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 1.120 2008/10/26 04:29:19 sephe 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 #include "opt_ddb.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/kernel.h> 48 #include <sys/proc.h> 49 #include <sys/rtprio.h> 50 #include <sys/queue.h> 51 #include <sys/sysctl.h> 52 #include <sys/kthread.h> 53 #include <machine/cpu.h> 54 #include <sys/lock.h> 55 #include <sys/caps.h> 56 #include <sys/spinlock.h> 57 #include <sys/ktr.h> 58 59 #include <sys/thread2.h> 60 #include <sys/spinlock2.h> 61 62 #include <vm/vm.h> 63 #include <vm/vm_param.h> 64 #include <vm/vm_kern.h> 65 #include <vm/vm_object.h> 66 #include <vm/vm_page.h> 67 #include <vm/vm_map.h> 68 #include <vm/vm_pager.h> 69 #include <vm/vm_extern.h> 70 71 #include <machine/stdarg.h> 72 #include <machine/smp.h> 73 74 #ifdef DDB 75 #include <ddb/ddb.h> 76 #endif 77 78 static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads"); 79 80 static int untimely_switch = 0; 81 #ifdef INVARIANTS 82 static int panic_on_cscount = 0; 83 #endif 84 static __int64_t switch_count = 0; 85 static __int64_t preempt_hit = 0; 86 static __int64_t preempt_miss = 0; 87 static __int64_t preempt_weird = 0; 88 static __int64_t token_contention_count = 0; 89 static __int64_t mplock_contention_count = 0; 90 static int lwkt_use_spin_port; 91 static struct objcache *thread_cache; 92 93 /* 94 * We can make all thread ports use the spin backend instead of the thread 95 * backend. This should only be set to debug the spin backend. 96 */ 97 TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port); 98 99 SYSCTL_INT(_lwkt, OID_AUTO, untimely_switch, CTLFLAG_RW, &untimely_switch, 0, ""); 100 #ifdef INVARIANTS 101 SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, ""); 102 #endif 103 SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, ""); 104 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, ""); 105 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, ""); 106 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, ""); 107 #ifdef INVARIANTS 108 SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count, CTLFLAG_RW, 109 &token_contention_count, 0, "spinning due to token contention"); 110 SYSCTL_QUAD(_lwkt, OID_AUTO, mplock_contention_count, CTLFLAG_RW, 111 &mplock_contention_count, 0, "spinning due to MPLOCK contention"); 112 #endif 113 114 /* 115 * Kernel Trace 116 */ 117 #if !defined(KTR_GIANT_CONTENTION) 118 #define KTR_GIANT_CONTENTION KTR_ALL 119 #endif 120 121 KTR_INFO_MASTER(giant); 122 KTR_INFO(KTR_GIANT_CONTENTION, giant, beg, 0, "thread=%p", sizeof(void *)); 123 KTR_INFO(KTR_GIANT_CONTENTION, giant, end, 1, "thread=%p", sizeof(void *)); 124 125 #define loggiant(name) KTR_LOG(giant_ ## name, curthread) 126 127 /* 128 * These helper procedures handle the runq, they can only be called from 129 * within a critical section. 130 * 131 * WARNING! Prior to SMP being brought up it is possible to enqueue and 132 * dequeue threads belonging to other cpus, so be sure to use td->td_gd 133 * instead of 'mycpu' when referencing the globaldata structure. Once 134 * SMP live enqueuing and dequeueing only occurs on the current cpu. 135 */ 136 static __inline 137 void 138 _lwkt_dequeue(thread_t td) 139 { 140 if (td->td_flags & TDF_RUNQ) { 141 int nq = td->td_pri & TDPRI_MASK; 142 struct globaldata *gd = td->td_gd; 143 144 td->td_flags &= ~TDF_RUNQ; 145 TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq); 146 /* runqmask is passively cleaned up by the switcher */ 147 } 148 } 149 150 static __inline 151 void 152 _lwkt_enqueue(thread_t td) 153 { 154 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_TSLEEPQ|TDF_BLOCKQ)) == 0) { 155 int nq = td->td_pri & TDPRI_MASK; 156 struct globaldata *gd = td->td_gd; 157 158 td->td_flags |= TDF_RUNQ; 159 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq); 160 gd->gd_runqmask |= 1 << nq; 161 } 162 } 163 164 static __boolean_t 165 _lwkt_thread_ctor(void *obj, void *privdata, int ocflags) 166 { 167 struct thread *td = (struct thread *)obj; 168 169 td->td_kstack = NULL; 170 td->td_kstack_size = 0; 171 td->td_flags = TDF_ALLOCATED_THREAD; 172 return (1); 173 } 174 175 static void 176 _lwkt_thread_dtor(void *obj, void *privdata) 177 { 178 struct thread *td = (struct thread *)obj; 179 180 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD, 181 ("_lwkt_thread_dtor: not allocated from objcache")); 182 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack && 183 td->td_kstack_size > 0, 184 ("_lwkt_thread_dtor: corrupted stack")); 185 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); 186 } 187 188 /* 189 * Initialize the lwkt s/system. 190 */ 191 void 192 lwkt_init(void) 193 { 194 /* An objcache has 2 magazines per CPU so divide cache size by 2. */ 195 thread_cache = objcache_create_mbacked(M_THREAD, sizeof(struct thread), 196 NULL, CACHE_NTHREADS/2, 197 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL); 198 } 199 200 /* 201 * Schedule a thread to run. As the current thread we can always safely 202 * schedule ourselves, and a shortcut procedure is provided for that 203 * function. 204 * 205 * (non-blocking, self contained on a per cpu basis) 206 */ 207 void 208 lwkt_schedule_self(thread_t td) 209 { 210 crit_enter_quick(td); 211 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!")); 212 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 213 _lwkt_enqueue(td); 214 crit_exit_quick(td); 215 } 216 217 /* 218 * Deschedule a thread. 