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 1.116 2008/06/16 02:00:05 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 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/kernel.h> 47 #include <sys/proc.h> 48 #include <sys/rtprio.h> 49 #include <sys/queue.h> 50 #include <sys/sysctl.h> 51 #include <sys/kthread.h> 52 #include <machine/cpu.h> 53 #include <sys/lock.h> 54 #include <sys/caps.h> 55 #include <sys/spinlock.h> 56 #include <sys/ktr.h> 57 58 #include <sys/thread2.h> 59 #include <sys/spinlock2.h> 60 61 #include <vm/vm.h> 62 #include <vm/vm_param.h> 63 #include <vm/vm_kern.h> 64 #include <vm/vm_object.h> 65 #include <vm/vm_page.h> 66 #include <vm/vm_map.h> 67 #include <vm/vm_pager.h> 68 #include <vm/vm_extern.h> 69 70 #include <machine/stdarg.h> 71 #include <machine/smp.h> 72 73 static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads"); 74 75 static int untimely_switch = 0; 76 #ifdef INVARIANTS 77 static int panic_on_cscount = 0; 78 #endif 79 static __int64_t switch_count = 0; 80 static __int64_t preempt_hit = 0; 81 static __int64_t preempt_miss = 0; 82 static __int64_t preempt_weird = 0; 83 static __int64_t token_contention_count = 0; 84 static __int64_t mplock_contention_count = 0; 85 static int lwkt_use_spin_port; 86 static struct objcache *thread_cache; 87 88 /* 89 * We can make all thread ports use the spin backend instead of the thread 90 * backend. This should only be set to debug the spin backend. 91 */ 92 TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port); 93 94 SYSCTL_INT(_lwkt, OID_AUTO, untimely_switch, CTLFLAG_RW, &untimely_switch, 0, ""); 95 #ifdef INVARIANTS 96 SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, ""); 97 #endif 98 SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, ""); 99 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, ""); 100 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, ""); 101 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, ""); 102 #ifdef INVARIANTS 103 SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count, CTLFLAG_RW, 104 &token_contention_count, 0, "spinning due to token contention"); 105 SYSCTL_QUAD(_lwkt, OID_AUTO, mplock_contention_count, CTLFLAG_RW, 106 &mplock_contention_count, 0, "spinning due to MPLOCK contention"); 107 #endif 108 109 /* 110 * Kernel Trace 111 */ 112 #if !defined(KTR_GIANT_CONTENTION) 113 #define KTR_GIANT_CONTENTION KTR_ALL 114 #endif 115 116 KTR_INFO_MASTER(giant); 117 KTR_INFO(KTR_GIANT_CONTENTION, giant, beg, 0, "thread=%p", sizeof(void *)); 118 KTR_INFO(KTR_GIANT_CONTENTION, giant, end, 1, "thread=%p", sizeof(void *)); 119 120 #define loggiant(name) KTR_LOG(giant_ ## name, curthread) 121 122 /* 123 * These helper procedures handle the runq, they can only be called from 124 * within a critical section. 125 * 126 * WARNING! Prior to SMP being brought up it is possible to enqueue and 127 * dequeue threads belonging to other cpus, so be sure to use td->td_gd 128 * instead of 'mycpu' when referencing the globaldata structure. Once 129 * SMP live enqueuing and dequeueing only occurs on the current cpu. 130 */ 131 static __inline 132 void 133 _lwkt_dequeue(thread_t td) 134 { 135 if (td->td_flags & TDF_RUNQ) { 136 int nq = td->td_pri & TDPRI_MASK; 137 struct globaldata *gd = td->td_gd; 138 139 td->td_flags &= ~TDF_RUNQ; 140 TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq); 141 /* runqmask is passively cleaned up by the switcher */ 142 } 143 } 144 145 static __inline 146 void 147 _lwkt_enqueue(thread_t td) 148 { 149 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_TSLEEPQ|TDF_BLOCKQ)) == 0) { 150 int nq = td->td_pri & TDPRI_MASK; 151 struct globaldata *gd = td->td_gd; 152 153 td->td_flags |= TDF_RUNQ; 154 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq); 155 gd->gd_runqmask |= 1 << nq; 156 } 157 } 158 159 static __boolean_t 160 _lwkt_thread_ctor(void *obj, void *privdata, int ocflags) 161 { 162 struct thread *td = (struct thread *)obj; 163 164 td->td_kstack = NULL; 165 td->td_kstack_size = 0; 166 td->td_flags = TDF_ALLOCATED_THREAD; 167 return (1); 168 } 169 170 static void 171 _lwkt_thread_dtor(void *obj, void *privdata) 172 { 173 struct thread *td = (struct thread *)obj; 174 175 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD, 176 ("_lwkt_thread_dtor: not allocated from objcache")); 177 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack && 178 td->td_kstack_size > 0, 179 ("_lwkt_thread_dtor: corrupted stack")); 180 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); 181 } 182 183 /* 184 * Initialize the lwkt s/system. 185 */ 186 void 187 lwkt_init(void) 188 { 189 /* An objcache has 2 magazines per CPU so divide cache size by 2. */ 190 thread_cache = objcache_create_mbacked(M_THREAD, sizeof(struct thread), 0, 191 CACHE_NTHREADS/2, _lwkt_thread_ctor, _lwkt_thread_dtor, 192 NULL); 193 } 194 195 /* 196 * Schedule a thread to run. As the current thread we can always safely 197 * schedule ourselves, and a shortcut procedure is provided for that 198 * function. 199 * 200 * (non-blocking, self contained on a per cpu basis) 201 */ 202 void 203 lwkt_schedule_self(thread_t td) 204 { 205 crit_enter_quick(td); 206 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!")); 207 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 208 _lwkt_enqueue(td); 209 crit_exit_quick(td); 210 } 211 212 /* 213 * Deschedule a thread. 