| 1 | /* |
| 2 | * Copyright (c) 2003 Matthew Dillon <dillon@backplane.com> |
| 3 | * All rights reserved. |
| 4 | * |
| 5 | * Redistribution and use in source and binary forms, with or without |
| 6 | * modification, are permitted provided that the following conditions |
| 7 | * are met: |
| 8 | * 1. Redistributions of source code must retain the above copyright |
| 9 | * notice, this list of conditions and the following disclaimer. |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright |
| 11 | * notice, this list of conditions and the following disclaimer in the |
| 12 | * documentation and/or other materials provided with the distribution. |
| 13 | * |
| 14 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
| 15 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 16 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 17 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| 18 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 19 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 20 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 21 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 22 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 23 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 24 | * SUCH DAMAGE. |
| 25 | * |
| 26 | * Each cpu in a system has its own self-contained light weight kernel |
| 27 | * thread scheduler, which means that generally speaking we only need |
| 28 | * to use a critical section to prevent hicups. |
| 29 | * |
| 30 | * $DragonFly: src/sys/kern/lwkt_thread.c,v 1.15 2003/07/06 21:23:51 dillon Exp $ |
| 31 | */ |
| 32 | |
| 33 | #include <sys/param.h> |
| 34 | #include <sys/systm.h> |
| 35 | #include <sys/kernel.h> |
| 36 | #include <sys/proc.h> |
| 37 | #include <sys/rtprio.h> |
| 38 | #include <sys/queue.h> |
| 39 | #include <sys/thread2.h> |
| 40 | #include <sys/sysctl.h> |
| 41 | #include <sys/kthread.h> |
| 42 | #include <machine/cpu.h> |
| 43 | #include <sys/lock.h> |
| 44 | |
| 45 | #include <vm/vm.h> |
| 46 | #include <vm/vm_param.h> |
| 47 | #include <vm/vm_kern.h> |
| 48 | #include <vm/vm_object.h> |
| 49 | #include <vm/vm_page.h> |
| 50 | #include <vm/vm_map.h> |
| 51 | #include <vm/vm_pager.h> |
| 52 | #include <vm/vm_extern.h> |
| 53 | #include <vm/vm_zone.h> |
| 54 | |
| 55 | #include <machine/stdarg.h> |
| 56 | |
| 57 | static int untimely_switch = 0; |
| 58 | SYSCTL_INT(_lwkt, OID_AUTO, untimely_switch, CTLFLAG_RW, &untimely_switch, 0, ""); |
| 59 | static quad_t switch_count = 0; |
| 60 | SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, ""); |
| 61 | static quad_t preempt_hit = 0; |
| 62 | SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, ""); |
| 63 | static quad_t preempt_miss = 0; |
| 64 | SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, ""); |
| 65 | static quad_t preempt_weird = 0; |
| 66 | SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, ""); |
| 67 | |
| 68 | /* |
| 69 | * These helper procedures handle the runq, they can only be called from |
| 70 | * within a critical section. |
| 71 | */ |
| 72 | static __inline |
| 73 | void |
| 74 | _lwkt_dequeue(thread_t td) |
| 75 | { |
| 76 | if (td->td_flags & TDF_RUNQ) { |
| 77 | int nq = td->td_pri & TDPRI_MASK; |
| 78 | struct globaldata *gd = mycpu; |
| 79 | |
| 80 | td->td_flags &= ~TDF_RUNQ; |
| 81 | TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq); |
| 82 | /* runqmask is passively cleaned up by the switcher */ |
| 83 | } |
| 84 | } |
| 85 | |
| 86 | static __inline |
| 87 | void |
| 88 | _lwkt_enqueue(thread_t td) |
| 89 | { |
| 90 | if ((td->td_flags & TDF_RUNQ) == 0) { |
| 91 | int nq = td->td_pri & TDPRI_MASK; |
| 92 | struct globaldata *gd = mycpu; |
| 93 | |
| 94 | td->td_flags |= TDF_RUNQ; |
| 95 | TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq); |
| 96 | gd->gd_runqmask |= 1 << nq; |
| 97 | #if 0 |
| 98 | /* |
| 99 | * YYY needs cli/sti protection? gd_reqpri set by interrupt |
| 100 | * when made pending. need better mechanism. |
| 101 | */ |
| 102 | if (gd->gd_reqpri < (td->td_pri & TDPRI_MASK)) |
| 103 | gd->gd_reqpri = (td->td_pri & TDPRI_MASK); |
| 104 | #endif |
| 105 | } |
| 106 | } |
| 107 | |
| 108 | /* |
| 109 | * LWKTs operate on a per-cpu basis |
| 110 | * |
| 111 | * WARNING! Called from early boot, 'mycpu' may not work yet. |
| 112 | */ |
| 113 | void |
| 114 | lwkt_gdinit(struct globaldata *gd) |
| 115 | { |
| 116 | int i; |
| 117 | |
| 118 | for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i) |
