1 /* $NetBSD: kern_softint.c,v 1.33 2010/12/20 00:25:46 matt Exp $ */ 2 3 /*- 4 * Copyright (c) 2007, 2008 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Andrew Doran. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /* 33 * Generic software interrupt framework. 34 * 35 * Overview 36 * 37 * The soft interrupt framework provides a mechanism to schedule a 38 * low priority callback that runs with thread context. It allows 39 * for dynamic registration of software interrupts, and for fair 40 * queueing and prioritization of those interrupts. The callbacks 41 * can be scheduled to run from nearly any point in the kernel: by 42 * code running with thread context, by code running from a 43 * hardware interrupt handler, and at any interrupt priority 44 * level. 45 * 46 * Priority levels 47 * 48 * Since soft interrupt dispatch can be tied to the underlying 49 * architecture's interrupt dispatch code, it can be limited 50 * both by the capabilities of the hardware and the capabilities 51 * of the interrupt dispatch code itself. The number of priority 52 * levels is restricted to four. In order of priority (lowest to 53 * highest) the levels are: clock, bio, net, serial. 54 * 55 * The names are symbolic and in isolation do not have any direct 56 * connection with a particular kind of device activity: they are 57 * only meant as a guide. 58 * 59 * The four priority levels map directly to scheduler priority 60 * levels, and where the architecture implements 'fast' software 61 * interrupts, they also map onto interrupt priorities. The 62 * interrupt priorities are intended to be hidden from machine 63 * independent code, which should use thread-safe mechanisms to 64 * synchronize with software interrupts (for example: mutexes). 65 * 66 * Capabilities 67 * 68 * Software interrupts run with limited machine context. In 69 * particular, they do not posess any address space context. They 70 * should not try to operate on user space addresses, or to use 71 * virtual memory facilities other than those noted as interrupt 72 * safe. 73 * 74 * Unlike hardware interrupts, software interrupts do have thread 75 * context. They may block on synchronization objects, sleep, and 76 * resume execution at a later time. 77 * 78 * Since software interrupts are a limited resource and run with 79 * higher priority than most other LWPs in the system, all 80 * block-and-resume activity by a software interrupt must be kept 81 * short to allow futher processing at that level to continue. By 82 * extension, code running with process context must take care to 83 * ensure that any lock that may be taken from a software interrupt 84 * can not be held for more than a short period of time. 85 * 86 * The kernel does not allow software interrupts to use facilities 87 * or perform actions that may block for a significant amount of 88 * time. This means that it's not valid for a software interrupt 89 * to sleep on condition variables or wait for resources to become 90 * available (for example, memory). 91 * 92 * Per-CPU operation 93 * 94 * If a soft interrupt is triggered on a CPU, it can only be 95 * dispatched on the same CPU. Each LWP dedicated to handling a 96 * soft interrupt is bound to its home CPU, so if the LWP blocks 97 * and needs to run again, it can only run there. Nearly all data 98 * structures used to manage software interrupts are per-CPU. 99 * 100 * The per-CPU requirement is intended to reduce "ping-pong" of 101 * cache lines between CPUs: lines occupied by data structures 102 * used to manage the soft interrupts, and lines occupied by data 103 * items being passed down to the soft interrupt. As a positive 104 * side effect, this also means that the soft interrupt dispatch 105 * code does not need to to use spinlocks to synchronize. 