214 * 215 * (non-blocking, self contained on a per cpu basis) 216 */ 217 void 218 lwkt_deschedule_self(thread_t td) 219 { 220 crit_enter_quick(td); 221 _lwkt_dequeue(td); 222 crit_exit_quick(td); 223 } 224 225 /* 226 * LWKTs operate on a per-cpu basis 227 * 228 * WARNING! Called from early boot, 'mycpu' may not work yet. 229 */ 230 void 231 lwkt_gdinit(struct globaldata *gd) 232 { 233 int i; 234 235 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i) 236 TAILQ_INIT(&gd->gd_tdrunq[i]); 237 gd->gd_runqmask = 0; 238 TAILQ_INIT(&gd->gd_tdallq); 239 } 240 241 /* 242 * Create a new thread. The thread must be associated with a process context 243 * or LWKT start address before it can be scheduled. If the target cpu is 244 * -1 the thread will be created on the current cpu. 245 * 246 * If you intend to create a thread without a process context this function 247 * does everything except load the startup and switcher function. 248 */ 249 thread_t 250 lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags) 251 { 252 globaldata_t gd = mycpu; 253 void *stack; 254 255 /* 256 * If static thread storage is not supplied allocate a thread. Reuse 257 * a cached free thread if possible. gd_freetd is used to keep an exiting 258 * thread intact through the exit. 259 */ 260 if (td == NULL) { 261 if ((td = gd->gd_freetd) != NULL) 262 gd->gd_freetd = NULL; 263 else 264 td = objcache_get(thread_cache, M_WAITOK); 265 KASSERT((td->td_flags & 266 (TDF_ALLOCATED_THREAD|TDF_RUNNING)) == TDF_ALLOCATED_THREAD, 267 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags)); 268 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK); 269 } 270 271 /* 272 * Try to reuse cached stack. 273 */ 274 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) { 275 if (flags & TDF_ALLOCATED_STACK) { 276 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size); 277 stack = NULL; 278 } 279 } 280 if (stack == NULL) { 281 stack = (void *)kmem_alloc(&kernel_map, stksize); 282 flags |= TDF_ALLOCATED_STACK; 283 } 284 if (cpu < 0) 285 lwkt_init_thread(td, stack, stksize, flags, gd); 286 else 287 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu)); 288 return(td); 289 } 290 291 /* 292 * Initialize a preexisting thread structure. This function is used by 293 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread. 294 * 295 * All threads start out in a critical section at a priority of 296 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as 297 * appropriate. This function may send an IPI message when the 298 * requested cpu is not the current cpu and consequently gd_tdallq may 299 * not be initialized synchronously from the point of view of the originating 300 * cpu. 301 * 302 * NOTE! we have to be careful in regards to creating threads for other cpus 303 * if SMP has not yet been activated. 304 */ 305 #ifdef SMP 306 307 static void 308 lwkt_init_thread_remote(void *arg) 309 { 310 thread_t td = arg; 311 312 /* 313 * Protected by critical section held by IPI dispatch 314 */ 315 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq); 316 } 317 318 #endif 319 320 void 321 lwkt_init_thread(thread_t td, void *stack, int stksize, int flags, 322 struct globaldata *gd) 323 { 324 globaldata_t mygd = mycpu; 325 326 bzero(td, sizeof(struct thread)); 327 td->td_kstack = stack; 328 td->td_kstack_size = stksize; 329 td->td_flags = flags; 330 td->td_gd = gd; 331 td->td_pri = TDPRI_KERN_DAEMON + TDPRI_CRIT; 332 #ifdef SMP 333 if ((flags & TDF_MPSAFE) == 0) 334 td->td_mpcount = 1; 335 #endif 336 if (lwkt_use_spin_port) 337 lwkt_initport_spin(&td->td_msgport); 338 else 339 lwkt_initport_thread(&td->td_msgport, td); 340 pmap_init_thread(td); 341 #ifdef SMP 342 /* 343 * Normally initializing a thread for a remote cpu requires sending an 344 * IPI. However, the idlethread is setup before the other cpus are 345 * activated so we have to treat it as a special case. XXX manipulation 346 * of gd_tdallq requires the BGL. 347 */ 348 if (gd == mygd || td == &gd->gd_idlethread) { 349 crit_enter_gd(mygd); 350 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 351 crit_exit_gd(mygd); 352 } else { 353 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td); 354 } 355 #else 356 crit_enter_gd(mygd); 357 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 358 crit_exit_gd(mygd); 359 #endif 360 } 361 362 void 363 lwkt_set_comm(thread_t td, const char *ctl, ...) 364 { 365 __va_list va; 366 367 __va_start(va, ctl); 368 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va); 369 __va_end(va); 370 } 371 372 void 373 lwkt_hold(thread_t td) 374 { 375 ++td->td_refs; 376 } 377 378 void 379 lwkt_rele(thread_t td) 380 { 381 KKASSERT(td->td_refs > 0); 382 --td->td_refs; 383 } 384 385 void 386 lwkt_wait_free(thread_t td) 387 { 388 while (td->td_refs) 389 tsleep(td, 0, "tdreap", hz); 390 } 391 392 void 393 lwkt_free_thread(thread_t td) 394 { 395 KASSERT((td->td_flags & TDF_RUNNING) == 0, 396 ("lwkt_free_thread: did not exit! %p", td)); 397 398 if (td->td_flags & TDF_ALLOCATED_THREAD) { 399 objcache_put(thread_cache, td); 400 } else if (td->td_flags & TDF_ALLOCATED_STACK) { 401 /* client-allocated struct with internally allocated stack */ 402 KASSERT(td->td_kstack && td->td_kstack_size > 0, 403 ("lwkt_free_thread: corrupted stack")); 404 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); 405 td->td_kstack = NULL; 406 td->td_kstack_size = 0; 407 } 408 } 409 410 411 /* 412 * Switch to the next runnable lwkt. If no LWKTs are runnable then 413 * switch to the idlethread. Switching must occur within a critical 414 * section to avoid races with the scheduling queue. 