| 119 | TAILQ_INIT(&gd->gd_tdrunq[i]); |
| 120 | gd->gd_runqmask = 0; |
| 121 | TAILQ_INIT(&gd->gd_tdallq); |
| 122 | } |
| 123 | |
| 124 | /* |
| 125 | * Initialize a thread wait structure prior to first use. |
| 126 | * |
| 127 | * NOTE! called from low level boot code, we cannot do anything fancy! |
| 128 | */ |
| 129 | void |
| 130 | lwkt_init_wait(lwkt_wait_t w) |
| 131 | { |
| 132 | TAILQ_INIT(&w->wa_waitq); |
| 133 | } |
| 134 | |
| 135 | /* |
| 136 | * Create a new thread. The thread must be associated with a process context |
| 137 | * or LWKT start address before it can be scheduled. |
| 138 | * |
| 139 | * If you intend to create a thread without a process context this function |
| 140 | * does everything except load the startup and switcher function. |
| 141 | */ |
| 142 | thread_t |
| 143 | lwkt_alloc_thread(struct thread *td) |
| 144 | { |
| 145 | void *stack; |
| 146 | int flags = 0; |
| 147 | |
| 148 | if (td == NULL) { |
| 149 | crit_enter(); |
| 150 | if (mycpu->gd_tdfreecount > 0) { |
| 151 | --mycpu->gd_tdfreecount; |
| 152 | td = TAILQ_FIRST(&mycpu->gd_tdfreeq); |
| 153 | KASSERT(td != NULL && (td->td_flags & TDF_EXITED), |
| 154 | ("lwkt_alloc_thread: unexpected NULL or corrupted td")); |
| 155 | TAILQ_REMOVE(&mycpu->gd_tdfreeq, td, td_threadq); |
| 156 | crit_exit(); |
| 157 | stack = td->td_kstack; |
| 158 | flags = td->td_flags & (TDF_ALLOCATED_STACK|TDF_ALLOCATED_THREAD); |
| 159 | } else { |
| 160 | crit_exit(); |
| 161 | td = zalloc(thread_zone); |
| 162 | td->td_kstack = NULL; |
| 163 | flags |= TDF_ALLOCATED_THREAD; |
| 164 | } |
| 165 | } |
| 166 | if ((stack = td->td_kstack) == NULL) { |
| 167 | stack = (void *)kmem_alloc(kernel_map, UPAGES * PAGE_SIZE); |
| 168 | flags |= TDF_ALLOCATED_STACK; |
| 169 | } |
| 170 | lwkt_init_thread(td, stack, flags, mycpu); |
| 171 | return(td); |
| 172 | } |
| 173 | |
| 174 | /* |
| 175 | * Initialize a preexisting thread structure. This function is used by |
| 176 | * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread. |
| 177 | * |
| 178 | * NOTE! called from low level boot code, we cannot do anything fancy! |
| 179 | */ |
| 180 | void |
| 181 | lwkt_init_thread(thread_t td, void *stack, int flags, struct globaldata *gd) |
| 182 | { |
| 183 | bzero(td, sizeof(struct thread)); |
| 184 | td->td_kstack = stack; |
| 185 | td->td_flags |= flags; |
| 186 | td->td_gd = gd; |
| 187 | td->td_pri = TDPRI_CRIT; |
| 188 | td->td_cpu = gd->gd_cpuid; /* YYY don't need this if have td_gd */ |
| 189 | pmap_init_thread(td); |
| 190 | crit_enter(); |
| 191 | TAILQ_INSERT_TAIL(&mycpu->gd_tdallq, td, td_allq); |
| 192 | crit_exit(); |
| 193 | } |
| 194 | |
| 195 | void |
| 196 | lwkt_set_comm(thread_t td, const char *ctl, ...) |
| 197 | { |
| 198 | va_list va; |
| 199 | |
| 200 | va_start(va, ctl); |
| 201 | vsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va); |
| 202 | va_end(va); |
| 203 | } |
| 204 | |
| 205 | void |
| 206 | lwkt_hold(thread_t td) |
| 207 | { |
| 208 | ++td->td_refs; |
| 209 | } |
| 210 | |
| 211 | void |
| 212 | lwkt_rele(thread_t td) |
| 213 | { |
| 214 | KKASSERT(td->td_refs > 0); |
| 215 | --td->td_refs; |
| 216 | } |
| 217 | |
| 218 | void |
| 219 | lwkt_wait_free(thread_t td) |
| 220 | { |
| 221 | while (td->td_refs) |
| 222 | tsleep(td, PWAIT, "tdreap", hz); |
| 223 | } |
| 224 | |
| 225 | void |
| 226 | lwkt_free_thread(thread_t td) |
| 227 | { |
| 228 | struct globaldata *gd = mycpu; |
| 229 | |
| 230 | KASSERT(td->td_flags & TDF_EXITED, |
| 231 | ("lwkt_free_thread: did not exit! %p", td)); |
| 232 | |
| 233 | crit_enter(); |
| 234 | TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); |
| 235 | if (gd->gd_tdfreecount < CACHE_NTHREADS && |
| 236 | (td->td_flags & TDF_ALLOCATED_THREAD) |
| 237 | ) { |
| 238 | ++gd->gd_tdfreecount; |
| 239 | TAILQ_INSERT_HEAD(&gd->gd_tdfreeq, td, td_threadq); |
| 240 | crit_exit(); |
| 241 | } else { |
| 242 | crit_exit(); |
| 243 | if (td->td_kstack && (td->td_flags & TDF_ALLOCATED_STACK)) { |
| 244 | kmem_free(kernel_map, |
| 245 | (vm_offset_t)td->td_kstack, UPAGES * PAGE_SIZE); |
| 246 | /* gd invalid */ |
| 247 | td->td_kstack = NULL; |
| 248 | } |
| 249 | if (td->td_flags & TDF_ALLOCATED_THREAD) |
| 250 | zfree(thread_zone, td); |
| 251 | } |
| 252 | } |
| 253 | |
| 254 | |
| 255 | /* |
| 256 | * Switch to the next runnable lwkt. If no LWKTs are runnable then |
| 257 | * switch to the idlethread. Switching must occur within a critical |
| 258 | * section to avoid races with the scheduling queue. |
