| 1 | /* |
| 2 | * Copyright (c) 2003-2011 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/kinfo.h> |
| 48 | #include <sys/queue.h> |
| 49 | #include <sys/sysctl.h> |
| 50 | #include <sys/kthread.h> |
| 51 | #include <machine/cpu.h> |
| 52 | #include <sys/lock.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 | #ifdef _KERNEL_VIRTUAL |
| 75 | #include <pthread.h> |
| 76 | #endif |
| 77 | |
| 78 | #if !defined(KTR_CTXSW) |
| 79 | #define KTR_CTXSW KTR_ALL |
| 80 | #endif |
| 81 | KTR_INFO_MASTER(ctxsw); |
| 82 | KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "#cpu[%d].td = %p", int cpu, struct thread *td); |
| 83 | KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "#cpu[%d].td = %p", int cpu, struct thread *td); |
| 84 | KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "#threads[%p].name = %s", struct thread *td, char *comm); |
| 85 | KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "#threads[%p].name = <dead>", struct thread *td); |
| 86 | |
| 87 | static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads"); |
| 88 | |
| 89 | #ifdef INVARIANTS |
| 90 | static int panic_on_cscount = 0; |
| 91 | #endif |
| 92 | static __int64_t switch_count = 0; |
| 93 | static __int64_t preempt_hit = 0; |
| 94 | static __int64_t preempt_miss = 0; |
| 95 | static __int64_t preempt_weird = 0; |
| 96 | static int lwkt_use_spin_port; |
| 97 | static struct objcache *thread_cache; |
| 98 | int cpu_mwait_spin = 0; |
| 99 | |
| 100 | static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame); |
| 101 | static void lwkt_setcpu_remote(void *arg); |
| 102 | |
| 103 | extern void cpu_heavy_restore(void); |
| 104 | extern void cpu_lwkt_restore(void); |
| 105 | extern void cpu_kthread_restore(void); |
| 106 | extern void cpu_idle_restore(void); |
| 107 | |
| 108 | /* |
| 109 | * We can make all thread ports use the spin backend instead of the thread |
| 110 | * backend. This should only be set to debug the spin backend. |
| 111 | */ |
| 112 | TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port); |
| 113 | |
| 114 | #ifdef INVARIANTS |
| 115 | SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, |
| 116 | "Panic if attempting to switch lwkt's while mastering cpusync"); |
| 117 | #endif |
| 118 | SYSCTL_INT(_hw, OID_AUTO, cpu_mwait_spin, CTLFLAG_RW, &cpu_mwait_spin, 0, |
| 119 | "monitor/mwait target state"); |
| 120 | SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, |
| 121 | "Number of switched threads"); |
| 122 | SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, |
| 123 | "Successful preemption events"); |
| 124 | SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, |
| 125 | "Failed preemption events"); |
| 126 | SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, |
| 127 | "Number of preempted threads."); |
| 128 | static int fairq_enable = 0; |
| 129 | SYSCTL_INT(_lwkt, OID_AUTO, fairq_enable, CTLFLAG_RW, |
| 130 | &fairq_enable, 0, "Turn on fairq priority accumulators"); |
| 131 | static int fairq_bypass = -1; |
| 132 | SYSCTL_INT(_lwkt, OID_AUTO, fairq_bypass, CTLFLAG_RW, |
| 133 | &fairq_bypass, 0, "Allow fairq to bypass td on token failure"); |
| 134 | extern int lwkt_sched_debug; |
| 135 | int lwkt_sched_debug = 0; |
| 136 | SYSCTL_INT(_lwkt, OID_AUTO, sched_debug, CTLFLAG_RW, |
| 137 | &lwkt_sched_debug, 0, "Scheduler debug"); |
| 138 | static int lwkt_spin_loops = 10; |
| 139 | SYSCTL_INT(_lwkt, OID_AUTO, spin_loops, CTLFLAG_RW, |
| 140 | &lwkt_spin_loops, 0, "Scheduler spin loops until sorted decon"); |
| 141 | static int lwkt_spin_reseq = 0; |
| 142 | SYSCTL_INT(_lwkt, OID_AUTO, spin_reseq, CTLFLAG_RW, |
| 143 | &lwkt_spin_reseq, 0, "Scheduler resequencer enable"); |
| 144 | static int lwkt_spin_monitor = 0; |
| 145 | SYSCTL_INT(_lwkt, OID_AUTO, spin_monitor, CTLFLAG_RW, |
| 146 | &lwkt_spin_monitor, 0, "Scheduler uses monitor/mwait"); |
| 147 | static int lwkt_spin_fatal = 0; /* disabled */ |
| 148 | SYSCTL_INT(_lwkt, OID_AUTO, spin_fatal, CTLFLAG_RW, |
| 149 | &lwkt_spin_fatal, 0, "LWKT scheduler spin loops till fatal panic"); |
| 150 | static int preempt_enable = 1; |
| 151 | SYSCTL_INT(_lwkt, OID_AUTO, preempt_enable, CTLFLAG_RW, |
| 152 | &preempt_enable, 0, "Enable preemption"); |
| 153 | static int lwkt_cache_threads = 0; |
| 154 | SYSCTL_INT(_lwkt, OID_AUTO, cache_threads, CTLFLAG_RD, |
| 155 | &lwkt_cache_threads, 0, "thread+kstack cache"); |
| 156 | |
| 157 | #ifndef _KERNEL_VIRTUAL |
| 158 | static __cachealign int lwkt_cseq_rindex; |
| 159 | static __cachealign int lwkt_cseq_windex; |
| 160 | #endif |
| 161 | |
| 162 | /* |
| 163 | * These helper procedures handle the runq, they can only be called from |
| 164 | * within a critical section. |
| 165 | * |
| 166 | * WARNING! Prior to SMP being brought up it is possible to enqueue and |
| 167 | * dequeue threads belonging to other cpus, so be sure to use td->td_gd |
| 168 | * instead of 'mycpu' when referencing the globaldata structure. Once |
| 169 | * SMP live enqueuing and dequeueing only occurs on the current cpu. |
| 170 | */ |
| 171 | static __inline |
| 172 | void |
| 173 | _lwkt_dequeue(thread_t td) |
| 174 | { |
| 175 | if (td->td_flags & TDF_RUNQ) { |
| 176 | struct globaldata *gd = td->td_gd; |
| 177 | |
| 178 | td->td_flags &= ~TDF_RUNQ; |
| 179 | TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq); |
| 180 | --gd->gd_tdrunqcount; |
| 181 | if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL) |
| 182 | atomic_clear_int(&gd->gd_reqflags, RQF_RUNNING); |
| 183 | } |
| 184 | } |
| 185 | |
| 186 | /* |
| 187 | * Priority enqueue. |
| 188 | * |
| 189 | * There are a limited number of lwkt threads runnable since user |
| 190 | * processes only schedule one at a time per cpu. However, there can |
| 191 | * be many user processes in kernel mode exiting from a tsleep() which |
| 192 | * become runnable. |
| 193 | * |
| 194 | * NOTE: lwkt_schedulerclock() will force a round-robin based on td_pri and |
| 195 | * will ignore user priority. This is to ensure that user threads in |
| 196 | * kernel mode get cpu at some point regardless of what the user |
| 197 | * scheduler thinks. |
| 198 | */ |
| 199 | static __inline |
| 200 | void |
| 201 | _lwkt_enqueue(thread_t td) |
| 202 | { |
| 203 | thread_t xtd; |
| 204 | |
| 205 | if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) { |
| 206 | struct globaldata *gd = td->td_gd; |
| 207 | |
| 208 | td->td_flags |= TDF_RUNQ; |
| 209 | xtd = TAILQ_FIRST(&gd->gd_tdrunq); |
| 210 | if (xtd == NULL) { |
| 211 | TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq); |
| 212 | atomic_set_int(&gd->gd_reqflags, RQF_RUNNING); |
| 213 | } else { |
| 214 | /* |
| 215 | * NOTE: td_upri - higher numbers more desireable, same sense |
| 216 | * as td_pri (typically reversed from lwp_upri). |
| 217 | * |
| 218 | * In the equal priority case we want the best selection |
| 219 | * at the beginning so the less desireable selections know |
| 220 | * that they have to setrunqueue/go-to-another-cpu, even |
| 221 | * though it means switching back to the 'best' selection. |
| 222 | * This also avoids degenerate situations when many threads |
| 223 | * are runnable or waking up at the same time. |
| 224 | * |
| 225 | * If upri matches exactly place at end/round-robin. |
| 226 | */ |
| 227 | while (xtd && |
| 228 | (xtd->td_pri >= td->td_pri || |
| 229 | (xtd->td_pri == td->td_pri && |
| 230 | xtd->td_upri >= td->td_upri))) { |
| 231 | xtd = TAILQ_NEXT(xtd, td_threadq); |
| 232 | } |
| 233 | if (xtd) |
| 234 | TAILQ_INSERT_BEFORE(xtd, td, td_threadq); |
| 235 | else |
| 236 | TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq); |
| 237 | } |
| 238 | ++gd->gd_tdrunqcount; |
| 239 | |
| 240 | /* |
| 241 | * Request a LWKT reschedule if we are now at the head of the queue. |
| 242 | */ |
| 243 | if (TAILQ_FIRST(&gd->gd_tdrunq) == td) |
| 244 | need_lwkt_resched(); |
| 245 | } |
| 246 | } |
| 247 | |