106 * 107 * Generic implementation 108 * 109 * A generic, low performance implementation is provided that 110 * works across all architectures, with no machine-dependent 111 * modifications needed. This implementation uses the scheduler, 112 * and so has a number of restrictions: 113 * 114 * 1) The software interrupts are not currently preemptive, so 115 * must wait for the currently executing LWP to yield the CPU. 116 * This can introduce latency. 117 * 118 * 2) An expensive context switch is required for a software 119 * interrupt to be handled. 120 * 121 * 'Fast' software interrupts 122 * 123 * If an architectures defines __HAVE_FAST_SOFTINTS, it implements 124 * the fast mechanism. Threads running either in the kernel or in 125 * userspace will be interrupted, but will not be preempted. When 126 * the soft interrupt completes execution, the interrupted LWP 127 * is resumed. Interrupt dispatch code must provide the minimum 128 * level of context necessary for the soft interrupt to block and 129 * be resumed at a later time. The machine-dependent dispatch 130 * path looks something like the following: 131 * 132 * softintr() 133 * { 134 * go to IPL_HIGH if necessary for switch; 135 * save any necessary registers in a format that can be 136 * restored by cpu_switchto if the softint blocks; 137 * arrange for cpu_switchto() to restore into the 138 * trampoline function; 139 * identify LWP to handle this interrupt; 140 * switch to the LWP's stack; 141 * switch register stacks, if necessary; 142 * assign new value of curlwp; 143 * call MI softint_dispatch, passing old curlwp and IPL 144 * to execute interrupt at; 145 * switch back to old stack; 146 * switch back to old register stack, if necessary; 147 * restore curlwp; 148 * return to interrupted LWP; 149 * } 150 * 151 * If the soft interrupt blocks, a trampoline function is returned 152 * to in the context of the interrupted LWP, as arranged for by 153 * softint(): 154 * 155 * softint_ret() 156 * { 157 * unlock soft interrupt LWP; 158 * resume interrupt processing, likely returning to 159 * interrupted LWP or dispatching another, different 160 * interrupt; 161 * } 162 * 163 * Once the soft interrupt has fired (and even if it has blocked), 164 * no further soft interrupts at that level will be triggered by 165 * MI code until the soft interrupt handler has ceased execution. 166 * If a soft interrupt handler blocks and is resumed, it resumes 167 * execution as a normal LWP (kthread) and gains VM context. Only 168 * when it has completed and is ready to fire again will it 169 * interrupt other threads. 170 * 171 * Future directions 172 * 173 * Provide a cheap way to direct software interrupts to remote 174 * CPUs. Provide a way to enqueue work items into the handler 175 * record, removing additional spl calls (see subr_workqueue.c). 