| 259 | * |
| 260 | * We always have full control over our cpu's run queue. Other cpus |
| 261 | * that wish to manipulate our queue must use the cpu_*msg() calls to |
| 262 | * talk to our cpu, so a critical section is all that is needed and |
| 263 | * the result is very, very fast thread switching. |
| 264 | * |
| 265 | * We always 'own' our own thread and the threads on our run queue,l |
| 266 | * due to TDF_RUNNING or TDF_RUNQ being set. We can safely clear |
| 267 | * TDF_RUNNING while in a critical section. |
| 268 | * |
| 269 | * The td_switch() function must be called while in the critical section. |
| 270 | * This function saves as much state as is appropriate for the type of |
| 271 | * thread. |
| 272 | * |
| 273 | * (self contained on a per cpu basis) |
| 274 | */ |
| 275 | void |
| 276 | lwkt_switch(void) |
| 277 | { |
| 278 | struct globaldata *gd; |
| 279 | thread_t td = curthread; |
| 280 | thread_t ntd; |
| 281 | #ifdef SMP |
| 282 | int mpheld; |
| 283 | #endif |
| 284 | |
| 285 | if (mycpu->gd_intr_nesting_level && td->td_preempted == NULL) |
| 286 | panic("lwkt_switch: cannot switch from within an interrupt, yet\n"); |
| 287 | |
| 288 | crit_enter(); |
| 289 | ++switch_count; |
| 290 | |
| 291 | #ifdef SMP |
| 292 | /* |
| 293 | * td_mpcount cannot be used to determine if we currently hold the |
| 294 | * MP lock because get_mplock() will increment it prior to attempting |
| 295 | * to get the lock, and switch out if it can't. Look at the actual lock. |
| 296 | */ |
| 297 | mpheld = MP_LOCK_HELD(); |
| 298 | #endif |
| 299 | if ((ntd = td->td_preempted) != NULL) { |
| 300 | /* |
| 301 | * We had preempted another thread on this cpu, resume the preempted |
| 302 | * thread. This occurs transparently, whether the preempted thread |
| 303 | * was scheduled or not (it may have been preempted after descheduling |
| 304 | * itself). |
| 305 | * |
| 306 | * We have to setup the MP lock for the original thread after backing |
| 307 | * out the adjustment that was made to curthread when the original |
| 308 | * was preempted. |
| 309 | */ |
| 310 | KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK); |
| 311 | #ifdef SMP |
| 312 | if (ntd->td_mpcount) { |
| 313 | td->td_mpcount -= ntd->td_mpcount; |
| 314 | KKASSERT(td->td_mpcount >= 0); |
| 315 | } |
| 316 | #endif |
| 317 | ntd->td_flags |= TDF_PREEMPT_DONE; |
| 318 | /* YYY release mp lock on switchback if original doesn't need it */ |
| 319 | } else { |
| 320 | /* |
| 321 | * Priority queue / round-robin at each priority. Note that user |
| 322 | * processes run at a fixed, low priority and the user process |
| 323 | * scheduler deals with interactions between user processes |
| 324 | * by scheduling and descheduling them from the LWKT queue as |
| 325 | * necessary. |
| 326 | * |
| 327 | * We have to adjust the MP lock for the target thread. If we |
| 328 | * need the MP lock and cannot obtain it we try to locate a |
| 329 | * thread that does not need the MP lock. |
| 330 | */ |
| 331 | gd = mycpu; |
| 332 | again: |
| 333 | if (gd->gd_runqmask) { |
| 334 | int nq = bsrl(gd->gd_runqmask); |
| 335 | if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) { |
| 336 | gd->gd_runqmask &= ~(1 << nq); |
| 337 | goto again; |
| 338 | } |
| 339 | #ifdef SMP |
| 340 | if (ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) { |
| 341 | /* |
| 342 | * Target needs MP lock and we couldn't get it. |
| 343 | */ |
| 344 | u_int32_t rqmask = gd->gd_runqmask; |
| 345 | while (rqmask) { |
| 346 | TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) { |
| 347 | if (ntd->td_mpcount == 0) |
| 348 | break; |
| 349 | } |
| 350 | if (ntd) |
| 351 | break; |
| 352 | rqmask &= ~(1 << nq); |
| 353 | nq = bsrl(rqmask); |
| 354 | } |
| 355 | if (ntd == NULL) { |
| 356 | ntd = gd->gd_idletd; |
| 357 | } else { |
| 358 | TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); |
| 359 | TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); |
| 360 | } |
| 361 | } else { |
| 362 | TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); |
| 363 | TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); |
| 364 | } |
| 365 | #else |
| 366 | TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq); |
| 367 | TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq); |
| 368 | #endif |
| 369 | } else { |
| 370 | ntd = gd->gd_idletd; |
| 371 | } |
| 372 | } |
| 373 | KASSERT(ntd->td_pri >= TDPRI_CRIT, |
| 374 | ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri)); |