| 248 | static __boolean_t |
| 249 | _lwkt_thread_ctor(void *obj, void *privdata, int ocflags) |
| 250 | { |
| 251 | struct thread *td = (struct thread *)obj; |
| 252 | |
| 253 | td->td_kstack = NULL; |
| 254 | td->td_kstack_size = 0; |
| 255 | td->td_flags = TDF_ALLOCATED_THREAD; |
| 256 | td->td_mpflags = 0; |
| 257 | return (1); |
| 258 | } |
| 259 | |
| 260 | static void |
| 261 | _lwkt_thread_dtor(void *obj, void *privdata) |
| 262 | { |
| 263 | struct thread *td = (struct thread *)obj; |
| 264 | |
| 265 | KASSERT(td->td_flags & TDF_ALLOCATED_THREAD, |
| 266 | ("_lwkt_thread_dtor: not allocated from objcache")); |
| 267 | KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack && |
| 268 | td->td_kstack_size > 0, |
| 269 | ("_lwkt_thread_dtor: corrupted stack")); |
| 270 | kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); |
| 271 | td->td_kstack = NULL; |
| 272 | td->td_flags = 0; |
| 273 | } |
| 274 | |
| 275 | /* |
| 276 | * Initialize the lwkt s/system. |
| 277 | * |
| 278 | * Nominally cache up to 32 thread + kstack structures. Cache more on |
| 279 | * systems with a lot of cpu cores. |
| 280 | */ |
| 281 | void |
| 282 | lwkt_init(void) |
| 283 | { |
| 284 | TUNABLE_INT("lwkt.cache_threads", &lwkt_cache_threads); |
| 285 | if (lwkt_cache_threads == 0) { |
| 286 | lwkt_cache_threads = ncpus * 4; |
| 287 | if (lwkt_cache_threads < 32) |
| 288 | lwkt_cache_threads = 32; |
| 289 | } |
| 290 | thread_cache = objcache_create_mbacked( |
| 291 | M_THREAD, sizeof(struct thread), |
| 292 | 0, lwkt_cache_threads, |
| 293 | _lwkt_thread_ctor, _lwkt_thread_dtor, NULL); |
| 294 | } |
| 295 | |
| 296 | /* |
| 297 | * Schedule a thread to run. As the current thread we can always safely |
| 298 | * schedule ourselves, and a shortcut procedure is provided for that |
| 299 | * function. |
| 300 | * |
| 301 | * (non-blocking, self contained on a per cpu basis) |
| 302 | */ |
| 303 | void |
| 304 | lwkt_schedule_self(thread_t td) |
| 305 | { |
| 306 | KKASSERT((td->td_flags & TDF_MIGRATING) == 0); |
| 307 | crit_enter_quick(td); |
| 308 | KASSERT(td != &td->td_gd->gd_idlethread, |
| 309 | ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!")); |
| 310 | KKASSERT(td->td_lwp == NULL || |
| 311 | (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0); |
| 312 | _lwkt_enqueue(td); |
| 313 | crit_exit_quick(td); |
| 314 | } |
| 315 | |
| 316 | /* |
| 317 | * Deschedule a thread. |
| 318 | * |
| 319 | * (non-blocking, self contained on a per cpu basis) |
| 320 | */ |
| 321 | void |
| 322 | lwkt_deschedule_self(thread_t td) |
| 323 | { |
| 324 | crit_enter_quick(td); |
| 325 | _lwkt_dequeue(td); |
| 326 | crit_exit_quick(td); |
| 327 | } |
| 328 | |
| 329 | /* |
| 330 | * LWKTs operate on a per-cpu basis |
| 331 | * |
| 332 | * WARNING! Called from early boot, 'mycpu' may not work yet. |
| 333 | */ |
| 334 | void |
| 335 | lwkt_gdinit(struct globaldata *gd) |
| 336 | { |
| 337 | TAILQ_INIT(&gd->gd_tdrunq); |
| 338 | TAILQ_INIT(&gd->gd_tdallq); |
| 339 | } |
| 340 | |
| 341 | /* |
| 342 | * Create a new thread. The thread must be associated with a process context |
| 343 | * or LWKT start address before it can be scheduled. If the target cpu is |
| 344 | * -1 the thread will be created on the current cpu. |
| 345 | * |
| 346 | * If you intend to create a thread without a process context this function |
| 347 | * does everything except load the startup and switcher function. |
| 348 | */ |
| 349 | thread_t |
| 350 | lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags) |
| 351 | { |
| 352 | static int cpu_rotator; |
| 353 | globaldata_t gd = mycpu; |
| 354 | void *stack; |
| 355 | |
| 356 | /* |
| 357 | * If static thread storage is not supplied allocate a thread. Reuse |
| 358 | * a cached free thread if possible. gd_freetd is used to keep an exiting |
| 359 | * thread intact through the exit. |
| 360 | */ |
| 361 | if (td == NULL) { |
| 362 | crit_enter_gd(gd); |
| 363 | if ((td = gd->gd_freetd) != NULL) { |
| 364 | KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK| |
| 365 | TDF_RUNQ)) == 0); |
| 366 | gd->gd_freetd = NULL; |
| 367 | } else { |
| 368 | td = objcache_get(thread_cache, M_WAITOK); |
| 369 | KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK| |
| 370 | TDF_RUNQ)) == 0); |
| 371 | } |
| 372 | crit_exit_gd(gd); |
| 373 | KASSERT((td->td_flags & |
| 374 | (TDF_ALLOCATED_THREAD|TDF_RUNNING|TDF_PREEMPT_LOCK)) == |
| 375 | TDF_ALLOCATED_THREAD, |
| 376 | ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags)); |
| 377 | flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK); |
| 378 | } |
| 379 | |
| 380 | /* |
| 381 | * Try to reuse cached stack. |
| 382 | */ |
| 383 | if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) { |
| 384 | if (flags & TDF_ALLOCATED_STACK) { |
| 385 | kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size); |
| 386 | stack = NULL; |
| 387 | } |
| 388 | } |
| 389 | if (stack == NULL) { |
| 390 | stack = (void *)kmem_alloc_stack(&kernel_map, stksize); |
| 391 | flags |= TDF_ALLOCATED_STACK; |
| 392 | } |
| 393 | if (cpu < 0) { |
| 394 | cpu = ++cpu_rotator; |
| 395 | cpu_ccfence(); |
| 396 | cpu %= ncpus; |
| 397 | } |
| 398 | lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu)); |
| 399 | return(td); |
| 400 | } |
| 401 | |
| 402 | /* |
| 403 | * Initialize a preexisting thread structure. This function is used by |
| 404 | * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread. |
| 405 | * |
| 406 | * All threads start out in a critical section at a priority of |
| 407 | * TDPRI_KERN_DAEMON. Higher level code will modify the priority as |
| 408 | * appropriate. This function may send an IPI message when the |
| 409 | * requested cpu is not the current cpu and consequently gd_tdallq may |
| 410 | * not be initialized synchronously from the point of view of the originating |
| 411 | * cpu. |
| 412 | * |
| 413 | * NOTE! we have to be careful in regards to creating threads for other cpus |
| 414 | * if SMP has not yet been activated. |
| 415 | */ |
| 416 | static void |
| 417 | lwkt_init_thread_remote(void *arg) |
| 418 | { |
| 419 | thread_t td = arg; |
| 420 | |
| 421 | /* |
| 422 | * Protected by critical section held by IPI dispatch |
| 423 | */ |
| 424 | TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq); |
| 425 | } |
| 426 | |
| 427 | /* |
| 428 | * lwkt core thread structural initialization. |
| 429 | * |
| 430 | * NOTE: All threads are initialized as mpsafe threads. |
| 431 | */ |
| 432 | void |
| 433 | lwkt_init_thread(thread_t td, void *stack, int stksize, int flags, |
| 434 | struct globaldata *gd) |
| 435 | { |
| 436 | globaldata_t mygd = mycpu; |
| 437 | |
| 438 | bzero(td, sizeof(struct thread)); |
| 439 | td->td_kstack = stack; |
| 440 | td->td_kstack_size = stksize; |
| 441 | td->td_flags = flags; |
| 442 | td->td_mpflags = 0; |
| 443 | td->td_type = TD_TYPE_GENERIC; |
| 444 | td->td_gd = gd; |
| 445 | td->td_pri = TDPRI_KERN_DAEMON; |
| 446 | td->td_critcount = 1; |
| 447 | td->td_toks_have = NULL; |
| 448 | td->td_toks_stop = &td->td_toks_base; |
| 449 | if (lwkt_use_spin_port || (flags & TDF_FORCE_SPINPORT)) |
| 450 | lwkt_initport_spin(&td->td_msgport, td); |
| 451 | else |
| 452 | lwkt_initport_thread(&td->td_msgport, td); |
| 453 | pmap_init_thread(td); |
| 454 | /* |
| 455 | * Normally initializing a thread for a remote cpu requires sending an |
| 456 | * IPI. However, the idlethread is setup before the other cpus are |
| 457 | * activated so we have to treat it as a special case. XXX manipulation |
| 458 | * of gd_tdallq requires the BGL. |
| 459 | */ |
| 460 | if (gd == mygd || td == &gd->gd_idlethread) { |
| 461 | crit_enter_gd(mygd); |
| 462 | TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); |
| 463 | crit_exit_gd(mygd); |
| 464 | } else { |
| 465 | lwkt_send_ipiq(gd, lwkt_init_thread_remote, td); |
| 466 | } |
| 467 | dsched_new_thread(td); |
| 468 | } |
| 469 | |
