not currently being preempted 754 * - We are able to satisfy the target's MP lock requirements (if any). 755 * 756 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically 757 * this is called via lwkt_schedule() through the td_preemptable callback. 758 * critpri is the managed critical priority that we should ignore in order 759 * to determine whether preemption is possible (aka usually just the crit 760 * priority of lwkt_schedule() itself). 761 * 762 * XXX at the moment we run the target thread in a critical section during 763 * the preemption in order to prevent the target from taking interrupts 764 * that *WE* can't. Preemption is strictly limited to interrupt threads 765 * and interrupt-like threads, outside of a critical section, and the 766 * preempted source thread will be resumed the instant the target blocks 767 * whether or not the source is scheduled (i.e. preemption is supposed to 768 * be as transparent as possible). 769 * 770 * The target thread inherits our MP count (added to its own) for the 771 * duration of the preemption in order to preserve the atomicy of the 772 * MP lock during the preemption. Therefore, any preempting targets must be 773 * careful in regards to MP assertions. Note that the MP count may be 774 * out of sync with the physical mp_lock, but we do not have to preserve 775 * the original ownership of the lock if it was out of synch (that is, we 776 * can leave it synchronized on return). 777 */ 778 void 779 lwkt_preempt(thread_t ntd, int critpri) 780 { 781 struct globaldata *gd = mycpu; 782 thread_t td; 783 #ifdef SMP 784 int mpheld; 785 int savecnt; 786 #endif 787 788 /* 789 * The caller has put us in a critical section. We can only preempt 790 * if the caller of the caller was not in a critical section (basically 791 * a local interrupt), as determined by the 'critpri' parameter. We 792 * also acn't preempt if the caller is holding any spinlocks (even if 793 * he isn't in a critical section). This also handles the tokens test. 794 * 795 * YYY The target thread must be in a critical section (else it must 796 * inherit our critical section? I dunno yet). 797 * 798 * Set need_lwkt_resched() unconditionally for now YYY. 799 */ 800 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri)); 801 802 td = gd->gd_curthread; 803 if ((ntd->td_pri & TDPRI_MASK) <= (td->td_pri & TDPRI_MASK)) { 804 ++preempt_miss; 805 return; 806 } 807 if ((td->td_pri & ~TDPRI_MASK) > critpri) { 808 ++preempt_miss; 809 need_lwkt_resched(); 810 return; 811 } 812 #ifdef SMP 813 if (ntd->td_gd != gd) { 814 ++preempt_miss; 815 need_lwkt_resched(); 816 return; 817 } 818 #endif 819 /* 820 * Take the easy way out and do not preempt if the target is holding 821 * any spinlocks. We could test whether the thread(s) being 822 * preempted interlock against the target thread's tokens and whether 823 * we can get all the target thread's tokens, but this situation 824 * should not occur very often so its easier to simply not preempt. 825 * Also, plain spinlocks are impossible to figure out at this point so 826 * just don't preempt. 827 */ 828 if (gd->gd_spinlock_rd || gd->gd_spinlocks_wr) { 829 ++preempt_miss; 830 need_lwkt_resched(); 831 return; 832 } 833 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) { 834 ++preempt_weird; 835 need_lwkt_resched(); 836 return; 837 } 838 if (ntd->td_preempted) { 839 ++preempt_hit; 840 need_lwkt_resched(); 841 return; 842 } 843 #ifdef SMP 844 /* 845 * note: an interrupt might have occured just as we were transitioning 846 * to or from the MP lock. In this case td_mpcount will be pre-disposed 847 * (non-zero) but not actually synchronized with the actual state of the 848 * lock. We can use it to imply an MP lock requirement for the 849 * preemption but we cannot use it to test whether we hold the MP lock 850 * or not. 851 */ 852 savecnt = td->td_mpcount; 853 mpheld = MP_LOCK_HELD(); 854 ntd->td_mpcount += td->td_mpcount; 855 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) { 856 ntd->td_mpcount -= td->td_mpcount; 857 ++preempt_miss; 858 need_lwkt_resched(); 859 return; 860 } 861 #endif 862 863 /* 864 * Since we are able to preempt the current thread, there is no need to 865 * call need_lwkt_resched(). 