219 * 220 * (non-blocking, self contained on a per cpu basis) 221 */ 222 void 223 lwkt_deschedule_self(thread_t td) 224 { 225 crit_enter_quick(td); 226 _lwkt_dequeue(td); 227 crit_exit_quick(td); 228 } 229 230 /* 231 * LWKTs operate on a per-cpu basis 232 * 233 * WARNING! Called from early boot, 'mycpu' may not work yet. 234 */ 235 void 236 lwkt_gdinit(struct globaldata *gd) 237 { 238 int i; 239 240 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i) 241 TAILQ_INIT(&gd->gd_tdrunq[i]); 242 gd->gd_runqmask = 0; 243 TAILQ_INIT(&gd->gd_tdallq); 244 } 245 246 /* 247 * Create a new thread. The thread must be associated with a process context 248 * or LWKT start address before it can be scheduled. If the target cpu is 249 * -1 the thread will be created on the current cpu. 250 * 251 * If you intend to create a thread without a process context this function 252 * does everything except load the startup and switcher function. 253 */ 254 thread_t 255 lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags) 256 { 257 globaldata_t gd = mycpu; 258 void *stack; 259 260 /* 261 * If static thread storage is not supplied allocate a thread. Reuse 262 * a cached free thread if possible. gd_freetd is used to keep an exiting 263 * thread intact through the exit. 264 */ 265 if (td == NULL) { 266 if ((td = gd->gd_freetd) != NULL) 267 gd->gd_freetd = NULL; 268 else 269 td = objcache_get(thread_cache, M_WAITOK); 270 KASSERT((td->td_flags & 271 (TDF_ALLOCATED_THREAD|TDF_RUNNING)) == TDF_ALLOCATED_THREAD, 272 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags)); 273 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK); 274 } 275 276 /* 277 * Try to reuse cached stack. 278 */ 279 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) { 280 if (flags & TDF_ALLOCATED_STACK) { 281 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size); 282 stack = NULL; 283 } 284 } 285 if (stack == NULL) { 286 stack = (void *)kmem_alloc(&kernel_map, stksize); 287 flags |= TDF_ALLOCATED_STACK; 288 } 289 if (cpu < 0) 290 lwkt_init_thread(td, stack, stksize, flags, gd); 291 else 292 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu)); 293 return(td); 294 } 295 296 /* 297 * Initialize a preexisting thread structure. This function is used by 298 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread. 299 * 300 * All threads start out in a critical section at a priority of 301 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as 302 * appropriate. This function may send an IPI message when the 303 * requested cpu is not the current cpu and consequently gd_tdallq may 304 * not be initialized synchronously from the point of view of the originating 305 * cpu. 306 * 307 * NOTE! we have to be careful in regards to creating threads for other cpus 308 * if SMP has not yet been activated. 309 */ 310 #ifdef SMP 311 312 static void 313 lwkt_init_thread_remote(void *arg) 314 { 315 thread_t td = arg; 316 317 /* 318 * Protected by critical section held by IPI dispatch 319 */ 320 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq); 321 } 322 323 #endif 324 325 void 326 lwkt_init_thread(thread_t td, void *stack, int stksize, int flags, 327 struct globaldata *gd) 328 { 329 globaldata_t mygd = mycpu; 330 331 bzero(td, sizeof(struct thread)); 332 td->td_kstack = stack; 333 td->td_kstack_size = stksize; 334 td->td_flags = flags; 335 td->td_gd = gd; 336 td->td_pri = TDPRI_KERN_DAEMON + TDPRI_CRIT; 337 #ifdef SMP 338 if ((flags & TDF_MPSAFE) == 0) 339 td->td_mpcount = 1; 340 #endif 341 if (lwkt_use_spin_port) 342 lwkt_initport_spin(&td->td_msgport); 343 else 344 lwkt_initport_thread(&td->td_msgport, td); 345 pmap_init_thread(td); 346 #ifdef SMP 347 /* 348 * Normally initializing a thread for a remote cpu requires sending an 349 * IPI. However, the idlethread is setup before the other cpus are 350 * activated so we have to treat it as a special case. XXX manipulation 351 * of gd_tdallq requires the BGL. 352 */ 353 if (gd == mygd || td == &gd->gd_idlethread) { 354 crit_enter_gd(mygd); 355 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 356 crit_exit_gd(mygd); 357 } else { 358 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td); 359 } 360 #else 361 crit_enter_gd(mygd); 362 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 363 crit_exit_gd(mygd); 364 #endif 365 } 366 367 void 368 lwkt_set_comm(thread_t td, const char *ctl, ...) 369 { 370 __va_list va; 371 372 __va_start(va, ctl); 373 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va); 374 __va_end(va); 375 } 376 377 void 378 lwkt_hold(thread_t td) 379 { 380 ++td->td_refs; 381 } 382 383 void 384 lwkt_rele(thread_t td) 385 { 386 KKASSERT(td->td_refs > 0); 387 --td->td_refs; 388 } 389 390 void 391 lwkt_wait_free(thread_t td) 392 { 393 while (td->td_refs) 394 tsleep(td, 0, "tdreap", hz); 395 } 396 397 void 398 lwkt_free_thread(thread_t td) 399 { 400 KASSERT((td->td_flags & TDF_RUNNING) == 0, 401 ("lwkt_free_thread: did not exit! %p", td)); 402 403 if (td->td_flags & TDF_ALLOCATED_THREAD) { 404 objcache_put(thread_cache, td); 405 } else if (td->td_flags & TDF_ALLOCATED_STACK) { 406 /* client-allocated struct with internally allocated stack */ 407 KASSERT(td->td_kstack && td->td_kstack_size > 0, 408 ("lwkt_free_thread: corrupted stack")); 409 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); 410 td->td_kstack = NULL; 411 td->td_kstack_size = 0; 412 } 413 } 414 415 416 /* 417 * Switch to the next runnable lwkt. If no LWKTs are runnable then 418 * switch to the idlethread. Switching must occur within a critical 419 * section to avoid races with the scheduling queue. 