| 375 | |
| 376 | /* |
| 377 | * Do the actual switch. If the new target does not need the MP lock |
| 378 | * and we are holding it, release the MP lock. If the new target requires |
| 379 | * the MP lock we have already acquired it for the target. |
| 380 | */ |
| 381 | #ifdef SMP |
| 382 | if (ntd->td_mpcount == 0 ) { |
| 383 | if (MP_LOCK_HELD()) |
| 384 | cpu_rel_mplock(); |
| 385 | } else { |
| 386 | ASSERT_MP_LOCK_HELD(); |
| 387 | } |
| 388 | #endif |
| 389 | |
| 390 | if (td != ntd) { |
| 391 | td->td_switch(ntd); |
| 392 | } |
| 393 | crit_exit(); |
| 394 | } |
| 395 | |
| 396 | /* |
| 397 | * Request that the target thread preempt the current thread. This only |
| 398 | * works if: |
| 399 | * |
| 400 | * + We aren't trying to preempt ourselves (it can happen!) |
| 401 | * + We are not currently being preempted |
| 402 | * + The target is not currently being preempted |
| 403 | * + The target either does not need the MP lock or we can get it |
| 404 | * for the target immediately. |
| 405 | * |
| 406 | * XXX at the moment we run the target thread in a critical section during |
| 407 | * the preemption in order to prevent the target from taking interrupts |
| 408 | * that *WE* can't. Preemption is strictly limited to interrupt threads |
| 409 | * and interrupt-like threads, outside of a critical section, and the |
| 410 | * preempted source thread will be resumed the instant the target blocks |
| 411 | * whether or not the source is scheduled (i.e. preemption is supposed to |
| 412 | * be as transparent as possible). |
| 413 | * |
| 414 | * This call is typically made from an interrupt handler like sched_ithd() |
| 415 | * which will only run if the current thread is not in a critical section, |
| 416 | * so we optimize the priority check a bit. |
| 417 | * |
| 418 | * CAREFUL! either we or the target thread may get interrupted during the |
| 419 | * switch. |
| 420 | * |
| 421 | * The target thread inherits our MP count (added to its own) for the |
| 422 | * duration of the preemption in order to preserve the atomicy of the |
| 423 | * preemption. |
| 424 | */ |
| 425 | void |
| 426 | lwkt_preempt(thread_t ntd, int id) |
| 427 | { |
| 428 | thread_t td = curthread; |
| 429 | #ifdef SMP |
| 430 | int mpheld; |
| 431 | #endif |
| 432 | |
| 433 | /* |
| 434 | * The caller has put us in a critical section, and in order to have |
| 435 | * gotten here in the first place the thread the caller interrupted |
| 436 | * cannot have been in a critical section before. |
| 437 | */ |
| 438 | KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri)); |
| 439 | KASSERT((td->td_pri & ~TDPRI_MASK) == TDPRI_CRIT, ("BADPRI %d", td->td_pri)); |
| 440 | |
| 441 | if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) { |
| 442 | ++preempt_weird; |
| 443 | return; |
| 444 | } |
| 445 | if (ntd->td_preempted) { |
| 446 | ++preempt_hit; |
| 447 | return; |
| 448 | } |
| 449 | if ((ntd->td_pri & TDPRI_MASK) <= (td->td_pri & TDPRI_MASK)) { |
| 450 | ++preempt_miss; |
| 451 | return; |
| 452 | } |
| 453 | #ifdef SMP |
| 454 | mpheld = MP_LOCK_HELD(); |
| 455 | ntd->td_mpcount += td->td_mpcount; |
| 456 | if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) { |
| 457 | ntd->td_mpcount -= td->td_mpcount; |
| 458 | ++preempt_miss; |
| 459 | return; |
| 460 | } |
| 461 | #endif |
| 462 | |
| 463 | ++preempt_hit; |
| 464 | ntd->td_preempted = td; |
| 465 | td->td_flags |= TDF_PREEMPT_LOCK; |
| 466 | td->td_switch(ntd); |
| 467 | KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE)); |
| 468 | ntd->td_preempted = NULL; |
| 469 | td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE); |
| 470 | } |
| 471 | |
| 472 | /* |
| 473 | * Yield our thread while higher priority threads are pending. This is |
| 474 | * typically called when we leave a critical section but it can be safely |
| 475 | * called while we are in a critical section. |
| 476 | * |
| 477 | * This function will not generally yield to equal priority threads but it |
| 478 | * can occur as a side effect. Note that lwkt_switch() is called from |
| 479 | * inside the critical section to pervent its own crit_exit() from reentering |
| 480 | * lwkt_yield_quick(). |
| 481 | * |
| 482 | * gd_reqpri indicates that *something* changed, e.g. an interrupt or softint |
| 483 | * came along but was blocked and made pending. |
| 484 | * |
| 485 | * (self contained on a per cpu basis) |
| 486 | */ |
| 487 | void |
| 488 | lwkt_yield_quick(void) |
| 489 | { |
| 490 | thread_t td = curthread; |