| 470 | void |
| 471 | lwkt_set_comm(thread_t td, const char *ctl, ...) |
| 472 | { |
| 473 | __va_list va; |
| 474 | |
| 475 | __va_start(va, ctl); |
| 476 | kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va); |
| 477 | __va_end(va); |
| 478 | KTR_LOG(ctxsw_newtd, td, td->td_comm); |
| 479 | } |
| 480 | |
| 481 | /* |
| 482 | * Prevent the thread from getting destroyed. Note that unlike PHOLD/PRELE |
| 483 | * this does not prevent the thread from migrating to another cpu so the |
| 484 | * gd_tdallq state is not protected by this. |
| 485 | */ |
| 486 | void |
| 487 | lwkt_hold(thread_t td) |
| 488 | { |
| 489 | atomic_add_int(&td->td_refs, 1); |
| 490 | } |
| 491 | |
| 492 | void |
| 493 | lwkt_rele(thread_t td) |
| 494 | { |
| 495 | KKASSERT(td->td_refs > 0); |
| 496 | atomic_add_int(&td->td_refs, -1); |
| 497 | } |
| 498 | |
| 499 | void |
| 500 | lwkt_free_thread(thread_t td) |
| 501 | { |
| 502 | KKASSERT(td->td_refs == 0); |
| 503 | KKASSERT((td->td_flags & (TDF_RUNNING | TDF_PREEMPT_LOCK | |
| 504 | TDF_RUNQ | TDF_TSLEEPQ)) == 0); |
| 505 | if (td->td_flags & TDF_ALLOCATED_THREAD) { |
| 506 | objcache_put(thread_cache, td); |
| 507 | } else if (td->td_flags & TDF_ALLOCATED_STACK) { |
| 508 | /* client-allocated struct with internally allocated stack */ |
| 509 | KASSERT(td->td_kstack && td->td_kstack_size > 0, |
| 510 | ("lwkt_free_thread: corrupted stack")); |
| 511 | kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size); |
| 512 | td->td_kstack = NULL; |
| 513 | td->td_kstack_size = 0; |
| 514 | } |
| 515 | |
| 516 | KTR_LOG(ctxsw_deadtd, td); |
| 517 | } |
| 518 | |
| 519 | |
| 520 | /* |
| 521 | * Switch to the next runnable lwkt. If no LWKTs are runnable then |
| 522 | * switch to the idlethread. Switching must occur within a critical |
| 523 | * section to avoid races with the scheduling queue. |
| 524 | * |
| 525 | * We always have full control over our cpu's run queue. Other cpus |
| 526 | * that wish to manipulate our queue must use the cpu_*msg() calls to |
| 527 | * talk to our cpu, so a critical section is all that is needed and |
| 528 | * the result is very, very fast thread switching. |
| 529 | * |
| 530 | * The LWKT scheduler uses a fixed priority model and round-robins at |
| 531 | * each priority level. User process scheduling is a totally |
| 532 | * different beast and LWKT priorities should not be confused with |
| 533 | * user process priorities. |
| 534 | * |
| 535 | * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch() |
| 536 | * is not called by the current thread in the preemption case, only when |
| 537 | * the preempting thread blocks (in order to return to the original thread). |
| 538 | * |
| 539 | * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread |
| 540 | * migration and tsleep deschedule the current lwkt thread and call |
| 541 | * lwkt_switch(). In particular, the target cpu of the migration fully |
| 542 | * expects the thread to become non-runnable and can deadlock against |
| 543 | * cpusync operations if we run any IPIs prior to switching the thread out. |
| 544 | * |
| 545 | * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF |
| 546 | * THE CURRENT THREAD HAS BEEN DESCHEDULED! |
| 547 | */ |
| 548 | void |
| 549 | lwkt_switch(void) |
| 550 | { |
| 551 | globaldata_t gd = mycpu; |
| 552 | thread_t td = gd->gd_curthread; |
| 553 | thread_t ntd; |
| 554 | int spinning = 0; |
| 555 | |
| 556 | KKASSERT(gd->gd_processing_ipiq == 0); |
| 557 | KKASSERT(td->td_flags & TDF_RUNNING); |
| 558 | |
| 559 | /* |
| 560 | * Switching from within a 'fast' (non thread switched) interrupt or IPI |
| 561 | * is illegal. However, we may have to do it anyway if we hit a fatal |
| 562 | * kernel trap or we have paniced. |
| 563 | * |
| 564 | * If this case occurs save and restore the interrupt nesting level. |
| 565 | */ |
| 566 | if (gd->gd_intr_nesting_level) { |
| 567 | int savegdnest; |
| 568 | int savegdtrap; |
| 569 | |
| 570 | if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) { |
| 571 | panic("lwkt_switch: Attempt to switch from a " |
| 572 | "fast interrupt, ipi, or hard code section, " |
| 573 | "td %p\n", |
| 574 | td); |
| 575 | } else { |
| 576 | savegdnest = gd->gd_intr_nesting_level; |
| 577 | savegdtrap = gd->gd_trap_nesting_level; |
| 578 | gd->gd_intr_nesting_level = 0; |
| 579 | gd->gd_trap_nesting_level = 0; |
| 580 | if ((td->td_flags & TDF_PANICWARN) == 0) { |
| 581 | td->td_flags |= TDF_PANICWARN; |
| 582 | kprintf("Warning: thread switch from interrupt, IPI, " |
| 583 | "or hard code section.\n" |
| 584 | "thread %p (%s)\n", td, td->td_comm); |
| 585 | print_backtrace(-1); |
| 586 | } |
| 587 | lwkt_switch(); |
| 588 | gd->gd_intr_nesting_level = savegdnest; |
| 589 | gd->gd_trap_nesting_level = savegdtrap; |
| 590 | return; |
| 591 | } |
| 592 | } |
| 593 | |
| 594 | /* |
| 595 | * Release our current user process designation if we are blocking |
| 596 | * or if a user reschedule was requested. |
| 597 | * |
| 598 | * NOTE: This function is NOT called if we are switching into or |
| 599 | * returning from a preemption. |
| 600 | * |
| 601 | * NOTE: Releasing our current user process designation may cause |
| 602 | * it to be assigned to another thread, which in turn will |
| 603 | * cause us to block in the usched acquire code when we attempt |
| 604 | * to return to userland. |
| 605 | * |
| 606 | * NOTE: On SMP systems this can be very nasty when heavy token |
| 607 | * contention is present so we want to be careful not to |
| 608 | * release the designation gratuitously. |
| 609 | */ |
| 610 | if (td->td_release && |
| 611 | (user_resched_wanted() || (td->td_flags & TDF_RUNQ) == 0)) { |
| 612 | td->td_release(td); |
| 613 | } |
| 614 | |
| 615 | /* |
| 616 | * Release all tokens |
| 617 | */ |
| 618 | crit_enter_gd(gd); |
| 619 | if (TD_TOKS_HELD(td)) |
| 620 | lwkt_relalltokens(td); |
| 621 | |
| 622 | /* |
| 623 | * We had better not be holding any spin locks, but don't get into an |
| 624 | * endless panic loop. |
| 625 | */ |
| 626 | KASSERT(gd->gd_spinlocks == 0 || panicstr != NULL, |
| 627 | ("lwkt_switch: still holding %d exclusive spinlocks!", |
| 628 | gd->gd_spinlocks)); |
| 629 | |
| 630 | |
| 631 | #ifdef INVARIANTS |
| 632 | if (td->td_cscount) { |
| 633 | kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n", |
| 634 | td); |
| 635 | if (panic_on_cscount) |
| 636 | panic("switching while mastering cpusync"); |
| 637 | } |
| 638 | #endif |
| 639 | |
| 640 | /* |
| 641 | * If we had preempted another thread on this cpu, resume the preempted |
| 642 | * thread. This occurs transparently, whether the preempted thread |
| 643 | * was scheduled or not (it may have been preempted after descheduling |
| 644 | * itself). |
| 645 | * |
| 646 | * We have to setup the MP lock for the original thread after backing |
| 647 | * out the adjustment that was made to curthread when the original |
| 648 | * was preempted. |
| 649 | */ |
| 650 | if ((ntd = td->td_preempted) != NULL) { |
| 651 | KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK); |
| 652 | ntd->td_flags |= TDF_PREEMPT_DONE; |
| 653 | |
| 654 | /* |
| 655 | * The interrupt may have woken a thread up, we need to properly |
| 656 | * set the reschedule flag if the originally interrupted thread is |
| 657 | * at a lower priority. |
| 658 | * |
| 659 | * The interrupt may not have descheduled. |
| 660 | */ |
| 661 | if (TAILQ_FIRST(&gd->gd_tdrunq) != ntd) |
| 662 | need_lwkt_resched(); |
| 663 | goto havethread_preempted; |
| 664 | } |
| 665 | |
| 666 | /* |
| 667 | * If we cannot obtain ownership of the tokens we cannot immediately |
| 668 | * schedule the target thread. |
| 669 | * |
| 670 | * Reminder: Again, we cannot afford to run any IPIs in this path if |
| 671 | * the current thread has been descheduled. |
| 672 | */ |
| 673 | for (;;) { |
| 674 | clear_lwkt_resched(); |
| 675 | |
| 676 | /* |