866 */ 867 ++preempt_hit; 868 ntd->td_preempted = td; 869 td->td_flags |= TDF_PREEMPT_LOCK; 870 td->td_switch(ntd); 871 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE)); 872 #ifdef SMP 873 KKASSERT(savecnt == td->td_mpcount); 874 mpheld = MP_LOCK_HELD(); 875 if (mpheld && td->td_mpcount == 0) 876 cpu_rel_mplock(); 877 else if (mpheld == 0 && td->td_mpcount) 878 panic("lwkt_preempt(): MP lock was not held through"); 879 #endif 880 ntd->td_preempted = NULL; 881 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE); 882 } 883 884 /* 885 * Yield our thread while higher priority threads are pending. This is 886 * typically called when we leave a critical section but it can be safely 887 * called while we are in a critical section. 888 * 889 * This function will not generally yield to equal priority threads but it 890 * can occur as a side effect. Note that lwkt_switch() is called from 891 * inside the critical section to prevent its own crit_exit() from reentering 892 * lwkt_yield_quick(). 893 * 894 * gd_reqflags indicates that *something* changed, e.g. an interrupt or softint 895 * came along but was blocked and made pending. 896 * 897 * (self contained on a per cpu basis) 898 */ 899 void 900 lwkt_yield_quick(void) 901 { 902 globaldata_t gd = mycpu; 903 thread_t td = gd->gd_curthread; 904 905 /* 906 * gd_reqflags is cleared in splz if the cpl is 0. If we were to clear 907 * it with a non-zero cpl then we might not wind up calling splz after 908 * a task switch when the critical section is exited even though the 909 * new task could accept the interrupt. 910 * 911 * XXX from crit_exit() only called after last crit section is released. 912 * If called directly will run splz() even if in a critical section. 913 * 914 * td_nest_count prevent deep nesting via splz() or doreti(). Note that 915 * except for this special case, we MUST call splz() here to handle any 916 * pending ints, particularly after we switch, or we might accidently 917 * halt the cpu with interrupts pending. 918 */ 919 if (gd->gd_reqflags && td->td_nest_count < 2) 920 splz(); 921 922 /* 923 * YYY enabling will cause wakeup() to task-switch, which really 924 * confused the old 4.x code. This is a good way to simulate 925 * preemption and MP without actually doing preemption or MP, because a 926 * lot of code assumes that wakeup() does not block. 927 */ 928 if (untimely_switch && td->td_nest_count == 0 && 929 gd->gd_intr_nesting_level == 0 930 ) { 931 crit_enter_quick(td); 932 /* 933 * YYY temporary hacks until we disassociate the userland scheduler 934 * from the LWKT scheduler. 935 */ 936 if (td->td_flags & TDF_RUNQ) { 937 lwkt_switch(); /* will not reenter yield function */ 938 } else { 939 lwkt_schedule_self(td); /* make sure we are scheduled */ 940 lwkt_switch(); /* will not reenter yield function */ 941 lwkt_deschedule_self(td); /* make sure we are descheduled */ 942 } 943 crit_exit_noyield(td); 944 } 945 } 946 947 /* 948 * This implements a normal yield which, unlike _quick, will yield to equal 949 * priority threads as well. Note that gd_reqflags tests will be handled by 950 * the crit_exit() call in lwkt_switch(). 951 * 952 * (self contained on a per cpu basis) 953 */ 954 void 955 lwkt_yield(void) 956 { 957 lwkt_schedule_self(curthread); 958 lwkt_switch(); 959 } 960 961 /* 962 * Generic schedule. Possibly schedule threads belonging to other cpus and 963 * deal with threads that might be blocked on a wait queue. 964 * 965 * We have a little helper inline function which does additional work after 966 * the thread has been enqueued, including dealing with preemption and 967 * setting need_lwkt_resched() (which prevents the kernel from returning 968 * to userland until it has processed higher priority threads). 