420 * 421 * We always have full control over our cpu's run queue. Other cpus 422 * that wish to manipulate our queue must use the cpu_*msg() calls to 423 * talk to our cpu, so a critical section is all that is needed and 424 * the result is very, very fast thread switching. 425 * 426 * The LWKT scheduler uses a fixed priority model and round-robins at 427 * each priority level. User process scheduling is a totally 428 * different beast and LWKT priorities should not be confused with 429 * user process priorities. 430 * 431 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch() 432 * cleans it up. Note that the td_switch() function cannot do anything that 433 * requires the MP lock since the MP lock will have already been setup for 434 * the target thread (not the current thread). It's nice to have a scheduler 435 * that does not need the MP lock to work because it allows us to do some 436 * really cool high-performance MP lock optimizations. 437 * 438 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch() 439 * is not called by the current thread in the preemption case, only when 440 * the preempting thread blocks (in order to return to the original thread). 441 */ 442 void 443 lwkt_switch(void) 444 { 445 globaldata_t gd = mycpu; 446 thread_t td = gd->gd_curthread; 447 thread_t ntd; 448 #ifdef SMP 449 int mpheld; 450 #endif 451 452 /* 453 * Switching from within a 'fast' (non thread switched) interrupt or IPI 454 * is illegal. However, we may have to do it anyway if we hit a fatal 455 * kernel trap or we have paniced. 456 * 457 * If this case occurs save and restore the interrupt nesting level. 458 */ 459 if (gd->gd_intr_nesting_level) { 460 int savegdnest; 461 int savegdtrap; 462 463 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) { 464 panic("lwkt_switch: cannot switch from within " 465 "a fast interrupt, yet, td %p\n", td); 466 } else { 467 savegdnest = gd->gd_intr_nesting_level; 468 savegdtrap = gd->gd_trap_nesting_level; 469 gd->gd_intr_nesting_level = 0; 470 gd->gd_trap_nesting_level = 0; 471 if ((td->td_flags & TDF_PANICWARN) == 0) { 472 td->td_flags |= TDF_PANICWARN; 473 kprintf("Warning: thread switch from interrupt or IPI, " 474 "thread %p (%s)\n", td, td->td_comm); 475 #ifdef DDB 476 db_print_backtrace(); 477 #endif 478 } 479 lwkt_switch(); 480 gd->gd_intr_nesting_level = savegdnest; 481 gd->gd_trap_nesting_level = savegdtrap; 482 return; 483 } 484 } 485 486 /* 487 * Passive release (used to transition from user to kernel mode 488 * when we block or switch rather then when we enter the kernel). 489 * This function is NOT called if we are switching into a preemption 490 * or returning from a preemption. Typically this causes us to lose 491 * our current process designation (if we have one) and become a true 492 * LWKT thread, and may also hand the current process designation to 493 * another process and schedule thread. 494 */ 495 if (td->td_release) 496 td->td_release(td); 497 498 crit_enter_gd(gd); 499 if (td->td_toks) 500 lwkt_relalltokens(td); 501 502 /* 503 * We had better not be holding any spin locks, but don't get into an 504 * endless panic loop. 505 */ 506 KASSERT(gd->gd_spinlock_rd == NULL || panicstr != NULL, 507 ("lwkt_switch: still holding a shared spinlock %p!", 508 gd->gd_spinlock_rd)); 509 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL, 510 ("lwkt_switch: still holding %d exclusive spinlocks!", 511 gd->gd_spinlocks_wr)); 512 513 514 #ifdef SMP 515 /* 516 * td_mpcount cannot be used to determine if we currently hold the 517 * MP lock because get_mplock() will increment it prior to attempting 518 * to get the lock, and switch out if it can't. Our ownership of 519 * the actual lock will remain stable while we are in a critical section 520 * (but, of course, another cpu may own or release the lock so the 521 * actual value of mp_lock is not stable). 522 */ 523 mpheld = MP_LOCK_HELD(); 524 #ifdef INVARIANTS 525 if (td->td_cscount) { 526 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n", 527 td); 528 if (panic_on_cscount) 529 panic("switching while mastering cpusync"); 530 } 531 #endif 532 #endif 533 if ((ntd = td->td_preempted) != NULL) { 534 /* 535 * We had preempted another thread on this cpu, resume the preempted 536 * thread. This occurs transparently, whether the preempted thread 537 * was scheduled or not (it may have been preempted after descheduling 538 * itself). 539 * 540 * We have to setup the MP lock for the original thread after backing 541 * out the adjustment that was made to curthread when the original 542 * was preempted. 543 */ 544 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK); 545 #ifdef SMP 546 if (ntd->td_mpcount && mpheld == 0) { 547 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d", 548 td, ntd, td->td_mpcount, ntd->td_mpcount); 549 } 550 if (ntd->td_mpcount) { 551 td->td_mpcount -= ntd->td_mpcount; 552 KKASSERT(td->td_mpcount >= 0); 553 } 554 #endif 555 ntd->td_flags |= TDF_PREEMPT_DONE; 556 557 /* 558 * XXX. The interrupt may have woken a thread up, we need to properly 559 * set the reschedule flag if the originally interrupted thread is at 560 * a lower priority. 