| 677 | * Hotpath - pull the head of the run queue and attempt to schedule |
| 678 | * it. |
| 679 | */ |
| 680 | ntd = TAILQ_FIRST(&gd->gd_tdrunq); |
| 681 | |
| 682 | if (ntd == NULL) { |
| 683 | /* |
| 684 | * Runq is empty, switch to idle to allow it to halt. |
| 685 | */ |
| 686 | ntd = &gd->gd_idlethread; |
| 687 | if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) |
| 688 | ASSERT_NO_TOKENS_HELD(ntd); |
| 689 | cpu_time.cp_msg[0] = 0; |
| 690 | cpu_time.cp_stallpc = 0; |
| 691 | goto haveidle; |
| 692 | } |
| 693 | |
| 694 | /* |
| 695 | * Hotpath - schedule ntd. |
| 696 | * |
| 697 | * NOTE: For UP there is no mplock and lwkt_getalltokens() |
| 698 | * always succeeds. |
| 699 | */ |
| 700 | if (TD_TOKS_NOT_HELD(ntd) || |
| 701 | lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops))) |
| 702 | { |
| 703 | goto havethread; |
| 704 | } |
| 705 | |
| 706 | /* |
| 707 | * Coldpath (SMP only since tokens always succeed on UP) |
| 708 | * |
| 709 | * We had some contention on the thread we wanted to schedule. |
| 710 | * What we do now is try to find a thread that we can schedule |
| 711 | * in its stead. |
| 712 | * |
| 713 | * The coldpath scan does NOT rearrange threads in the run list. |
| 714 | * The lwkt_schedulerclock() will assert need_lwkt_resched() on |
| 715 | * the next tick whenever the current head is not the current thread. |
| 716 | */ |
| 717 | #ifdef INVARIANTS |
| 718 | ++ntd->td_contended; |
| 719 | #endif |
| 720 | ++gd->gd_cnt.v_token_colls; |
| 721 | |
| 722 | if (fairq_bypass > 0) |
| 723 | goto skip; |
| 724 | |
| 725 | while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) { |
| 726 | #ifndef NO_LWKT_SPLIT_USERPRI |
| 727 | /* |
| 728 | * Never schedule threads returning to userland or the |
| 729 | * user thread scheduler helper thread when higher priority |
| 730 | * threads are present. The runq is sorted by priority |
| 731 | * so we can give up traversing it when we find the first |
| 732 | * low priority thread. |
| 733 | */ |
| 734 | if (ntd->td_pri < TDPRI_KERN_LPSCHED) { |
| 735 | ntd = NULL; |
| 736 | break; |
| 737 | } |
| 738 | #endif |
| 739 | |
| 740 | /* |
| 741 | * Try this one. |
| 742 | */ |
| 743 | if (TD_TOKS_NOT_HELD(ntd) || |
| 744 | lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops))) { |
| 745 | goto havethread; |
| 746 | } |
| 747 | #ifdef INVARIANTS |
| 748 | ++ntd->td_contended; |
| 749 | #endif |
| 750 | ++gd->gd_cnt.v_token_colls; |
| 751 | } |
| 752 | |
| 753 | skip: |
| 754 | /* |
| 755 | * We exhausted the run list, meaning that all runnable threads |
| 756 | * are contested. |
| 757 | */ |
| 758 | cpu_pause(); |
| 759 | #ifdef _KERNEL_VIRTUAL |
| 760 | pthread_yield(); |
| 761 | #endif |
| 762 | ntd = &gd->gd_idlethread; |
| 763 | if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) |
| 764 | ASSERT_NO_TOKENS_HELD(ntd); |
| 765 | /* contention case, do not clear contention mask */ |
| 766 | |
| 767 | /* |
| 768 | * We are going to have to retry but if the current thread is not |
| 769 | * on the runq we instead switch through the idle thread to get away |
| 770 | * from the current thread. We have to flag for lwkt reschedule |
| 771 | * to prevent the idle thread from halting. |
| 772 | * |
| 773 | * NOTE: A non-zero spinning is passed to lwkt_getalltokens() to |
| 774 | * instruct it to deal with the potential for deadlocks by |
| 775 | * ordering the tokens by address. |
| 776 | */ |
| 777 | if ((td->td_flags & TDF_RUNQ) == 0) { |
| 778 | need_lwkt_resched(); /* prevent hlt */ |
| 779 | goto haveidle; |
| 780 | } |
| 781 | #if defined(INVARIANTS) && defined(__x86_64__) |
| 782 | if ((read_rflags() & PSL_I) == 0) { |
| 783 | cpu_enable_intr(); |
| 784 | panic("lwkt_switch() called with interrupts disabled"); |
| 785 | } |
| 786 | #endif |
| 787 | |
| 788 | /* |
| 789 | * Number iterations so far. After a certain point we switch to |
| 790 | * a sorted-address/monitor/mwait version of lwkt_getalltokens() |
| 791 | */ |
| 792 | if (spinning < 0x7FFFFFFF) |
| 793 | ++spinning; |
| 794 | |
| 795 | #ifndef _KERNEL_VIRTUAL |
| 796 | /* |
| 797 | * lwkt_getalltokens() failed in sorted token mode, we can use |
| 798 | * monitor/mwait in this case. |
| 799 | */ |
| 800 | if (spinning >= lwkt_spin_loops && |
| 801 | (cpu_mi_feature & CPU_MI_MONITOR) && |
| 802 | lwkt_spin_monitor) |
| 803 | { |
| 804 | cpu_mmw_pause_int(&gd->gd_reqflags, |
| 805 | (gd->gd_reqflags | RQF_SPINNING) & |
| 806 | ~RQF_IDLECHECK_WK_MASK, |
| 807 | cpu_mwait_spin); |
| 808 | } |
| 809 | #endif |
| 810 | |
| 811 | /* |
| 812 | * We already checked that td is still scheduled so this should be |
| 813 | * safe. |
| 814 | */ |
| 815 | splz_check(); |
| 816 | |
| 817 | #ifndef _KERNEL_VIRTUAL |
| 818 | /* |
| 819 | * This experimental resequencer is used as a fall-back to reduce |
| 820 | * hw cache line contention by placing each core's scheduler into a |
| 821 | * time-domain-multplexed slot. |
| 822 | * |
| 823 | * The resequencer is disabled by default. It's functionality has |
| 824 | * largely been superceeded by the token algorithm which limits races |
| 825 | * to a subset of cores. |
| 826 | * |
| 827 | * The resequencer algorithm tends to break down when more than |
| 828 | * 20 cores are contending. What appears to happen is that new |
| 829 | * tokens can be obtained out of address-sorted order by new cores |
| 830 | * while existing cores languish in long delays between retries and |
| 831 | * wind up being starved-out of the token acquisition. |
| 832 | */ |
| 833 | if (lwkt_spin_reseq && spinning >= lwkt_spin_reseq) { |
| 834 | int cseq = atomic_fetchadd_int(&lwkt_cseq_windex, 1); |
| 835 | int oseq; |
| 836 | |
| 837 | while ((oseq = lwkt_cseq_rindex) != cseq) { |
| 838 | cpu_ccfence(); |
| 839 | #if 1 |
| 840 | if (cpu_mi_feature & CPU_MI_MONITOR) { |
| 841 | cpu_mmw_pause_int(&lwkt_cseq_rindex, oseq, cpu_mwait_spin); |
| 842 | } else { |
| 843 | #endif |
| 844 | cpu_pause(); |
| 845 | cpu_lfence(); |
| 846 | #if 1 |
| 847 | } |
| 848 | #endif |
| 849 | } |
| 850 | DELAY(1); |
| 851 | atomic_add_int(&lwkt_cseq_rindex, 1); |
| 852 | } |
| 853 | #endif |
| 854 | /* highest level for(;;) loop */ |
| 855 | } |
| 856 | |
| 857 | havethread: |
| 858 | /* |
| 859 | * Clear gd_idle_repeat when doing a normal switch to a non-idle |
| 860 | * thread. |
| 861 | */ |
| 862 | ntd->td_wmesg = NULL; |
| 863 | ++gd->gd_cnt.v_swtch; |
| 864 | gd->gd_idle_repeat = 0; |
| 865 | |
| 866 | havethread_preempted: |
| 867 | /* |
| 868 | * If the new target does not need the MP lock and we are holding it, |
| 869 | * release the MP lock. If the new target requires the MP lock we have |
| 870 | * already acquired it for the target. |
| 871 | */ |
| 872 | ; |
| 873 | haveidle: |
| 874 | KASSERT(ntd->td_critcount, |
| 875 | ("priority problem in lwkt_switch %d %d", |
| 876 | td->td_critcount, ntd->td_critcount)); |
| 877 | |
| 878 | if (td != ntd) { |
| 879 | /* |
| 880 | * Execute the actual thread switch operation. This function |
| 881 | * returns to the current thread and returns the previous thread |
| 882 | * (which may be different from the thread we switched to). |
| 883 | * |
| 884 | * We are responsible for marking ntd as TDF_RUNNING. |
| 885 | */ |
| 886 | KKASSERT((ntd->td_flags & TDF_RUNNING) == 0); |
| 887 | ++switch_count; |
| 888 | KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd); |
| 889 | ntd->td_flags |= TDF_RUNNING; |
| 890 | lwkt_switch_return(td->td_switch(ntd)); |
| 891 | /* ntd invalid, td_switch() can return a different thread_t */ |
| 892 | } |
| 893 | |
| 894 | /* |
| 895 | * catch-all. XXX is this strictly needed? |
| 896 | */ |
| 897 | splz_check(); |
| 898 | |
| 899 | /* NOTE: current cpu may have changed after switch */ |
| 900 | crit_exit_quick(td); |
| 901 | } |
| 902 | |
| 903 | /* |
| 904 | * Called by assembly in the td_switch (thread restore path) for thread |
