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 35 /* 36 * Each cpu in a system has its own self-contained light weight kernel 37 * thread scheduler, which means that generally speaking we only need 38 * to use a critical section to avoid problems. Foreign thread 39 * scheduling is queued via (async) IPIs. 40 */ 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/kernel.h> 45 #include <sys/proc.h> 46 #include <sys/rtprio.h> 47 #include <sys/queue.h> 48 #include <sys/sysctl.h> 49 #include <sys/kthread.h> 50 #include <machine/cpu.h> 51 #include <sys/lock.h> 52 #include <sys/caps.h> 53 #include <sys/spinlock.h> 54 #include <sys/ktr.h> 55 56 #include <sys/thread2.h> 57 #include <sys/spinlock2.h> 58 #include <sys/mplock2.h> 59 60 #include <vm/vm.h> 61 #include <vm/vm_param.h> 62 #include <vm/vm_kern.h> 63 #include <vm/vm_object.h> 64 #include <vm/vm_page.h> 65 #include <vm/vm_map.h> 66 #include <vm/vm_pager.h> 67 #include <vm/vm_extern.h> 68 69 #include <machine/stdarg.h> 70 #include <machine/smp.h> 71 72 #if !defined(KTR_CTXSW) 73 #define KTR_CTXSW KTR_ALL 74 #endif 75 KTR_INFO_MASTER(ctxsw); 76 KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "sw %p > %p", 2 * sizeof(struct thread *)); 77 KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "pre %p > %p", 2 * sizeof(struct thread *)); 78 79 static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads"); 80 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 __debugvar = 0; 89 static int lwkt_use_spin_port; 90 static struct objcache *thread_cache; 91 92 #ifdef SMP 93 static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame); 94 #endif 95 96 extern void cpu_heavy_restore(void); 97 extern void cpu_lwkt_restore(void); 98 extern void cpu_kthread_restore(void); 99 extern void cpu_idle_restore(void); 100 101 #ifdef __x86_64__ 102 103 static int 104 jg_tos_ok(struct thread *td) 105 { 106 void *tos; 107 int tos_ok; 108 109 if (td == NULL) { 110 return 1; 111 } 112 KKASSERT(td->td_sp != NULL); 113 tos = ((void **)td->td_sp)[0]; 114 tos_ok = 0; 115 if ((tos == cpu_heavy_restore) || (tos == cpu_lwkt_restore) || 116 (tos == cpu_kthread_restore) || (tos == cpu_idle_restore)) { 117 tos_ok = 1; 118 } 119 return tos_ok; 120 } 121 122 #endif 123 124 /* 125 * We can make all thread ports use the spin backend instead of the thread 126 * backend. This should only be set to debug the spin backend. 127 */ 128 TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port); 129 130 #ifdef INVARIANTS 131 SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, ""); 132 #endif 133 SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, ""); 134 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, ""); 135 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, ""); 136 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, ""); 137 #ifdef INVARIANTS 138 SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count, CTLFLAG_RW, 139 &token_contention_count, 0, "spinning due to token contention"); 140 #endif 141 142 /* 143 * These helper procedures handle the runq, they can only be called from 144 * within a critical section. 145 * 146 * WARNING! Prior to SMP being brought up it is possible to enqueue and 147 * dequeue threads belonging to other cpus, so be sure to use td->td_gd 148 * instead of 'mycpu' when referencing the globaldata structure. Once 149 * SMP live enqueuing and dequeueing only occurs on the current cpu. 150 */ 151 static __inline 152 void 153 _lwkt_dequeue(thread_t td) 154 { 155 if (td->td_flags & TDF_RUNQ) { 156 int nq = td->td_pri & TDPRI_MASK; 157 struct globaldata *gd = td->td_gd; 158 159 td->td_flags &= ~TDF_RUNQ; 160 TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq); 161 /* runqmask is passively cleaned up by the switcher */ 162 } 163 } 164 165 static __inline 166 void 167 _lwkt_enqueue(thread_t td) 168 { 169 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) { 170 int nq = td->td_pri & TDPRI_MASK; 171 struct globaldata *gd = td->td_gd; 172 173 td->td_flags |= TDF_RUNQ; 174 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq); 175 gd->gd_runqmask |= 1 << nq; 176 } 177 } 178 179 static __boolean_t 180 _lwkt_thread_ctor(void *obj, void *privdata, int ocflags) 181 { 182 struct thread *td = (struct thread *)obj; 183 184 td->td_kstack = NULL; 185 td->td_kstack_size = 0; 186 td->td_flags = TDF_ALLOCATED_THREAD; 187 return (1); 188 } 189 190 static void 191 _lwkt_thread_dtor(void *obj, void *privdata) 192 { 193 struct thread *td = (struct thread *)obj; 194 195 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD, 196 ("_lwkt_thread_dtor: not allocated from objcache")); 197 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack && 198 td->td_kstack_size > 0, 199 ("_lwkt_thread_dtor: corrupted stack")); 200 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); 201 } 202 203 /* 204 * Initialize the lwkt s/system. 205 */ 206 void 207 lwkt_init(void) 208 { 209 /* An objcache has 2 magazines per CPU so divide cache size by 2. */ 210 thread_cache = objcache_create_mbacked(M_THREAD, sizeof(struct thread), 211 NULL, CACHE_NTHREADS/2, 212 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL); 213 } 214 215 /* 216 * Schedule a thread to run. As the current thread we can always safely 217 * schedule ourselves, and a shortcut procedure is provided for that 218 * function. 219 * 220 * (non-blocking, self contained on a per cpu basis) 221 */ 222 void 223 lwkt_schedule_self(thread_t td) 224 { 225 crit_enter_quick(td); 226 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!")); 227 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 228 _lwkt_enqueue(td); 229 crit_exit_quick(td); 230 } 231 232 /* 233 * Deschedule a thread. 