176 */ 177 178 #include <sys/cdefs.h> 179 __KERNEL_RCSID(0, "$NetBSD: kern_softint.c,v 1.33 2010/12/20 00:25:46 matt Exp $"); 180 181 #include <sys/param.h> 182 #include <sys/malloc.h> 183 #include <sys/proc.h> 184 #include <sys/intr.h> 185 #include <sys/mutex.h> 186 #include <sys/kthread.h> 187 #include <sys/evcnt.h> 188 #include <sys/cpu.h> 189 #include <sys/xcall.h> 190 191 #include <net/netisr.h> 192 193 #include <uvm/uvm_extern.h> 194 195 /* This could overlap with signal info in struct lwp. */ 196 typedef struct softint { 197 SIMPLEQ_HEAD(, softhand) si_q; 198 struct lwp *si_lwp; 199 struct cpu_info *si_cpu; 200 uintptr_t si_machdep; 201 struct evcnt si_evcnt; 202 struct evcnt si_evcnt_block; 203 int si_active; 204 char si_name[8]; 205 char si_name_block[8+6]; 206 } softint_t; 207 208 typedef struct softhand { 209 SIMPLEQ_ENTRY(softhand) sh_q; 210 void (*sh_func)(void *); 211 void *sh_arg; 212 softint_t *sh_isr; 213 u_int sh_flags; 214 } softhand_t; 215 216 typedef struct softcpu { 217 struct cpu_info *sc_cpu; 218 softint_t sc_int[SOFTINT_COUNT]; 219 softhand_t sc_hand[1]; 220 } softcpu_t; 221 222 static void softint_thread(void *); 223 224 u_int softint_bytes = 8192; 225 u_int softint_timing; 226 static u_int softint_max; 227 static kmutex_t softint_lock; 228 static void *softint_netisrs[NETISR_MAX]; 229 230 /* 231 * softint_init_isr: 232 * 233 * Initialize a single interrupt level for a single CPU. 234 */ 235 static void 236 softint_init_isr(softcpu_t *sc, const char *desc, pri_t pri, u_int level) 237 { 238 struct cpu_info *ci; 239 softint_t *si; 240 int error; 241 242 si = &sc->sc_int[level]; 243 ci = sc->sc_cpu; 244 si->si_cpu = ci; 245 246 SIMPLEQ_INIT(&si->si_q); 247 248 error = kthread_create(pri, KTHREAD_MPSAFE | KTHREAD_INTR | 249 KTHREAD_IDLE, ci, softint_thread, si, &si->si_lwp, 250 "soft%s/%u", desc, ci->ci_index); 251 if (error != 0) 252 panic("softint_init_isr: error %d", error); 253 254 snprintf(si->si_name, sizeof(si->si_name), "%s/%u", desc, 255 ci->ci_index); 256 evcnt_attach_dynamic(&si->si_evcnt, EVCNT_TYPE_MISC, NULL, 257 "softint", si->si_name); 258 snprintf(si->si_name_block, sizeof(si->si_name_block), "%s block/%u", 259 desc, ci->ci_index); 260 evcnt_attach_dynamic(&si->si_evcnt_block, EVCNT_TYPE_MISC, NULL, 261 "softint", si->si_name_block); 262 263 si->si_lwp->l_private = si; 264 softint_init_md(si->si_lwp, level, &si->si_machdep); 265 } 266 /* 267 * softint_init: 268 * 269 * Initialize per-CPU data structures. Called from mi_cpu_attach(). 270 */ 271 void 272 softint_init(struct cpu_info *ci) 273 { 274 static struct cpu_info *first; 275 softcpu_t *sc, *scfirst; 276 softhand_t *sh, *shmax; 277 278 if (first == NULL) { 279 /* Boot CPU. */ 280 first = ci; 281 mutex_init(&softint_lock, MUTEX_DEFAULT, IPL_NONE); 282 softint_bytes = round_page(softint_bytes); 283 softint_max = (softint_bytes - sizeof(softcpu_t)) / 284 sizeof(softhand_t); 285 } 286 287 sc = (softcpu_t *)uvm_km_alloc(kernel_map, softint_bytes, 0, 288 UVM_KMF_WIRED | UVM_KMF_ZERO); 289 if (sc == NULL) 290 panic("softint_init_cpu: cannot allocate memory"); 291 292 ci->ci_data.cpu_softcpu = sc; 293 ci->ci_data.cpu_softints = 0; 294 sc->sc_cpu = ci; 295 296 softint_init_isr(sc, "net", PRI_SOFTNET, SOFTINT_NET); 297 softint_init_isr(sc, "bio", PRI_SOFTBIO, SOFTINT_BIO); 298 softint_init_isr(sc, "clk", PRI_SOFTCLOCK, SOFTINT_CLOCK); 299 softint_init_isr(sc, "ser", PRI_SOFTSERIAL, SOFTINT_SERIAL); 300 301 if (first != ci) { 302 mutex_enter(&softint_lock); 303 scfirst = first->ci_data.cpu_softcpu; 304 sh = sc->sc_hand; 305 memcpy(sh, scfirst->sc_hand, sizeof(*sh) * softint_max); 306 /* Update pointers for this CPU. */ 307 for (shmax = sh + softint_max; sh < shmax; sh++) { 308 if (sh->sh_func == NULL) 309 continue; 310 sh->sh_isr = 311 &sc->sc_int[sh->sh_flags & SOFTINT_LVLMASK]; 312 } 313 mutex_exit(&softint_lock); 314 } else { 315 /* 316 * Establish handlers for legacy net interrupts. 