561 */ 562 if (gd->gd_runqmask > (2 << (ntd->td_pri & TDPRI_MASK)) - 1) 563 need_lwkt_resched(); 564 /* YYY release mp lock on switchback if original doesn't need it */ 565 } else { 566 /* 567 * Priority queue / round-robin at each priority. Note that user 568 * processes run at a fixed, low priority and the user process 569 * scheduler deals with interactions between user processes 570 * by scheduling and descheduling them from the LWKT queue as 571 * necessary. 572 * 573 * We have to adjust the MP lock for the target thread. If we 574 * need the MP lock and cannot obtain it we try to locate a 575 * thread that does not need the MP lock. If we cannot, we spin 576 * instead of HLT. 577 * 578 * A similar issue exists for the tokens held by the target thread. 579 * If we cannot obtain ownership of the tokens we cannot immediately 580 * schedule the thread. 581 */ 582 583 /* 584 * If an LWKT reschedule was requested, well that is what we are 585 * doing now so clear it. 586 */ 587 clear_lwkt_resched(); 588 again: 589 if (gd->gd_runqmask) { 590 int nq = bsrl(gd->gd_runqmask); 591 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) { 592 gd->gd_runqmask &= ~(1 << nq); 593 goto again; 594 } 595 #ifdef SMP 596 /* 597 * THREAD SELECTION FOR AN SMP MACHINE BUILD 598 * 599 * If the target needs the MP lock and we couldn't get it, 600 * or if the target is holding tokens and we could not 601 * gain ownership of the tokens, continue looking for a 602 * thread to schedule and spin instead of HLT if we can't. 603 * 604 * NOTE: the mpheld variable invalid after this conditional, it 605 * can change due to both cpu_try_mplock() returning success 606 * AND interactions in lwkt_getalltokens() due to the fact that 607 * we are trying to check the mpcount of a thread other then 608 * the current thread. Because of this, if the current thread 609 * is not holding td_mpcount, an IPI indirectly run via 610 * lwkt_getalltokens() can obtain and release the MP lock and 611 * cause the core MP lock to be released. 612 */ 613 if ((ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) || 614 (ntd->td_toks && lwkt_getalltokens(ntd) == 0) 615 ) { 616 u_int32_t rqmask = gd->gd_runqmask; 617 618 mpheld = MP_LOCK_HELD(); 619 ntd = NULL; 620 while (rqmask) { 621 TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) { 622 if (ntd->td_mpcount && !mpheld && !cpu_try_mplock()) { 623 /* spinning due to MP lock being held */ 624 #ifdef INVARIANTS 625 ++mplock_contention_count; 626 #endif 627 /* mplock still not held, 'mpheld' still valid */ 628 continue; 629 } 630 631 /* 632 * mpheld state invalid after getalltokens call returns 633 * failure, but the variable is only needed for 634 * the loop. 635 */ 636 if (ntd->td_toks && !lwkt_getalltokens(ntd)) { 637 /* spinning due to token contention */ 638 #ifdef INVARIANTS 639 ++token_contention_count; 640 #endif 641 mpheld = MP_LOCK_HELD(); 642 continue; 643 } 644 break; 645 } 646 if (ntd) 647 break; 648 rqmask &= ~(1 << nq); 649 nq = bsrl(rqmask); 650 } 651 if (ntd == NULL) { 652 cpu_mplock_contested(); 653 ntd = &gd->gd_idlethread; 654 ntd->td_flags |= TDF_IDLE_NOHLT; 655 goto using_idle_thread; 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 ++gd->gd_cnt.v_swtch; 663 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 664 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 665 } 666 #else 667 /* 668 * THREAD SELECTION FOR A UP MACHINE BUILD. We don't have to 669 * worry about tokens or the BGL. However, we still have 670 * to call lwkt_getalltokens() in order to properly detect 671 * stale tokens. This call cannot fail for a UP build! 672 */ 673 lwkt_getalltokens(ntd); 674 ++gd->gd_cnt.v_swtch; 675 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 676 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 677 #endif 678 } else { 679 /* 680 * We have nothing to run but only let the idle loop halt 681 * the cpu if there are no pending interrupts. 682 */ 683 ntd = &gd->gd_idlethread; 684 if (gd->gd_reqflags & RQF_IDLECHECK_MASK) 685 ntd->td_flags |= TDF_IDLE_NOHLT; 686 #ifdef SMP 687 using_idle_thread: 688 /* 689 * The idle thread should not be holding the MP lock unless we 690 * are trapping in the kernel or in a panic. Since we select the 691 * idle thread unconditionally when no other thread is available, 692 * if the MP lock is desired during a panic or kernel trap, we 693 * have to loop in the scheduler until we get it. 694 */ 695 if (ntd->td_mpcount) { 696 mpheld = MP_LOCK_HELD(); 697 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) { 698 panic("Idle thread %p was holding the BGL!", ntd); 699 } else if (mpheld == 0) { 700 cpu_mplock_contested(); 701 goto again; 702 } 703 } 704 #endif 705 } 706 } 707 KASSERT(ntd->td_pri >= TDPRI_CRIT, 708 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri)); 709 710 /* 711 * Do the actual switch. If the new target does not need the MP lock 712 * and we are holding it, release the MP lock. If the new target requires 713 * the MP lock we have already acquired it for the target. 