234 * 235 * (non-blocking, self contained on a per cpu basis) 236 */ 237 void 238 lwkt_deschedule_self(thread_t td) 239 { 240 crit_enter_quick(td); 241 _lwkt_dequeue(td); 242 crit_exit_quick(td); 243 } 244 245 /* 246 * LWKTs operate on a per-cpu basis 247 * 248 * WARNING! Called from early boot, 'mycpu' may not work yet. 249 */ 250 void 251 lwkt_gdinit(struct globaldata *gd) 252 { 253 int i; 254 255 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i) 256 TAILQ_INIT(&gd->gd_tdrunq[i]); 257 gd->gd_runqmask = 0; 258 TAILQ_INIT(&gd->gd_tdallq); 259 } 260 261 /* 262 * Create a new thread. The thread must be associated with a process context 263 * or LWKT start address before it can be scheduled. If the target cpu is 264 * -1 the thread will be created on the current cpu. 265 * 266 * If you intend to create a thread without a process context this function 267 * does everything except load the startup and switcher function. 268 */ 269 thread_t 270 lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags) 271 { 272 globaldata_t gd = mycpu; 273 void *stack; 274 275 /* 276 * If static thread storage is not supplied allocate a thread. Reuse 277 * a cached free thread if possible. gd_freetd is used to keep an exiting 278 * thread intact through the exit. 279 */ 280 if (td == NULL) { 281 if ((td = gd->gd_freetd) != NULL) 282 gd->gd_freetd = NULL; 283 else 284 td = objcache_get(thread_cache, M_WAITOK); 285 KASSERT((td->td_flags & 286 (TDF_ALLOCATED_THREAD|TDF_RUNNING)) == TDF_ALLOCATED_THREAD, 287 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags)); 288 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK); 289 } 290 291 /* 292 * Try to reuse cached stack. 293 */ 294 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) { 295 if (flags & TDF_ALLOCATED_STACK) { 296 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size); 297 stack = NULL; 298 } 299 } 300 if (stack == NULL) { 301 stack = (void *)kmem_alloc(&kernel_map, stksize); 302 flags |= TDF_ALLOCATED_STACK; 303 } 304 if (cpu < 0) 305 lwkt_init_thread(td, stack, stksize, flags, gd); 306 else 307 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu)); 308 return(td); 309 } 310 311 /* 312 * Initialize a preexisting thread structure. This function is used by 313 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread. 314 * 315 * All threads start out in a critical section at a priority of 316 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as 317 * appropriate. This function may send an IPI message when the 318 * requested cpu is not the current cpu and consequently gd_tdallq may 319 * not be initialized synchronously from the point of view of the originating 320 * cpu. 321 * 322 * NOTE! we have to be careful in regards to creating threads for other cpus 323 * if SMP has not yet been activated. 324 */ 325 #ifdef SMP 326 327 static void 328 lwkt_init_thread_remote(void *arg) 329 { 330 thread_t td = arg; 331 332 /* 333 * Protected by critical section held by IPI dispatch 334 */ 335 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq); 336 } 337 338 #endif 339 340 void 341 lwkt_init_thread(thread_t td, void *stack, int stksize, int flags, 342 struct globaldata *gd) 343 { 344 globaldata_t mygd = mycpu; 345 346 bzero(td, sizeof(struct thread)); 347 td->td_kstack = stack; 348 td->td_kstack_size = stksize; 349 td->td_flags = flags; 350 td->td_gd = gd; 351 td->td_pri = TDPRI_KERN_DAEMON + TDPRI_CRIT; 352 #ifdef SMP 353 if ((flags & TDF_MPSAFE) == 0) 354 td->td_mpcount = 1; 355 #endif 356 if (lwkt_use_spin_port) 357 lwkt_initport_spin(&td->td_msgport); 358 else 359 lwkt_initport_thread(&td->td_msgport, td); 360 pmap_init_thread(td); 361 #ifdef SMP 362 /* 363 * Normally initializing a thread for a remote cpu requires sending an 364 * IPI. However, the idlethread is setup before the other cpus are 365 * activated so we have to treat it as a special case. XXX manipulation 366 * of gd_tdallq requires the BGL. 367 */ 368 if (gd == mygd || td == &gd->gd_idlethread) { 369 crit_enter_gd(mygd); 370 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 371 crit_exit_gd(mygd); 372 } else { 373 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td); 374 } 375 #else 376 crit_enter_gd(mygd); 377 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 378 crit_exit_gd(mygd); 379 #endif 380 } 381 382 void 383 lwkt_set_comm(thread_t td, const char *ctl, ...) 384 { 385 __va_list va; 386 387 __va_start(va, ctl); 388 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va); 389 __va_end(va); 390 } 391 392 void 393 lwkt_hold(thread_t td) 394 { 395 ++td->td_refs; 396 } 397 398 void 399 lwkt_rele(thread_t td) 400 { 401 KKASSERT(td->td_refs > 0); 402 --td->td_refs; 403 } 404 405 void 406 lwkt_wait_free(thread_t td) 407 { 408 while (td->td_refs) 409 tsleep(td, 0, "tdreap", hz); 410 } 411 412 void 413 lwkt_free_thread(thread_t td) 414 { 415 KASSERT((td->td_flags & TDF_RUNNING) == 0, 416 ("lwkt_free_thread: did not exit! %p", td)); 417 418 if (td->td_flags & TDF_ALLOCATED_THREAD) { 419 objcache_put(thread_cache, td); 420 } else if (td->td_flags & TDF_ALLOCATED_STACK) { 421 /* client-allocated struct with internally allocated stack */ 422 KASSERT(td->td_kstack && td->td_kstack_size > 0, 423 ("lwkt_free_thread: corrupted stack")); 424 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); 425 td->td_kstack = NULL; 426 td->td_kstack_size = 0; 427 } 428 } 429 430 431 /* 432 * Switch to the next runnable lwkt. If no LWKTs are runnable then 433 * switch to the idlethread. Switching must occur within a critical 434 * section to avoid races with the scheduling queue. 