| 905 | * bootstrap cases which do not 'return' to lwkt_switch(). |
| 906 | */ |
| 907 | void |
| 908 | lwkt_switch_return(thread_t otd) |
| 909 | { |
| 910 | globaldata_t rgd; |
| 911 | |
| 912 | /* |
| 913 | * Check if otd was migrating. Now that we are on ntd we can finish |
| 914 | * up the migration. This is a bit messy but it is the only place |
| 915 | * where td is known to be fully descheduled. |
| 916 | * |
| 917 | * We can only activate the migration if otd was migrating but not |
| 918 | * held on the cpu due to a preemption chain. We still have to |
| 919 | * clear TDF_RUNNING on the old thread either way. |
| 920 | * |
| 921 | * We are responsible for clearing the previously running thread's |
| 922 | * TDF_RUNNING. |
| 923 | */ |
| 924 | if ((rgd = otd->td_migrate_gd) != NULL && |
| 925 | (otd->td_flags & TDF_PREEMPT_LOCK) == 0) { |
| 926 | KKASSERT((otd->td_flags & (TDF_MIGRATING | TDF_RUNNING)) == |
| 927 | (TDF_MIGRATING | TDF_RUNNING)); |
| 928 | otd->td_migrate_gd = NULL; |
| 929 | otd->td_flags &= ~TDF_RUNNING; |
| 930 | lwkt_send_ipiq(rgd, lwkt_setcpu_remote, otd); |
| 931 | } else { |
| 932 | otd->td_flags &= ~TDF_RUNNING; |
| 933 | } |
| 934 | |
| 935 | /* |
| 936 | * Final exit validations (see lwp_wait()). Note that otd becomes |
| 937 | * invalid the *instant* we set TDF_MP_EXITSIG. |
| 938 | */ |
| 939 | while (otd->td_flags & TDF_EXITING) { |
| 940 | u_int mpflags; |
| 941 | |
| 942 | mpflags = otd->td_mpflags; |
| 943 | cpu_ccfence(); |
| 944 | |
| 945 | if (mpflags & TDF_MP_EXITWAIT) { |
| 946 | if (atomic_cmpset_int(&otd->td_mpflags, mpflags, |
| 947 | mpflags | TDF_MP_EXITSIG)) { |
| 948 | wakeup(otd); |
| 949 | break; |
| 950 | } |
| 951 | } else { |
| 952 | if (atomic_cmpset_int(&otd->td_mpflags, mpflags, |
| 953 | mpflags | TDF_MP_EXITSIG)) { |
| 954 | wakeup(otd); |
| 955 | break; |
| 956 | } |
| 957 | } |
| 958 | } |
| 959 | } |
| 960 | |
| 961 | /* |
| 962 | * Request that the target thread preempt the current thread. Preemption |
| 963 | * can only occur if our only critical section is the one that we were called |
| 964 | * with, the relative priority of the target thread is higher, and the target |
| 965 | * thread holds no tokens. This also only works if we are not holding any |
| 966 | * spinlocks (obviously). |
| 967 | * |
| 968 | * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically |
| 969 | * this is called via lwkt_schedule() through the td_preemptable callback. |
| 970 | * critcount is the managed critical priority that we should ignore in order |
| 971 | * to determine whether preemption is possible (aka usually just the crit |
| 972 | * priority of lwkt_schedule() itself). |
| 973 | * |
| 974 | * Preemption is typically limited to interrupt threads. |
| 975 | * |
| 976 | * Operation works in a fairly straight-forward manner. The normal |
| 977 | * scheduling code is bypassed and we switch directly to the target |
| 978 | * thread. When the target thread attempts to block or switch away |
| 979 | * code at the base of lwkt_switch() will switch directly back to our |
| 980 | * thread. Our thread is able to retain whatever tokens it holds and |
| 981 | * if the target needs one of them the target will switch back to us |
| 982 | * and reschedule itself normally. |
| 983 | */ |
| 984 | void |
| 985 | lwkt_preempt(thread_t ntd, int critcount) |
| 986 | { |
| 987 | struct globaldata *gd = mycpu; |
| 988 | thread_t xtd; |
| 989 | thread_t td; |
| 990 | int save_gd_intr_nesting_level; |
| 991 | |
| 992 | /* |
| 993 | * The caller has put us in a critical section. We can only preempt |
| 994 | * if the caller of the caller was not in a critical section (basically |
| 995 | * a local interrupt), as determined by the 'critcount' parameter. We |
| 996 | * also can't preempt if the caller is holding any spinlocks (even if |
| 997 | * he isn't in a critical section). This also handles the tokens test. |
| 998 | * |
| 999 | * YYY The target thread must be in a critical section (else it must |
| 1000 | * inherit our critical section? I dunno yet). |
| 1001 | */ |
| 1002 | KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri)); |
| 1003 | |
| 1004 | td = gd->gd_curthread; |
| 1005 | if (preempt_enable == 0) { |
| 1006 | ++preempt_miss; |
| 1007 | return; |
| 1008 | } |
| 1009 | if (ntd->td_pri <= td->td_pri) { |
| 1010 | ++preempt_miss; |
| 1011 | return; |
| 1012 | } |
| 1013 | if (td->td_critcount > critcount) { |
| 1014 | ++preempt_miss; |
| 1015 | return; |
| 1016 | } |
| 1017 | if (td->td_cscount) { |
| 1018 | ++preempt_miss; |
| 1019 | return; |
| 1020 | } |
| 1021 | if (ntd->td_gd != gd) { |
| 1022 | ++preempt_miss; |
| 1023 | return; |
| 1024 | } |
| 1025 | /* |
| 1026 | * We don't have to check spinlocks here as they will also bump |
| 1027 | * td_critcount. |
| 1028 | * |
| 1029 | * Do not try to preempt if the target thread is holding any tokens. |
| 1030 | * We could try to acquire the tokens but this case is so rare there |
| 1031 | * is no need to support it. |
| 1032 | */ |
| 1033 | KKASSERT(gd->gd_spinlocks == 0); |
| 1034 | |
| 1035 | if (TD_TOKS_HELD(ntd)) { |
| 1036 | ++preempt_miss; |
| 1037 | return; |
| 1038 | } |
| 1039 | if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) { |
| 1040 | ++preempt_weird; |
| 1041 | return; |
| 1042 | } |
| 1043 | if (ntd->td_preempted) { |
| 1044 | ++preempt_hit; |
| 1045 | return; |
| 1046 | } |
| 1047 | KKASSERT(gd->gd_processing_ipiq == 0); |
| 1048 | |
| 1049 | /* |
| 1050 | * Since we are able to preempt the current thread, there is no need to |
| 1051 | * call need_lwkt_resched(). |
| 1052 | * |
| 1053 | * We must temporarily clear gd_intr_nesting_level around the switch |
| 1054 | * since switchouts from the target thread are allowed (they will just |
| 1055 | * return to our thread), and since the target thread has its own stack. |
| 1056 | * |
| 1057 | * A preemption must switch back to the original thread, assert the |
| 1058 | * case. |
| 1059 | */ |
| 1060 | ++preempt_hit; |
| 1061 | ntd->td_preempted = td; |
| 1062 | td->td_flags |= TDF_PREEMPT_LOCK; |
| 1063 | KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd); |
| 1064 | save_gd_intr_nesting_level = gd->gd_intr_nesting_level; |
| 1065 | gd->gd_intr_nesting_level = 0; |
| 1066 | |
| 1067 | KKASSERT((ntd->td_flags & TDF_RUNNING) == 0); |
| 1068 | ntd->td_flags |= TDF_RUNNING; |
| 1069 | xtd = td->td_switch(ntd); |
| 1070 | KKASSERT(xtd == ntd); |
| 1071 | lwkt_switch_return(xtd); |
| 1072 | gd->gd_intr_nesting_level = save_gd_intr_nesting_level; |
| 1073 | |
| 1074 | KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE)); |
| 1075 | ntd->td_preempted = NULL; |
| 1076 | td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE); |
| 1077 | } |
| 1078 | |
| 1079 | /* |
| 1080 | * Conditionally call splz() if gd_reqflags indicates work is pending. |
| 1081 | * This will work inside a critical section but not inside a hard code |
| 1082 | * section. |
| 1083 | * |
| 1084 | * (self contained on a per cpu basis) |
| 1085 | */ |
| 1086 | void |
| 1087 | splz_check(void) |
| 1088 | { |
| 1089 | globaldata_t gd = mycpu; |
| 1090 | thread_t td = gd->gd_curthread; |
| 1091 | |
| 1092 | if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && |
| 1093 | gd->gd_intr_nesting_level == 0 && |
| 1094 | td->td_nest_count < 2) |
| 1095 | { |
| 1096 | splz(); |
| 1097 | } |
| 1098 | } |
| 1099 | |
| 1100 | /* |
| 1101 | * This version is integrated into crit_exit, reqflags has already |
| 1102 | * been tested but td_critcount has not. |
| 1103 | * |
| 1104 | * We only want to execute the splz() on the 1->0 transition of |
| 1105 | * critcount and not in a hard code section or if too deeply nested. |
| 1106 | * |
| 1107 | * NOTE: gd->gd_spinlocks is implied to be 0 when td_critcount is 0. |
| 1108 | */ |
| 1109 | void |
| 1110 | lwkt_maybe_splz(thread_t td) |
| 1111 | { |
| 1112 | globaldata_t gd = td->td_gd; |
| 1113 | |