969 * 970 * It is possible for this routine to be called after a failed _enqueue 971 * (due to the target thread migrating, sleeping, or otherwise blocked). 972 * We have to check that the thread is actually on the run queue! 973 */ 974 static __inline 975 void 976 _lwkt_schedule_post(globaldata_t gd, thread_t ntd, int cpri) 977 { 978 if (ntd->td_flags & TDF_RUNQ) { 979 if (ntd->td_preemptable) { 980 ntd->td_preemptable(ntd, cpri); /* YYY +token */ 981 } else if ((ntd->td_flags & TDF_NORESCHED) == 0 && 982 (ntd->td_pri & TDPRI_MASK) > (gd->gd_curthread->td_pri & TDPRI_MASK) 983 ) { 984 need_lwkt_resched(); 985 } 986 } 987 } 988 989 void 990 lwkt_schedule(thread_t td) 991 { 992 globaldata_t mygd = mycpu; 993 994 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule(): scheduling gd_idlethread is illegal!")); 995 crit_enter_gd(mygd); 996 KKASSERT(td->td_proc == NULL || (td->td_proc->p_flag & P_ONRUNQ) == 0); 997 if (td == mygd->gd_curthread) { 998 _lwkt_enqueue(td); 999 } else { 1000 /* 1001 * If we own the thread, there is no race (since we are in a 1002 * critical section). If we do not own the thread there might 1003 * be a race but the target cpu will deal with it. 1004 */ 1005 #ifdef SMP 1006 if (td->td_gd == mygd) { 1007 _lwkt_enqueue(td); 1008 _lwkt_schedule_post(mygd, td, TDPRI_CRIT); 1009 } else { 1010 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_schedule, td); 1011 } 1012 #else 1013 _lwkt_enqueue(td); 1014 _lwkt_schedule_post(mygd, td, TDPRI_CRIT); 1015 #endif 1016 } 1017 crit_exit_gd(mygd); 1018 } 1019 1020 #ifdef SMP 1021 1022 /* 1023 * Thread migration using a 'Pull' method. The thread may or may not be 1024 * the current thread. It MUST be descheduled and in a stable state. 1025 * lwkt_giveaway() must be called on the cpu owning the thread. 1026 * 1027 * At any point after lwkt_giveaway() is called, the target cpu may 1028 * 'pull' the thread by calling lwkt_acquire(). 1029 * 1030 * MPSAFE - must be called under very specific conditions. 1031 */ 1032 void 1033 lwkt_giveaway(thread_t td) 1034 { 1035 globaldata_t gd = mycpu; 1036 1037 crit_enter_gd(gd); 1038 KKASSERT(td->td_gd == gd); 1039 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); 1040 td->td_flags |= TDF_MIGRATING; 1041 crit_exit_gd(gd); 1042 } 1043 1044 void 1045 lwkt_acquire(thread_t td) 1046 { 1047 globaldata_t gd; 1048 globaldata_t mygd; 1049 1050 KKASSERT(td->td_flags & TDF_MIGRATING); 1051 gd = td->td_gd; 1052 mygd = mycpu; 1053 if (gd != mycpu) { 1054 cpu_lfence(); 1055 KKASSERT((td->td_flags & TDF_RUNQ) == 0); 1056 crit_enter_gd(mygd); 1057 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) 1058 cpu_lfence(); 1059 td->td_gd = mygd; 1060 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1061 td->td_flags &= ~TDF_MIGRATING; 1062 crit_exit_gd(mygd); 1063 } else { 1064 crit_enter_gd(mygd); 1065 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1066 td->td_flags &= ~TDF_MIGRATING; 1067 crit_exit_gd(mygd); 1068 } 1069 } 1070 1071 #endif 1072 1073 /* 1074 * Generic deschedule. Descheduling threads other then your own should be 1075 * done only in carefully controlled circumstances. Descheduling is 1076 * asynchronous. 1077 * 1078 * This function may block if the cpu has run out of messages. 1079 */ 1080 void 1081 lwkt_deschedule(thread_t td) 1082 { 1083 crit_enter(); 1084 #ifdef SMP 1085 if (td == curthread) { 1086 _lwkt_dequeue(td); 1087 } else { 1088 if (td->td_gd == mycpu) { 1089 _lwkt_dequeue(td); 1090 } else { 1091 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td); 1092 } 1093 } 1094 #else 1095 _lwkt_dequeue(td); 1096 #endif 1097 crit_exit(); 1098 } 1099 1100 /* 1101 * Set the target thread's priority. This routine does not automatically 1102 * switch to a higher priority thread, LWKT threads are not designed for 1103 * continuous priority changes. Yield if you want to switch. 