435 * 436 * We always have full control over our cpu's run queue. Other cpus 437 * that wish to manipulate our queue must use the cpu_*msg() calls to 438 * talk to our cpu, so a critical section is all that is needed and 439 * the result is very, very fast thread switching. 440 * 441 * The LWKT scheduler uses a fixed priority model and round-robins at 442 * each priority level. User process scheduling is a totally 443 * different beast and LWKT priorities should not be confused with 444 * user process priorities. 445 * 446 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch() 447 * cleans it up. Note that the td_switch() function cannot do anything that 448 * requires the MP lock since the MP lock will have already been setup for 449 * the target thread (not the current thread). It's nice to have a scheduler 450 * that does not need the MP lock to work because it allows us to do some 451 * really cool high-performance MP lock optimizations. 452 * 453 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch() 454 * is not called by the current thread in the preemption case, only when 455 * the preempting thread blocks (in order to return to the original thread). 456 */ 457 void 458 lwkt_switch(void) 459 { 460 globaldata_t gd = mycpu; 461 thread_t td = gd->gd_curthread; 462 thread_t ntd; 463 #ifdef SMP 464 int mpheld; 465 #endif 466 467 /* 468 * Switching from within a 'fast' (non thread switched) interrupt or IPI 469 * is illegal. However, we may have to do it anyway if we hit a fatal 470 * kernel trap or we have paniced. 471 * 472 * If this case occurs save and restore the interrupt nesting level. 473 */ 474 if (gd->gd_intr_nesting_level) { 475 int savegdnest; 476 int savegdtrap; 477 478 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) { 479 panic("lwkt_switch: cannot switch from within " 480 "a fast interrupt, yet, td %p\n", td); 481 } else { 482 savegdnest = gd->gd_intr_nesting_level; 483 savegdtrap = gd->gd_trap_nesting_level; 484 gd->gd_intr_nesting_level = 0; 485 gd->gd_trap_nesting_level = 0; 486 if ((td->td_flags & TDF_PANICWARN) == 0) { 487 td->td_flags |= TDF_PANICWARN; 488 kprintf("Warning: thread switch from interrupt or IPI, " 489 "thread %p (%s)\n", td, td->td_comm); 490 print_backtrace(); 491 } 492 lwkt_switch(); 493 gd->gd_intr_nesting_level = savegdnest; 494 gd->gd_trap_nesting_level = savegdtrap; 495 return; 496 } 497 } 498 499 /* 500 * Passive release (used to transition from user to kernel mode 501 * when we block or switch rather then when we enter the kernel). 502 * This function is NOT called if we are switching into a preemption 503 * or returning from a preemption. Typically this causes us to lose 504 * our current process designation (if we have one) and become a true 505 * LWKT thread, and may also hand the current process designation to 506 * another process and schedule thread. 507 */ 508 if (td->td_release) 509 td->td_release(td); 510 511 crit_enter_gd(gd); 512 if (td->td_toks) 513 lwkt_relalltokens(td); 514 515 /* 516 * We had better not be holding any spin locks, but don't get into an 517 * endless panic loop. 518 */ 519 KASSERT(gd->gd_spinlock_rd == NULL || panicstr != NULL, 520 ("lwkt_switch: still holding a shared spinlock %p!", 521 gd->gd_spinlock_rd)); 522 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL, 523 ("lwkt_switch: still holding %d exclusive spinlocks!", 524 gd->gd_spinlocks_wr)); 525 526 527 #ifdef SMP 528 /* 529 * td_mpcount cannot be used to determine if we currently hold the 530 * MP lock because get_mplock() will increment it prior to attempting 531 * to get the lock, and switch out if it can't. Our ownership of 532 * the actual lock will remain stable while we are in a critical section 533 * (but, of course, another cpu may own or release the lock so the 534 * actual value of mp_lock is not stable). 535 */ 536 mpheld = MP_LOCK_HELD(); 537 #ifdef INVARIANTS 538 if (td->td_cscount) { 539 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n", 540 td); 541 if (panic_on_cscount) 542 panic("switching while mastering cpusync"); 543 } 544 #endif 545 #endif 546 if ((ntd = td->td_preempted) != NULL) { 547 /* 548 * We had preempted another thread on this cpu, resume the preempted 549 * thread. This occurs transparently, whether the preempted thread 550 * was scheduled or not (it may have been preempted after descheduling 551 * itself). 552 * 553 * We have to setup the MP lock for the original thread after backing 554 * out the adjustment that was made to curthread when the original 555 * was preempted. 556 */ 557 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK); 558 #ifdef SMP 559 if (ntd->td_mpcount && mpheld == 0) { 560 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d", 561 td, ntd, td->td_mpcount, ntd->td_mpcount); 562 } 563 if (ntd->td_mpcount) { 564 td->td_mpcount -= ntd->td_mpcount; 565 KKASSERT(td->td_mpcount >= 0); 566 } 567 #endif 568 ntd->td_flags |= TDF_PREEMPT_DONE; 569 570 /* 571 * The interrupt may have woken a thread up, we need to properly 572 * set the reschedule flag if the originally interrupted thread is 573 * at a lower priority. 574 */ 575 if (gd->gd_runqmask > (2 << (ntd->td_pri & TDPRI_MASK)) - 1) 576 need_lwkt_resched(); 577 /* YYY release mp lock on switchback if original doesn't need it */ 578 } else { 579 /* 580 * Priority queue / round-robin at each priority. Note that user 581 * processes run at a fixed, low priority and the user process 582 * scheduler deals with interactions between user processes 583 * by scheduling and descheduling them from the LWKT queue as 584 * necessary. 