317 * XXX Needs to go away. 318 */ 319 #define DONETISR(n, f) \ 320 softint_netisrs[(n)] = softint_establish(SOFTINT_NET|SOFTINT_MPSAFE,\ 321 (void (*)(void *))(f), NULL) 322 #include <net/netisr_dispatch.h> 323 } 324 } 325 326 /* 327 * softint_establish: 328 * 329 * Register a software interrupt handler. 330 */ 331 void * 332 softint_establish(u_int flags, void (*func)(void *), void *arg) 333 { 334 CPU_INFO_ITERATOR cii; 335 struct cpu_info *ci; 336 softcpu_t *sc; 337 softhand_t *sh; 338 u_int level, index; 339 340 level = (flags & SOFTINT_LVLMASK); 341 KASSERT(level < SOFTINT_COUNT); 342 KASSERT((flags & SOFTINT_IMPMASK) == 0); 343 344 mutex_enter(&softint_lock); 345 346 /* Find a free slot. */ 347 sc = curcpu()->ci_data.cpu_softcpu; 348 for (index = 1; index < softint_max; index++) { 349 if (sc->sc_hand[index].sh_func == NULL) 350 break; 351 } 352 if (index == softint_max) { 353 mutex_exit(&softint_lock); 354 printf("WARNING: softint_establish: table full, " 355 "increase softint_bytes\n"); 356 return NULL; 357 } 358 359 /* Set up the handler on each CPU. */ 360 if (ncpu < 2) { 361 /* XXX hack for machines with no CPU_INFO_FOREACH() early on */ 362 sc = curcpu()->ci_data.cpu_softcpu; 363 sh = &sc->sc_hand[index]; 364 sh->sh_isr = &sc->sc_int[level]; 365 sh->sh_func = func; 366 sh->sh_arg = arg; 367 sh->sh_flags = flags; 368 } else for (CPU_INFO_FOREACH(cii, ci)) { 369 sc = ci->ci_data.cpu_softcpu; 370 sh = &sc->sc_hand[index]; 371 sh->sh_isr = &sc->sc_int[level]; 372 sh->sh_func = func; 373 sh->sh_arg = arg; 374 sh->sh_flags = flags; 375 } 376 377 mutex_exit(&softint_lock); 378 379 return (void *)((uint8_t *)&sc->sc_hand[index] - (uint8_t *)sc); 380 } 381 382 /* 383 * softint_disestablish: 384 * 385 * Unregister a software interrupt handler. The soft interrupt could 386 * still be active at this point, but the caller commits not to try 387 * and trigger it again once this call is made. The caller must not 388 * hold any locks that could be taken from soft interrupt context, 389 * because we will wait for the softint to complete if it's still 390 * running. 391 */ 392 void 393 softint_disestablish(void *arg) 394 { 395 CPU_INFO_ITERATOR cii; 396 struct cpu_info *ci; 397 softcpu_t *sc; 398 softhand_t *sh; 399 uintptr_t offset; 400 uint64_t where; 401 u_int flags; 402 403 offset = (uintptr_t)arg; 404 KASSERT(offset != 0 && offset < softint_bytes); 405 406 /* 407 * Run a cross call so we see up to date values of sh_flags from 408 * all CPUs. Once softint_disestablish() is called, the caller 409 * commits to not trigger the interrupt and set SOFTINT_ACTIVE on 410 * it again. So, we are only looking for handler records with 411 * SOFTINT_ACTIVE already set. 412 */ 413 where = xc_broadcast(0, (xcfunc_t)nullop, NULL, NULL); 414 xc_wait(where); 415 416 for (;;) { 417 /* Collect flag values from each CPU. */ 418 flags = 0; 419 for (CPU_INFO_FOREACH(cii, ci)) { 420 sc = ci->ci_data.cpu_softcpu; 421 sh = (softhand_t *)((uint8_t *)sc + offset); 422 KASSERT(sh->sh_func != NULL); 423 flags |= sh->sh_flags; 424 } 425 /* Inactive on all CPUs? */ 426 if ((flags & SOFTINT_ACTIVE) == 0) { 427 break; 428 } 429 /* Oops, still active. Wait for it to clear. */ 430 (void)kpause("softdis", false, 1, NULL); 431 } 432 433 /* Clear the handler on each CPU. */ 434 mutex_enter(&softint_lock); 435 for (CPU_INFO_FOREACH(cii, ci)) { 436 sc = ci->ci_data.cpu_softcpu; 437 sh = (softhand_t *)((uint8_t *)sc + offset); 438 KASSERT(sh->sh_func != NULL); 439 sh->sh_func = NULL; 440 } 441 mutex_exit(&softint_lock); 442 } 443 444 /* 445 * softint_schedule: 446 * 447 * Trigger a software interrupt. Must be called from a hardware 448 * interrupt handler, or with preemption disabled (since we are 449 * using the value of curcpu()). 