| 491 | |
| 492 | if ((td->td_pri & TDPRI_MASK) < mycpu->gd_reqpri) { |
| 493 | mycpu->gd_reqpri = 0; |
| 494 | splz(); |
| 495 | } |
| 496 | |
| 497 | /* |
| 498 | * YYY enabling will cause wakeup() to task-switch, which really |
| 499 | * confused the old 4.x code. This is a good way to simulate |
| 500 | * preemption and MP without actually doing preemption or MP, because a |
| 501 | * lot of code assumes that wakeup() does not block. |
| 502 | */ |
| 503 | if (untimely_switch && mycpu->gd_intr_nesting_level == 0) { |
| 504 | crit_enter(); |
| 505 | /* |
| 506 | * YYY temporary hacks until we disassociate the userland scheduler |
| 507 | * from the LWKT scheduler. |
| 508 | */ |
| 509 | if (td->td_flags & TDF_RUNQ) { |
| 510 | lwkt_switch(); /* will not reenter yield function */ |
| 511 | } else { |
| 512 | lwkt_schedule_self(); /* make sure we are scheduled */ |
| 513 | lwkt_switch(); /* will not reenter yield function */ |
| 514 | lwkt_deschedule_self(); /* make sure we are descheduled */ |
| 515 | } |
| 516 | crit_exit_noyield(); |
| 517 | } |
| 518 | } |
| 519 | |
| 520 | /* |
| 521 | * This implements a normal yield which, unlike _quick, will yield to equal |
| 522 | * priority threads as well. Note that gd_reqpri tests will be handled by |
| 523 | * the crit_exit() call in lwkt_switch(). |
| 524 | * |
| 525 | * (self contained on a per cpu basis) |
| 526 | */ |
| 527 | void |
| 528 | lwkt_yield(void) |
| 529 | { |
| 530 | lwkt_schedule_self(); |
| 531 | lwkt_switch(); |
| 532 | } |
| 533 | |
| 534 | /* |
| 535 | * Schedule a thread to run. As the current thread we can always safely |
| 536 | * schedule ourselves, and a shortcut procedure is provided for that |
| 537 | * function. |
| 538 | * |
| 539 | * (non-blocking, self contained on a per cpu basis) |
| 540 | */ |
| 541 | void |
| 542 | lwkt_schedule_self(void) |
| 543 | { |
| 544 | thread_t td = curthread; |
| 545 | |
| 546 | crit_enter(); |
| 547 | KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!")); |
| 548 | _lwkt_enqueue(td); |
| 549 | if (td->td_proc && td->td_proc->p_stat == SSLEEP) |
| 550 | panic("SCHED SELF PANIC"); |
| 551 | crit_exit(); |
| 552 | } |
| 553 | |
| 554 | /* |
| 555 | * Generic schedule. Possibly schedule threads belonging to other cpus and |
| 556 | * deal with threads that might be blocked on a wait queue. |
| 557 | * |
| 558 | * This function will queue requests asynchronously when possible, but may |
| 559 | * block if no request structures are available. Upon return the caller |
| 560 | * should note that the scheduling request may not yet have been processed |
| 561 | * by the target cpu. |
| 562 | * |
| 563 | * YYY this is one of the best places to implement any load balancing code. |
| 564 | * Load balancing can be accomplished by requesting other sorts of actions |
| 565 | * for the thread in question. |
| 566 | */ |
| 567 | void |
| 568 | lwkt_schedule(thread_t td) |
| 569 | { |
| 570 | if ((td->td_flags & TDF_PREEMPT_LOCK) == 0 && td->td_proc |
| 571 | && td->td_proc->p_stat == SSLEEP |
| 572 | ) { |
| 573 | printf("PANIC schedule curtd = %p (%d %d) target %p (%d %d)\n", |
| 574 | curthread, |
| 575 | curthread->td_proc ? curthread->td_proc->p_pid : -1, |
| 576 | curthread->td_proc ? curthread->td_proc->p_stat : -1, |
| 577 | td, |
| 578 | td->td_proc ? curthread->td_proc->p_pid : -1, |
| 579 | td->td_proc ? curthread->td_proc->p_stat : -1 |
| 580 | ); |
| 581 | panic("SCHED PANIC"); |
| 582 | } |
| 583 | crit_enter(); |
| 584 | if (td == curthread) { |
| 585 | _lwkt_enqueue(td); |
| 586 | } else { |
| 587 | lwkt_wait_t w; |
| 588 | |
| 589 | /* |
| 590 | * If the thread is on a wait list we have to send our scheduling |
| 591 | * request to the owner of the wait structure. Otherwise we send |
| 592 | * the scheduling request to the cpu owning the thread. Races |
| 593 | * are ok, the target will forward the message as necessary (the |
| 594 | * message may chase the thread around before it finally gets |
| 595 | * acted upon). |
| 596 | * |
| 597 | * (remember, wait structures use stable storage) |
| 598 | */ |
| 599 | if ((w = td->td_wait) != NULL) { |
| 600 | if (lwkt_havetoken(&w->wa_token)) { |
| 601 | TAILQ_REMOVE(&w->wa_waitq, td, td_threadq); |
| 602 | --w->wa_count; |
| 603 | td->td_wait = NULL; |
| 604 | if (td->td_cpu == mycpu->gd_cpuid) { |
| 605 | _lwkt_enqueue(td); |
| 606 | } else { |
| 607 | panic("lwkt_schedule: cpu mismatch1"); |
| 608 | #if 0 |
| 609 | lwkt_cpu_msg_union_t msg = lwkt_getcpumsg(); |