585 * 586 * We have to adjust the MP lock for the target thread. If we 587 * need the MP lock and cannot obtain it we try to locate a 588 * thread that does not need the MP lock. If we cannot, we spin 589 * instead of HLT. 590 * 591 * A similar issue exists for the tokens held by the target thread. 592 * If we cannot obtain ownership of the tokens we cannot immediately 593 * schedule the thread. 594 */ 595 596 /* 597 * If an LWKT reschedule was requested, well that is what we are 598 * doing now so clear it. 599 */ 600 clear_lwkt_resched(); 601 again: 602 if (gd->gd_runqmask) { 603 int nq = bsrl(gd->gd_runqmask); 604 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) { 605 gd->gd_runqmask &= ~(1 << nq); 606 goto again; 607 } 608 #ifdef SMP 609 /* 610 * THREAD SELECTION FOR AN SMP MACHINE BUILD 611 * 612 * If the target needs the MP lock and we couldn't get it, 613 * or if the target is holding tokens and we could not 614 * gain ownership of the tokens, continue looking for a 615 * thread to schedule and spin instead of HLT if we can't. 616 * 617 * NOTE: the mpheld variable invalid after this conditional, it 618 * can change due to both cpu_try_mplock() returning success 619 * AND interactions in lwkt_getalltokens() due to the fact that 620 * we are trying to check the mpcount of a thread other then 621 * the current thread. Because of this, if the current thread 622 * is not holding td_mpcount, an IPI indirectly run via 623 * lwkt_getalltokens() can obtain and release the MP lock and 624 * cause the core MP lock to be released. 625 */ 626 if ((ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) || 627 (ntd->td_toks && lwkt_getalltokens(ntd) == 0) 628 ) { 629 u_int32_t rqmask = gd->gd_runqmask; 630 631 mpheld = MP_LOCK_HELD(); 632 ntd = NULL; 633 while (rqmask) { 634 TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) { 635 if (ntd->td_mpcount && !mpheld && !cpu_try_mplock()) { 636 /* spinning due to MP lock being held */ 637 continue; 638 } 639 640 /* 641 * mpheld state invalid after getalltokens call returns 642 * failure, but the variable is only needed for 643 * the loop. 644 */ 645 if (ntd->td_toks && !lwkt_getalltokens(ntd)) { 646 /* spinning due to token contention */ 647 #ifdef INVARIANTS 648 ++token_contention_count; 649 #endif 650 mpheld = MP_LOCK_HELD(); 651 continue; 652 } 653 break; 654 } 655 if (ntd) 656 break; 657 rqmask &= ~(1 << nq); 658 nq = bsrl(rqmask); 659 660 /* 661 * We have two choices. We can either refuse to run a 662 * user thread when a kernel thread needs the MP lock 663 * but could not get it, or we can allow it to run but 664 * then expect an IPI (hopefully) later on to force a 665 * reschedule when the MP lock might become available. 666 */ 667 if (nq < TDPRI_KERN_LPSCHED) { 668 break; /* for now refuse to run */ 669 #if 0 670 if (chain_mplock == 0) 671 break; 672 /* continue loop, allow user threads to be scheduled */ 673 #endif 674 } 675 } 676 677 /* 678 * Case where a (kernel) thread needed the MP lock and could 679 * not get one, and we may or may not have found another 680 * thread which does not need the MP lock to run while 681 * we wait (ntd). 682 */ 683 if (ntd == NULL) { 684 ntd = &gd->gd_idlethread; 685 ntd->td_flags |= TDF_IDLE_NOHLT; 686 set_mplock_contention_mask(gd); 687 cpu_mplock_contested(); 688 goto using_idle_thread; 689 } else { 690 clr_mplock_contention_mask(gd); 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 } 695 } else { 696 clr_mplock_contention_mask(gd); 697 ++gd->gd_cnt.v_swtch; 698 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 699 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 700 } 701 #else 702 /* 703 * THREAD SELECTION FOR A UP MACHINE BUILD. We don't have to 704 * worry about tokens or the BGL. However, we still have 705 * to call lwkt_getalltokens() in order to properly detect 706 * stale tokens. This call cannot fail for a UP build! 707 */ 708 lwkt_getalltokens(ntd); 709 ++gd->gd_cnt.v_swtch; 710 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 711 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 712 #endif 713 } else { 714 /* 715 * We have nothing to run but only let the idle loop halt 716 * the cpu if there are no pending interrupts. 717 */ 718 ntd = &gd->gd_idlethread; 719 if (gd->gd_reqflags & RQF_IDLECHECK_MASK) 720 ntd->td_flags |= TDF_IDLE_NOHLT; 721 #ifdef SMP 722 using_idle_thread: 723 /* 724 * The idle thread should not be holding the MP lock unless we 725 * are trapping in the kernel or in a panic. Since we select the 726 * idle thread unconditionally when no other thread is available, 727 * if the MP lock is desired during a panic or kernel trap, we 728 * have to loop in the scheduler until we get it. 729 */ 730 if (ntd->td_mpcount) { 731 mpheld = MP_LOCK_HELD(); 732 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) 733 panic("Idle thread %p was holding the BGL!", ntd); 734 if (mpheld == 0) 735 goto again; 736 } 737 #endif 738 } 739 } 740 KASSERT(ntd->td_pri >= TDPRI_CRIT, 741 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri)); 742 743 /* 744 * Do the actual switch. If the new target does not need the MP lock 745 * and we are holding it, release the MP lock. If the new target requires 746 * the MP lock we have already acquired it for the target. 