714 */ 715 #ifdef SMP 716 if (ntd->td_mpcount == 0 ) { 717 if (MP_LOCK_HELD()) 718 cpu_rel_mplock(); 719 } else { 720 ASSERT_MP_LOCK_HELD(ntd); 721 } 722 #endif 723 if (td != ntd) { 724 ++switch_count; 725 td->td_switch(ntd); 726 } 727 /* NOTE: current cpu may have changed after switch */ 728 crit_exit_quick(td); 729 } 730 731 /* 732 * Request that the target thread preempt the current thread. Preemption 733 * only works under a specific set of conditions: 734 * 735 * - We are not preempting ourselves 736 * - The target thread is owned by the current cpu 737 * - We are not currently being preempted 738 * - The target is not currently being preempted 739 * - We are not holding any spin locks 740 * - The target thread is not holding any tokens 741 * - We are able to satisfy the target's MP lock requirements (if any). 742 * 743 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically 744 * this is called via lwkt_schedule() through the td_preemptable callback. 745 * critpri is the managed critical priority that we should ignore in order 746 * to determine whether preemption is possible (aka usually just the crit 747 * priority of lwkt_schedule() itself). 748 * 749 * XXX at the moment we run the target thread in a critical section during 750 * the preemption in order to prevent the target from taking interrupts 751 * that *WE* can't. Preemption is strictly limited to interrupt threads 752 * and interrupt-like threads, outside of a critical section, and the 753 * preempted source thread will be resumed the instant the target blocks 754 * whether or not the source is scheduled (i.e. preemption is supposed to 755 * be as transparent as possible). 756 * 757 * The target thread inherits our MP count (added to its own) for the 758 * duration of the preemption in order to preserve the atomicy of the 759 * MP lock during the preemption. Therefore, any preempting targets must be 760 * careful in regards to MP assertions. Note that the MP count may be 761 * out of sync with the physical mp_lock, but we do not have to preserve 762 * the original ownership of the lock if it was out of synch (that is, we 763 * can leave it synchronized on return). 764 */ 765 void 766 lwkt_preempt(thread_t ntd, int critpri) 767 { 768 struct globaldata *gd = mycpu; 769 thread_t td; 770 #ifdef SMP 771 int mpheld; 772 int savecnt; 773 #endif 774 775 /* 776 * The caller has put us in a critical section. We can only preempt 777 * if the caller of the caller was not in a critical section (basically 778 * a local interrupt), as determined by the 'critpri' parameter. We 779 * also can't preempt if the caller is holding any spinlocks (even if 780 * he isn't in a critical section). This also handles the tokens test. 781 * 782 * YYY The target thread must be in a critical section (else it must 783 * inherit our critical section? I dunno yet). 784 * 785 * Set need_lwkt_resched() unconditionally for now YYY. 786 */ 787 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri)); 788 789 td = gd->gd_curthread; 790 if ((ntd->td_pri & TDPRI_MASK) <= (td->td_pri & TDPRI_MASK)) { 791 ++preempt_miss; 792 return; 793 } 794 if ((td->td_pri & ~TDPRI_MASK) > critpri) { 795 ++preempt_miss; 796 need_lwkt_resched(); 797 return; 798 } 799 #ifdef SMP 800 if (ntd->td_gd != gd) { 801 ++preempt_miss; 802 need_lwkt_resched(); 803 return; 804 } 805 #endif 806 /* 807 * Take the easy way out and do not preempt if we are holding 808 * any spinlocks. We could test whether the thread(s) being 809 * preempted interlock against the target thread's tokens and whether 810 * we can get all the target thread's tokens, but this situation 811 * should not occur very often so its easier to simply not preempt. 812 * Also, plain spinlocks are impossible to figure out at this point so 813 * just don't preempt. 814 * 815 * Do not try to preempt if the target thread is holding any tokens. 816 * We could try to acquire the tokens but this case is so rare there 817 * is no need to support it. 818 */ 819 if (gd->gd_spinlock_rd || gd->gd_spinlocks_wr) { 820 ++preempt_miss; 821 need_lwkt_resched(); 822 return; 823 } 824 if (ntd->td_toks) { 825 ++preempt_miss; 826 need_lwkt_resched(); 827 return; 828 } 829 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) { 830 ++preempt_weird; 831 need_lwkt_resched(); 832 return; 833 } 834 if (ntd->td_preempted) { 835 ++preempt_hit; 836 need_lwkt_resched(); 837 return; 838 } 839 #ifdef SMP 840 /* 841 * note: an interrupt might have occured just as we were transitioning 842 * to or from the MP lock. In this case td_mpcount will be pre-disposed 843 * (non-zero) but not actually synchronized with the actual state of the 844 * lock. We can use it to imply an MP lock requirement for the 845 * preemption but we cannot use it to test whether we hold the MP lock 846 * or not. 847 */ 848 savecnt = td->td_mpcount; 849 mpheld = MP_LOCK_HELD(); 850 ntd->td_mpcount += td->td_mpcount; 851 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) { 852 ntd->td_mpcount -= td->td_mpcount; 853 ++preempt_miss; 854 need_lwkt_resched(); 855 return; 856 } 857 #endif 858 859 /* 860 * Since we are able to preempt the current thread, there is no need to 861 * call need_lwkt_resched(). 