| 1114 | if (td->td_critcount == 0 && |
| 1115 | gd->gd_intr_nesting_level == 0 && |
| 1116 | td->td_nest_count < 2) |
| 1117 | { |
| 1118 | splz(); |
| 1119 | } |
| 1120 | } |
| 1121 | |
| 1122 | /* |
| 1123 | * Drivers which set up processing co-threads can call this function to |
| 1124 | * run the co-thread at a higher priority and to allow it to preempt |
| 1125 | * normal threads. |
| 1126 | */ |
| 1127 | void |
| 1128 | lwkt_set_interrupt_support_thread(void) |
| 1129 | { |
| 1130 | thread_t td = curthread; |
| 1131 | |
| 1132 | lwkt_setpri_self(TDPRI_INT_SUPPORT); |
| 1133 | td->td_flags |= TDF_INTTHREAD; |
| 1134 | td->td_preemptable = lwkt_preempt; |
| 1135 | } |
| 1136 | |
| 1137 | |
| 1138 | /* |
| 1139 | * This function is used to negotiate a passive release of the current |
| 1140 | * process/lwp designation with the user scheduler, allowing the user |
| 1141 | * scheduler to schedule another user thread. The related kernel thread |
| 1142 | * (curthread) continues running in the released state. |
| 1143 | */ |
| 1144 | void |
| 1145 | lwkt_passive_release(struct thread *td) |
| 1146 | { |
| 1147 | struct lwp *lp = td->td_lwp; |
| 1148 | |
| 1149 | #ifndef NO_LWKT_SPLIT_USERPRI |
| 1150 | td->td_release = NULL; |
| 1151 | lwkt_setpri_self(TDPRI_KERN_USER); |
| 1152 | #endif |
| 1153 | |
| 1154 | lp->lwp_proc->p_usched->release_curproc(lp); |
| 1155 | } |
| 1156 | |
| 1157 | |
| 1158 | /* |
| 1159 | * This implements a LWKT yield, allowing a kernel thread to yield to other |
| 1160 | * kernel threads at the same or higher priority. This function can be |
| 1161 | * called in a tight loop and will typically only yield once per tick. |
| 1162 | * |
| 1163 | * Most kernel threads run at the same priority in order to allow equal |
| 1164 | * sharing. |
| 1165 | * |
| 1166 | * (self contained on a per cpu basis) |
| 1167 | */ |
| 1168 | void |
| 1169 | lwkt_yield(void) |
| 1170 | { |
| 1171 | globaldata_t gd = mycpu; |
| 1172 | thread_t td = gd->gd_curthread; |
| 1173 | |
| 1174 | if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2) |
| 1175 | splz(); |
| 1176 | if (lwkt_resched_wanted()) { |
| 1177 | lwkt_schedule_self(curthread); |
| 1178 | lwkt_switch(); |
| 1179 | } |
| 1180 | } |
| 1181 | |
| 1182 | /* |
| 1183 | * The quick version processes pending interrupts and higher-priority |
| 1184 | * LWKT threads but will not round-robin same-priority LWKT threads. |
| 1185 | * |
| 1186 | * When called while attempting to return to userland the only same-pri |
| 1187 | * threads are the ones which have already tried to become the current |
| 1188 | * user process. |
| 1189 | */ |
| 1190 | void |
| 1191 | lwkt_yield_quick(void) |
| 1192 | { |
| 1193 | globaldata_t gd = mycpu; |
| 1194 | thread_t td = gd->gd_curthread; |
| 1195 | |
| 1196 | if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2) |
| 1197 | splz(); |
| 1198 | if (lwkt_resched_wanted()) { |
| 1199 | crit_enter(); |
| 1200 | if (TAILQ_FIRST(&gd->gd_tdrunq) == td) { |
| 1201 | clear_lwkt_resched(); |
| 1202 | } else { |
| 1203 | lwkt_schedule_self(curthread); |
| 1204 | lwkt_switch(); |
| 1205 | } |
| 1206 | crit_exit(); |
| 1207 | } |
| 1208 | } |
| 1209 | |
| 1210 | /* |
| 1211 | * This yield is designed for kernel threads with a user context. |
| 1212 | * |
| 1213 | * The kernel acting on behalf of the user is potentially cpu-bound, |
| 1214 | * this function will efficiently allow other threads to run and also |
| 1215 | * switch to other processes by releasing. |
| 1216 | * |
| 1217 | * The lwkt_user_yield() function is designed to have very low overhead |
| 1218 | * if no yield is determined to be needed. |
| 1219 | */ |
| 1220 | void |
| 1221 | lwkt_user_yield(void) |
| 1222 | { |
| 1223 | globaldata_t gd = mycpu; |
| 1224 | thread_t td = gd->gd_curthread; |
| 1225 | |
| 1226 | /* |
| 1227 | * Always run any pending interrupts in case we are in a critical |
| 1228 | * section. |
| 1229 | */ |
| 1230 | if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2) |
| 1231 | splz(); |
| 1232 | |
| 1233 | /* |
| 1234 | * Switch (which forces a release) if another kernel thread needs |
| 1235 | * the cpu, if userland wants us to resched, or if our kernel |
| 1236 | * quantum has run out. |
| 1237 | */ |
| 1238 | if (lwkt_resched_wanted() || |
| 1239 | user_resched_wanted()) |
| 1240 | { |
| 1241 | lwkt_switch(); |
| 1242 | } |
| 1243 | |
| 1244 | #if 0 |
| 1245 | /* |
| 1246 | * Reacquire the current process if we are released. |
| 1247 | * |
| 1248 | * XXX not implemented atm. The kernel may be holding locks and such, |
| 1249 | * so we want the thread to continue to receive cpu. |
| 1250 | */ |
| 1251 | if (td->td_release == NULL && lp) { |
| 1252 | lp->lwp_proc->p_usched->acquire_curproc(lp); |
| 1253 | td->td_release = lwkt_passive_release; |
| 1254 | lwkt_setpri_self(TDPRI_USER_NORM); |
| 1255 | } |
| 1256 | #endif |
| 1257 | } |
| 1258 | |
| 1259 | /* |
| 1260 | * Generic schedule. Possibly schedule threads belonging to other cpus and |
| 1261 | * deal with threads that might be blocked on a wait queue. |
| 1262 | * |
| 1263 | * We have a little helper inline function which does additional work after |
| 1264 | * the thread has been enqueued, including dealing with preemption and |
| 1265 | * setting need_lwkt_resched() (which prevents the kernel from returning |
| 1266 | * to userland until it has processed higher priority threads). |
| 1267 | * |
| 1268 | * It is possible for this routine to be called after a failed _enqueue |
| 1269 | * (due to the target thread migrating, sleeping, or otherwise blocked). |
| 1270 | * We have to check that the thread is actually on the run queue! |
| 1271 | */ |
| 1272 | static __inline |
| 1273 | void |
| 1274 | _lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount) |
| 1275 | { |
| 1276 | if (ntd->td_flags & TDF_RUNQ) { |
| 1277 | if (ntd->td_preemptable) { |
| 1278 | ntd->td_preemptable(ntd, ccount); /* YYY +token */ |
| 1279 | } |
| 1280 | } |
| 1281 | } |
| 1282 | |
| 1283 | static __inline |
| 1284 | void |
| 1285 | _lwkt_schedule(thread_t td) |
| 1286 | { |
| 1287 | globaldata_t mygd = mycpu; |
| 1288 | |
| 1289 | KASSERT(td != &td->td_gd->gd_idlethread, |
| 1290 | ("lwkt_schedule(): scheduling gd_idlethread is illegal!")); |
| 1291 | KKASSERT((td->td_flags & TDF_MIGRATING) == 0); |
| 1292 | crit_enter_gd(mygd); |
| 1293 | KKASSERT(td->td_lwp == NULL || |
| 1294 | (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0); |
| 1295 | |
| 1296 | if (td == mygd->gd_curthread) { |
| 1297 | _lwkt_enqueue(td); |
| 1298 | } else { |
| 1299 | /* |
| 1300 | * If we own the thread, there is no race (since we are in a |
| 1301 | * critical section). If we do not own the thread there might |
| 1302 | * be a race but the target cpu will deal with it. |
| 1303 | */ |
| 1304 | if (td->td_gd == mygd) { |
| 1305 | _lwkt_enqueue(td); |
| 1306 | _lwkt_schedule_post(mygd, td, 1); |
| 1307 | } else { |
| 1308 | lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0); |
| 1309 | } |
| 1310 | } |
| 1311 | crit_exit_gd(mygd); |
| 1312 | } |
| 1313 | |
| 1314 | void |
| 1315 | lwkt_schedule(thread_t td) |
| 1316 | { |
| 1317 | _lwkt_schedule(td); |
| 1318 | } |
| 1319 | |
| 1320 | void |
| 1321 | lwkt_schedule_noresched(thread_t td) /* XXX not impl */ |
| 1322 | { |
| 1323 | _lwkt_schedule(td); |
| 1324 | } |
| 1325 | |
| 1326 | /* |
| 1327 | * When scheduled remotely if frame != NULL the IPIQ is being |
| 1328 | * run via doreti or an interrupt then preemption can be allowed. |
| 1329 | * |
| 1330 | * To allow preemption we have to drop the critical section so only |
| 1331 | * one is present in _lwkt_schedule_post. |
| 1332 | */ |
| 1333 | static void |
| 1334 | lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame) |
| 1335 | { |
| 1336 | thread_t td = curthread; |
| 1337 | thread_t ntd = arg; |
| 1338 | |
| 1339 | if (frame && ntd->td_preemptable) { |