747 */ 748 #ifdef SMP 749 if (ntd->td_mpcount == 0 ) { 750 if (MP_LOCK_HELD()) 751 cpu_rel_mplock(); 752 } else { 753 ASSERT_MP_LOCK_HELD(ntd); 754 } 755 #endif 756 if (td != ntd) { 757 ++switch_count; 758 #ifdef __x86_64__ 759 { 760 int tos_ok __debugvar = jg_tos_ok(ntd); 761 KKASSERT(tos_ok); 762 } 763 #endif 764 KTR_LOG(ctxsw_sw, td, ntd); 765 td->td_switch(ntd); 766 } 767 /* NOTE: current cpu may have changed after switch */ 768 crit_exit_quick(td); 769 } 770 771 /* 772 * Request that the target thread preempt the current thread. Preemption 773 * only works under a specific set of conditions: 774 * 775 * - We are not preempting ourselves 776 * - The target thread is owned by the current cpu 777 * - We are not currently being preempted 778 * - The target is not currently being preempted 779 * - We are not holding any spin locks 780 * - The target thread is not holding any tokens 781 * - We are able to satisfy the target's MP lock requirements (if any). 782 * 783 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically 784 * this is called via lwkt_schedule() through the td_preemptable callback. 785 * critpri is the managed critical priority that we should ignore in order 786 * to determine whether preemption is possible (aka usually just the crit 787 * priority of lwkt_schedule() itself). 788 * 789 * XXX at the moment we run the target thread in a critical section during 790 * the preemption in order to prevent the target from taking interrupts 791 * that *WE* can't. Preemption is strictly limited to interrupt threads 792 * and interrupt-like threads, outside of a critical section, and the 793 * preempted source thread will be resumed the instant the target blocks 794 * whether or not the source is scheduled (i.e. preemption is supposed to 795 * be as transparent as possible). 796 * 797 * The target thread inherits our MP count (added to its own) for the 798 * duration of the preemption in order to preserve the atomicy of the 799 * MP lock during the preemption. Therefore, any preempting targets must be 800 * careful in regards to MP assertions. Note that the MP count may be 801 * out of sync with the physical mp_lock, but we do not have to preserve 802 * the original ownership of the lock if it was out of synch (that is, we 803 * can leave it synchronized on return). 804 */ 805 void 806 lwkt_preempt(thread_t ntd, int critpri) 807 { 808 struct globaldata *gd = mycpu; 809 thread_t td; 810 #ifdef SMP 811 int mpheld; 812 int savecnt; 813 #endif 814 815 /* 816 * The caller has put us in a critical section. We can only preempt 817 * if the caller of the caller was not in a critical section (basically 818 * a local interrupt), as determined by the 'critpri' parameter. We 819 * also can't preempt if the caller is holding any spinlocks (even if 820 * he isn't in a critical section). This also handles the tokens test. 821 * 822 * YYY The target thread must be in a critical section (else it must 823 * inherit our critical section? I dunno yet). 824 * 825 * Set need_lwkt_resched() unconditionally for now YYY. 826 */ 827 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri)); 828 829 td = gd->gd_curthread; 830 if ((ntd->td_pri & TDPRI_MASK) <= (td->td_pri & TDPRI_MASK)) { 831 ++preempt_miss; 832 return; 833 } 834 if ((td->td_pri & ~TDPRI_MASK) > critpri) { 835 ++preempt_miss; 836 need_lwkt_resched(); 837 return; 838 } 839 #ifdef SMP 840 if (ntd->td_gd != gd) { 841 ++preempt_miss; 842 need_lwkt_resched(); 843 return; 844 } 845 #endif 846 /* 847 * Take the easy way out and do not preempt if we are holding 848 * any spinlocks. We could test whether the thread(s) being 849 * preempted interlock against the target thread's tokens and whether 850 * we can get all the target thread's tokens, but this situation 851 * should not occur very often so its easier to simply not preempt. 852 * Also, plain spinlocks are impossible to figure out at this point so 853 * just don't preempt. 854 * 855 * Do not try to preempt if the target thread is holding any tokens. 856 * We could try to acquire the tokens but this case is so rare there 857 * is no need to support it. 858 */ 859 if (gd->gd_spinlock_rd || gd->gd_spinlocks_wr) { 860 ++preempt_miss; 861 need_lwkt_resched(); 862 return; 863 } 864 if (ntd->td_toks) { 865 ++preempt_miss; 866 need_lwkt_resched(); 867 return; 868 } 869 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) { 870 ++preempt_weird; 871 need_lwkt_resched(); 872 return; 873 } 874 if (ntd->td_preempted) { 875 ++preempt_hit; 876 need_lwkt_resched(); 877 return; 878 } 879 #ifdef SMP 880 /* 881 * note: an interrupt might have occured just as we were transitioning 882 * to or from the MP lock. In this case td_mpcount will be pre-disposed 883 * (non-zero) but not actually synchronized with the actual state of the 884 * lock. We can use it to imply an MP lock requirement for the 885 * preemption but we cannot use it to test whether we hold the MP lock 886 * or not. 887 */ 888 savecnt = td->td_mpcount; 889 mpheld = MP_LOCK_HELD(); 890 ntd->td_mpcount += td->td_mpcount; 891 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) { 892 ntd->td_mpcount -= td->td_mpcount; 893 ++preempt_miss; 894 need_lwkt_resched(); 895 return; 896 } 897 #endif 898 899 /* 900 * Since we are able to preempt the current thread, there is no need to 901 * call need_lwkt_resched(). 902 */ 903 ++preempt_hit; 904 ntd->td_preempted = td; 905 td->td_flags |= TDF_PREEMPT_LOCK; 906 KTR_LOG(ctxsw_pre, td, ntd); 907 td->td_switch(ntd); 908 909 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE)); 910 #ifdef SMP 911 KKASSERT(savecnt == td->td_mpcount); 912 mpheld = MP_LOCK_HELD(); 913 if (mpheld && td->td_mpcount == 0) 914 cpu_rel_mplock(); 915 else if (mpheld == 0 && td->td_mpcount) 916 panic("lwkt_preempt(): MP lock was not held through"); 917 #endif 918 ntd->td_preempted = NULL; 919 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE); 920 } 921 922 /* 923 * Conditionally call splz() if gd_reqflags indicates work is pending. 