sys/kern/lwkt_token.c

   1 /*
   2  * Copyright (c) 2003,2004 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  * $DragonFly: src/sys/kern/lwkt_token.c,v 1.13 2005/04/18 01:03:28 dillon Exp $
  35  */
  36
  37 #ifdef _KERNEL
  38
  39 #include <sys/param.h>
  40 #include <sys/systm.h>
  41 #include <sys/kernel.h>
  42 #include <sys/proc.h>
  43 #include <sys/rtprio.h>
  44 #include <sys/queue.h>
  45 #include <sys/thread2.h>
  46 #include <sys/sysctl.h>
  47 #include <sys/kthread.h>
  48 #include <machine/cpu.h>
  49 #include <sys/lock.h>
  50 #include <sys/caps.h>
  51
  52 #include <vm/vm.h>
  53 #include <vm/vm_param.h>
  54 #include <vm/vm_kern.h>
  55 #include <vm/vm_object.h>
  56 #include <vm/vm_page.h>
  57 #include <vm/vm_map.h>
  58 #include <vm/vm_pager.h>
  59 #include <vm/vm_extern.h>
  60 #include <vm/vm_zone.h>
  61
  62 #include <machine/stdarg.h>
  63 #include <machine/ipl.h>
  64 #include <machine/smp.h>
  65
  66 #define THREAD_STACK    (UPAGES * PAGE_SIZE)
  67
  68 #else
  69
  70 #include <sys/stdint.h>
  71 #include <libcaps/thread.h>
  72 #include <sys/thread.h>
  73 #include <sys/msgport.h>
  74 #include <sys/errno.h>
  75 #include <libcaps/globaldata.h>
  76 #include <machine/cpufunc.h>
  77 #include <sys/thread2.h>
  78 #include <sys/msgport2.h>
  79 #include <stdio.h>
  80 #include <stdlib.h>
  81 #include <string.h>
  82 #include <machine/lock.h>
  83 #include <machine/cpu.h>
  84
  85 #endif
  86
  87 #define MAKE_TOKENS_SPIN
  88 /* #define MAKE_TOKENS_YIELD */
  89
  90 #ifndef LWKT_NUM_POOL_TOKENS
  91 #define LWKT_NUM_POOL_TOKENS    1024    /* power of 2 */
  92 #endif
  93 #define LWKT_MASK_POOL_TOKENS   (LWKT_NUM_POOL_TOKENS - 1)
  94
  95 #ifdef INVARIANTS
  96 static int token_debug = 0;
  97 #endif
  98
  99 static void lwkt_reqtoken_remote(void *data);
 100
 101 static lwkt_token       pool_tokens[LWKT_NUM_POOL_TOKENS];
 102
 103 #ifdef _KERNEL
 104
 105 #ifdef INVARIANTS
 106 SYSCTL_INT(_lwkt, OID_AUTO, token_debug, CTLFLAG_RW, &token_debug, 0, "");
 107 #endif
 108
 109 #endif
 110
 111 #ifdef SMP
 112
 113 /*
 114  * Determine if we own all the tokens in the token reference list.
 115  * Return 1 on success, 0 on failure.
 116  *
 117  * As a side effect, queue requests for tokens we want which are owned
 118  * by other cpus.  The magic number is used to communicate when the
 119  * target cpu has processed the request.  Note, however, that the
 120  * target cpu may not be able to assign the token to us which is why
 121  * the scheduler must spin.
 122  */
 123 int
 124 lwkt_chktokens(thread_t td)
 125 {
 126     globaldata_t gd = td->td_gd;        /* mycpu */
 127     lwkt_tokref_t refs;
 128     globaldata_t dgd;
 129     lwkt_token_t tok;
 130     int r = 1;
 131
 132     for (refs = td->td_toks; refs; refs = refs->tr_next) {
 133         tok = refs->tr_tok;
 134         if ((dgd = tok->t_cpu) != gd) {
 135             cpu_mb1();
 136             r = 0;
 137
 138             /*
 139              * Queue a request to the target cpu, exit the loop early if
 140              * we are unable to queue the IPI message.  The magic number
 141              * flags whether we have a pending ipi request queued or not.
 142              * It can be set from MAGIC2 to MAGIC1 by a remote cpu but can
 143              * only be set from MAGIC1 to MAGIC2 by our cpu.