415 * 416 * We always have full control over our cpu's run queue. Other cpus 417 * that wish to manipulate our queue must use the cpu_*msg() calls to 418 * talk to our cpu, so a critical section is all that is needed and 419 * the result is very, very fast thread switching. 420 * 421 * The LWKT scheduler uses a fixed priority model and round-robins at 422 * each priority level. User process scheduling is a totally 423 * different beast and LWKT priorities should not be confused with 424 * user process priorities. 425 * 426 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch() 427 * cleans it up. Note that the td_switch() function cannot do anything that 428 * requires the MP lock since the MP lock will have already been setup for 429 * the target thread (not the current thread). It's nice to have a scheduler 430 * that does not need the MP lock to work because it allows us to do some 431 * really cool high-performance MP lock optimizations. 432 * 433 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch() 434 * is not called by the current thread in the preemption case, only when 435 * the preempting thread blocks (in order to return to the original thread). 436 */ 437 void 438 lwkt_switch(void) 439 { 440 globaldata_t gd = mycpu; 441 thread_t td = gd->gd_curthread; 442 thread_t ntd; 443 #ifdef SMP 444 int mpheld; 445 #endif 446 447 /* 448 * Switching from within a 'fast' (non thread switched) interrupt or IPI 449 * is illegal. However, we may have to do it anyway if we hit a fatal 450 * kernel trap or we have paniced. 451 * 452 * If this case occurs save and restore the interrupt nesting level. 453 */ 454 if (gd->gd_intr_nesting_level) { 455 int savegdnest; 456 int savegdtrap; 457 458 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) { 459 panic("lwkt_switch: cannot switch from within " 460 "a fast interrupt, yet, td %p\n", td); 461 } else { 462 savegdnest = gd->gd_intr_nesting_level; 463 savegdtrap = gd->gd_trap_nesting_level; 464 gd->gd_intr_nesting_level = 0; 465 gd->gd_trap_nesting_level = 0; 466 if ((td->td_flags & TDF_PANICWARN) == 0) { 467 td->td_flags |= TDF_PANICWARN; 468 kprintf("Warning: thread switch from interrupt or IPI, " 469 "thread %p (%s)\n", td, td->td_comm); 470 #ifdef DDB 471 db_print_backtrace(); 472 #endif 473 } 474 lwkt_switch(); 475 gd->gd_intr_nesting_level = savegdnest; 476 gd->gd_trap_nesting_level = savegdtrap; 477 return; 478 } 479 } 480 481 /* 482 * Passive release (used to transition from user to kernel mode 483 * when we block or switch rather then when we enter the kernel). 484 * This function is NOT called if we are switching into a preemption 485 * or returning from a preemption. Typically this causes us to lose 486 * our current process designation (if we have one) and become a true 487 * LWKT thread, and may also hand the current process designation to 488 * another process and schedule thread. 489 */ 490 if (td->td_release) 491 td->td_release(td); 492 493 crit_enter_gd(gd); 494 if (td->td_toks) 495 lwkt_relalltokens(td); 496 497 /* 498 * We had better not be holding any spin locks, but don't get into an 499 * endless panic loop. 500 */ 501 KASSERT(gd->gd_spinlock_rd == NULL || panicstr != NULL, 502 ("lwkt_switch: still holding a shared spinlock %p!", 503 gd->gd_spinlock_rd)); 504 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL, 505 ("lwkt_switch: still holding %d exclusive spinlocks!", 506 gd->gd_spinlocks_wr)); 507 508 509 #ifdef SMP 510 /* 511 * td_mpcount cannot be used to determine if we currently hold the 512 * MP lock because get_mplock() will increment it prior to attempting 513 * to get the lock, and switch out if it can't. Our ownership of 514 * the actual lock will remain stable while we are in a critical section 515 * (but, of course, another cpu may own or release the lock so the 516 * actual value of mp_lock is not stable). 517 */ 518 mpheld = MP_LOCK_HELD(); 519 #ifdef INVARIANTS 520 if (td->td_cscount) { 521 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n", 522 td); 523 if (panic_on_cscount) 524 panic("switching while mastering cpusync"); 525 } 526 #endif 527 #endif 528 if ((ntd = td->td_preempted) != NULL) { 529 /* 530 * We had preempted another thread on this cpu, resume the preempted 531 * thread. This occurs transparently, whether the preempted thread 532 * was scheduled or not (it may have been preempted after descheduling 533 * itself). 534 * 535 * We have to setup the MP lock for the original thread after backing 536 * out the adjustment that was made to curthread when the original 537 * was preempted. 538 */ 539 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK); 540 #ifdef SMP 541 if (ntd->td_mpcount && mpheld == 0) { 542 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d", 543 td, ntd, td->td_mpcount, ntd->td_mpcount); 544 } 545 if (ntd->td_mpcount) { 546 td->td_mpcount -= ntd->td_mpcount; 547 KKASSERT(td->td_mpcount >= 0); 548 } 549 #endif 550 ntd->td_flags |= TDF_PREEMPT_DONE; 551 552 /* 553 * XXX. The interrupt may have woken a thread up, we need to properly 554 * set the reschedule flag if the originally interrupted thread is at 555 * a lower priority. 