924 * 925 * td_nest_count prevents deep nesting via splz() or doreti() which 926 * might otherwise blow out the kernel stack. Note that except for 927 * this special case, we MUST call splz() here to handle any 928 * pending ints, particularly after we switch, or we might accidently 929 * halt the cpu with interrupts pending. 930 * 931 * (self contained on a per cpu basis) 932 */ 933 void 934 splz_check(void) 935 { 936 globaldata_t gd = mycpu; 937 thread_t td = gd->gd_curthread; 938 939 if (gd->gd_reqflags && td->td_nest_count < 2) 940 splz(); 941 } 942 943 /* 944 * This implements a normal yield which will yield to equal priority 945 * threads as well as higher priority threads. Note that gd_reqflags 946 * tests will be handled by 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 * This function is used along with the lwkt_passive_recover() inline 959 * by the trap code to negotiate a passive release of the current 960 * process/lwp designation with the user scheduler. 961 */ 962 void 963 lwkt_passive_release(struct thread *td) 964 { 965 struct lwp *lp = td->td_lwp; 966 967 td->td_release = NULL; 968 lwkt_setpri_self(TDPRI_KERN_USER); 969 lp->lwp_proc->p_usched->release_curproc(lp); 970 } 971 972 /* 973 * Make a kernel thread act as if it were in user mode with regards 974 * to scheduling, to avoid becoming cpu-bound in the kernel. Kernel 975 * loops which may be potentially cpu-bound can call lwkt_user_yield(). 976 * 977 * The lwkt_user_yield() function is designed to have very low overhead 978 * if no yield is determined to be needed. 979 */ 980 void 981 lwkt_user_yield(void) 982 { 983 thread_t td = curthread; 984 struct lwp *lp = td->td_lwp; 985 986 #ifdef SMP 987 /* 988 * XXX SEVERE TEMPORARY HACK. A cpu-bound operation running in the 989 * kernel can prevent other cpus from servicing interrupt threads 990 * which still require the MP lock (which is a lot of them). This 991 * has a chaining effect since if the interrupt is blocked, so is 992 * the event, so normal scheduling will not pick up on the problem. 993 */ 994 if (mp_lock_contention_mask && td->td_mpcount) { 995 yield_mplock(td); 996 } 997 #endif 998 999 /* 1000 * Another kernel thread wants the cpu 1001 */ 1002 if (lwkt_resched_wanted()) 1003 lwkt_switch(); 1004 1005 /* 1006 * If the user scheduler has asynchronously determined that the current 1007 * process (when running in user mode) needs to lose the cpu then make 1008 * sure we are released. 1009 */ 1010 if (user_resched_wanted()) { 1011 if (td->td_release) 1012 td->td_release(td); 1013 } 1014 1015 /* 1016 * If we are released reduce our priority 1017 */ 1018 if (td->td_release == NULL) { 1019 if (lwkt_check_resched(td) > 0) 1020 lwkt_switch(); 1021 if (lp) { 1022 lp->lwp_proc->p_usched->acquire_curproc(lp); 1023 td->td_release = lwkt_passive_release; 1024 lwkt_setpri_self(TDPRI_USER_NORM); 1025 } 1026 } 1027 } 1028 1029 /* 1030 * Return 0 if no runnable threads are pending at the same or higher 1031 * priority as the passed thread. 1032 * 1033 * Return 1 if runnable threads are pending at the same priority. 1034 * 1035 * Return 2 if runnable threads are pending at a higher priority. 1036 */ 1037 int 1038 lwkt_check_resched(thread_t td) 1039 { 1040 int pri = td->td_pri & TDPRI_MASK; 1041 1042 if (td->td_gd->gd_runqmask > (2 << pri) - 1) 1043 return(2); 1044 if (TAILQ_NEXT(td, td_threadq)) 1045 return(1); 1046 return(0); 1047 } 1048 1049 /* 1050 * Generic schedule. Possibly schedule threads belonging to other cpus and 1051 * deal with threads that might be blocked on a wait queue. 1052 * 1053 * We have a little helper inline function which does additional work after 1054 * the thread has been enqueued, including dealing with preemption and 1055 * setting need_lwkt_resched() (which prevents the kernel from returning 1056 * to userland until it has processed higher priority threads). 1057 * 1058 * It is possible for this routine to be called after a failed _enqueue 1059 * (due to the target thread migrating, sleeping, or otherwise blocked). 1060 * We have to check that the thread is actually on the run queue! 1061 * 1062 * reschedok is an optimized constant propagated from lwkt_schedule() or 1063 * lwkt_schedule_noresched(). By default it is non-zero, causing a 1064 * reschedule to be requested if the target thread has a higher priority. 1065 * The port messaging code will set MSG_NORESCHED and cause reschedok to 1066 * be 0, prevented undesired reschedules. 1067 */ 1068 static __inline 1069 void 1070 _lwkt_schedule_post(globaldata_t gd, thread_t ntd, int cpri, int reschedok) 1071 { 1072 thread_t otd; 1073 1074 if (ntd->td_flags & TDF_RUNQ) { 1075 if (ntd->td_preemptable && reschedok) { 1076 ntd->td_preemptable(ntd, cpri); /* YYY +token */ 1077 } else if (reschedok) { 1078 otd = curthread; 1079 if ((ntd->td_pri & TDPRI_MASK) > (otd->td_pri & TDPRI_MASK)) 1080 need_lwkt_resched(); 1081 } 1082 } 1083 } 1084 1085 static __inline 1086 void 1087 _lwkt_schedule(thread_t td, int reschedok) 1088 { 1089 globaldata_t mygd = mycpu; 1090 1091 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule(): scheduling gd_idlethread is illegal!")); 1092 crit_enter_gd(mygd); 1093 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 1094 if (td == mygd->gd_curthread) { 1095 _lwkt_enqueue(td); 1096 } else { 1097 /* 1098 * If we own the thread, there is no race (since we are in a 1099 * critical section). If we do not own the thread there might 1100 * be a race but the target cpu will deal with it. 1101 */ 1102 #ifdef SMP 1103 if (td->td_gd == mygd) { 1104 _lwkt_enqueue(td); 1105 _lwkt_schedule_post(mygd, td, TDPRI_CRIT, reschedok); 1106 } else { 1107 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0); 1108 } 1109 #else 1110 _lwkt_enqueue(td); 1111 _lwkt_schedule_post(mygd, td, TDPRI_CRIT, reschedok); 1112 #endif 1113 } 1114 crit_exit_gd(mygd); 1115 } 1116 1117 void 1118 lwkt_schedule(thread_t td) 1119 { 1120 _lwkt_schedule(td, 1); 1121 } 1122 1123 void 1124 lwkt_schedule_noresched(thread_t td) 1125 { 1126 _lwkt_schedule(td, 0); 1127 } 1128 1129 #ifdef SMP 1130 1131 /* 1132 * When scheduled remotely if frame != NULL the IPIQ is being 1133 * run via doreti or an interrupt then preemption can be allowed. 