 144              */
 145             if (refs->tr_magic == LWKT_TOKREF_MAGIC1) {
 146                 refs->tr_magic = LWKT_TOKREF_MAGIC2;    /* MP synched slowreq*/
 147                 refs->tr_reqgd = gd;
 148                 tok->t_reqcpu = gd;     /* MP unsynchronized 'fast' req */
 149                 if (lwkt_send_ipiq_nowait(dgd, lwkt_reqtoken_remote, refs)) {
 150                     /* failed */
 151                     refs->tr_magic = LWKT_TOKREF_MAGIC1;
 152                     break;
 153                 }
 154             }
 155         }
 156     }
 157     return(r);
 158 }
 159
 160 #endif
 161
 162 /*
 163  * Check if we already own the token.  Return 1 on success, 0 on failure.
 164  */
 165 int
 166 lwkt_havetoken(lwkt_token_t tok)
 167 {
 168     globaldata_t gd = mycpu;
 169     thread_t td = gd->gd_curthread;
 170     lwkt_tokref_t ref;
 171
 172     for (ref = td->td_toks; ref; ref = ref->tr_next) {
 173         if (ref->tr_tok == tok)
 174             return(1);
 175     }
 176     return(0);
 177 }
 178
 179 int
 180 lwkt_havetokref(lwkt_tokref_t xref)
 181 {
 182     globaldata_t gd = mycpu;
 183     thread_t td = gd->gd_curthread;
 184     lwkt_tokref_t ref;
 185
 186     for (ref = td->td_toks; ref; ref = ref->tr_next) {
 187         if (ref == xref)
 188             return(1);
 189     }
 190     return(0);
 191 }
 192
 193 #ifdef SMP
 194
 195 /*
 196  * Returns 1 if it is ok to give a token away, 0 if it is not.
 197  */
 198 static int
 199 lwkt_oktogiveaway_token(lwkt_token_t tok)
 200 {
 201     globaldata_t gd = mycpu;
 202     lwkt_tokref_t ref;
 203     thread_t td;
 204
 205     for (td = gd->gd_curthread; td; td = td->td_preempted) {
 206         for (ref = td->td_toks; ref; ref = ref->tr_next) {
 207             if (ref->tr_tok == tok)
 208                 return(0);
 209         }
 210     }
 211     return(1);
 212 }
 213
 214 #endif
 215
 216 /*
 217  * Acquire a serializing token
 218  */
 219
 220 static __inline
 221 void
 222 _lwkt_gettokref(lwkt_tokref_t ref)
 223 {
 224     lwkt_token_t tok;
 225     globaldata_t gd;
 226     thread_t td;
 227
 228     gd = mycpu;                 /* our cpu */
 229     KKASSERT(ref->tr_magic == LWKT_TOKREF_MAGIC1);
 230     td = gd->gd_curthread;      /* our thread */
 231
 232     /*
 233      * Link the request into our thread's list.  This interlocks against
 234      * remote requests from other cpus and prevents the token from being
 235      * given away if our cpu already owns it.  This also allows us to
 236      * avoid using a critical section.
 237      */
 238     ref->tr_next = td->td_toks;
 239     cpu_mb1();          /* order memory / we can be interrupted */
 240     td->td_toks = ref;
 241
 242     /*
 243      * If our cpu does not own the token then let the scheduler deal with
 244      * it.  We are guarenteed to own the tokens on our thread's token
 245      * list when we are switched back in.
 246      *
 247      * Otherwise make sure the token is not held by a thread we are
 248      * preempting.  If it is, let the scheduler deal with it.
 249      */
 250     tok = ref->tr_tok;
 251 #ifdef SMP
 252     if (tok->t_cpu != gd) {
 253         /*
 254          * Temporarily operate on tokens synchronously.  We have to fix
 255          * a number of interlocks and especially the softupdates code to
 256          * be able to properly yield.  ZZZ
 257          */
 258 #if defined(MAKE_TOKENS_SPIN)
 259         int x = 40000000;
 260         int y = 10;
 261         crit_enter();
 262         while (lwkt_chktokens(td) == 0) {
 263             lwkt_process_ipiq();
 264             lwkt_drain_token_requests();
 265             if (--x == 0) {
 266                 x = 40000000;
 267                 printf("CHKTOKEN looping on cpu %d\n", gd->gd_cpuid);
 268 #ifdef _KERNEL
 269                 if (--y == 0)
 270                         panic("CHKTOKEN looping on cpu %d", gd->gd_cpuid);
 271 #endif
 272             }
 273             splz();
 274         }
 275         crit_exit();
 276 #elif defined(MAKE_TOKENS_YIELD)
 277         lwkt_yield();
 278 #else
 279 #error MAKE_TOKENS_XXX ?