450 */ 451 void 452 softint_schedule(void *arg) 453 { 454 softhand_t *sh; 455 softint_t *si; 456 uintptr_t offset; 457 int s; 458 459 KASSERT(kpreempt_disabled()); 460 461 /* Find the handler record for this CPU. */ 462 offset = (uintptr_t)arg; 463 KASSERT(offset != 0 && offset < softint_bytes); 464 sh = (softhand_t *)((uint8_t *)curcpu()->ci_data.cpu_softcpu + offset); 465 466 /* If it's already pending there's nothing to do. */ 467 if ((sh->sh_flags & SOFTINT_PENDING) != 0) { 468 return; 469 } 470 471 /* 472 * Enqueue the handler into the LWP's pending list. 473 * If the LWP is completely idle, then make it run. 474 */ 475 s = splhigh(); 476 if ((sh->sh_flags & SOFTINT_PENDING) == 0) { 477 si = sh->sh_isr; 478 sh->sh_flags |= SOFTINT_PENDING; 479 SIMPLEQ_INSERT_TAIL(&si->si_q, sh, sh_q); 480 if (si->si_active == 0) { 481 si->si_active = 1; 482 softint_trigger(si->si_machdep); 483 } 484 } 485 splx(s); 486 } 487 488 /* 489 * softint_execute: 490 * 491 * Invoke handlers for the specified soft interrupt. 492 * Must be entered at splhigh. Will drop the priority 493 * to the level specified, but returns back at splhigh. 494 */ 495 static inline void 496 softint_execute(softint_t *si, lwp_t *l, int s) 497 { 498 softhand_t *sh; 499 bool havelock; 500 501 #ifdef __HAVE_FAST_SOFTINTS 502 KASSERT(si->si_lwp == curlwp); 503 #else 504 /* May be running in user context. */ 505 #endif 506 KASSERT(si->si_cpu == curcpu()); 507 KASSERT(si->si_lwp->l_wchan == NULL); 508 KASSERT(si->si_active); 509 510 havelock = false; 511 512 /* 513 * Note: due to priority inheritance we may have interrupted a 514 * higher priority LWP. Since the soft interrupt must be quick 515 * and is non-preemptable, we don't bother yielding. 516 */ 517 518 while (!SIMPLEQ_EMPTY(&si->si_q)) { 519 /* 520 * Pick the longest waiting handler to run. We block 521 * interrupts but do not lock in order to do this, as 522 * we are protecting against the local CPU only. 523 */ 524 sh = SIMPLEQ_FIRST(&si->si_q); 525 SIMPLEQ_REMOVE_HEAD(&si->si_q, sh_q); 526 KASSERT((sh->sh_flags & SOFTINT_PENDING) != 0); 527 KASSERT((sh->sh_flags & SOFTINT_ACTIVE) == 0); 528 sh->sh_flags ^= (SOFTINT_PENDING | SOFTINT_ACTIVE); 529 splx(s); 530 531 /* Run the handler. */ 532 if (sh->sh_flags & SOFTINT_MPSAFE) { 533 if (havelock) { 534 KERNEL_UNLOCK_ONE(l); 535 havelock = false; 536 } 537 } else if (!havelock) { 538 KERNEL_LOCK(1, l); 539 havelock = true; 540 } 541 (*sh->sh_func)(sh->sh_arg); 542 543 (void)splhigh(); 544 KASSERT((sh->sh_flags & SOFTINT_ACTIVE) != 0); 545 sh->sh_flags ^= SOFTINT_ACTIVE; 546 } 547 548 if (havelock) { 549 KERNEL_UNLOCK_ONE(l); 550 } 551 552 /* 553 * Unlocked, but only for statistics. 554 * Should be per-CPU to prevent cache ping-pong. 555 */ 556 curcpu()->ci_data.cpu_nsoft++; 557 558 KASSERT(si->si_cpu == curcpu()); 559 KASSERT(si->si_lwp->l_wchan == NULL); 560 KASSERT(si->si_active); 561 si->si_evcnt.ev_count++; 562 si->si_active = 0; 563 } 564 565 /* 566 * softint_block: 567 * 568 * Update statistics when the soft interrupt blocks. 