862 */ 863 ++preempt_hit; 864 ntd->td_preempted = td; 865 td->td_flags |= TDF_PREEMPT_LOCK; 866 td->td_switch(ntd); 867 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE)); 868 #ifdef SMP 869 KKASSERT(savecnt == td->td_mpcount); 870 mpheld = MP_LOCK_HELD(); 871 if (mpheld && td->td_mpcount == 0) 872 cpu_rel_mplock(); 873 else if (mpheld == 0 && td->td_mpcount) 874 panic("lwkt_preempt(): MP lock was not held through"); 875 #endif 876 ntd->td_preempted = NULL; 877 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE); 878 } 879 880 /* 881 * Yield our thread while higher priority threads are pending. This is 882 * typically called when we leave a critical section but it can be safely 883 * called while we are in a critical section. 884 * 885 * This function will not generally yield to equal priority threads but it 886 * can occur as a side effect. Note that lwkt_switch() is called from 887 * inside the critical section to prevent its own crit_exit() from reentering 888 * lwkt_yield_quick(). 889 * 890 * gd_reqflags indicates that *something* changed, e.g. an interrupt or softint 891 * came along but was blocked and made pending. 892 * 893 * (self contained on a per cpu basis) 894 */ 895 void 896 lwkt_yield_quick(void) 897 { 898 globaldata_t gd = mycpu; 899 thread_t td = gd->gd_curthread; 900 901 /* 902 * gd_reqflags is cleared in splz if the cpl is 0. If we were to clear 903 * it with a non-zero cpl then we might not wind up calling splz after 904 * a task switch when the critical section is exited even though the 905 * new task could accept the interrupt. 906 * 907 * XXX from crit_exit() only called after last crit section is released. 908 * If called directly will run splz() even if in a critical section. 909 * 910 * td_nest_count prevent deep nesting via splz() or doreti(). Note that 911 * except for this special case, we MUST call splz() here to handle any 912 * pending ints, particularly after we switch, or we might accidently 913 * halt the cpu with interrupts pending. 914 */ 915 if (gd->gd_reqflags && td->td_nest_count < 2) 916 splz(); 917 918 /* 919 * YYY enabling will cause wakeup() to task-switch, which really 920 * confused the old 4.x code. This is a good way to simulate 921 * preemption and MP without actually doing preemption or MP, because a 922 * lot of code assumes that wakeup() does not block. 923 */ 924 if (untimely_switch && td->td_nest_count == 0 && 925 gd->gd_intr_nesting_level == 0 926 ) { 927 crit_enter_quick(td); 928 /* 929 * YYY temporary hacks until we disassociate the userland scheduler 930 * from the LWKT scheduler. 931 */ 932 if (td->td_flags & TDF_RUNQ) { 933 lwkt_switch(); /* will not reenter yield function */ 934 } else { 935 lwkt_schedule_self(td); /* make sure we are scheduled */ 936 lwkt_switch(); /* will not reenter yield function */ 937 lwkt_deschedule_self(td); /* make sure we are descheduled */ 938 } 939 crit_exit_noyield(td); 940 } 941 } 942 943 /* 944 * This implements a normal yield which, unlike _quick, will yield to equal 945 * priority threads as well. Note that gd_reqflags tests will be handled by 946 * the crit_exit() call in lwkt_switch(). 947 * 948 * (self contained on a per cpu basis) 949 */ 950 void 951 lwkt_yield(void) 952 { 953 lwkt_schedule_self(curthread); 954 lwkt_switch(); 955 } 956 957 /* 958 * Generic schedule. Possibly schedule threads belonging to other cpus and 959 * deal with threads that might be blocked on a wait queue. 960 * 961 * We have a little helper inline function which does additional work after 962 * the thread has been enqueued, including dealing with preemption and 963 * setting need_lwkt_resched() (which prevents the kernel from returning 964 * to userland until it has processed higher priority threads). 965 * 966 * It is possible for this routine to be called after a failed _enqueue 967 * (due to the target thread migrating, sleeping, or otherwise blocked). 968 * We have to check that the thread is actually on the run queue! 969 * 970 * reschedok is an optimized constant propagated from lwkt_schedule() or 971 * lwkt_schedule_noresched(). By default it is non-zero, causing a 972 * reschedule to be requested if the target thread has a higher priority. 973 * The port messaging code will set MSG_NORESCHED and cause reschedok to 974 * be 0, prevented undesired reschedules. 975 */ 976 static __inline 977 void 978 _lwkt_schedule_post(globaldata_t gd, thread_t ntd, int cpri, int reschedok) 979 { 980 int mypri; 981 982 if (ntd->td_flags & TDF_RUNQ) { 983 if (ntd->td_preemptable && reschedok) { 984 ntd->td_preemptable(ntd, cpri); /* YYY +token */ 985 } else if (reschedok) { 986 /* 987 * This is a little sticky. Due to the passive release function 988 * the LWKT priority can wiggle around for threads acting in 989 * the kernel on behalf of a user process. We do not want this 990 * to effect the comparison per-say. 991 * 992 * What will happen is that the current user process will be 993 * allowed to run until the next hardclock at which time a 994 * forced need_lwkt_resched() will allow the other kernel mode 995 * threads to get in their two cents. This prevents cavitation. 