| 1340 | crit_exit_noyield(td); |
| 1341 | _lwkt_schedule(ntd); |
| 1342 | crit_enter_quick(td); |
| 1343 | } else { |
| 1344 | _lwkt_schedule(ntd); |
| 1345 | } |
| 1346 | } |
| 1347 | |
| 1348 | /* |
| 1349 | * Thread migration using a 'Pull' method. The thread may or may not be |
| 1350 | * the current thread. It MUST be descheduled and in a stable state. |
| 1351 | * lwkt_giveaway() must be called on the cpu owning the thread. |
| 1352 | * |
| 1353 | * At any point after lwkt_giveaway() is called, the target cpu may |
| 1354 | * 'pull' the thread by calling lwkt_acquire(). |
| 1355 | * |
| 1356 | * We have to make sure the thread is not sitting on a per-cpu tsleep |
| 1357 | * queue or it will blow up when it moves to another cpu. |
| 1358 | * |
| 1359 | * MPSAFE - must be called under very specific conditions. |
| 1360 | */ |
| 1361 | void |
| 1362 | lwkt_giveaway(thread_t td) |
| 1363 | { |
| 1364 | globaldata_t gd = mycpu; |
| 1365 | |
| 1366 | crit_enter_gd(gd); |
| 1367 | if (td->td_flags & TDF_TSLEEPQ) |
| 1368 | tsleep_remove(td); |
| 1369 | KKASSERT(td->td_gd == gd); |
| 1370 | TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); |
| 1371 | td->td_flags |= TDF_MIGRATING; |
| 1372 | crit_exit_gd(gd); |
| 1373 | } |
| 1374 | |
| 1375 | void |
| 1376 | lwkt_acquire(thread_t td) |
| 1377 | { |
| 1378 | globaldata_t gd; |
| 1379 | globaldata_t mygd; |
| 1380 | int retry = 10000000; |
| 1381 | |
| 1382 | KKASSERT(td->td_flags & TDF_MIGRATING); |
| 1383 | gd = td->td_gd; |
| 1384 | mygd = mycpu; |
| 1385 | if (gd != mycpu) { |
| 1386 | cpu_lfence(); |
| 1387 | KKASSERT((td->td_flags & TDF_RUNQ) == 0); |
| 1388 | crit_enter_gd(mygd); |
| 1389 | DEBUG_PUSH_INFO("lwkt_acquire"); |
| 1390 | while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) { |
| 1391 | lwkt_process_ipiq(); |
| 1392 | cpu_lfence(); |
| 1393 | if (--retry == 0) { |
| 1394 | kprintf("lwkt_acquire: stuck: td %p td->td_flags %08x\n", |
| 1395 | td, td->td_flags); |
| 1396 | retry = 10000000; |
| 1397 | } |
| 1398 | #ifdef _KERNEL_VIRTUAL |
| 1399 | pthread_yield(); |
| 1400 | #endif |
| 1401 | } |
| 1402 | DEBUG_POP_INFO(); |
| 1403 | cpu_mfence(); |
| 1404 | td->td_gd = mygd; |
| 1405 | TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); |
| 1406 | td->td_flags &= ~TDF_MIGRATING; |
| 1407 | crit_exit_gd(mygd); |
| 1408 | } else { |
| 1409 | crit_enter_gd(mygd); |
| 1410 | TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); |
| 1411 | td->td_flags &= ~TDF_MIGRATING; |
| 1412 | crit_exit_gd(mygd); |
| 1413 | } |
| 1414 | } |
| 1415 | |
| 1416 | /* |
| 1417 | * Generic deschedule. Descheduling threads other then your own should be |
| 1418 | * done only in carefully controlled circumstances. Descheduling is |
| 1419 | * asynchronous. |
| 1420 | * |
| 1421 | * This function may block if the cpu has run out of messages. |
| 1422 | */ |
| 1423 | void |
| 1424 | lwkt_deschedule(thread_t td) |
| 1425 | { |
| 1426 | crit_enter(); |
| 1427 | if (td == curthread) { |
| 1428 | _lwkt_dequeue(td); |
| 1429 | } else { |
| 1430 | if (td->td_gd == mycpu) { |
| 1431 | _lwkt_dequeue(td); |
| 1432 | } else { |
| 1433 | lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td); |
| 1434 | } |
| 1435 | } |
| 1436 | crit_exit(); |
| 1437 | } |
| 1438 | |
| 1439 | /* |
| 1440 | * Set the target thread's priority. This routine does not automatically |
| 1441 | * switch to a higher priority thread, LWKT threads are not designed for |
| 1442 | * continuous priority changes. Yield if you want to switch. |
| 1443 | */ |
| 1444 | void |
| 1445 | lwkt_setpri(thread_t td, int pri) |
| 1446 | { |
| 1447 | if (td->td_pri != pri) { |
| 1448 | KKASSERT(pri >= 0); |
| 1449 | crit_enter(); |
| 1450 | if (td->td_flags & TDF_RUNQ) { |
| 1451 | KKASSERT(td->td_gd == mycpu); |
| 1452 | _lwkt_dequeue(td); |
| 1453 | td->td_pri = pri; |
| 1454 | _lwkt_enqueue(td); |
| 1455 | } else { |
| 1456 | td->td_pri = pri; |
| 1457 | } |
| 1458 | crit_exit(); |
| 1459 | } |
| 1460 | } |
| 1461 | |
| 1462 | /* |
| 1463 | * Set the initial priority for a thread prior to it being scheduled for |
| 1464 | * the first time. The thread MUST NOT be scheduled before or during |
| 1465 | * this call. The thread may be assigned to a cpu other then the current |
| 1466 | * cpu. |
| 1467 | * |
| 1468 | * Typically used after a thread has been created with TDF_STOPPREQ, |
| 1469 | * and before the thread is initially scheduled. |
| 1470 | */ |
| 1471 | void |
| 1472 | lwkt_setpri_initial(thread_t td, int pri) |
| 1473 | { |
| 1474 | KKASSERT(pri >= 0); |
| 1475 | KKASSERT((td->td_flags & TDF_RUNQ) == 0); |
| 1476 | td->td_pri = pri; |
| 1477 | } |
| 1478 | |
| 1479 | void |
| 1480 | lwkt_setpri_self(int pri) |
| 1481 | { |
| 1482 | thread_t td = curthread; |
| 1483 | |
| 1484 | KKASSERT(pri >= 0 && pri <= TDPRI_MAX); |
| 1485 | crit_enter(); |
| 1486 | if (td->td_flags & TDF_RUNQ) { |
| 1487 | _lwkt_dequeue(td); |
| 1488 | td->td_pri = pri; |
| 1489 | _lwkt_enqueue(td); |
| 1490 | } else { |
| 1491 | td->td_pri = pri; |
| 1492 | } |
| 1493 | crit_exit(); |
| 1494 | } |
| 1495 | |
| 1496 | /* |
| 1497 | * hz tick scheduler clock for LWKT threads |
| 1498 | */ |
| 1499 | void |
| 1500 | lwkt_schedulerclock(thread_t td) |
| 1501 | { |
| 1502 | globaldata_t gd = td->td_gd; |
| 1503 | thread_t xtd; |
| 1504 | |
| 1505 | if (TAILQ_FIRST(&gd->gd_tdrunq) == td) { |
| 1506 | /* |
| 1507 | * If the current thread is at the head of the runq shift it to the |
| 1508 | * end of any equal-priority threads and request a LWKT reschedule |
| 1509 | * if it moved. |
| 1510 | * |
| 1511 | * Ignore upri in this situation. There will only be one user thread |
| 1512 | * in user mode, all others will be user threads running in kernel |
| 1513 | * mode and we have to make sure they get some cpu. |
| 1514 | */ |
| 1515 | xtd = TAILQ_NEXT(td, td_threadq); |
| 1516 | if (xtd && xtd->td_pri == td->td_pri) { |
| 1517 | TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq); |
| 1518 | while (xtd && xtd->td_pri == td->td_pri) |
| 1519 | xtd = TAILQ_NEXT(xtd, td_threadq); |
| 1520 | if (xtd) |
| 1521 | TAILQ_INSERT_BEFORE(xtd, td, td_threadq); |
| 1522 | else |
| 1523 | TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq); |
| 1524 | need_lwkt_resched(); |
| 1525 | } |
| 1526 | } else { |
| 1527 | /* |
| 1528 | * If we scheduled a thread other than the one at the head of the |
| 1529 | * queue always request a reschedule every tick. |
| 1530 | */ |
| 1531 | need_lwkt_resched(); |
| 1532 | } |
| 1533 | } |
| 1534 | |
| 1535 | /* |
| 1536 | * Migrate the current thread to the specified cpu. |
| 1537 | * |
| 1538 | * This is accomplished by descheduling ourselves from the current cpu |
| 1539 | * and setting td_migrate_gd. The lwkt_switch() code will detect that the |
| 1540 | * 'old' thread wants to migrate after it has been completely switched out |
| 1541 | * and will complete the migration. |
| 1542 | * |
| 1543 | * TDF_MIGRATING prevents scheduling races while the thread is being migrated. |
| 1544 | * |
| 1545 | * We must be sure to release our current process designation (if a user |
| 1546 | * process) before clearing out any tsleepq we are on because the release |
| 1547 | * code may re-add us. |
| 1548 | * |
| 1549 | * We must be sure to remove ourselves from the current cpu's tsleepq |
| 1550 | * before potentially moving to another queue. The thread can be on |
| 1551 | * a tsleepq due to a left-over tsleep_interlock(). |
| 1552 | */ |
| 1553 | |
| 1554 | void |
| 1555 | lwkt_setcpu_self(globaldata_t rgd) |
| 1556 | { |
| 1557 | thread_t td = curthread; |
| 1558 | |
| 1559 | if (td->td_gd != rgd) { |
| 1560 | crit_enter_quick(td); |
| 1561 | |
| 1562 | if (td->td_release) |
| 1563 | td->td_release(td); |
| 1564 | if (td->td_flags & TDF_TSLEEPQ) |
| 1565 | tsleep_remove(td); |
| 1566 | |
| 1567 | /* |
| 1568 | * Set TDF_MIGRATING to prevent a spurious reschedule while we are |