556 */ 557 if (gd->gd_runqmask > (2 << (ntd->td_pri & TDPRI_MASK)) - 1) 558 need_lwkt_resched(); 559 /* YYY release mp lock on switchback if original doesn't need it */ 560 } else { 561 /* 562 * Priority queue / round-robin at each priority. Note that user 563 * processes run at a fixed, low priority and the user process 564 * scheduler deals with interactions between user processes 565 * by scheduling and descheduling them from the LWKT queue as 566 * necessary. 567 * 568 * We have to adjust the MP lock for the target thread. If we 569 * need the MP lock and cannot obtain it we try to locate a 570 * thread that does not need the MP lock. If we cannot, we spin 571 * instead of HLT. 572 * 573 * A similar issue exists for the tokens held by the target thread. 574 * If we cannot obtain ownership of the tokens we cannot immediately 575 * schedule the thread. 576 */ 577 578 /* 579 * If an LWKT reschedule was requested, well that is what we are 580 * doing now so clear it. 581 */ 582 clear_lwkt_resched(); 583 again: 584 if (gd->gd_runqmask) { 585 int nq = bsrl(gd->gd_runqmask); 586 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) { 587 gd->gd_runqmask &= ~(1 << nq); 588 goto again; 589 } 590 #ifdef SMP 591 /* 592 * THREAD SELECTION FOR AN SMP MACHINE BUILD 593 * 594 * If the target needs the MP lock and we couldn't get it, 595 * or if the target is holding tokens and we could not 596 * gain ownership of the tokens, continue looking for a 597 * thread to schedule and spin instead of HLT if we can't. 598 * 599 * NOTE: the mpheld variable invalid after this conditional, it 600 * can change due to both cpu_try_mplock() returning success 601 * AND interactions in lwkt_getalltokens() due to the fact that 602 * we are trying to check the mpcount of a thread other then 603 * the current thread. Because of this, if the current thread 604 * is not holding td_mpcount, an IPI indirectly run via 605 * lwkt_getalltokens() can obtain and release the MP lock and 606 * cause the core MP lock to be released. 607 */ 608 if ((ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) || 609 (ntd->td_toks && lwkt_getalltokens(ntd) == 0) 610 ) { 611 u_int32_t rqmask = gd->gd_runqmask; 612 613 mpheld = MP_LOCK_HELD(); 614 ntd = NULL; 615 while (rqmask) { 616 TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) { 617 if (ntd->td_mpcount && !mpheld && !cpu_try_mplock()) { 618 /* spinning due to MP lock being held */ 619 #ifdef INVARIANTS 620 ++mplock_contention_count; 621 #endif 622 /* mplock still not held, 'mpheld' still valid */ 623 continue; 624 } 625 626 /* 627 * mpheld state invalid after getalltokens call returns 628 * failure, but the variable is only needed for 629 * the loop. 630 */ 631 if (ntd->td_toks && !lwkt_getalltokens(ntd)) { 632 /* spinning due to token contention */ 633 #ifdef INVARIANTS 634 ++token_contention_count; 635 #endif 636 mpheld = MP_LOCK_HELD(); 637 continue; 638 } 639 break; 640 } 641 if (ntd) 642 break; 643 rqmask &= ~(1 << nq); 644 nq = bsrl(rqmask); 645 } 646 if (ntd == NULL) { 647 cpu_mplock_contested(); 648 ntd = &gd->gd_idlethread; 649 ntd->td_flags |= TDF_IDLE_NOHLT; 650 goto using_idle_thread; 651 } else { 652 ++gd->gd_cnt.v_swtch; 653 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 654 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 655 } 656 } else { 657 ++gd->gd_cnt.v_swtch; 658 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 659 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 660 } 661 #else 662 /* 663 * THREAD SELECTION FOR A UP MACHINE BUILD. We don't have to 664 * worry about tokens or the BGL. However, we still have 665 * to call lwkt_getalltokens() in order to properly detect 666 * stale tokens. This call cannot fail for a UP build! 667 */ 668 lwkt_getalltokens(ntd); 669 ++gd->gd_cnt.v_swtch; 670 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 671 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 672 #endif 673 } else { 674 /* 675 * We have nothing to run but only let the idle loop halt 676 * the cpu if there are no pending interrupts. 677 */ 678 ntd = &gd->gd_idlethread; 679 if (gd->gd_reqflags & RQF_IDLECHECK_MASK) 680 ntd->td_flags |= TDF_IDLE_NOHLT; 681 #ifdef SMP 682 using_idle_thread: 683 /* 684 * The idle thread should not be holding the MP lock unless we 685 * are trapping in the kernel or in a panic. Since we select the 686 * idle thread unconditionally when no other thread is available, 687 * if the MP lock is desired during a panic or kernel trap, we 688 * have to loop in the scheduler until we get it. 689 */ 690 if (ntd->td_mpcount) { 691 mpheld = MP_LOCK_HELD(); 692 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) { 693 panic("Idle thread %p was holding the BGL!", ntd); 694 } else if (mpheld == 0) { 695 cpu_mplock_contested(); 696 goto again; 697 } 698 } 699 #endif 700 } 701 } 702 KASSERT(ntd->td_pri >= TDPRI_CRIT, 703 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri)); 704 705 /* 706 * Do the actual switch. If the new target does not need the MP lock 707 * and we are holding it, release the MP lock. If the new target requires 708 * the MP lock we have already acquired it for the target. 