996 */ 997 mypri = gd->gd_curthread->td_pri & TDPRI_MASK; 998 if (mypri >= TDPRI_USER_IDLE && mypri <= TDPRI_USER_REAL) 999 mypri = TDPRI_KERN_USER; 1000 1001 if ((ntd->td_pri & TDPRI_MASK) > mypri) 1002 need_lwkt_resched(); 1003 } 1004 } 1005 } 1006 1007 static __inline 1008 void 1009 _lwkt_schedule(thread_t td, int reschedok) 1010 { 1011 globaldata_t mygd = mycpu; 1012 1013 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule(): scheduling gd_idlethread is illegal!")); 1014 crit_enter_gd(mygd); 1015 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 1016 if (td == mygd->gd_curthread) { 1017 _lwkt_enqueue(td); 1018 } else { 1019 /* 1020 * If we own the thread, there is no race (since we are in a 1021 * critical section). If we do not own the thread there might 1022 * be a race but the target cpu will deal with it. 1023 */ 1024 #ifdef SMP 1025 if (td->td_gd == mygd) { 1026 _lwkt_enqueue(td); 1027 _lwkt_schedule_post(mygd, td, TDPRI_CRIT, reschedok); 1028 } else { 1029 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_schedule, td); 1030 } 1031 #else 1032 _lwkt_enqueue(td); 1033 _lwkt_schedule_post(mygd, td, TDPRI_CRIT, reschedok); 1034 #endif 1035 } 1036 crit_exit_gd(mygd); 1037 } 1038 1039 void 1040 lwkt_schedule(thread_t td) 1041 { 1042 _lwkt_schedule(td, 1); 1043 } 1044 1045 void 1046 lwkt_schedule_noresched(thread_t td) 1047 { 1048 _lwkt_schedule(td, 0); 1049 } 1050 1051 #ifdef SMP 1052 1053 /* 1054 * Thread migration using a 'Pull' method. The thread may or may not be 1055 * the current thread. It MUST be descheduled and in a stable state. 1056 * lwkt_giveaway() must be called on the cpu owning the thread. 1057 * 1058 * At any point after lwkt_giveaway() is called, the target cpu may 1059 * 'pull' the thread by calling lwkt_acquire(). 1060 * 1061 * MPSAFE - must be called under very specific conditions. 1062 */ 1063 void 1064 lwkt_giveaway(thread_t td) 1065 { 1066 globaldata_t gd = mycpu; 1067 1068 crit_enter_gd(gd); 1069 KKASSERT(td->td_gd == gd); 1070 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); 1071 td->td_flags |= TDF_MIGRATING; 1072 crit_exit_gd(gd); 1073 } 1074 1075 void 1076 lwkt_acquire(thread_t td) 1077 { 1078 globaldata_t gd; 1079 globaldata_t mygd; 1080 1081 KKASSERT(td->td_flags & TDF_MIGRATING); 1082 gd = td->td_gd; 1083 mygd = mycpu; 1084 if (gd != mycpu) { 1085 cpu_lfence(); 1086 KKASSERT((td->td_flags & TDF_RUNQ) == 0); 1087 crit_enter_gd(mygd); 1088 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) { 1089 #ifdef SMP 1090 lwkt_process_ipiq(); 1091 #endif 1092 cpu_lfence(); 1093 } 1094 td->td_gd = mygd; 1095 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1096 td->td_flags &= ~TDF_MIGRATING; 1097 crit_exit_gd(mygd); 1098 } else { 1099 crit_enter_gd(mygd); 1100 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1101 td->td_flags &= ~TDF_MIGRATING; 1102 crit_exit_gd(mygd); 1103 } 1104 } 1105 1106 #endif 1107 1108 /* 1109 * Generic deschedule. Descheduling threads other then your own should be 1110 * done only in carefully controlled circumstances. Descheduling is 1111 * asynchronous. 1112 * 1113 * This function may block if the cpu has run out of messages. 1114 */ 1115 void 1116 lwkt_deschedule(thread_t td) 1117 { 1118 crit_enter(); 1119 #ifdef SMP 1120 if (td == curthread) { 1121 _lwkt_dequeue(td); 1122 } else { 1123 if (td->td_gd == mycpu) { 1124 _lwkt_dequeue(td); 1125 } else { 1126 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td); 1127 } 1128 } 1129 #else 1130 _lwkt_dequeue(td); 1131 #endif 1132 crit_exit(); 1133 } 1134 1135 /* 1136 * Set the target thread's priority. This routine does not automatically 1137 * switch to a higher priority thread, LWKT threads are not designed for 1138 * continuous priority changes. Yield if you want to switch. 1139 * 1140 * We have to retain the critical section count which uses the high bits 1141 * of the td_pri field. The specified priority may also indicate zero or 1142 * more critical sections by adding TDPRI_CRIT*N. 1143 * 1144 * Note that we requeue the thread whether it winds up on a different runq 1145 * or not. uio_yield() depends on this and the routine is not normally 1146 * called with the same priority otherwise. 1147 */ 1148 void 1149 lwkt_setpri(thread_t td, int pri) 1150 { 1151 KKASSERT(pri >= 0); 1152 KKASSERT(td->td_gd == mycpu); 1153 crit_enter(); 1154 if (td->td_flags & TDF_RUNQ) { 1155 _lwkt_dequeue(td); 1156 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1157 _lwkt_enqueue(td); 1158 } else { 1159 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1160 } 1161 crit_exit(); 1162 } 1163 1164 void 1165 lwkt_setpri_self(int pri) 1166 { 1167 thread_t td = curthread; 1168 1169 KKASSERT(pri >= 0 && pri <= TDPRI_MAX); 1170 crit_enter(); 1171 if (td->td_flags & TDF_RUNQ) { 1172 _lwkt_dequeue(td); 1173 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1174 _lwkt_enqueue(td); 1175 } else { 1176 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1177 } 1178 crit_exit(); 1179 } 1180 1181 /* 1182 * Migrate the current thread to the specified cpu. 1183 * 1184 * This is accomplished by descheduling ourselves from the current cpu, 1185 * moving our thread to the tdallq of the target cpu, IPI messaging the 1186 * target cpu, and switching out. TDF_MIGRATING prevents scheduling 1187 * races while the thread is being migrated. 