1104 * 1105 * We have to retain the critical section count which uses the high bits 1106 * of the td_pri field. The specified priority may also indicate zero or 1107 * more critical sections by adding TDPRI_CRIT*N. 1108 * 1109 * Note that we requeue the thread whether it winds up on a different runq 1110 * or not. uio_yield() depends on this and the routine is not normally 1111 * called with the same priority otherwise. 1112 */ 1113 void 1114 lwkt_setpri(thread_t td, int pri) 1115 { 1116 KKASSERT(pri >= 0); 1117 KKASSERT(td->td_gd == mycpu); 1118 crit_enter(); 1119 if (td->td_flags & TDF_RUNQ) { 1120 _lwkt_dequeue(td); 1121 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1122 _lwkt_enqueue(td); 1123 } else { 1124 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1125 } 1126 crit_exit(); 1127 } 1128 1129 void 1130 lwkt_setpri_self(int pri) 1131 { 1132 thread_t td = curthread; 1133 1134 KKASSERT(pri >= 0 && pri <= TDPRI_MAX); 1135 crit_enter(); 1136 if (td->td_flags & TDF_RUNQ) { 1137 _lwkt_dequeue(td); 1138 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1139 _lwkt_enqueue(td); 1140 } else { 1141 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1142 } 1143 crit_exit(); 1144 } 1145 1146 /* 1147 * Determine if there is a runnable thread at a higher priority then 1148 * the current thread. lwkt_setpri() does not check this automatically. 1149 * Return 1 if there is, 0 if there isn't. 1150 * 1151 * Example: if bit 31 of runqmask is set and the current thread is priority 1152 * 30, then we wind up checking the mask: 0x80000000 against 0x7fffffff. 1153 * 1154 * If nq reaches 31 the shift operation will overflow to 0 and we will wind 1155 * up comparing against 0xffffffff, a comparison that will always be false. 1156 */ 1157 int 1158 lwkt_checkpri_self(void) 1159 { 1160 globaldata_t gd = mycpu; 1161 thread_t td = gd->gd_curthread; 1162 int nq = td->td_pri & TDPRI_MASK; 1163 1164 while (gd->gd_runqmask > (__uint32_t)(2 << nq) - 1) { 1165 if (TAILQ_FIRST(&gd->gd_tdrunq[nq + 1])) 1166 return(1); 1167 ++nq; 1168 } 1169 return(0); 1170 } 1171 1172 /* 1173 * Migrate the current thread to the specified cpu. 1174 * 1175 * This is accomplished by descheduling ourselves from the current cpu, 1176 * moving our thread to the tdallq of the target cpu, IPI messaging the 1177 * target cpu, and switching out. TDF_MIGRATING prevents scheduling 1178 * races while the thread is being migrated. 1179 */ 1180 #ifdef SMP 1181 static void lwkt_setcpu_remote(void *arg); 1182 #endif 1183 1184 void 1185 lwkt_setcpu_self(globaldata_t rgd) 1186 { 1187 #ifdef SMP 1188 thread_t td = curthread; 1189 1190 if (td->td_gd != rgd) { 1191 crit_enter_quick(td); 1192 td->td_flags |= TDF_MIGRATING; 1193 lwkt_deschedule_self(td); 1194 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1195 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td); 1196 lwkt_switch(); 1197 /* we are now on the target cpu */ 1198 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq); 1199 crit_exit_quick(td); 1200 } 1201 #endif 1202 } 1203 1204 void 1205 lwkt_migratecpu(int cpuid) 1206 { 1207 #ifdef SMP 1208 globaldata_t rgd; 1209 1210 rgd = globaldata_find(cpuid); 1211 lwkt_setcpu_self(rgd); 1212 #endif 1213 } 1214 1215 /* 1216 * Remote IPI for cpu migration (called while in a critical section so we 1217 * do not have to enter another one). The thread has already been moved to 1218 * our cpu's allq, but we must wait for the thread to be completely switched 1219 * out on the originating cpu before we schedule it on ours or the stack 1220 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD 1221 * change to main memory. 1222 * 1223 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races 1224 * against wakeups. It is best if this interface is used only when there 1225 * are no pending events that might try to schedule the thread. 