| 610 | initScheduleReqMsg_Wait(&msg.mu_SchedReq, td, w); |
| 611 | cpu_sendnormsg(&msg.mu_Msg); |
| 612 | #endif |
| 613 | } |
| 614 | } else { |
| 615 | panic("lwkt_schedule: cpu mismatch2"); |
| 616 | #if 0 |
| 617 | lwkt_cpu_msg_union_t msg = lwkt_getcpumsg(); |
| 618 | initScheduleReqMsg_Wait(&msg.mu_SchedReq, td, w); |
| 619 | cpu_sendnormsg(&msg.mu_Msg); |
| 620 | #endif |
| 621 | } |
| 622 | } else { |
| 623 | /* |
| 624 | * If the wait structure is NULL and we own the thread, there |
| 625 | * is no race (since we are in a critical section). If we |
| 626 | * do not own the thread there might be a race but the |
| 627 | * target cpu will deal with it. |
| 628 | */ |
| 629 | if (td->td_cpu == mycpu->gd_cpuid) { |
| 630 | _lwkt_enqueue(td); |
| 631 | } else { |
| 632 | panic("lwkt_schedule: cpu mismatch3"); |
| 633 | #if 0 |
| 634 | lwkt_cpu_msg_union_t msg = lwkt_getcpumsg(); |
| 635 | initScheduleReqMsg_Thread(&msg.mu_SchedReq, td); |
| 636 | cpu_sendnormsg(&msg.mu_Msg); |
| 637 | #endif |
| 638 | } |
| 639 | } |
| 640 | } |
| 641 | crit_exit(); |
| 642 | } |
| 643 | |
| 644 | /* |
| 645 | * Deschedule a thread. |
| 646 | * |
| 647 | * (non-blocking, self contained on a per cpu basis) |
| 648 | */ |
| 649 | void |
| 650 | lwkt_deschedule_self(void) |
| 651 | { |
| 652 | thread_t td = curthread; |
| 653 | |
| 654 | crit_enter(); |
| 655 | KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!")); |
| 656 | _lwkt_dequeue(td); |
| 657 | crit_exit(); |
| 658 | } |
| 659 | |
| 660 | /* |
| 661 | * Generic deschedule. Descheduling threads other then your own should be |
| 662 | * done only in carefully controlled circumstances. Descheduling is |
| 663 | * asynchronous. |
| 664 | * |
| 665 | * This function may block if the cpu has run out of messages. |
| 666 | */ |
| 667 | void |
| 668 | lwkt_deschedule(thread_t td) |
| 669 | { |
| 670 | crit_enter(); |
| 671 | if (td == curthread) { |
| 672 | _lwkt_dequeue(td); |
| 673 | } else { |
| 674 | if (td->td_cpu == mycpu->gd_cpuid) { |
| 675 | _lwkt_dequeue(td); |
| 676 | } else { |
| 677 | panic("lwkt_deschedule: cpu mismatch"); |
| 678 | #if 0 |
| 679 | lwkt_cpu_msg_union_t msg = lwkt_getcpumsg(); |
| 680 | initDescheduleReqMsg_Thread(&msg.mu_DeschedReq, td); |
| 681 | cpu_sendnormsg(&msg.mu_Msg); |
| 682 | #endif |
| 683 | } |
| 684 | } |
| 685 | crit_exit(); |
| 686 | } |
| 687 | |
| 688 | /* |
| 689 | * Set the target thread's priority. This routine does not automatically |
| 690 | * switch to a higher priority thread, LWKT threads are not designed for |
| 691 | * continuous priority changes. Yield if you want to switch. |
| 692 | * |
| 693 | * We have to retain the critical section count which uses the high bits |
| 694 | * of the td_pri field. The specified priority may also indicate zero or |
| 695 | * more critical sections by adding TDPRI_CRIT*N. |
| 696 | */ |
| 697 | void |
| 698 | lwkt_setpri(thread_t td, int pri) |
| 699 | { |
| 700 | KKASSERT(pri >= 0); |
| 701 | crit_enter(); |
| 702 | if (td->td_flags & TDF_RUNQ) { |
| 703 | _lwkt_dequeue(td); |
| 704 | td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; |
| 705 | _lwkt_enqueue(td); |
| 706 | } else { |
| 707 | td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; |
| 708 | } |
| 709 | crit_exit(); |
| 710 | } |
| 711 | |
| 712 | void |
| 713 | lwkt_setpri_self(int pri) |
| 714 | { |
| 715 | thread_t td = curthread; |
| 716 | |
| 717 | KKASSERT(pri >= 0 && pri <= TDPRI_MAX); |
| 718 | crit_enter(); |
| 719 | if (td->td_flags & TDF_RUNQ) { |
| 720 | _lwkt_dequeue(td); |
| 721 | td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; |
| 722 | _lwkt_enqueue(td); |
| 723 | } else { |
| 724 | td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri; |
| 725 | } |
| 726 | crit_exit(); |
| 727 | } |
| 728 | |
| 729 | struct proc * |
| 730 | lwkt_preempted_proc(void) |
| 731 | { |
| 732 | thread_t td = curthread; |
| 733 | while (td->td_preempted) |
| 734 | td = td->td_preempted; |
| 735 | return(td->td_proc); |
| 736 | } |
| 737 | |
| 738 | |
| 739 | /* |
| 740 | * This function deschedules the current thread and blocks on the specified |
| 741 | * wait queue. We obtain ownership of the wait queue in order to block |
| 742 | * on it. A generation number is used to interlock the wait queue in case |
| 743 | * it gets signalled while we are blocked waiting on the token. |
| 744 | * |
| 745 | * Note: alternatively we could dequeue our thread and then message the |