| 1569 | * trying to deschedule ourselves and switch away, then deschedule |
| 1570 | * ourself, remove us from tdallq, and set td_migrate_gd. Finally, |
| 1571 | * call lwkt_switch() to complete the operation. |
| 1572 | */ |
| 1573 | td->td_flags |= TDF_MIGRATING; |
| 1574 | lwkt_deschedule_self(td); |
| 1575 | TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); |
| 1576 | td->td_migrate_gd = rgd; |
| 1577 | lwkt_switch(); |
| 1578 | |
| 1579 | /* |
| 1580 | * We are now on the target cpu |
| 1581 | */ |
| 1582 | KKASSERT(rgd == mycpu); |
| 1583 | TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq); |
| 1584 | crit_exit_quick(td); |
| 1585 | } |
| 1586 | } |
| 1587 | |
| 1588 | void |
| 1589 | lwkt_migratecpu(int cpuid) |
| 1590 | { |
| 1591 | globaldata_t rgd; |
| 1592 | |
| 1593 | rgd = globaldata_find(cpuid); |
| 1594 | lwkt_setcpu_self(rgd); |
| 1595 | } |
| 1596 | |
| 1597 | /* |
| 1598 | * Remote IPI for cpu migration (called while in a critical section so we |
| 1599 | * do not have to enter another one). |
| 1600 | * |
| 1601 | * The thread (td) has already been completely descheduled from the |
| 1602 | * originating cpu and we can simply assert the case. The thread is |
| 1603 | * assigned to the new cpu and enqueued. |
| 1604 | * |
| 1605 | * The thread will re-add itself to tdallq when it resumes execution. |
| 1606 | */ |
| 1607 | static void |
| 1608 | lwkt_setcpu_remote(void *arg) |
| 1609 | { |
| 1610 | thread_t td = arg; |
| 1611 | globaldata_t gd = mycpu; |
| 1612 | |
| 1613 | KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0); |
| 1614 | td->td_gd = gd; |
| 1615 | cpu_mfence(); |
| 1616 | td->td_flags &= ~TDF_MIGRATING; |
| 1617 | KKASSERT(td->td_migrate_gd == NULL); |
| 1618 | KKASSERT(td->td_lwp == NULL || |
| 1619 | (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0); |
| 1620 | _lwkt_enqueue(td); |
| 1621 | } |
| 1622 | |
| 1623 | struct lwp * |
| 1624 | lwkt_preempted_proc(void) |
| 1625 | { |
| 1626 | thread_t td = curthread; |
| 1627 | while (td->td_preempted) |
| 1628 | td = td->td_preempted; |
| 1629 | return(td->td_lwp); |
| 1630 | } |
| 1631 | |
| 1632 | /* |
| 1633 | * Create a kernel process/thread/whatever. It shares it's address space |
| 1634 | * with proc0 - ie: kernel only. |
| 1635 | * |
| 1636 | * If the cpu is not specified one will be selected. In the future |
| 1637 | * specifying a cpu of -1 will enable kernel thread migration between |
| 1638 | * cpus. |
| 1639 | */ |
| 1640 | int |
| 1641 | lwkt_create(void (*func)(void *), void *arg, struct thread **tdp, |
| 1642 | thread_t template, int tdflags, int cpu, const char *fmt, ...) |
| 1643 | { |
| 1644 | thread_t td; |
| 1645 | __va_list ap; |
| 1646 | |
| 1647 | td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu, |
| 1648 | tdflags); |
| 1649 | if (tdp) |
| 1650 | *tdp = td; |
| 1651 | cpu_set_thread_handler(td, lwkt_exit, func, arg); |
| 1652 | |
| 1653 | /* |
| 1654 | * Set up arg0 for 'ps' etc |
| 1655 | */ |
| 1656 | __va_start(ap, fmt); |
| 1657 | kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap); |
| 1658 | __va_end(ap); |
| 1659 | |
| 1660 | /* |
| 1661 | * Schedule the thread to run |
| 1662 | */ |
| 1663 | if (td->td_flags & TDF_NOSTART) |
| 1664 | td->td_flags &= ~TDF_NOSTART; |
| 1665 | else |
| 1666 | lwkt_schedule(td); |
| 1667 | return 0; |
| 1668 | } |
| 1669 | |
| 1670 | /* |
| 1671 | * Destroy an LWKT thread. Warning! This function is not called when |
| 1672 | * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and |
| 1673 | * uses a different reaping mechanism. |
| 1674 | */ |
| 1675 | void |
| 1676 | lwkt_exit(void) |
| 1677 | { |
| 1678 | thread_t td = curthread; |
| 1679 | thread_t std; |
| 1680 | globaldata_t gd; |
| 1681 | |
| 1682 | /* |
| 1683 | * Do any cleanup that might block here |
| 1684 | */ |
| 1685 | if (td->td_flags & TDF_VERBOSE) |
| 1686 | kprintf("kthread %p %s has exited\n", td, td->td_comm); |
| 1687 | biosched_done(td); |
| 1688 | dsched_exit_thread(td); |
| 1689 | |
| 1690 | /* |
| 1691 | * Get us into a critical section to interlock gd_freetd and loop |
| 1692 | * until we can get it freed. |
| 1693 | * |
| 1694 | * We have to cache the current td in gd_freetd because objcache_put()ing |
| 1695 | * it would rip it out from under us while our thread is still active. |
| 1696 | * |
| 1697 | * We are the current thread so of course our own TDF_RUNNING bit will |
| 1698 | * be set, so unlike the lwp reap code we don't wait for it to clear. |
| 1699 | */ |
| 1700 | gd = mycpu; |
| 1701 | crit_enter_quick(td); |
| 1702 | for (;;) { |
| 1703 | if (td->td_refs) { |
| 1704 | tsleep(td, 0, "tdreap", 1); |
| 1705 | continue; |
| 1706 | } |
| 1707 | if ((std = gd->gd_freetd) != NULL) { |
| 1708 | KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0); |
| 1709 | gd->gd_freetd = NULL; |
| 1710 | objcache_put(thread_cache, std); |
| 1711 | continue; |
| 1712 | } |
| 1713 | break; |
| 1714 | } |
| 1715 | |
| 1716 | /* |
| 1717 | * Remove thread resources from kernel lists and deschedule us for |
| 1718 | * the last time. We cannot block after this point or we may end |
| 1719 | * up with a stale td on the tsleepq. |
| 1720 | * |
| 1721 | * None of this may block, the critical section is the only thing |
| 1722 | * protecting tdallq and the only thing preventing new lwkt_hold() |
| 1723 | * thread refs now. |
| 1724 | */ |
| 1725 | if (td->td_flags & TDF_TSLEEPQ) |
| 1726 | tsleep_remove(td); |
| 1727 | lwkt_deschedule_self(td); |
| 1728 | lwkt_remove_tdallq(td); |
| 1729 | KKASSERT(td->td_refs == 0); |
| 1730 | |
| 1731 | /* |
| 1732 | * Final cleanup |
| 1733 | */ |
| 1734 | KKASSERT(gd->gd_freetd == NULL); |
| 1735 | if (td->td_flags & TDF_ALLOCATED_THREAD) |
| 1736 | gd->gd_freetd = td; |
| 1737 | cpu_thread_exit(); |
| 1738 | } |
| 1739 | |
| 1740 | void |
| 1741 | lwkt_remove_tdallq(thread_t td) |
| 1742 | { |
| 1743 | KKASSERT(td->td_gd == mycpu); |
| 1744 | TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); |
| 1745 | } |
| 1746 | |
| 1747 | /* |
| 1748 | * Code reduction and branch prediction improvements. Call/return |
| 1749 | * overhead on modern cpus often degenerates into 0 cycles due to |
| 1750 | * the cpu's branch prediction hardware and return pc cache. We |
| 1751 | * can take advantage of this by not inlining medium-complexity |
| 1752 | * functions and we can also reduce the branch prediction impact |
| 1753 | * by collapsing perfectly predictable branches into a single |
| 1754 | * procedure instead of duplicating it. |
| 1755 | * |
| 1756 | * Is any of this noticeable? Probably not, so I'll take the |
| 1757 | * smaller code size. |
| 1758 | */ |
| 1759 | void |
| 1760 | crit_exit_wrapper(__DEBUG_CRIT_ARG__) |
| 1761 | { |
| 1762 | _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__); |
| 1763 | } |
| 1764 | |
| 1765 | void |
| 1766 | crit_panic(void) |
| 1767 | { |
| 1768 | thread_t td = curthread; |
| 1769 | int lcrit = td->td_critcount; |
| 1770 | |
| 1771 | td->td_critcount = 0; |
| 1772 | panic("td_critcount is/would-go negative! %p %d", td, lcrit); |
| 1773 | /* NOT REACHED */ |
| 1774 | } |
| 1775 | |
| 1776 | /* |
| 1777 | * Called from debugger/panic on cpus which have been stopped. We must still |
| 1778 | * process the IPIQ while stopped, even if we were stopped while in a critical |
| 1779 | * section (XXX). |
| 1780 | * |
| 1781 | * If we are dumping also try to process any pending interrupts. This may |
| 1782 | * or may not work depending on the state of the cpu at the point it was |
| 1783 | * stopped. |
| 1784 | */ |
| 1785 | void |
| 1786 | lwkt_smp_stopped(void) |
| 1787 | { |
| 1788 | globaldata_t gd = mycpu; |
| 1789 | |
| 1790 | crit_enter_gd(gd); |
| 1791 | if (dumping) { |
| 1792 | lwkt_process_ipiq(); |
| 1793 | splz(); |
| 1794 | } else { |
| 1795 | lwkt_process_ipiq(); |
| 1796 | } |
| 1797 | crit_exit_gd(gd); |
| 1798 | } |