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 <sys/dsched.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 #if !defined(KTR_CTXSW) 75 #define KTR_CTXSW KTR_ALL 76 #endif 77 KTR_INFO_MASTER(ctxsw); 78 KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "sw %p > %p", 2 * sizeof(struct thread *)); 79 KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "pre %p > %p", 2 * sizeof(struct thread *)); 80 KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "new_td %p %s", sizeof (struct thread *) + 81 sizeof(char *)); 82 KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "dead_td %p", sizeof (struct thread *)); 83 84 static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads"); 85 86 #ifdef INVARIANTS 87 static int panic_on_cscount = 0; 88 #endif 89 static __int64_t switch_count = 0; 90 static __int64_t preempt_hit = 0; 91 static __int64_t preempt_miss = 0; 92 static __int64_t preempt_weird = 0; 93 static __int64_t token_contention_count __debugvar = 0; 94 static int lwkt_use_spin_port; 95 static struct objcache *thread_cache; 96 97 #ifdef SMP 98 static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame); 99 #endif 100 101 extern void cpu_heavy_restore(void); 102 extern void cpu_lwkt_restore(void); 103 extern void cpu_kthread_restore(void); 104 extern void cpu_idle_restore(void); 105 106 #ifdef __x86_64__ 107 108 static int 109 jg_tos_ok(struct thread *td) 110 { 111 void *tos; 112 int tos_ok; 113 114 if (td == NULL) { 115 return 1; 116 } 117 KKASSERT(td->td_sp != NULL); 118 tos = ((void **)td->td_sp)[0]; 119 tos_ok = 0; 120 if ((tos == cpu_heavy_restore) || (tos == cpu_lwkt_restore) || 121 (tos == cpu_kthread_restore) || (tos == cpu_idle_restore)) { 122 tos_ok = 1; 123 } 124 return tos_ok; 125 } 126 127 #endif 128 129 /* 130 * We can make all thread ports use the spin backend instead of the thread 131 * backend. This should only be set to debug the spin backend. 132 */ 133 TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port); 134 135 #ifdef INVARIANTS 136 SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, ""); 137 #endif 138 SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, ""); 139 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, ""); 140 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, ""); 141 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, ""); 142 #ifdef INVARIANTS 143 SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count, CTLFLAG_RW, 144 &token_contention_count, 0, "spinning due to token contention"); 145 #endif 146 147 /* 148 * These helper procedures handle the runq, they can only be called from 149 * within a critical section. 150 * 151 * WARNING! Prior to SMP being brought up it is possible to enqueue and 152 * dequeue threads belonging to other cpus, so be sure to use td->td_gd 153 * instead of 'mycpu' when referencing the globaldata structure. Once 154 * SMP live enqueuing and dequeueing only occurs on the current cpu. 155 */ 156 static __inline 157 void 158 _lwkt_dequeue(thread_t td) 159 { 160 if (td->td_flags & TDF_RUNQ) { 161 int nq = td->td_pri & TDPRI_MASK; 162 struct globaldata *gd = td->td_gd; 163 164 td->td_flags &= ~TDF_RUNQ; 165 TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq); 166 /* runqmask is passively cleaned up by the switcher */ 167 } 168 } 169 170 static __inline 171 void 172 _lwkt_enqueue(thread_t td) 173 { 174 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) { 175 int nq = td->td_pri & TDPRI_MASK; 176 struct globaldata *gd = td->td_gd; 177 178 td->td_flags |= TDF_RUNQ; 179 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq); 180 gd->gd_runqmask |= 1 << nq; 181 } 182 } 183 184 static __boolean_t 185 _lwkt_thread_ctor(void *obj, void *privdata, int ocflags) 186 { 187 struct thread *td = (struct thread *)obj; 188 189 td->td_kstack = NULL; 190 td->td_kstack_size = 0; 191 td->td_flags = TDF_ALLOCATED_THREAD; 192 return (1); 193 } 194 195 static void 196 _lwkt_thread_dtor(void *obj, void *privdata) 197 { 198 struct thread *td = (struct thread *)obj; 199 200 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD, 201 ("_lwkt_thread_dtor: not allocated from objcache")); 202 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack && 203 td->td_kstack_size > 0, 204 ("_lwkt_thread_dtor: corrupted stack")); 205 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); 206 } 207 208 /* 209 * Initialize the lwkt s/system. 210 */ 211 void 212 lwkt_init(void) 213 { 214 /* An objcache has 2 magazines per CPU so divide cache size by 2. */ 215 thread_cache = objcache_create_mbacked(M_THREAD, sizeof(struct thread), 216 NULL, CACHE_NTHREADS/2, 217 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL); 218 } 219 220 /* 221 * Schedule a thread to run. As the current thread we can always safely 222 * schedule ourselves, and a shortcut procedure is provided for that 223 * function. 224 * 225 * (non-blocking, self contained on a per cpu basis) 226 */ 227 void 228 lwkt_schedule_self(thread_t td) 229 { 230 crit_enter_quick(td); 231 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!")); 232 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 233 _lwkt_enqueue(td); 234 crit_exit_quick(td); 235 } 236 237 /* 238 * Deschedule a thread. 