| 746 | * target cpu owning the wait queue. YYY implement as sysctl. |
| 747 | * |
| 748 | * Note: wait queue signals normally ping-pong the cpu as an optimization. |
| 749 | */ |
| 750 | void |
| 751 | lwkt_block(lwkt_wait_t w, const char *wmesg, int *gen) |
| 752 | { |
| 753 | thread_t td = curthread; |
| 754 | |
| 755 | lwkt_gettoken(&w->wa_token); |
| 756 | if (w->wa_gen == *gen) { |
| 757 | _lwkt_dequeue(td); |
| 758 | TAILQ_INSERT_TAIL(&w->wa_waitq, td, td_threadq); |
| 759 | ++w->wa_count; |
| 760 | td->td_wait = w; |
| 761 | td->td_wmesg = wmesg; |
| 762 | lwkt_switch(); |
| 763 | } |
| 764 | /* token might be lost, doesn't matter for gen update */ |
| 765 | *gen = w->wa_gen; |
| 766 | lwkt_reltoken(&w->wa_token); |
| 767 | } |
| 768 | |
| 769 | /* |
| 770 | * Signal a wait queue. We gain ownership of the wait queue in order to |
| 771 | * signal it. Once a thread is removed from the wait queue we have to |
| 772 | * deal with the cpu owning the thread. |
| 773 | * |
| 774 | * Note: alternatively we could message the target cpu owning the wait |
| 775 | * queue. YYY implement as sysctl. |
| 776 | */ |
| 777 | void |
| 778 | lwkt_signal(lwkt_wait_t w) |
| 779 | { |
| 780 | thread_t td; |
| 781 | int count; |
| 782 | |
| 783 | lwkt_gettoken(&w->wa_token); |
| 784 | ++w->wa_gen; |
| 785 | count = w->wa_count; |
| 786 | while ((td = TAILQ_FIRST(&w->wa_waitq)) != NULL && count) { |
| 787 | --count; |
| 788 | --w->wa_count; |
| 789 | TAILQ_REMOVE(&w->wa_waitq, td, td_threadq); |
| 790 | td->td_wait = NULL; |
| 791 | td->td_wmesg = NULL; |
| 792 | if (td->td_cpu == mycpu->gd_cpuid) { |
| 793 | _lwkt_enqueue(td); |
| 794 | } else { |
| 795 | #if 0 |
| 796 | lwkt_cpu_msg_union_t msg = lwkt_getcpumsg(); |
| 797 | initScheduleReqMsg_Thread(&msg.mu_SchedReq, td); |
| 798 | cpu_sendnormsg(&msg.mu_Msg); |
| 799 | #endif |
| 800 | panic("lwkt_signal: cpu mismatch"); |
| 801 | } |
| 802 | lwkt_regettoken(&w->wa_token); |
| 803 | } |
| 804 | lwkt_reltoken(&w->wa_token); |
| 805 | } |
| 806 | |
| 807 | /* |
| 808 | * Aquire ownership of a token |
| 809 | * |
| 810 | * Aquire ownership of a token. The token may have spl and/or critical |
| 811 | * section side effects, depending on its purpose. These side effects |
| 812 | * guarentee that you will maintain ownership of the token as long as you |
| 813 | * do not block. If you block you may lose access to the token (but you |
| 814 | * must still release it even if you lose your access to it). |
| 815 | * |
| 816 | * Note that the spl and critical section characteristics of a token |
| 817 | * may not be changed once the token has been initialized. |
| 818 | */ |
| 819 | int |
| 820 | lwkt_gettoken(lwkt_token_t tok) |
| 821 | { |
| 822 | /* |
| 823 | * Prevent preemption so the token can't be taken away from us once |
| 824 | * we gain ownership of it. Use a synchronous request which might |
| 825 | * block. The request will be forwarded as necessary playing catchup |
| 826 | * to the token. |
| 827 | */ |
| 828 | crit_enter(); |
| 829 | #if 0 |
| 830 | while (tok->t_cpu != mycpu->gd_cpuid) { |
| 831 | lwkt_cpu_msg_union msg; |
| 832 | initTokenReqMsg(&msg.mu_TokenReq); |
| 833 | cpu_domsg(&msg); |
| 834 | } |
| 835 | #endif |
| 836 | /* |
| 837 | * leave us in a critical section on return. This will be undone |
| 838 | * by lwkt_reltoken(). Bump the generation number. |
| 839 | */ |
| 840 | return(++tok->t_gen); |
| 841 | } |
| 842 | |
| 843 | /* |
| 844 | * Release your ownership of a token. Releases must occur in reverse |
| 845 | * order to aquisitions, eventually so priorities can be unwound properly |
| 846 | * like SPLs. At the moment the actual implemention doesn't care. |
| 847 | * |
| 848 | * We can safely hand a token that we own to another cpu without notifying |
| 849 | * it, but once we do we can't get it back without requesting it (unless |
| 850 | * the other cpu hands it back to us before we check). |
| 851 | * |
| 852 | * We might have lost the token, so check that. |
| 853 | */ |
| 854 | void |
| 855 | lwkt_reltoken(lwkt_token_t tok) |
| 856 | { |
| 857 | if (tok->t_cpu == mycpu->gd_cpuid) { |
| 858 | tok->t_cpu = tok->t_reqcpu; |
| 859 | } |
| 860 | crit_exit(); |
| 861 | } |
| 862 | |
| 863 | /* |
| 864 | * Reacquire a token that might have been lost and compare and update the |
| 865 | * generation number. 0 is returned if the generation has not changed |
| 866 | * (nobody else obtained the token while we were blocked, on this cpu or |
| 867 | * any other cpu). |
| 868 | * |