709 */ 710 #ifdef SMP 711 if (ntd->td_mpcount == 0 ) { 712 if (MP_LOCK_HELD()) 713 cpu_rel_mplock(); 714 } else { 715 ASSERT_MP_LOCK_HELD(ntd); 716 } 717 #endif 718 if (td != ntd) { 719 ++switch_count; 720 td->td_switch(ntd); 721 } 722 /* NOTE: current cpu may have changed after switch */ 723 crit_exit_quick(td); 724 } 725 726 /* 727 * Request that the target thread preempt the current thread. Preemption 728 * only works under a specific set of conditions: 729 * 730 * - We are not preempting ourselves 731 * - The target thread is owned by the current cpu 732 * - We are not currently being preempted 733 * - The target is not currently being preempted 734 * - We are not holding any spin locks 735 * - The target thread is not holding any tokens 736 * - We are able to satisfy the target's MP lock requirements (if any). 737 * 738 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically 739 * this is called via lwkt_schedule() through the td_preemptable callback. 740 * critpri is the managed critical priority that we should ignore in order 741 * to determine whether preemption is possible (aka usually just the crit 742 * priority of lwkt_schedule() itself). 743 * 744 * XXX at the moment we run the target thread in a critical section during 745 * the preemption in order to prevent the target from taking interrupts 746 * that *WE* can't. Preemption is strictly limited to interrupt threads 747 * and interrupt-like threads, outside of a critical section, and the 748 * preempted source thread will be resumed the instant the target blocks 749 * whether or not the source is scheduled (i.e. preemption is supposed to 750 * be as transparent as possible). 751 * 752 * The target thread inherits our MP count (added to its own) for the 753 * duration of the preemption in order to preserve the atomicy of the 754 * MP lock during the preemption. Therefore, any preempting targets must be 755 * careful in regards to MP assertions. Note that the MP count may be 756 * out of sync with the physical mp_lock, but we do not have to preserve 757 * the original ownership of the lock if it was out of synch (that is, we 758 * can leave it synchronized on return). 759 */ 760 void 761 lwkt_preempt(thread_t ntd, int critpri) 762 { 763 struct globaldata *gd = mycpu; 764 thread_t td; 765 #ifdef SMP 766 int mpheld; 767 int savecnt; 768 #endif 769 770 /* 771 * The caller has put us in a critical section. We can only preempt 772 * if the caller of the caller was not in a critical section (basically 773 * a local interrupt), as determined by the 'critpri' parameter. We 774 * also can't preempt if the caller is holding any spinlocks (even if 775 * he isn't in a critical section). This also handles the tokens test. 776 * 777 * YYY The target thread must be in a critical section (else it must 778 * inherit our critical section? I dunno yet). 779 * 780 * Set need_lwkt_resched() unconditionally for now YYY. 781 */ 782 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri)); 783 784 td = gd->gd_curthread; 785 if ((ntd->td_pri & TDPRI_MASK) <= (td->td_pri & TDPRI_MASK)) { 786 ++preempt_miss; 787 return; 788 } 789 if ((td->td_pri & ~TDPRI_MASK) > critpri) { 790 ++preempt_miss; 791 need_lwkt_resched(); 792 return; 793 } 794 #ifdef SMP 795 if (ntd->td_gd != gd) { 796 ++preempt_miss; 797 need_lwkt_resched(); 798 return; 799 } 800 #endif 801 /* 802 * Take the easy way out and do not preempt if we are holding 803 * any spinlocks. We could test whether the thread(s) being 804 * preempted interlock against the target thread's tokens and whether 805 * we can get all the target thread's tokens, but this situation 806 * should not occur very often so its easier to simply not preempt. 807 * Also, plain spinlocks are impossible to figure out at this point so 808 * just don't preempt. 809 * 810 * Do not try to preempt if the target thread is holding any tokens. 811 * We could try to acquire the tokens but this case is so rare there 812 * is no need to support it. 813 */ 814 if (gd->gd_spinlock_rd || gd->gd_spinlocks_wr) { 815 ++preempt_miss; 816 need_lwkt_resched(); 817 return; 818 } 819 if (ntd->td_toks) { 820 ++preempt_miss; 821 need_lwkt_resched(); 822 return; 823 } 824 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) { 825 ++preempt_weird; 826 need_lwkt_resched(); 827 return; 828 } 829 if (ntd->td_preempted) { 830 ++preempt_hit; 831 need_lwkt_resched(); 832 return; 833 } 834 #ifdef SMP 835 /* 836 * note: an interrupt might have occured just as we were transitioning 837 * to or from the MP lock. In this case td_mpcount will be pre-disposed 838 * (non-zero) but not actually synchronized with the actual state of the 839 * lock. We can use it to imply an MP lock requirement for the 840 * preemption but we cannot use it to test whether we hold the MP lock 841 * or not. 842 */ 843 savecnt = td->td_mpcount; 844 mpheld = MP_LOCK_HELD(); 845 ntd->td_mpcount += td->td_mpcount; 846 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) { 847 ntd->td_mpcount -= td->td_mpcount; 848 ++preempt_miss; 849 need_lwkt_resched(); 850 return; 851 } 852 #endif 853 854 /* 855 * Since we are able to preempt the current thread, there is no need to 856 * call need_lwkt_resched(). 