239 * 240 * (non-blocking, self contained on a per cpu basis) 241 */ 242 void 243 lwkt_deschedule_self(thread_t td) 244 { 245 crit_enter_quick(td); 246 _lwkt_dequeue(td); 247 crit_exit_quick(td); 248 } 249 250 /* 251 * LWKTs operate on a per-cpu basis 252 * 253 * WARNING! Called from early boot, 'mycpu' may not work yet. 254 */ 255 void 256 lwkt_gdinit(struct globaldata *gd) 257 { 258 int i; 259 260 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i) 261 TAILQ_INIT(&gd->gd_tdrunq[i]); 262 gd->gd_runqmask = 0; 263 TAILQ_INIT(&gd->gd_tdallq); 264 } 265 266 /* 267 * Create a new thread. The thread must be associated with a process context 268 * or LWKT start address before it can be scheduled. If the target cpu is 269 * -1 the thread will be created on the current cpu. 270 * 271 * If you intend to create a thread without a process context this function 272 * does everything except load the startup and switcher function. 273 */ 274 thread_t 275 lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags) 276 { 277 globaldata_t gd = mycpu; 278 void *stack; 279 280 /* 281 * If static thread storage is not supplied allocate a thread. Reuse 282 * a cached free thread if possible. gd_freetd is used to keep an exiting 283 * thread intact through the exit. 284 */ 285 if (td == NULL) { 286 if ((td = gd->gd_freetd) != NULL) 287 gd->gd_freetd = NULL; 288 else 289 td = objcache_get(thread_cache, M_WAITOK); 290 KASSERT((td->td_flags & 291 (TDF_ALLOCATED_THREAD|TDF_RUNNING)) == TDF_ALLOCATED_THREAD, 292 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags)); 293 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK); 294 } 295 296 /* 297 * Try to reuse cached stack. 298 */ 299 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) { 300 if (flags & TDF_ALLOCATED_STACK) { 301 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size); 302 stack = NULL; 303 } 304 } 305 if (stack == NULL) { 306 stack = (void *)kmem_alloc(&kernel_map, stksize); 307 flags |= TDF_ALLOCATED_STACK; 308 } 309 if (cpu < 0) 310 lwkt_init_thread(td, stack, stksize, flags, gd); 311 else 312 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu)); 313 return(td); 314 } 315 316 /* 317 * Initialize a preexisting thread structure. This function is used by 318 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread. 319 * 320 * All threads start out in a critical section at a priority of 321 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as 322 * appropriate. This function may send an IPI message when the 323 * requested cpu is not the current cpu and consequently gd_tdallq may 324 * not be initialized synchronously from the point of view of the originating 325 * cpu. 326 * 327 * NOTE! we have to be careful in regards to creating threads for other cpus 328 * if SMP has not yet been activated. 329 */ 330 #ifdef SMP 331 332 static void 333 lwkt_init_thread_remote(void *arg) 334 { 335 thread_t td = arg; 336 337 /* 338 * Protected by critical section held by IPI dispatch 339 */ 340 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq); 341 } 342 343 #endif 344 345 void 346 lwkt_init_thread(thread_t td, void *stack, int stksize, int flags, 347 struct globaldata *gd) 348 { 349 globaldata_t mygd = mycpu; 350 351 bzero(td, sizeof(struct thread)); 352 td->td_kstack = stack; 353 td->td_kstack_size = stksize; 354 td->td_flags = flags; 355 td->td_gd = gd; 356 td->td_pri = TDPRI_KERN_DAEMON + TDPRI_CRIT; 357 #ifdef SMP 358 if ((flags & TDF_MPSAFE) == 0) 359 td->td_mpcount = 1; 360 #endif 361 if (lwkt_use_spin_port) 362 lwkt_initport_spin(&td->td_msgport); 363 else 364 lwkt_initport_thread(&td->td_msgport, td); 365 pmap_init_thread(td); 366 #ifdef SMP 367 /* 368 * Normally initializing a thread for a remote cpu requires sending an 369 * IPI. However, the idlethread is setup before the other cpus are 370 * activated so we have to treat it as a special case. XXX manipulation 371 * of gd_tdallq requires the BGL. 372 */ 373 if (gd == mygd || td == &gd->gd_idlethread) { 374 crit_enter_gd(mygd); 375 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 376 crit_exit_gd(mygd); 377 } else { 378 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td); 379 } 380 #else 381 crit_enter_gd(mygd); 382 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); 383 crit_exit_gd(mygd); 384 #endif 385 386 dsched_new_thread(td); 387 } 388 389 void 390 lwkt_set_comm(thread_t td, const char *ctl, ...) 391 { 392 __va_list va; 393 394 __va_start(va, ctl); 395 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va); 396 __va_end(va); 397 KTR_LOG(ctxsw_newtd, td, &td->td_comm[0]); 398 } 399 400 void 401 lwkt_hold(thread_t td) 402 { 403 ++td->td_refs; 404 } 405 406 void 407 lwkt_rele(thread_t td) 408 { 409 KKASSERT(td->td_refs > 0); 410 --td->td_refs; 411 } 412 413 void 414 lwkt_wait_free(thread_t td) 415 { 416 while (td->td_refs) 417 tsleep(td, 0, "tdreap", hz); 418 } 419 420 void 421 lwkt_free_thread(thread_t td) 422 { 423 KASSERT((td->td_flags & TDF_RUNNING) == 0, 424 ("lwkt_free_thread: did not exit! %p", td)); 425 426 if (td->td_flags & TDF_ALLOCATED_THREAD) { 427 objcache_put(thread_cache, td); 428 } else if (td->td_flags & TDF_ALLOCATED_STACK) { 429 /* client-allocated struct with internally allocated stack */ 430 KASSERT(td->td_kstack && td->td_kstack_size > 0, 431 ("lwkt_free_thread: corrupted stack")); 432 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); 433 td->td_kstack = NULL; 434 td->td_kstack_size = 0; 435 } 436 KTR_LOG(ctxsw_deadtd, td); 437 } 438 439 440 /* 441 * Switch to the next runnable lwkt. If no LWKTs are runnable then 442 * switch to the idlethread. Switching must occur within a critical 443 * section to avoid races with the scheduling queue. 444 * 445 * We always have full control over our cpu's run queue. Other cpus 446 * that wish to manipulate our queue must use the cpu_*msg() calls to 447 * talk to our cpu, so a critical section is all that is needed and 448 * the result is very, very fast thread switching. 