1134 * 1135 * To allow preemption we have to drop the critical section so only 1136 * one is present in _lwkt_schedule_post. 1137 */ 1138 static void 1139 lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame) 1140 { 1141 thread_t td = curthread; 1142 thread_t ntd = arg; 1143 1144 if (frame && ntd->td_preemptable) { 1145 crit_exit_noyield(td); 1146 _lwkt_schedule(ntd, 1); 1147 crit_enter_quick(td); 1148 } else { 1149 _lwkt_schedule(ntd, 1); 1150 } 1151 } 1152 1153 /* 1154 * Thread migration using a 'Pull' method. The thread may or may not be 1155 * the current thread. It MUST be descheduled and in a stable state. 1156 * lwkt_giveaway() must be called on the cpu owning the thread. 1157 * 1158 * At any point after lwkt_giveaway() is called, the target cpu may 1159 * 'pull' the thread by calling lwkt_acquire(). 1160 * 1161 * We have to make sure the thread is not sitting on a per-cpu tsleep 1162 * queue or it will blow up when it moves to another cpu. 1163 * 1164 * MPSAFE - must be called under very specific conditions. 1165 */ 1166 void 1167 lwkt_giveaway(thread_t td) 1168 { 1169 globaldata_t gd = mycpu; 1170 1171 crit_enter_gd(gd); 1172 if (td->td_flags & TDF_TSLEEPQ) 1173 tsleep_remove(td); 1174 KKASSERT(td->td_gd == gd); 1175 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); 1176 td->td_flags |= TDF_MIGRATING; 1177 crit_exit_gd(gd); 1178 } 1179 1180 void 1181 lwkt_acquire(thread_t td) 1182 { 1183 globaldata_t gd; 1184 globaldata_t mygd; 1185 1186 KKASSERT(td->td_flags & TDF_MIGRATING); 1187 gd = td->td_gd; 1188 mygd = mycpu; 1189 if (gd != mycpu) { 1190 cpu_lfence(); 1191 KKASSERT((td->td_flags & TDF_RUNQ) == 0); 1192 crit_enter_gd(mygd); 1193 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) { 1194 #ifdef SMP 1195 lwkt_process_ipiq(); 1196 #endif 1197 cpu_lfence(); 1198 } 1199 td->td_gd = mygd; 1200 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1201 td->td_flags &= ~TDF_MIGRATING; 1202 crit_exit_gd(mygd); 1203 } else { 1204 crit_enter_gd(mygd); 1205 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1206 td->td_flags &= ~TDF_MIGRATING; 1207 crit_exit_gd(mygd); 1208 } 1209 } 1210 1211 #endif 1212 1213 /* 1214 * Generic deschedule. Descheduling threads other then your own should be 1215 * done only in carefully controlled circumstances. Descheduling is 1216 * asynchronous. 1217 * 1218 * This function may block if the cpu has run out of messages. 1219 */ 1220 void 1221 lwkt_deschedule(thread_t td) 1222 { 1223 crit_enter(); 1224 #ifdef SMP 1225 if (td == curthread) { 1226 _lwkt_dequeue(td); 1227 } else { 1228 if (td->td_gd == mycpu) { 1229 _lwkt_dequeue(td); 1230 } else { 1231 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td); 1232 } 1233 } 1234 #else 1235 _lwkt_dequeue(td); 1236 #endif 1237 crit_exit(); 1238 } 1239 1240 /* 1241 * Set the target thread's priority. This routine does not automatically 1242 * switch to a higher priority thread, LWKT threads are not designed for 1243 * continuous priority changes. Yield if you want to switch. 1244 * 1245 * We have to retain the critical section count which uses the high bits 1246 * of the td_pri field. The specified priority may also indicate zero or 1247 * more critical sections by adding TDPRI_CRIT*N. 1248 * 1249 * Note that we requeue the thread whether it winds up on a different runq 1250 * or not. uio_yield() depends on this and the routine is not normally 1251 * called with the same priority otherwise. 1252 */ 1253 void 1254 lwkt_setpri(thread_t td, int pri) 1255 { 1256 KKASSERT(pri >= 0); 1257 KKASSERT(td->td_gd == mycpu); 1258 crit_enter(); 1259 if (td->td_flags & TDF_RUNQ) { 1260 _lwkt_dequeue(td); 1261 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1262 _lwkt_enqueue(td); 1263 } else { 1264 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1265 } 1266 crit_exit(); 1267 } 1268 1269 /* 1270 * Set the initial priority for a thread prior to it being scheduled for 1271 * the first time. The thread MUST NOT be scheduled before or during 1272 * this call. The thread may be assigned to a cpu other then the current 1273 * cpu. 1274 * 1275 * Typically used after a thread has been created with TDF_STOPPREQ, 1276 * and before the thread is initially scheduled. 1277 */ 1278 void 1279 lwkt_setpri_initial(thread_t td, int pri) 1280 { 1281 KKASSERT(pri >= 0); 1282 KKASSERT((td->td_flags & TDF_RUNQ) == 0); 1283 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1284 } 1285 1286 void 1287 lwkt_setpri_self(int pri) 1288 { 1289 thread_t td = curthread; 1290 1291 KKASSERT(pri >= 0 && pri <= TDPRI_MAX); 1292 crit_enter(); 1293 if (td->td_flags & TDF_RUNQ) { 1294 _lwkt_dequeue(td); 1295 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1296 _lwkt_enqueue(td); 1297 } else { 1298 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1299 } 1300 crit_exit(); 1301 } 1302 1303 /* 1304 * Migrate the current thread to the specified cpu. 1305 * 1306 * This is accomplished by descheduling ourselves from the current cpu, 1307 * moving our thread to the tdallq of the target cpu, IPI messaging the 1308 * target cpu, and switching out. TDF_MIGRATING prevents scheduling 1309 * races while the thread is being migrated. 