857 */ 858 ++preempt_hit; 859 ntd->td_preempted = td; 860 td->td_flags |= TDF_PREEMPT_LOCK; 861 td->td_switch(ntd); 862 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE)); 863 #ifdef SMP 864 KKASSERT(savecnt == td->td_mpcount); 865 mpheld = MP_LOCK_HELD(); 866 if (mpheld && td->td_mpcount == 0) 867 cpu_rel_mplock(); 868 else if (mpheld == 0 && td->td_mpcount) 869 panic("lwkt_preempt(): MP lock was not held through"); 870 #endif 871 ntd->td_preempted = NULL; 872 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE); 873 } 874 875 /* 876 * Yield our thread while higher priority threads are pending. This is 877 * typically called when we leave a critical section but it can be safely 878 * called while we are in a critical section. 879 * 880 * This function will not generally yield to equal priority threads but it 881 * can occur as a side effect. Note that lwkt_switch() is called from 882 * inside the critical section to prevent its own crit_exit() from reentering 883 * lwkt_yield_quick(). 884 * 885 * gd_reqflags indicates that *something* changed, e.g. an interrupt or softint 886 * came along but was blocked and made pending. 887 * 888 * (self contained on a per cpu basis) 889 */ 890 void 891 lwkt_yield_quick(void) 892 { 893 globaldata_t gd = mycpu; 894 thread_t td = gd->gd_curthread; 895 896 /* 897 * gd_reqflags is cleared in splz if the cpl is 0. If we were to clear 898 * it with a non-zero cpl then we might not wind up calling splz after 899 * a task switch when the critical section is exited even though the 900 * new task could accept the interrupt. 901 * 902 * XXX from crit_exit() only called after last crit section is released. 903 * If called directly will run splz() even if in a critical section. 904 * 905 * td_nest_count prevent deep nesting via splz() or doreti(). Note that 906 * except for this special case, we MUST call splz() here to handle any 907 * pending ints, particularly after we switch, or we might accidently 908 * halt the cpu with interrupts pending. 909 */ 910 if (gd->gd_reqflags && td->td_nest_count < 2) 911 splz(); 912 913 /* 914 * YYY enabling will cause wakeup() to task-switch, which really 915 * confused the old 4.x code. This is a good way to simulate 916 * preemption and MP without actually doing preemption or MP, because a 917 * lot of code assumes that wakeup() does not block. 918 */ 919 if (untimely_switch && td->td_nest_count == 0 && 920 gd->gd_intr_nesting_level == 0 921 ) { 922 crit_enter_quick(td); 923 /* 924 * YYY temporary hacks until we disassociate the userland scheduler 925 * from the LWKT scheduler. 926 */ 927 if (td->td_flags & TDF_RUNQ) { 928 lwkt_switch(); /* will not reenter yield function */ 929 } else { 930 lwkt_schedule_self(td); /* make sure we are scheduled */ 931 lwkt_switch(); /* will not reenter yield function */ 932 lwkt_deschedule_self(td); /* make sure we are descheduled */ 933 } 934 crit_exit_noyield(td); 935 } 936 } 937 938 /* 939 * This implements a normal yield which, unlike _quick, will yield to equal 940 * priority threads as well. Note that gd_reqflags tests will be handled by 941 * the crit_exit() call in lwkt_switch(). 942 * 943 * (self contained on a per cpu basis) 944 */ 945 void 946 lwkt_yield(void) 947 { 948 lwkt_schedule_self(curthread); 949 lwkt_switch(); 950 } 951 952 /* 953 * Generic schedule. Possibly schedule threads belonging to other cpus and 954 * deal with threads that might be blocked on a wait queue. 955 * 956 * We have a little helper inline function which does additional work after 957 * the thread has been enqueued, including dealing with preemption and 958 * setting need_lwkt_resched() (which prevents the kernel from returning 959 * to userland until it has processed higher priority threads). 960 * 961 * It is possible for this routine to be called after a failed _enqueue 962 * (due to the target thread migrating, sleeping, or otherwise blocked). 963 * We have to check that the thread is actually on the run queue! 964 */ 965 static __inline 966 void 967 _lwkt_schedule_post(globaldata_t gd, thread_t ntd, int cpri) 968 { 969 if (ntd->td_flags & TDF_RUNQ) { 970 if (ntd->td_preemptable) { 971 ntd->td_preemptable(ntd, cpri); /* YYY +token */ 972 } else if ((ntd->td_flags & TDF_NORESCHED) == 0 && 973 (ntd->td_pri & TDPRI_MASK) > (gd->gd_curthread->td_pri & TDPRI_MASK) 974 ) { 975 need_lwkt_resched(); 976 } 977 } 978 } 979 980 void 981 lwkt_schedule(thread_t td) 982 { 983 globaldata_t mygd = mycpu; 984 985 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule(): scheduling gd_idlethread is illegal!")); 986 crit_enter_gd(mygd); 987 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 988 if (td == mygd->gd_curthread) { 989 _lwkt_enqueue(td); 990 } else { 991 /* 992 * If we own the thread, there is no race (since we are in a 993 * critical section). If we do not own the thread there might 994 * be a race but the target cpu will deal with it. 995 */ 996 #ifdef SMP 997 if (td->td_gd == mygd) { 998 _lwkt_enqueue(td); 999 _lwkt_schedule_post(mygd, td, TDPRI_CRIT); 1000 } else { 1001 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_schedule, td); 1002 } 1003 #else 1004 _lwkt_enqueue(td); 1005 _lwkt_schedule_post(mygd, td, TDPRI_CRIT); 1006 #endif 1007 } 1008 crit_exit_gd(mygd); 1009 } 1010 1011 #ifdef SMP 1012 1013 /* 1014 * Thread migration using a 'Pull' method. The thread may or may not be 1015 * the current thread. It MUST be descheduled and in a stable state. 