449 * 450 * The LWKT scheduler uses a fixed priority model and round-robins at 451 * each priority level. User process scheduling is a totally 452 * different beast and LWKT priorities should not be confused with 453 * user process priorities. 454 * 455 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch() 456 * cleans it up. Note that the td_switch() function cannot do anything that 457 * requires the MP lock since the MP lock will have already been setup for 458 * the target thread (not the current thread). It's nice to have a scheduler 459 * that does not need the MP lock to work because it allows us to do some 460 * really cool high-performance MP lock optimizations. 461 * 462 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch() 463 * is not called by the current thread in the preemption case, only when 464 * the preempting thread blocks (in order to return to the original thread). 465 */ 466 void 467 lwkt_switch(void) 468 { 469 globaldata_t gd = mycpu; 470 thread_t td = gd->gd_curthread; 471 thread_t ntd; 472 #ifdef SMP 473 int mpheld; 474 #endif 475 476 /* 477 * Switching from within a 'fast' (non thread switched) interrupt or IPI 478 * is illegal. However, we may have to do it anyway if we hit a fatal 479 * kernel trap or we have paniced. 480 * 481 * If this case occurs save and restore the interrupt nesting level. 482 */ 483 if (gd->gd_intr_nesting_level) { 484 int savegdnest; 485 int savegdtrap; 486 487 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) { 488 panic("lwkt_switch: cannot switch from within " 489 "a fast interrupt, yet, td %p\n", td); 490 } else { 491 savegdnest = gd->gd_intr_nesting_level; 492 savegdtrap = gd->gd_trap_nesting_level; 493 gd->gd_intr_nesting_level = 0; 494 gd->gd_trap_nesting_level = 0; 495 if ((td->td_flags & TDF_PANICWARN) == 0) { 496 td->td_flags |= TDF_PANICWARN; 497 kprintf("Warning: thread switch from interrupt or IPI, " 498 "thread %p (%s)\n", td, td->td_comm); 499 print_backtrace(-1); 500 } 501 lwkt_switch(); 502 gd->gd_intr_nesting_level = savegdnest; 503 gd->gd_trap_nesting_level = savegdtrap; 504 return; 505 } 506 } 507 508 /* 509 * Passive release (used to transition from user to kernel mode 510 * when we block or switch rather then when we enter the kernel). 511 * This function is NOT called if we are switching into a preemption 512 * or returning from a preemption. Typically this causes us to lose 513 * our current process designation (if we have one) and become a true 514 * LWKT thread, and may also hand the current process designation to 515 * another process and schedule thread. 516 */ 517 if (td->td_release) 518 td->td_release(td); 519 520 crit_enter_gd(gd); 521 if (td->td_toks) 522 lwkt_relalltokens(td); 523 524 /* 525 * We had better not be holding any spin locks, but don't get into an 526 * endless panic loop. 527 */ 528 KASSERT(gd->gd_spinlock_rd == NULL || panicstr != NULL, 529 ("lwkt_switch: still holding a shared spinlock %p!", 530 gd->gd_spinlock_rd)); 531 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL, 532 ("lwkt_switch: still holding %d exclusive spinlocks!", 533 gd->gd_spinlocks_wr)); 534 535 536 #ifdef SMP 537 /* 538 * td_mpcount cannot be used to determine if we currently hold the 539 * MP lock because get_mplock() will increment it prior to attempting 540 * to get the lock, and switch out if it can't. Our ownership of 541 * the actual lock will remain stable while we are in a critical section 542 * (but, of course, another cpu may own or release the lock so the 543 * actual value of mp_lock is not stable). 544 */ 545 mpheld = MP_LOCK_HELD(); 546 #ifdef INVARIANTS 547 if (td->td_cscount) { 548 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n", 549 td); 550 if (panic_on_cscount) 551 panic("switching while mastering cpusync"); 552 } 553 #endif 554 #endif 555 if ((ntd = td->td_preempted) != NULL) { 556 /* 557 * We had preempted another thread on this cpu, resume the preempted 558 * thread. This occurs transparently, whether the preempted thread 559 * was scheduled or not (it may have been preempted after descheduling 560 * itself). 561 * 562 * We have to setup the MP lock for the original thread after backing 563 * out the adjustment that was made to curthread when the original 564 * was preempted. 565 */ 566 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK); 567 #ifdef SMP 568 if (ntd->td_mpcount && mpheld == 0) { 569 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d", 570 td, ntd, td->td_mpcount, ntd->td_mpcount); 571 } 572 if (ntd->td_mpcount) { 573 td->td_mpcount -= ntd->td_mpcount; 574 KKASSERT(td->td_mpcount >= 0); 575 } 576 #endif 577 ntd->td_flags |= TDF_PREEMPT_DONE; 578 579 /* 580 * The interrupt may have woken a thread up, we need to properly 581 * set the reschedule flag if the originally interrupted thread is 582 * at a lower priority. 583 */ 584 if (gd->gd_runqmask > (2 << (ntd->td_pri & TDPRI_MASK)) - 1) 585 need_lwkt_resched(); 586 /* YYY release mp lock on switchback if original doesn't need it */ 587 } else { 588 /* 589 * Priority queue / round-robin at each priority. Note that user 590 * processes run at a fixed, low priority and the user process 591 * scheduler deals with interactions between user processes 592 * by scheduling and descheduling them from the LWKT queue as 593 * necessary. 594 * 595 * We have to adjust the MP lock for the target thread. If we 596 * need the MP lock and cannot obtain it we try to locate a 597 * thread that does not need the MP lock. If we cannot, we spin 598 * instead of HLT. 599 * 600 * A similar issue exists for the tokens held by the target thread. 601 * If we cannot obtain ownership of the tokens we cannot immediately 602 * schedule the thread. 