1310 * 1311 * We must be sure to remove ourselves from the current cpu's tsleepq 1312 * before potentially moving to another queue. The thread can be on 1313 * a tsleepq due to a left-over tsleep_interlock(). 1314 */ 1315 #ifdef SMP 1316 static void lwkt_setcpu_remote(void *arg); 1317 #endif 1318 1319 void 1320 lwkt_setcpu_self(globaldata_t rgd) 1321 { 1322 #ifdef SMP 1323 thread_t td = curthread; 1324 1325 if (td->td_gd != rgd) { 1326 crit_enter_quick(td); 1327 if (td->td_flags & TDF_TSLEEPQ) 1328 tsleep_remove(td); 1329 td->td_flags |= TDF_MIGRATING; 1330 lwkt_deschedule_self(td); 1331 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1332 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td); 1333 lwkt_switch(); 1334 /* we are now on the target cpu */ 1335 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq); 1336 crit_exit_quick(td); 1337 } 1338 #endif 1339 } 1340 1341 void 1342 lwkt_migratecpu(int cpuid) 1343 { 1344 #ifdef SMP 1345 globaldata_t rgd; 1346 1347 rgd = globaldata_find(cpuid); 1348 lwkt_setcpu_self(rgd); 1349 #endif 1350 } 1351 1352 /* 1353 * Remote IPI for cpu migration (called while in a critical section so we 1354 * do not have to enter another one). The thread has already been moved to 1355 * our cpu's allq, but we must wait for the thread to be completely switched 1356 * out on the originating cpu before we schedule it on ours or the stack 1357 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD 1358 * change to main memory. 1359 * 1360 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races 1361 * against wakeups. It is best if this interface is used only when there 1362 * are no pending events that might try to schedule the thread. 1363 */ 1364 #ifdef SMP 1365 static void 1366 lwkt_setcpu_remote(void *arg) 1367 { 1368 thread_t td = arg; 1369 globaldata_t gd = mycpu; 1370 1371 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) { 1372 #ifdef SMP 1373 lwkt_process_ipiq(); 1374 #endif 1375 cpu_lfence(); 1376 } 1377 td->td_gd = gd; 1378 cpu_sfence(); 1379 td->td_flags &= ~TDF_MIGRATING; 1380 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 1381 _lwkt_enqueue(td); 1382 } 1383 #endif 1384 1385 struct lwp * 1386 lwkt_preempted_proc(void) 1387 { 1388 thread_t td = curthread; 1389 while (td->td_preempted) 1390 td = td->td_preempted; 1391 return(td->td_lwp); 1392 } 1393 1394 /* 1395 * Create a kernel process/thread/whatever. It shares it's address space 1396 * with proc0 - ie: kernel only. 1397 * 1398 * NOTE! By default new threads are created with the MP lock held. A 1399 * thread which does not require the MP lock should release it by calling 1400 * rel_mplock() at the start of the new thread. 1401 */ 1402 int 1403 lwkt_create(void (*func)(void *), void *arg, 1404 struct thread **tdp, thread_t template, int tdflags, int cpu, 1405 const char *fmt, ...) 1406 { 1407 thread_t td; 1408 __va_list ap; 1409 1410 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu, 1411 tdflags); 1412 if (tdp) 1413 *tdp = td; 1414 cpu_set_thread_handler(td, lwkt_exit, func, arg); 1415 1416 /* 1417 * Set up arg0 for 'ps' etc 1418 */ 1419 __va_start(ap, fmt); 1420 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap); 1421 __va_end(ap); 1422 1423 /* 1424 * Schedule the thread to run 1425 */ 1426 if ((td->td_flags & TDF_STOPREQ) == 0) 1427 lwkt_schedule(td); 1428 else 1429 td->td_flags &= ~TDF_STOPREQ; 1430 return 0; 1431 } 1432 1433 /* 1434 * Destroy an LWKT thread. Warning! This function is not called when 1435 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and 1436 * uses a different reaping mechanism. 1437 */ 1438 void 1439 lwkt_exit(void) 1440 { 1441 thread_t td = curthread; 1442 thread_t std; 1443 globaldata_t gd; 1444 1445 if (td->td_flags & TDF_VERBOSE) 1446 kprintf("kthread %p %s has exited\n", td, td->td_comm); 1447 caps_exit(td); 1448 1449 /* 1450 * Get us into a critical section to interlock gd_freetd and loop 1451 * until we can get it freed. 1452 * 1453 * We have to cache the current td in gd_freetd because objcache_put()ing 1454 * it would rip it out from under us while our thread is still active. 1455 */ 1456 gd = mycpu; 1457 crit_enter_quick(td); 1458 while ((std = gd->gd_freetd) != NULL) { 1459 gd->gd_freetd = NULL; 1460 objcache_put(thread_cache, std); 1461 } 1462 1463 /* 1464 * Remove thread resources from kernel lists and deschedule us for 1465 * the last time. 1466 */ 1467 if (td->td_flags & TDF_TSLEEPQ) 1468 tsleep_remove(td); 1469 biosched_done(td); 1470 lwkt_deschedule_self(td); 1471 lwkt_remove_tdallq(td); 1472 if (td->td_flags & TDF_ALLOCATED_THREAD) 1473 gd->gd_freetd = td; 1474 cpu_thread_exit(); 1475 } 1476 1477 void 1478 lwkt_remove_tdallq(thread_t td) 1479 { 1480 KKASSERT(td->td_gd == mycpu); 1481 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1482 } 1483 1484 void 1485 crit_panic(void) 1486 { 1487 thread_t td = curthread; 1488 int lpri = td->td_pri; 1489 1490 td->td_pri = 0; 1491 panic("td_pri is/would-go negative! %p %d", td, lpri); 1492 } 1493 1494 #ifdef SMP 1495 1496 /* 1497 * Called from debugger/panic on cpus which have been stopped. We must still 1498 * process the IPIQ while stopped, even if we were stopped while in a critical 1499 * section (XXX). 1500 * 1501 * If we are dumping also try to process any pending interrupts. This may 1502 * or may not work depending on the state of the cpu at the point it was 1503 * stopped. 1504 */ 1505 void 1506 lwkt_smp_stopped(void) 1507 { 1508 globaldata_t gd = mycpu; 1509 1510 crit_enter_gd(gd); 1511 if (dumping) { 1512 lwkt_process_ipiq(); 1513 splz(); 1514 } else { 1515 lwkt_process_ipiq(); 1516 } 1517 crit_exit_gd(gd); 1518 } 1519 1520 #endif 1521