569 */ 570 void 571 softint_block(lwp_t *l) 572 { 573 softint_t *si = l->l_private; 574 575 KASSERT((l->l_pflag & LP_INTR) != 0); 576 si->si_evcnt_block.ev_count++; 577 } 578 579 /* 580 * schednetisr: 581 * 582 * Trigger a legacy network interrupt. XXX Needs to go away. 583 */ 584 void 585 schednetisr(int isr) 586 { 587 588 softint_schedule(softint_netisrs[isr]); 589 } 590 591 #ifndef __HAVE_FAST_SOFTINTS 592 593 #ifdef __HAVE_PREEMPTION 594 #error __HAVE_PREEMPTION requires __HAVE_FAST_SOFTINTS 595 #endif 596 597 /* 598 * softint_init_md: 599 * 600 * Slow path: perform machine-dependent initialization. 601 */ 602 void 603 softint_init_md(lwp_t *l, u_int level, uintptr_t *machdep) 604 { 605 softint_t *si; 606 607 *machdep = (1 << level); 608 si = l->l_private; 609 610 lwp_lock(l); 611 lwp_unlock_to(l, l->l_cpu->ci_schedstate.spc_mutex); 612 lwp_lock(l); 613 /* Cheat and make the KASSERT in softint_thread() happy. */ 614 si->si_active = 1; 615 l->l_stat = LSRUN; 616 sched_enqueue(l, false); 617 lwp_unlock(l); 618 } 619 620 /* 621 * softint_trigger: 622 * 623 * Slow path: cause a soft interrupt handler to begin executing. 624 * Called at IPL_HIGH. 625 */ 626 void 627 softint_trigger(uintptr_t machdep) 628 { 629 struct cpu_info *ci; 630 lwp_t *l; 631 632 l = curlwp; 633 ci = l->l_cpu; 634 ci->ci_data.cpu_softints |= machdep; 635 if (l == ci->ci_data.cpu_idlelwp) { 636 cpu_need_resched(ci, 0); 637 } else { 638 /* MI equivalent of aston() */ 639 cpu_signotify(l); 640 } 641 } 642 643 /* 644 * softint_thread: 645 * 646 * Slow path: MI software interrupt dispatch. 647 */ 648 void 649 softint_thread(void *cookie) 650 { 651 softint_t *si; 652 lwp_t *l; 653 int s; 654 655 l = curlwp; 656 si = l->l_private; 657 658 for (;;) { 659 /* 660 * Clear pending status and run it. We must drop the 661 * spl before mi_switch(), since IPL_HIGH may be higher 662 * than IPL_SCHED (and it is not safe to switch at a 663 * higher level). 664 */ 665 s = splhigh(); 666 l->l_cpu->ci_data.cpu_softints &= ~si->si_machdep; 667 softint_execute(si, l, s); 668 splx(s); 669 670 lwp_lock(l); 671 l->l_stat = LSIDL; 672 mi_switch(l); 673 } 674 } 675 676 /* 677 * softint_picklwp: 678 * 679 * Slow path: called from mi_switch() to pick the highest priority 680 * soft interrupt LWP that needs to run. 681 */ 682 lwp_t * 683 softint_picklwp(void) 684 { 685 struct cpu_info *ci; 686 u_int mask; 687 softint_t *si; 688 lwp_t *l; 689 690 ci = curcpu(); 691 si = ((softcpu_t *)ci->ci_data.cpu_softcpu)->sc_int; 692 mask = ci->ci_data.cpu_softints; 693 694 if ((mask & (1 << SOFTINT_SERIAL)) != 0) { 695 l = si[SOFTINT_SERIAL].si_lwp; 696 } else if ((mask & (1 << SOFTINT_NET)) != 0) { 697 l = si[SOFTINT_NET].si_lwp; 698 } else if ((mask & (1 << SOFTINT_BIO)) != 0) { 699 l = si[SOFTINT_BIO].si_lwp; 700 } else if ((mask & (1 << SOFTINT_CLOCK)) != 0) { 701 l = si[SOFTINT_CLOCK].si_lwp; 702 } else { 703 panic("softint_picklwp"); 704 } 705 706 return l; 707 } 708 709 /* 710 * softint_overlay: 711 * 712 * Slow path: called from lwp_userret() to run a soft interrupt 713 * within the context of a user thread. 