603 */ 604 605 /* 606 * If an LWKT reschedule was requested, well that is what we are 607 * doing now so clear it. 608 */ 609 clear_lwkt_resched(); 610 again: 611 if (gd->gd_runqmask) { 612 int nq = bsrl(gd->gd_runqmask); 613 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) { 614 gd->gd_runqmask &= ~(1 << nq); 615 goto again; 616 } 617 #ifdef SMP 618 /* 619 * THREAD SELECTION FOR AN SMP MACHINE BUILD 620 * 621 * If the target needs the MP lock and we couldn't get it, 622 * or if the target is holding tokens and we could not 623 * gain ownership of the tokens, continue looking for a 624 * thread to schedule and spin instead of HLT if we can't. 625 * 626 * NOTE: the mpheld variable invalid after this conditional, it 627 * can change due to both cpu_try_mplock() returning success 628 * AND interactions in lwkt_getalltokens() due to the fact that 629 * we are trying to check the mpcount of a thread other then 630 * the current thread. Because of this, if the current thread 631 * is not holding td_mpcount, an IPI indirectly run via 632 * lwkt_getalltokens() can obtain and release the MP lock and 633 * cause the core MP lock to be released. 634 */ 635 if ((ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) || 636 (ntd->td_toks && lwkt_getalltokens(ntd) == 0) 637 ) { 638 u_int32_t rqmask = gd->gd_runqmask; 639 640 mpheld = MP_LOCK_HELD(); 641 ntd = NULL; 642 while (rqmask) { 643 TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) { 644 if (ntd->td_mpcount && !mpheld && !cpu_try_mplock()) { 645 /* spinning due to MP lock being held */ 646 continue; 647 } 648 649 /* 650 * mpheld state invalid after getalltokens call returns 651 * failure, but the variable is only needed for 652 * the loop. 653 */ 654 if (ntd->td_toks && !lwkt_getalltokens(ntd)) { 655 /* spinning due to token contention */ 656 #ifdef INVARIANTS 657 ++token_contention_count; 658 #endif 659 mpheld = MP_LOCK_HELD(); 660 continue; 661 } 662 break; 663 } 664 if (ntd) 665 break; 666 rqmask &= ~(1 << nq); 667 nq = bsrl(rqmask); 668 669 /* 670 * We have two choices. We can either refuse to run a 671 * user thread when a kernel thread needs the MP lock 672 * but could not get it, or we can allow it to run but 673 * then expect an IPI (hopefully) later on to force a 674 * reschedule when the MP lock might become available. 675 */ 676 if (nq < TDPRI_KERN_LPSCHED) { 677 break; /* for now refuse to run */ 678 #if 0 679 if (chain_mplock == 0) 680 break; 681 /* continue loop, allow user threads to be scheduled */ 682 #endif 683 } 684 } 685 686 /* 687 * Case where a (kernel) thread needed the MP lock and could 688 * not get one, and we may or may not have found another 689 * thread which does not need the MP lock to run while 690 * we wait (ntd). 691 */ 692 if (ntd == NULL) { 693 ntd = &gd->gd_idlethread; 694 ntd->td_flags |= TDF_IDLE_NOHLT; 695 set_mplock_contention_mask(gd); 696 cpu_mplock_contested(); 697 goto using_idle_thread; 698 } else { 699 clr_mplock_contention_mask(gd); 700 ++gd->gd_cnt.v_swtch; 701 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 702 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 703 } 704 } else { 705 clr_mplock_contention_mask(gd); 706 ++gd->gd_cnt.v_swtch; 707 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 708 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 709 } 710 #else 711 /* 712 * THREAD SELECTION FOR A UP MACHINE BUILD. We don't have to 713 * worry about tokens or the BGL. However, we still have 714 * to call lwkt_getalltokens() in order to properly detect 715 * stale tokens. This call cannot fail for a UP build! 716 */ 717 lwkt_getalltokens(ntd); 718 ++gd->gd_cnt.v_swtch; 719 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); 720 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); 721 #endif 722 } else { 723 /* 724 * We have nothing to run but only let the idle loop halt 725 * the cpu if there are no pending interrupts. 726 */ 727 ntd = &gd->gd_idlethread; 728 if (gd->gd_reqflags & RQF_IDLECHECK_MASK) 729 ntd->td_flags |= TDF_IDLE_NOHLT; 730 #ifdef SMP 731 using_idle_thread: 732 /* 733 * The idle thread should not be holding the MP lock unless we 734 * are trapping in the kernel or in a panic. Since we select the 735 * idle thread unconditionally when no other thread is available, 736 * if the MP lock is desired during a panic or kernel trap, we 737 * have to loop in the scheduler until we get it. 738 */ 739 if (ntd->td_mpcount) { 740 mpheld = MP_LOCK_HELD(); 741 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) 742 panic("Idle thread %p was holding the BGL!", ntd); 743 if (mpheld == 0) 744 goto again; 745 } 746 #endif 747 } 748 } 749 KASSERT(ntd->td_pri >= TDPRI_CRIT, 750 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri)); 751 752 /* 753 * Do the actual switch. If the new target does not need the MP lock 754 * and we are holding it, release the MP lock. If the new target requires 755 * the MP lock we have already acquired it for the target. 756 */ 757 #ifdef SMP 758 if (ntd->td_mpcount == 0 ) { 759 if (MP_LOCK_HELD()) 760 cpu_rel_mplock(); 761 } else { 762 ASSERT_MP_LOCK_HELD(ntd); 763 } 764 #endif 765 if (td != ntd) { 766 ++switch_count; 767 #ifdef __x86_64__ 768 { 769 int tos_ok __debugvar = jg_tos_ok(ntd); 770 KKASSERT(tos_ok); 771 } 772 #endif 773 KTR_LOG(ctxsw_sw, td, ntd); 774 td->td_switch(ntd); 775 } 776 /* NOTE: current cpu may have changed after switch */ 777 crit_exit_quick(td); 778 } 779 780 /* 781 * Request that the target thread preempt the current thread. Preemption 782 * only works under a specific set of conditions: 783 * 784 * - We are not preempting ourselves 785 * - The target thread is owned by the current cpu 786 * - We are not currently being preempted 787 * - The target is not currently being preempted 788 * - We are not holding any spin locks 789 * - The target thread is not holding any tokens 790 * - We are able to satisfy the target's MP lock requirements (if any). 