| 869 | * This function returns with the token re-held whether the generation |
| 870 | * number changed or not. |
| 871 | */ |
| 872 | int |
| 873 | lwkt_gentoken(lwkt_token_t tok, int *gen) |
| 874 | { |
| 875 | if (lwkt_regettoken(tok) == *gen) { |
| 876 | return(0); |
| 877 | } else { |
| 878 | *gen = tok->t_gen; |
| 879 | return(-1); |
| 880 | } |
| 881 | } |
| 882 | |
| 883 | |
| 884 | /* |
| 885 | * Reacquire a token that might have been lost. Returns the generation |
| 886 | * number of the token. |
| 887 | */ |
| 888 | int |
| 889 | lwkt_regettoken(lwkt_token_t tok) |
| 890 | { |
| 891 | #if 0 |
| 892 | if (tok->t_cpu != mycpu->gd_cpuid) { |
| 893 | while (tok->t_cpu != mycpu->gd_cpuid) { |
| 894 | lwkt_cpu_msg_union msg; |
| 895 | initTokenReqMsg(&msg.mu_TokenReq); |
| 896 | cpu_domsg(&msg); |
| 897 | } |
| 898 | } |
| 899 | #endif |
| 900 | return(tok->t_gen); |
| 901 | } |
| 902 | |
| 903 | void |
| 904 | lwkt_inittoken(lwkt_token_t tok) |
| 905 | { |
| 906 | /* |
| 907 | * Zero structure and set cpu owner and reqcpu to cpu 0. |
| 908 | */ |
| 909 | bzero(tok, sizeof(*tok)); |
| 910 | } |
| 911 | |
| 912 | /* |
| 913 | * Create a kernel process/thread/whatever. It shares it's address space |
| 914 | * with proc0 - ie: kernel only. |
| 915 | * |
| 916 | * XXX should be renamed to lwkt_create() |
| 917 | * |
| 918 | * The thread will be entered with the MP lock held. |
| 919 | */ |
| 920 | int |
| 921 | lwkt_create(void (*func)(void *), void *arg, |
| 922 | struct thread **tdp, thread_t template, int tdflags, |
| 923 | const char *fmt, ...) |
| 924 | { |
| 925 | thread_t td; |
| 926 | va_list ap; |
| 927 | |
| 928 | td = *tdp = lwkt_alloc_thread(template); |
| 929 | cpu_set_thread_handler(td, kthread_exit, func, arg); |
| 930 | td->td_flags |= TDF_VERBOSE | tdflags; |
| 931 | #ifdef SMP |
| 932 | td->td_mpcount = 1; |
| 933 | #endif |
| 934 | |
| 935 | /* |
| 936 | * Set up arg0 for 'ps' etc |
| 937 | */ |
| 938 | va_start(ap, fmt); |
| 939 | vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap); |
| 940 | va_end(ap); |
| 941 | |
| 942 | /* |
| 943 | * Schedule the thread to run |
| 944 | */ |
| 945 | if ((td->td_flags & TDF_STOPREQ) == 0) |
| 946 | lwkt_schedule(td); |
| 947 | else |
| 948 | td->td_flags &= ~TDF_STOPREQ; |
| 949 | return 0; |
| 950 | } |
| 951 | |
| 952 | /* |
| 953 | * Destroy an LWKT thread. Warning! This function is not called when |
| 954 | * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and |
| 955 | * uses a different reaping mechanism. |
| 956 | */ |
| 957 | void |
| 958 | lwkt_exit(void) |
| 959 | { |
| 960 | thread_t td = curthread; |
| 961 | |
| 962 | if (td->td_flags & TDF_VERBOSE) |
| 963 | printf("kthread %p %s has exited\n", td, td->td_comm); |
| 964 | crit_enter(); |
| 965 | lwkt_deschedule_self(); |
| 966 | ++mycpu->gd_tdfreecount; |
| 967 | TAILQ_INSERT_TAIL(&mycpu->gd_tdfreeq, td, td_threadq); |
| 968 | cpu_thread_exit(); |
| 969 | } |
| 970 | |
| 971 | /* |
| 972 | * Create a kernel process/thread/whatever. It shares it's address space |
| 973 | * with proc0 - ie: kernel only. 5.x compatible. |
| 974 | */ |
| 975 | int |
| 976 | kthread_create(void (*func)(void *), void *arg, |
| 977 | struct thread **tdp, const char *fmt, ...) |
| 978 | { |
| 979 | thread_t td; |
| 980 | va_list ap; |
| 981 | |
| 982 | td = *tdp = lwkt_alloc_thread(NULL); |
| 983 | cpu_set_thread_handler(td, kthread_exit, func, arg); |
| 984 | td->td_flags |= TDF_VERBOSE; |
| 985 | #ifdef SMP |
| 986 | td->td_mpcount = 1; |
| 987 | #endif |
| 988 | |
| 989 | /* |
| 990 | * Set up arg0 for 'ps' etc |
| 991 | */ |
| 992 | va_start(ap, fmt); |
| 993 | vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap); |
| 994 | va_end(ap); |
| 995 | |
| 996 | /* |
| 997 | * Schedule the thread to run |
| 998 | */ |
| 999 | lwkt_schedule(td); |
| 1000 | return 0; |
| 1001 | } |
| 1002 | |
| 1003 | void |
| 1004 | crit_panic(void) |
| 1005 | { |
| 1006 | thread_t td = curthread; |
| 1007 | int lpri = td->td_pri; |
| 1008 | |
| 1009 | td->td_pri = 0; |
| 1010 | panic("td_pri is/would-go negative! %p %d", td, lpri); |
| 1011 | } |
| 1012 | |
| 1013 | /* |
| 1014 | * Destroy an LWKT thread. Warning! This function is not called when |
| 1015 | * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and |
| 1016 | * uses a different reaping mechanism. |
| 1017 | * |
| 1018 | * XXX duplicates lwkt_exit() |
| 1019 | */ |
| 1020 | void |
| 1021 | kthread_exit(void) |
| 1022 | { |
| 1023 | lwkt_exit(); |
| 1024 | } |
| 1025 | |