1016 * lwkt_giveaway() must be called on the cpu owning the thread. 1017 * 1018 * At any point after lwkt_giveaway() is called, the target cpu may 1019 * 'pull' the thread by calling lwkt_acquire(). 1020 * 1021 * MPSAFE - must be called under very specific conditions. 1022 */ 1023 void 1024 lwkt_giveaway(thread_t td) 1025 { 1026 globaldata_t gd = mycpu; 1027 1028 crit_enter_gd(gd); 1029 KKASSERT(td->td_gd == gd); 1030 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); 1031 td->td_flags |= TDF_MIGRATING; 1032 crit_exit_gd(gd); 1033 } 1034 1035 void 1036 lwkt_acquire(thread_t td) 1037 { 1038 globaldata_t gd; 1039 globaldata_t mygd; 1040 1041 KKASSERT(td->td_flags & TDF_MIGRATING); 1042 gd = td->td_gd; 1043 mygd = mycpu; 1044 if (gd != mycpu) { 1045 cpu_lfence(); 1046 KKASSERT((td->td_flags & TDF_RUNQ) == 0); 1047 crit_enter_gd(mygd); 1048 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) { 1049 #ifdef SMP 1050 lwkt_process_ipiq(); 1051 #endif 1052 cpu_lfence(); 1053 } 1054 td->td_gd = mygd; 1055 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1056 td->td_flags &= ~TDF_MIGRATING; 1057 crit_exit_gd(mygd); 1058 } else { 1059 crit_enter_gd(mygd); 1060 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1061 td->td_flags &= ~TDF_MIGRATING; 1062 crit_exit_gd(mygd); 1063 } 1064 } 1065 1066 #endif 1067 1068 /* 1069 * Generic deschedule. Descheduling threads other then your own should be 1070 * done only in carefully controlled circumstances. Descheduling is 1071 * asynchronous. 1072 * 1073 * This function may block if the cpu has run out of messages. 1074 */ 1075 void 1076 lwkt_deschedule(thread_t td) 1077 { 1078 crit_enter(); 1079 #ifdef SMP 1080 if (td == curthread) { 1081 _lwkt_dequeue(td); 1082 } else { 1083 if (td->td_gd == mycpu) { 1084 _lwkt_dequeue(td); 1085 } else { 1086 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td); 1087 } 1088 } 1089 #else 1090 _lwkt_dequeue(td); 1091 #endif 1092 crit_exit(); 1093 } 1094 1095 /* 1096 * Set the target thread's priority. This routine does not automatically 1097 * switch to a higher priority thread, LWKT threads are not designed for 1098 * continuous priority changes. Yield if you want to switch. 1099 * 1100 * We have to retain the critical section count which uses the high bits 1101 * of the td_pri field. The specified priority may also indicate zero or 1102 * more critical sections by adding TDPRI_CRIT*N. 1103 * 1104 * Note that we requeue the thread whether it winds up on a different runq 1105 * or not. uio_yield() depends on this and the routine is not normally 1106 * called with the same priority otherwise. 1107 */ 1108 void 1109 lwkt_setpri(thread_t td, int pri) 1110 { 1111 KKASSERT(pri >= 0); 1112 KKASSERT(td->td_gd == mycpu); 1113 crit_enter(); 1114 if (td->td_flags & TDF_RUNQ) { 1115 _lwkt_dequeue(td); 1116 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1117 _lwkt_enqueue(td); 1118 } else { 1119 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1120 } 1121 crit_exit(); 1122 } 1123 1124 void 1125 lwkt_setpri_self(int pri) 1126 { 1127 thread_t td = curthread; 1128 1129 KKASSERT(pri >= 0 && pri <= TDPRI_MAX); 1130 crit_enter(); 1131 if (td->td_flags & TDF_RUNQ) { 1132 _lwkt_dequeue(td); 1133 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1134 _lwkt_enqueue(td); 1135 } else { 1136 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1137 } 1138 crit_exit(); 1139 } 1140 1141 /* 1142 * Determine if there is a runnable thread at a higher priority then 1143 * the current thread. lwkt_setpri() does not check this automatically. 1144 * Return 1 if there is, 0 if there isn't. 1145 * 1146 * Example: if bit 31 of runqmask is set and the current thread is priority 1147 * 30, then we wind up checking the mask: 0x80000000 against 0x7fffffff. 1148 * 1149 * If nq reaches 31 the shift operation will overflow to 0 and we will wind 1150 * up comparing against 0xffffffff, a comparison that will always be false. 1151 */ 1152 int 1153 lwkt_checkpri_self(void) 1154 { 1155 globaldata_t gd = mycpu; 1156 thread_t td = gd->gd_curthread; 1157 int nq = td->td_pri & TDPRI_MASK; 1158 1159 while (gd->gd_runqmask > (__uint32_t)(2 << nq) - 1) { 1160 if (TAILQ_FIRST(&gd->gd_tdrunq[nq + 1])) 1161 return(1); 1162 ++nq; 1163 } 1164 return(0); 1165 } 1166 1167 /* 1168 * Migrate the current thread to the specified cpu. 1169 * 1170 * This is accomplished by descheduling ourselves from the current cpu, 1171 * moving our thread to the tdallq of the target cpu, IPI messaging the 1172 * target cpu, and switching out. TDF_MIGRATING prevents scheduling 1173 * races while the thread is being migrated. 