791 * 792 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically 793 * this is called via lwkt_schedule() through the td_preemptable callback. 794 * critpri is the managed critical priority that we should ignore in order 795 * to determine whether preemption is possible (aka usually just the crit 796 * priority of lwkt_schedule() itself). 797 * 798 * XXX at the moment we run the target thread in a critical section during 799 * the preemption in order to prevent the target from taking interrupts 800 * that *WE* can't. Preemption is strictly limited to interrupt threads 801 * and interrupt-like threads, outside of a critical section, and the 802 * preempted source thread will be resumed the instant the target blocks 803 * whether or not the source is scheduled (i.e. preemption is supposed to 804 * be as transparent as possible). 805 * 806 * The target thread inherits our MP count (added to its own) for the 807 * duration of the preemption in order to preserve the atomicy of the 808 * MP lock during the preemption. Therefore, any preempting targets must be 809 * careful in regards to MP assertions. Note that the MP count may be 810 * out of sync with the physical mp_lock, but we do not have to preserve 811 * the original ownership of the lock if it was out of synch (that is, we 812 * can leave it synchronized on return). 813 */ 814 void 815 lwkt_preempt(thread_t ntd, int critpri) 816 { 817 struct globaldata *gd = mycpu; 818 thread_t td; 819 #ifdef SMP 820 int mpheld; 821 int savecnt; 822 #endif 823 824 /* 825 * The caller has put us in a critical section. We can only preempt 826 * if the caller of the caller was not in a critical section (basically 827 * a local interrupt), as determined by the 'critpri' parameter. We 828 * also can't preempt if the caller is holding any spinlocks (even if 829 * he isn't in a critical section). This also handles the tokens test. 830 * 831 * YYY The target thread must be in a critical section (else it must 832 * inherit our critical section? I dunno yet). 833 * 834 * Set need_lwkt_resched() unconditionally for now YYY. 835 */ 836 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri)); 837 838 td = gd->gd_curthread; 839 if ((ntd->td_pri & TDPRI_MASK) <= (td->td_pri & TDPRI_MASK)) { 840 ++preempt_miss; 841 return; 842 } 843 if ((td->td_pri & ~TDPRI_MASK) > critpri) { 844 ++preempt_miss; 845 need_lwkt_resched(); 846 return; 847 } 848 #ifdef SMP 849 if (ntd->td_gd != gd) { 850 ++preempt_miss; 851 need_lwkt_resched(); 852 return; 853 } 854 #endif 855 /* 856 * Take the easy way out and do not preempt if we are holding 857 * any spinlocks. We could test whether the thread(s) being 858 * preempted interlock against the target thread's tokens and whether 859 * we can get all the target thread's tokens, but this situation 860 * should not occur very often so its easier to simply not preempt. 861 * Also, plain spinlocks are impossible to figure out at this point so 862 * just don't preempt. 863 * 864 * Do not try to preempt if the target thread is holding any tokens. 865 * We could try to acquire the tokens but this case is so rare there 866 * is no need to support it. 867 */ 868 if (gd->gd_spinlock_rd || gd->gd_spinlocks_wr) { 869 ++preempt_miss; 870 need_lwkt_resched(); 871 return; 872 } 873 if (ntd->td_toks) { 874 ++preempt_miss; 875 need_lwkt_resched(); 876 return; 877 } 878 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) { 879 ++preempt_weird; 880 need_lwkt_resched(); 881 return; 882 } 883 if (ntd->td_preempted) { 884 ++preempt_hit; 885 need_lwkt_resched(); 886 return; 887 } 888 #ifdef SMP 889 /* 890 * note: an interrupt might have occured just as we were transitioning 891 * to or from the MP lock. In this case td_mpcount will be pre-disposed 892 * (non-zero) but not actually synchronized with the actual state of the 893 * lock. We can use it to imply an MP lock requirement for the 894 * preemption but we cannot use it to test whether we hold the MP lock 895 * or not. 896 */ 897 savecnt = td->td_mpcount; 898 mpheld = MP_LOCK_HELD(); 899 ntd->td_mpcount += td->td_mpcount; 900 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) { 901 ntd->td_mpcount -= td->td_mpcount; 902 ++preempt_miss; 903 need_lwkt_resched(); 904 return; 905 } 906 #endif 907 908 /* 909 * Since we are able to preempt the current thread, there is no need to 910 * call need_lwkt_resched(). 911 */ 912 ++preempt_hit; 913 ntd->td_preempted = td; 914 td->td_flags |= TDF_PREEMPT_LOCK; 915 KTR_LOG(ctxsw_pre, td, ntd); 916 td->td_switch(ntd); 917 918 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE)); 919 #ifdef SMP 920 KKASSERT(savecnt == td->td_mpcount); 921 mpheld = MP_LOCK_HELD(); 922 if (mpheld && td->td_mpcount == 0) 923 cpu_rel_mplock(); 924 else if (mpheld == 0 && td->td_mpcount) 925 panic("lwkt_preempt(): MP lock was not held through"); 926 #endif 927 ntd->td_preempted = NULL; 928 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE); 929 } 930 931 /* 932 * Conditionally call splz() if gd_reqflags indicates work is pending. 933 * 934 * td_nest_count prevents deep nesting via splz() or doreti() which 935 * might otherwise blow out the kernel stack. Note that except for 936 * this special case, we MUST call splz() here to handle any 937 * pending ints, particularly after we switch, or we might accidently 938 * halt the cpu with interrupts pending. 