1226 */ 1227 #ifdef SMP 1228 static void 1229 lwkt_setcpu_remote(void *arg) 1230 { 1231 thread_t td = arg; 1232 globaldata_t gd = mycpu; 1233 1234 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) 1235 cpu_lfence(); 1236 td->td_gd = gd; 1237 cpu_sfence(); 1238 td->td_flags &= ~TDF_MIGRATING; 1239 KKASSERT(td->td_proc == NULL || (td->td_proc->p_flag & P_ONRUNQ) == 0); 1240 _lwkt_enqueue(td); 1241 } 1242 #endif 1243 1244 struct lwp * 1245 lwkt_preempted_proc(void) 1246 { 1247 thread_t td = curthread; 1248 while (td->td_preempted) 1249 td = td->td_preempted; 1250 return(td->td_lwp); 1251 } 1252 1253 /* 1254 * Create a kernel process/thread/whatever. It shares it's address space 1255 * with proc0 - ie: kernel only. 1256 * 1257 * NOTE! By default new threads are created with the MP lock held. A 1258 * thread which does not require the MP lock should release it by calling 1259 * rel_mplock() at the start of the new thread. 1260 */ 1261 int 1262 lwkt_create(void (*func)(void *), void *arg, 1263 struct thread **tdp, thread_t template, int tdflags, int cpu, 1264 const char *fmt, ...) 1265 { 1266 thread_t td; 1267 __va_list ap; 1268 1269 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu, 1270 tdflags | TDF_VERBOSE); 1271 if (tdp) 1272 *tdp = td; 1273 cpu_set_thread_handler(td, lwkt_exit, func, arg); 1274 1275 /* 1276 * Set up arg0 for 'ps' etc 1277 */ 1278 __va_start(ap, fmt); 1279 vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap); 1280 __va_end(ap); 1281 1282 /* 1283 * Schedule the thread to run 1284 */ 1285 if ((td->td_flags & TDF_STOPREQ) == 0) 1286 lwkt_schedule(td); 1287 else 1288 td->td_flags &= ~TDF_STOPREQ; 1289 return 0; 1290 } 1291 1292 /* 1293 * kthread_* is specific to the kernel and is not needed by userland. 1294 */ 1295 #ifdef _KERNEL 1296 1297 /* 1298 * Destroy an LWKT thread. Warning! This function is not called when 1299 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and 1300 * uses a different reaping mechanism. 1301 */ 1302 void 1303 lwkt_exit(void) 1304 { 1305 thread_t td = curthread; 1306 globaldata_t gd; 1307 1308 if (td->td_flags & TDF_VERBOSE) 1309 printf("kthread %p %s has exited\n", td, td->td_comm); 1310 caps_exit(td); 1311 crit_enter_quick(td); 1312 lwkt_deschedule_self(td); 1313 gd = mycpu; 1314 lwkt_remove_tdallq(td); 1315 if (td->td_flags & TDF_ALLOCATED_THREAD) { 1316 ++gd->gd_tdfreecount; 1317 TAILQ_INSERT_TAIL(&gd->gd_tdfreeq, td, td_threadq); 1318 } 1319 cpu_thread_exit(); 1320 } 1321 1322 void 1323 lwkt_remove_tdallq(thread_t td) 1324 { 1325 KKASSERT(td->td_gd == mycpu); 1326 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1327 } 1328 1329 #endif /* _KERNEL */ 1330 1331 void 1332 crit_panic(void) 1333 { 1334 thread_t td = curthread; 1335 int lpri = td->td_pri; 1336 1337 td->td_pri = 0; 1338 panic("td_pri is/would-go negative! %p %d", td, lpri); 1339 } 1340 1341 #ifdef SMP 1342 1343 /* 1344 * Called from debugger/panic on cpus which have been stopped. We must still 1345 * process the IPIQ while stopped, even if we were stopped while in a critical 1346 * section (XXX). 1347 * 1348 * If we are dumping also try to process any pending interrupts. This may 1349 * or may not work depending on the state of the cpu at the point it was 1350 * stopped. 1351 */ 1352 void 1353 lwkt_smp_stopped(void) 1354 { 1355 globaldata_t gd = mycpu; 1356 1357 crit_enter_gd(gd); 1358 if (dumping) { 1359 lwkt_process_ipiq(); 1360 splz(); 1361 } else { 1362 lwkt_process_ipiq(); 1363 } 1364 crit_exit_gd(gd); 1365 } 1366 1367 /* 1368 * get_mplock() calls this routine if it is unable to obtain the MP lock. 1369 * get_mplock() has already incremented td_mpcount. We must block and 1370 * not return until giant is held. 1371 * 1372 * All we have to do is lwkt_switch() away. The LWKT scheduler will not 1373 * reschedule the thread until it can obtain the giant lock for it. 1374 */ 1375 void 1376 lwkt_mp_lock_contested(void) 1377 { 1378 #ifdef _KERNEL 1379 loggiant(beg); 1380 #endif 1381 lwkt_switch(); 1382 #ifdef _KERNEL 1383 loggiant(end); 1384 #endif 1385 } 1386 1387 #endif 1388