714 */ 715 void 716 softint_overlay(void) 717 { 718 struct cpu_info *ci; 719 u_int softints, oflag; 720 softint_t *si; 721 pri_t obase; 722 lwp_t *l; 723 int s; 724 725 l = curlwp; 726 KASSERT((l->l_pflag & LP_INTR) == 0); 727 728 /* 729 * Arrange to elevate priority if the LWP blocks. Also, bind LWP 730 * to the CPU. Note: disable kernel preemption before doing that. 731 */ 732 s = splhigh(); 733 ci = l->l_cpu; 734 si = ((softcpu_t *)ci->ci_data.cpu_softcpu)->sc_int; 735 736 obase = l->l_kpribase; 737 l->l_kpribase = PRI_KERNEL_RT; 738 oflag = l->l_pflag; 739 l->l_pflag = oflag | LP_INTR | LP_BOUND; 740 741 while ((softints = ci->ci_data.cpu_softints) != 0) { 742 if ((softints & (1 << SOFTINT_SERIAL)) != 0) { 743 ci->ci_data.cpu_softints &= ~(1 << SOFTINT_SERIAL); 744 softint_execute(&si[SOFTINT_SERIAL], l, s); 745 continue; 746 } 747 if ((softints & (1 << SOFTINT_NET)) != 0) { 748 ci->ci_data.cpu_softints &= ~(1 << SOFTINT_NET); 749 softint_execute(&si[SOFTINT_NET], l, s); 750 continue; 751 } 752 if ((softints & (1 << SOFTINT_BIO)) != 0) { 753 ci->ci_data.cpu_softints &= ~(1 << SOFTINT_BIO); 754 softint_execute(&si[SOFTINT_BIO], l, s); 755 continue; 756 } 757 if ((softints & (1 << SOFTINT_CLOCK)) != 0) { 758 ci->ci_data.cpu_softints &= ~(1 << SOFTINT_CLOCK); 759 softint_execute(&si[SOFTINT_CLOCK], l, s); 760 continue; 761 } 762 } 763 l->l_pflag = oflag; 764 l->l_kpribase = obase; 765 splx(s); 766 } 767 768 #else /* !__HAVE_FAST_SOFTINTS */ 769 770 /* 771 * softint_thread: 772 * 773 * Fast path: the LWP is switched to without restoring any state, 774 * so we should not arrive here - there is a direct handoff between 775 * the interrupt stub and softint_dispatch(). 776 */ 777 void 778 softint_thread(void *cookie) 779 { 780 781 panic("softint_thread"); 782 } 783 784 /* 785 * softint_dispatch: 786 * 787 * Fast path: entry point from machine-dependent code. 788 */ 789 void 790 softint_dispatch(lwp_t *pinned, int s) 791 { 792 struct bintime now; 793 softint_t *si; 794 u_int timing; 795 lwp_t *l; 796 797 KASSERT((pinned->l_pflag & LP_RUNNING) != 0); 798 l = curlwp; 799 si = l->l_private; 800 801 /* 802 * Note the interrupted LWP, and mark the current LWP as running 803 * before proceeding. Although this must as a rule be done with 804 * the LWP locked, at this point no external agents will want to 805 * modify the interrupt LWP's state. 806 */ 807 timing = (softint_timing ? LP_TIMEINTR : 0); 808 l->l_switchto = pinned; 809 l->l_stat = LSONPROC; 810 l->l_pflag |= (LP_RUNNING | timing); 811 812 /* 813 * Dispatch the interrupt. If softints are being timed, charge 814 * for it. 815 */ 816 if (timing) 817 binuptime(&l->l_stime); 818 softint_execute(si, l, s); 819 if (timing) { 820 binuptime(&now); 821 updatertime(l, &now); 822 l->l_pflag &= ~LP_TIMEINTR; 823 } 824 825 /* 826 * If we blocked while handling the interrupt, the pinned LWP is 827 * gone so switch to the idle LWP. It will select a new LWP to 828 * run. 829 * 830 * We must drop the priority level as switching at IPL_HIGH could 831 * deadlock the system. We have already set si->si_active = 0, 832 * which means another interrupt at this level can be triggered. 833 * That's not be a problem: we are lowering to level 's' which will 834 * prevent softint_dispatch() from being reentered at level 's', 835 * until the priority is finally dropped to IPL_NONE on entry to 836 * the LWP chosen by lwp_exit_switchaway(). 837 */ 838 l->l_stat = LSIDL; 839 if (l->l_switchto == NULL) { 840 splx(s); 841 pmap_deactivate(l); 842 lwp_exit_switchaway(l); 843 /* NOTREACHED */ 844 } 845 l->l_switchto = NULL; 846 l->l_pflag &= ~LP_RUNNING; 847 } 848 849 #endif /* !__HAVE_FAST_SOFTINTS */ 850