939 * 940 * (self contained on a per cpu basis) 941 */ 942 void 943 splz_check(void) 944 { 945 globaldata_t gd = mycpu; 946 thread_t td = gd->gd_curthread; 947 948 if (gd->gd_reqflags && td->td_nest_count < 2) 949 splz(); 950 } 951 952 /* 953 * This implements a normal yield which will yield to equal priority 954 * threads as well as higher priority threads. Note that gd_reqflags 955 * tests will be handled by the crit_exit() call in lwkt_switch(). 956 * 957 * (self contained on a per cpu basis) 958 */ 959 void 960 lwkt_yield(void) 961 { 962 lwkt_schedule_self(curthread); 963 lwkt_switch(); 964 } 965 966 /* 967 * This function is used along with the lwkt_passive_recover() inline 968 * by the trap code to negotiate a passive release of the current 969 * process/lwp designation with the user scheduler. 970 */ 971 void 972 lwkt_passive_release(struct thread *td) 973 { 974 struct lwp *lp = td->td_lwp; 975 976 td->td_release = NULL; 977 lwkt_setpri_self(TDPRI_KERN_USER); 978 lp->lwp_proc->p_usched->release_curproc(lp); 979 } 980 981 /* 982 * Make a kernel thread act as if it were in user mode with regards 983 * to scheduling, to avoid becoming cpu-bound in the kernel. Kernel 984 * loops which may be potentially cpu-bound can call lwkt_user_yield(). 985 * 986 * The lwkt_user_yield() function is designed to have very low overhead 987 * if no yield is determined to be needed. 988 */ 989 void 990 lwkt_user_yield(void) 991 { 992 thread_t td = curthread; 993 struct lwp *lp = td->td_lwp; 994 995 #ifdef SMP 996 /* 997 * XXX SEVERE TEMPORARY HACK. A cpu-bound operation running in the 998 * kernel can prevent other cpus from servicing interrupt threads 999 * which still require the MP lock (which is a lot of them). This 1000 * has a chaining effect since if the interrupt is blocked, so is 1001 * the event, so normal scheduling will not pick up on the problem. 1002 */ 1003 if (mp_lock_contention_mask && td->td_mpcount) { 1004 yield_mplock(td); 1005 } 1006 #endif 1007 1008 /* 1009 * Another kernel thread wants the cpu 1010 */ 1011 if (lwkt_resched_wanted()) 1012 lwkt_switch(); 1013 1014 /* 1015 * If the user scheduler has asynchronously determined that the current 1016 * process (when running in user mode) needs to lose the cpu then make 1017 * sure we are released. 1018 */ 1019 if (user_resched_wanted()) { 1020 if (td->td_release) 1021 td->td_release(td); 1022 } 1023 1024 /* 1025 * If we are released reduce our priority 1026 */ 1027 if (td->td_release == NULL) { 1028 if (lwkt_check_resched(td) > 0) 1029 lwkt_switch(); 1030 if (lp) { 1031 lp->lwp_proc->p_usched->acquire_curproc(lp); 1032 td->td_release = lwkt_passive_release; 1033 lwkt_setpri_self(TDPRI_USER_NORM); 1034 } 1035 } 1036 } 1037 1038 /* 1039 * Return 0 if no runnable threads are pending at the same or higher 1040 * priority as the passed thread. 1041 * 1042 * Return 1 if runnable threads are pending at the same priority. 1043 * 1044 * Return 2 if runnable threads are pending at a higher priority. 1045 */ 1046 int 1047 lwkt_check_resched(thread_t td) 1048 { 1049 int pri = td->td_pri & TDPRI_MASK; 1050 1051 if (td->td_gd->gd_runqmask > (2 << pri) - 1) 1052 return(2); 1053 if (TAILQ_NEXT(td, td_threadq)) 1054 return(1); 1055 return(0); 1056 } 1057 1058 /* 1059 * Generic schedule. Possibly schedule threads belonging to other cpus and 1060 * deal with threads that might be blocked on a wait queue. 1061 * 1062 * We have a little helper inline function which does additional work after 1063 * the thread has been enqueued, including dealing with preemption and 1064 * setting need_lwkt_resched() (which prevents the kernel from returning 1065 * to userland until it has processed higher priority threads). 1066 * 1067 * It is possible for this routine to be called after a failed _enqueue 1068 * (due to the target thread migrating, sleeping, or otherwise blocked). 1069 * We have to check that the thread is actually on the run queue! 1070 * 1071 * reschedok is an optimized constant propagated from lwkt_schedule() or 1072 * lwkt_schedule_noresched(). By default it is non-zero, causing a 1073 * reschedule to be requested if the target thread has a higher priority. 1074 * The port messaging code will set MSG_NORESCHED and cause reschedok to 1075 * be 0, prevented undesired reschedules. 1076 */ 1077 static __inline 1078 void 1079 _lwkt_schedule_post(globaldata_t gd, thread_t ntd, int cpri, int reschedok) 1080 { 1081 thread_t otd; 1082 1083 if (ntd->td_flags & TDF_RUNQ) { 1084 if (ntd->td_preemptable && reschedok) { 1085 ntd->td_preemptable(ntd, cpri); /* YYY +token */ 1086 } else if (reschedok) { 1087 otd = curthread; 1088 if ((ntd->td_pri & TDPRI_MASK) > (otd->td_pri & TDPRI_MASK)) 1089 need_lwkt_resched(); 1090 } 1091 } 1092 } 1093 1094 static __inline 1095 void 1096 _lwkt_schedule(thread_t td, int reschedok) 1097 { 1098 globaldata_t mygd = mycpu; 1099 1100 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule(): scheduling gd_idlethread is illegal!")); 1101 crit_enter_gd(mygd); 1102 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 1103 if (td == mygd->gd_curthread) { 1104 _lwkt_enqueue(td); 1105 } else { 1106 /* 1107 * If we own the thread, there is no race (since we are in a 1108 * critical section). If we do not own the thread there might 1109 * be a race but the target cpu will deal with it. 1110 */ 1111 #ifdef SMP 1112 if (td->td_gd == mygd) { 1113 _lwkt_enqueue(td); 1114 _lwkt_schedule_post(mygd, td, TDPRI_CRIT, reschedok); 1115 } else { 1116 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0); 1117 } 1118 #else 1119 _lwkt_enqueue(td); 1120 _lwkt_schedule_post(mygd, td, TDPRI_CRIT, reschedok); 1121 #endif 1122 } 1123 crit_exit_gd(mygd); 1124 } 1125 1126 void 1127 lwkt_schedule(thread_t td) 1128 { 1129 _lwkt_schedule(td, 1); 1130 } 1131 1132 void 1133 lwkt_schedule_noresched(thread_t td) 1134 { 1135 _lwkt_schedule(td, 0); 1136 } 1137 1138 #ifdef SMP 1139 1140 /* 1141 * When scheduled remotely if frame != NULL the IPIQ is being 1142 * run via doreti or an interrupt then preemption can be allowed. 