1188 */ 1189 #ifdef SMP 1190 static void lwkt_setcpu_remote(void *arg); 1191 #endif 1192 1193 void 1194 lwkt_setcpu_self(globaldata_t rgd) 1195 { 1196 #ifdef SMP 1197 thread_t td = curthread; 1198 1199 if (td->td_gd != rgd) { 1200 crit_enter_quick(td); 1201 td->td_flags |= TDF_MIGRATING; 1202 lwkt_deschedule_self(td); 1203 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1204 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td); 1205 lwkt_switch(); 1206 /* we are now on the target cpu */ 1207 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq); 1208 crit_exit_quick(td); 1209 } 1210 #endif 1211 } 1212 1213 void 1214 lwkt_migratecpu(int cpuid) 1215 { 1216 #ifdef SMP 1217 globaldata_t rgd; 1218 1219 rgd = globaldata_find(cpuid); 1220 lwkt_setcpu_self(rgd); 1221 #endif 1222 } 1223 1224 /* 1225 * Remote IPI for cpu migration (called while in a critical section so we 1226 * do not have to enter another one). The thread has already been moved to 1227 * our cpu's allq, but we must wait for the thread to be completely switched 1228 * out on the originating cpu before we schedule it on ours or the stack 1229 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD 1230 * change to main memory. 1231 * 1232 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races 1233 * against wakeups. It is best if this interface is used only when there 1234 * are no pending events that might try to schedule the thread. 1235 */ 1236 #ifdef SMP 1237 static void 1238 lwkt_setcpu_remote(void *arg) 1239 { 1240 thread_t td = arg; 1241 globaldata_t gd = mycpu; 1242 1243 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) { 1244 #ifdef SMP 1245 lwkt_process_ipiq(); 1246 #endif 1247 cpu_lfence(); 1248 } 1249 td->td_gd = gd; 1250 cpu_sfence(); 1251 td->td_flags &= ~TDF_MIGRATING; 1252 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 1253 _lwkt_enqueue(td); 1254 } 1255 #endif 1256 1257 struct lwp * 1258 lwkt_preempted_proc(void) 1259 { 1260 thread_t td = curthread; 1261 while (td->td_preempted) 1262 td = td->td_preempted; 1263 return(td->td_lwp); 1264 } 1265 1266 /* 1267 * Create a kernel process/thread/whatever. It shares it's address space 1268 * with proc0 - ie: kernel only. 1269 * 1270 * NOTE! By default new threads are created with the MP lock held. A 1271 * thread which does not require the MP lock should release it by calling 1272 * rel_mplock() at the start of the new thread. 1273 */ 1274 int 1275 lwkt_create(void (*func)(void *), void *arg, 1276 struct thread **tdp, thread_t template, int tdflags, int cpu, 1277 const char *fmt, ...) 1278 { 1279 thread_t td; 1280 __va_list ap; 1281 1282 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu, 1283 tdflags); 1284 if (tdp) 1285 *tdp = td; 1286 cpu_set_thread_handler(td, lwkt_exit, func, arg); 1287 1288 /* 1289 * Set up arg0 for 'ps' etc 1290 */ 1291 __va_start(ap, fmt); 1292 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap); 1293 __va_end(ap); 1294 1295 /* 1296 * Schedule the thread to run 1297 */ 1298 if ((td->td_flags & TDF_STOPREQ) == 0) 1299 lwkt_schedule(td); 1300 else 1301 td->td_flags &= ~TDF_STOPREQ; 1302 return 0; 1303 } 1304 1305 /* 1306 * Destroy an LWKT thread. Warning! This function is not called when 1307 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and 1308 * uses a different reaping mechanism. 1309 */ 1310 void 1311 lwkt_exit(void) 1312 { 1313 thread_t td = curthread; 1314 thread_t std; 1315 globaldata_t gd; 1316 1317 if (td->td_flags & TDF_VERBOSE) 1318 kprintf("kthread %p %s has exited\n", td, td->td_comm); 1319 caps_exit(td); 1320 1321 /* 1322 * Get us into a critical section to interlock gd_freetd and loop 1323 * until we can get it freed. 1324 * 1325 * We have to cache the current td in gd_freetd because objcache_put()ing 1326 * it would rip it out from under us while our thread is still active. 1327 */ 1328 gd = mycpu; 1329 crit_enter_quick(td); 1330 while ((std = gd->gd_freetd) != NULL) { 1331 gd->gd_freetd = NULL; 1332 objcache_put(thread_cache, std); 1333 } 1334 lwkt_deschedule_self(td); 1335 lwkt_remove_tdallq(td); 1336 if (td->td_flags & TDF_ALLOCATED_THREAD) 1337 gd->gd_freetd = td; 1338 cpu_thread_exit(); 1339 } 1340 1341 void 1342 lwkt_remove_tdallq(thread_t td) 1343 { 1344 KKASSERT(td->td_gd == mycpu); 1345 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1346 } 1347 1348 void 1349 crit_panic(void) 1350 { 1351 thread_t td = curthread; 1352 int lpri = td->td_pri; 1353 1354 td->td_pri = 0; 1355 panic("td_pri is/would-go negative! %p %d", td, lpri); 1356 } 1357 1358 #ifdef SMP 1359 1360 /* 1361 * Called from debugger/panic on cpus which have been stopped. We must still 1362 * process the IPIQ while stopped, even if we were stopped while in a critical 1363 * section (XXX). 1364 * 1365 * If we are dumping also try to process any pending interrupts. This may 1366 * or may not work depending on the state of the cpu at the point it was 1367 * stopped. 1368 */ 1369 void 1370 lwkt_smp_stopped(void) 1371 { 1372 globaldata_t gd = mycpu; 1373 1374 crit_enter_gd(gd); 1375 if (dumping) { 1376 lwkt_process_ipiq(); 1377 splz(); 1378 } else { 1379 lwkt_process_ipiq(); 1380 } 1381 crit_exit_gd(gd); 1382 } 1383 1384 /* 1385 * get_mplock() calls this routine if it is unable to obtain the MP lock. 1386 * get_mplock() has already incremented td_mpcount. We must block and 1387 * not return until giant is held. 1388 * 1389 * All we have to do is lwkt_switch() away. The LWKT scheduler will not 1390 * reschedule the thread until it can obtain the giant lock for it. 1391 */ 1392 void 1393 lwkt_mp_lock_contested(void) 1394 { 1395 loggiant(beg); 1396 lwkt_switch(); 1397 loggiant(end); 1398 } 1399 1400 #endif 1401