1174 */ 1175 #ifdef SMP 1176 static void lwkt_setcpu_remote(void *arg); 1177 #endif 1178 1179 void 1180 lwkt_setcpu_self(globaldata_t rgd) 1181 { 1182 #ifdef SMP 1183 thread_t td = curthread; 1184 1185 if (td->td_gd != rgd) { 1186 crit_enter_quick(td); 1187 td->td_flags |= TDF_MIGRATING; 1188 lwkt_deschedule_self(td); 1189 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1190 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td); 1191 lwkt_switch(); 1192 /* we are now on the target cpu */ 1193 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq); 1194 crit_exit_quick(td); 1195 } 1196 #endif 1197 } 1198 1199 void 1200 lwkt_migratecpu(int cpuid) 1201 { 1202 #ifdef SMP 1203 globaldata_t rgd; 1204 1205 rgd = globaldata_find(cpuid); 1206 lwkt_setcpu_self(rgd); 1207 #endif 1208 } 1209 1210 /* 1211 * Remote IPI for cpu migration (called while in a critical section so we 1212 * do not have to enter another one). The thread has already been moved to 1213 * our cpu's allq, but we must wait for the thread to be completely switched 1214 * out on the originating cpu before we schedule it on ours or the stack 1215 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD 1216 * change to main memory. 1217 * 1218 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races 1219 * against wakeups. It is best if this interface is used only when there 1220 * are no pending events that might try to schedule the thread. 1221 */ 1222 #ifdef SMP 1223 static void 1224 lwkt_setcpu_remote(void *arg) 1225 { 1226 thread_t td = arg; 1227 globaldata_t gd = mycpu; 1228 1229 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) { 1230 #ifdef SMP 1231 lwkt_process_ipiq(); 1232 #endif 1233 cpu_lfence(); 1234 } 1235 td->td_gd = gd; 1236 cpu_sfence(); 1237 td->td_flags &= ~TDF_MIGRATING; 1238 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 1239 _lwkt_enqueue(td); 1240 } 1241 #endif 1242 1243 struct lwp * 1244 lwkt_preempted_proc(void) 1245 { 1246 thread_t td = curthread; 1247 while (td->td_preempted) 1248 td = td->td_preempted; 1249 return(td->td_lwp); 1250 } 1251 1252 /* 1253 * Create a kernel process/thread/whatever. It shares it's address space 1254 * with proc0 - ie: kernel only. 1255 * 1256 * NOTE! By default new threads are created with the MP lock held. A 1257 * thread which does not require the MP lock should release it by calling 1258 * rel_mplock() at the start of the new thread. 1259 */ 1260 int 1261 lwkt_create(void (*func)(void *), void *arg, 1262 struct thread **tdp, thread_t template, int tdflags, int cpu, 1263 const char *fmt, ...) 1264 { 1265 thread_t td; 1266 __va_list ap; 1267 1268 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu, 1269 tdflags); 1270 if (tdp) 1271 *tdp = td; 1272 cpu_set_thread_handler(td, lwkt_exit, func, arg); 1273 1274 /* 1275 * Set up arg0 for 'ps' etc 1276 */ 1277 __va_start(ap, fmt); 1278 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap); 1279 __va_end(ap); 1280 1281 /* 1282 * Schedule the thread to run 1283 */ 1284 if ((td->td_flags & TDF_STOPREQ) == 0) 1285 lwkt_schedule(td); 1286 else 1287 td->td_flags &= ~TDF_STOPREQ; 1288 return 0; 1289 } 1290 1291 /* 1292 * Destroy an LWKT thread. Warning! This function is not called when 1293 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and 1294 * uses a different reaping mechanism. 1295 */ 1296 void 1297 lwkt_exit(void) 1298 { 1299 thread_t td = curthread; 1300 thread_t std; 1301 globaldata_t gd; 1302 1303 if (td->td_flags & TDF_VERBOSE) 1304 kprintf("kthread %p %s has exited\n", td, td->td_comm); 1305 caps_exit(td); 1306 1307 /* 1308 * Get us into a critical section to interlock gd_freetd and loop 1309 * until we can get it freed. 1310 * 1311 * We have to cache the current td in gd_freetd because objcache_put()ing 1312 * it would rip it out from under us while our thread is still active. 1313 */ 1314 gd = mycpu; 1315 crit_enter_quick(td); 1316 while ((std = gd->gd_freetd) != NULL) { 1317 gd->gd_freetd = NULL; 1318 objcache_put(thread_cache, std); 1319 } 1320 lwkt_deschedule_self(td); 1321 lwkt_remove_tdallq(td); 1322 if (td->td_flags & TDF_ALLOCATED_THREAD) 1323 gd->gd_freetd = td; 1324 cpu_thread_exit(); 1325 } 1326 1327 void 1328 lwkt_remove_tdallq(thread_t td) 1329 { 1330 KKASSERT(td->td_gd == mycpu); 1331 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1332 } 1333 1334 void 1335 crit_panic(void) 1336 { 1337 thread_t td = curthread; 1338 int lpri = td->td_pri; 1339 1340 td->td_pri = 0; 1341 panic("td_pri is/would-go negative! %p %d", td, lpri); 1342 } 1343 1344 #ifdef SMP 1345 1346 /* 1347 * Called from debugger/panic on cpus which have been stopped. We must still 1348 * process the IPIQ while stopped, even if we were stopped while in a critical 1349 * section (XXX). 1350 * 1351 * If we are dumping also try to process any pending interrupts. This may 1352 * or may not work depending on the state of the cpu at the point it was 1353 * stopped. 1354 */ 1355 void 1356 lwkt_smp_stopped(void) 1357 { 1358 globaldata_t gd = mycpu; 1359 1360 crit_enter_gd(gd); 1361 if (dumping) { 1362 lwkt_process_ipiq(); 1363 splz(); 1364 } else { 1365 lwkt_process_ipiq(); 1366 } 1367 crit_exit_gd(gd); 1368 } 1369 1370 /* 1371 * get_mplock() calls this routine if it is unable to obtain the MP lock. 1372 * get_mplock() has already incremented td_mpcount. We must block and 1373 * not return until giant is held. 1374 * 1375 * All we have to do is lwkt_switch() away. The LWKT scheduler will not 1376 * reschedule the thread until it can obtain the giant lock for it. 1377 */ 1378 void 1379 lwkt_mp_lock_contested(void) 1380 { 1381 loggiant(beg); 1382 lwkt_switch(); 1383 loggiant(end); 1384 } 1385 1386 #endif 1387