1143 * 1144 * To allow preemption we have to drop the critical section so only 1145 * one is present in _lwkt_schedule_post. 1146 */ 1147 static void 1148 lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame) 1149 { 1150 thread_t td = curthread; 1151 thread_t ntd = arg; 1152 1153 if (frame && ntd->td_preemptable) { 1154 crit_exit_noyield(td); 1155 _lwkt_schedule(ntd, 1); 1156 crit_enter_quick(td); 1157 } else { 1158 _lwkt_schedule(ntd, 1); 1159 } 1160 } 1161 1162 /* 1163 * Thread migration using a 'Pull' method. The thread may or may not be 1164 * the current thread. It MUST be descheduled and in a stable state. 1165 * lwkt_giveaway() must be called on the cpu owning the thread. 1166 * 1167 * At any point after lwkt_giveaway() is called, the target cpu may 1168 * 'pull' the thread by calling lwkt_acquire(). 1169 * 1170 * We have to make sure the thread is not sitting on a per-cpu tsleep 1171 * queue or it will blow up when it moves to another cpu. 1172 * 1173 * MPSAFE - must be called under very specific conditions. 1174 */ 1175 void 1176 lwkt_giveaway(thread_t td) 1177 { 1178 globaldata_t gd = mycpu; 1179 1180 crit_enter_gd(gd); 1181 if (td->td_flags & TDF_TSLEEPQ) 1182 tsleep_remove(td); 1183 KKASSERT(td->td_gd == gd); 1184 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); 1185 td->td_flags |= TDF_MIGRATING; 1186 crit_exit_gd(gd); 1187 } 1188 1189 void 1190 lwkt_acquire(thread_t td) 1191 { 1192 globaldata_t gd; 1193 globaldata_t mygd; 1194 1195 KKASSERT(td->td_flags & TDF_MIGRATING); 1196 gd = td->td_gd; 1197 mygd = mycpu; 1198 if (gd != mycpu) { 1199 cpu_lfence(); 1200 KKASSERT((td->td_flags & TDF_RUNQ) == 0); 1201 crit_enter_gd(mygd); 1202 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) { 1203 #ifdef SMP 1204 lwkt_process_ipiq(); 1205 #endif 1206 cpu_lfence(); 1207 } 1208 td->td_gd = mygd; 1209 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1210 td->td_flags &= ~TDF_MIGRATING; 1211 crit_exit_gd(mygd); 1212 } else { 1213 crit_enter_gd(mygd); 1214 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); 1215 td->td_flags &= ~TDF_MIGRATING; 1216 crit_exit_gd(mygd); 1217 } 1218 } 1219 1220 #endif 1221 1222 /* 1223 * Generic deschedule. Descheduling threads other then your own should be 1224 * done only in carefully controlled circumstances. Descheduling is 1225 * asynchronous. 1226 * 1227 * This function may block if the cpu has run out of messages. 1228 */ 1229 void 1230 lwkt_deschedule(thread_t td) 1231 { 1232 crit_enter(); 1233 #ifdef SMP 1234 if (td == curthread) { 1235 _lwkt_dequeue(td); 1236 } else { 1237 if (td->td_gd == mycpu) { 1238 _lwkt_dequeue(td); 1239 } else { 1240 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td); 1241 } 1242 } 1243 #else 1244 _lwkt_dequeue(td); 1245 #endif 1246 crit_exit(); 1247 } 1248 1249 /* 1250 * Set the target thread's priority. This routine does not automatically 1251 * switch to a higher priority thread, LWKT threads are not designed for 1252 * continuous priority changes. Yield if you want to switch. 1253 * 1254 * We have to retain the critical section count which uses the high bits 1255 * of the td_pri field. The specified priority may also indicate zero or 1256 * more critical sections by adding TDPRI_CRIT*N. 1257 * 1258 * Note that we requeue the thread whether it winds up on a different runq 1259 * or not. uio_yield() depends on this and the routine is not normally 1260 * called with the same priority otherwise. 1261 */ 1262 void 1263 lwkt_setpri(thread_t td, int pri) 1264 { 1265 KKASSERT(pri >= 0); 1266 KKASSERT(td->td_gd == mycpu); 1267 crit_enter(); 1268 if (td->td_flags & TDF_RUNQ) { 1269 _lwkt_dequeue(td); 1270 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1271 _lwkt_enqueue(td); 1272 } else { 1273 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1274 } 1275 crit_exit(); 1276 } 1277 1278 /* 1279 * Set the initial priority for a thread prior to it being scheduled for 1280 * the first time. The thread MUST NOT be scheduled before or during 1281 * this call. The thread may be assigned to a cpu other then the current 1282 * cpu. 1283 * 1284 * Typically used after a thread has been created with TDF_STOPPREQ, 1285 * and before the thread is initially scheduled. 1286 */ 1287 void 1288 lwkt_setpri_initial(thread_t td, int pri) 1289 { 1290 KKASSERT(pri >= 0); 1291 KKASSERT((td->td_flags & TDF_RUNQ) == 0); 1292 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1293 } 1294 1295 void 1296 lwkt_setpri_self(int pri) 1297 { 1298 thread_t td = curthread; 1299 1300 KKASSERT(pri >= 0 && pri <= TDPRI_MAX); 1301 crit_enter(); 1302 if (td->td_flags & TDF_RUNQ) { 1303 _lwkt_dequeue(td); 1304 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1305 _lwkt_enqueue(td); 1306 } else { 1307 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; 1308 } 1309 crit_exit(); 1310 } 1311 1312 /* 1313 * Migrate the current thread to the specified cpu. 1314 * 1315 * This is accomplished by descheduling ourselves from the current cpu, 1316 * moving our thread to the tdallq of the target cpu, IPI messaging the 1317 * target cpu, and switching out. TDF_MIGRATING prevents scheduling 1318 * races while the thread is being migrated. 1319 * 1320 * We must be sure to remove ourselves from the current cpu's tsleepq 1321 * before potentially moving to another queue. The thread can be on 1322 * a tsleepq due to a left-over tsleep_interlock(). 1323 */ 1324 #ifdef SMP 1325 static void lwkt_setcpu_remote(void *arg); 1326 #endif 1327 1328 void 1329 lwkt_setcpu_self(globaldata_t rgd) 1330 { 1331 #ifdef SMP 1332 thread_t td = curthread; 1333 1334 if (td->td_gd != rgd) { 1335 crit_enter_quick(td); 1336 if (td->td_flags & TDF_TSLEEPQ) 1337 tsleep_remove(td); 1338 td->td_flags |= TDF_MIGRATING; 1339 lwkt_deschedule_self(td); 1340 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1341 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td); 1342 lwkt_switch(); 1343 /* we are now on the target cpu */ 1344 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq); 1345 crit_exit_quick(td); 1346 } 1347 #endif 1348 } 1349 1350 void 1351 lwkt_migratecpu(int cpuid) 1352 { 1353 #ifdef SMP 1354 globaldata_t rgd; 1355 1356 rgd = globaldata_find(cpuid); 1357 lwkt_setcpu_self(rgd); 1358 #endif 1359 } 1360 1361 /* 1362 * Remote IPI for cpu migration (called while in a critical section so we 1363 * do not have to enter another one). The thread has already been moved to 1364 * our cpu's allq, but we must wait for the thread to be completely switched 1365 * out on the originating cpu before we schedule it on ours or the stack 1366 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD 1367 * change to main memory. 1368 * 1369 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races 1370 * against wakeups. It is best if this interface is used only when there 1371 * are no pending events that might try to schedule the thread. 1372 */ 1373 #ifdef SMP 1374 static void 1375 lwkt_setcpu_remote(void *arg) 1376 { 1377 thread_t td = arg; 1378 globaldata_t gd = mycpu; 1379 1380 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) { 1381 #ifdef SMP 1382 lwkt_process_ipiq(); 1383 #endif 1384 cpu_lfence(); 1385 } 1386 td->td_gd = gd; 1387 cpu_sfence(); 1388 td->td_flags &= ~TDF_MIGRATING; 1389 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0); 1390 _lwkt_enqueue(td); 1391 } 1392 #endif 1393 1394 struct lwp * 1395 lwkt_preempted_proc(void) 1396 { 1397 thread_t td = curthread; 1398 while (td->td_preempted) 1399 td = td->td_preempted; 1400 return(td->td_lwp); 1401 } 1402 1403 /* 1404 * Create a kernel process/thread/whatever. It shares it's address space 1405 * with proc0 - ie: kernel only. 1406 * 1407 * NOTE! By default new threads are created with the MP lock held. A 1408 * thread which does not require the MP lock should release it by calling 1409 * rel_mplock() at the start of the new thread. 1410 */ 1411 int 1412 lwkt_create(void (*func)(void *), void *arg, 1413 struct thread **tdp, thread_t template, int tdflags, int cpu, 1414 const char *fmt, ...) 1415 { 1416 thread_t td; 1417 __va_list ap; 1418 1419 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu, 1420 tdflags); 1421 if (tdp) 1422 *tdp = td; 1423 cpu_set_thread_handler(td, lwkt_exit, func, arg); 1424 1425 /* 1426 * Set up arg0 for 'ps' etc 1427 */ 1428 __va_start(ap, fmt); 1429 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap); 1430 __va_end(ap); 1431 1432 /* 1433 * Schedule the thread to run 1434 */ 1435 if ((td->td_flags & TDF_STOPREQ) == 0) 1436 lwkt_schedule(td); 1437 else 1438 td->td_flags &= ~TDF_STOPREQ; 1439 return 0; 1440 } 1441 1442 /* 1443 * Destroy an LWKT thread. Warning! This function is not called when 1444 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and 1445 * uses a different reaping mechanism. 1446 */ 1447 void 1448 lwkt_exit(void) 1449 { 1450 thread_t td = curthread; 1451 thread_t std; 1452 globaldata_t gd; 1453 1454 if (td->td_flags & TDF_VERBOSE) 1455 kprintf("kthread %p %s has exited\n", td, td->td_comm); 1456 caps_exit(td); 1457 1458 /* 1459 * Get us into a critical section to interlock gd_freetd and loop 1460 * until we can get it freed. 1461 * 1462 * We have to cache the current td in gd_freetd because objcache_put()ing 1463 * it would rip it out from under us while our thread is still active. 1464 */ 1465 gd = mycpu; 1466 crit_enter_quick(td); 1467 while ((std = gd->gd_freetd) != NULL) { 1468 gd->gd_freetd = NULL; 1469 objcache_put(thread_cache, std); 1470 } 1471 1472 /* 1473 * Remove thread resources from kernel lists and deschedule us for 1474 * the last time. 1475 */ 1476 if (td->td_flags & TDF_TSLEEPQ) 1477 tsleep_remove(td); 1478 biosched_done(td); 1479 dsched_exit_thread(td); 1480 lwkt_deschedule_self(td); 1481 lwkt_remove_tdallq(td); 1482 if (td->td_flags & TDF_ALLOCATED_THREAD) 1483 gd->gd_freetd = td; 1484 cpu_thread_exit(); 1485 } 1486 1487 void 1488 lwkt_remove_tdallq(thread_t td) 1489 { 1490 KKASSERT(td->td_gd == mycpu); 1491 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); 1492 } 1493 1494 void 1495 crit_panic(void) 1496 { 1497 thread_t td = curthread; 1498 int lpri = td->td_pri; 1499 1500 td->td_pri = 0; 1501 panic("td_pri is/would-go negative! %p %d", td, lpri); 1502 } 1503 1504 #ifdef SMP 1505 1506 /* 1507 * Called from debugger/panic on cpus which have been stopped. We must still 1508 * process the IPIQ while stopped, even if we were stopped while in a critical 1509 * section (XXX). 1510 * 1511 * If we are dumping also try to process any pending interrupts. This may 1512 * or may not work depending on the state of the cpu at the point it was 1513 * stopped. 1514 */ 1515 void 1516 lwkt_smp_stopped(void) 1517 { 1518 globaldata_t gd = mycpu; 1519 1520 crit_enter_gd(gd); 1521 if (dumping) { 1522 lwkt_process_ipiq(); 1523 splz(); 1524 } else { 1525 lwkt_process_ipiq(); 1526 } 1527 crit_exit_gd(gd); 1528 } 1529 1530 #endif 1531