 280 #endif
 281         KKASSERT(tok->t_cpu == gd);
 282     } else /* NOTE CONDITIONAL */
 283 #endif
 284     if (td->td_preempted) {
 285         while ((td = td->td_preempted) != NULL) {
 286             lwkt_tokref_t scan;
 287             for (scan = td->td_toks; scan; scan = scan->tr_next) {
 288                 if (scan->tr_tok == tok) {
 289                     lwkt_yield();
 290                     KKASSERT(tok->t_cpu == gd);
 291                     goto breakout;
 292                 }
 293             }
 294         }
 295 breakout: ;
 296     }
 297     /* 'td' variable no longer valid due to preempt loop above */
 298 }
 299
 300
 301 /*
 302  * Attempt to acquire a serializing token
 303  */
 304 static __inline
 305 int
 306 _lwkt_trytokref(lwkt_tokref_t ref)
 307 {
 308     lwkt_token_t tok;
 309     globaldata_t gd;
 310     thread_t td;
 311
 312     gd = mycpu;                 /* our cpu */
 313     KKASSERT(ref->tr_magic == LWKT_TOKREF_MAGIC1);
 314     td = gd->gd_curthread;      /* our thread */
 315
 316     /*
 317      * Link the request into our thread's list.  This interlocks against
 318      * remote requests from other cpus and prevents the token from being
 319      * given away if our cpu already owns it.  This also allows us to
 320      * avoid using a critical section.
 321      */
 322     ref->tr_next = td->td_toks;
 323     cpu_mb1();          /* order memory / we can be interrupted */
 324     td->td_toks = ref;
 325
 326     /*
 327      * If our cpu does not own the token then stop now.
 328      *
 329      * Otherwise make sure the token is not held by a thread we are
 330      * preempting.  If it is, stop.
 331      */
 332     tok = ref->tr_tok;
 333 #ifdef SMP
 334     if (tok->t_cpu != gd) {
 335         td->td_toks = ref->tr_next;     /* remove ref */
 336         return(0);
 337     } else /* NOTE CONDITIONAL */
 338 #endif
 339     if (td->td_preempted) {
 340         while ((td = td->td_preempted) != NULL) {
 341             lwkt_tokref_t scan;
 342             for (scan = td->td_toks; scan; scan = scan->tr_next) {
 343                 if (scan->tr_tok == tok) {
 344                     td = gd->gd_curthread;      /* our thread */
 345                     td->td_toks = ref->tr_next; /* remove ref */
 346                     return(0);
 347                 }
 348             }
 349         }
 350     }
 351     /* 'td' variable no longer valid */
 352     return(1);
 353 }
 354
 355 void
 356 lwkt_gettoken(lwkt_tokref_t ref, lwkt_token_t tok)
 357 {
 358     lwkt_tokref_init(ref, tok);
 359     _lwkt_gettokref(ref);
 360 }
 361
 362 void
 363 lwkt_gettokref(lwkt_tokref_t ref)
 364 {
 365     _lwkt_gettokref(ref);
 366 }
 367
 368 int
 369 lwkt_trytoken(lwkt_tokref_t ref, lwkt_token_t tok)
 370 {
 371     lwkt_tokref_init(ref, tok);
 372     return(_lwkt_trytokref(ref));
 373 }
 374
 375 int
 376 lwkt_trytokref(lwkt_tokref_t ref)
 377 {
 378     return(_lwkt_trytokref(ref));
 379 }
 380
 381 /*
 382  * Release a serializing token
 383  */
 384 void
 385 lwkt_reltoken(lwkt_tokref *_ref)
 386 {
 387     lwkt_tokref *ref;
 388     lwkt_tokref **pref;
 389     lwkt_token_t tok;
 390     globaldata_t gd;
 391     thread_t td;
 392
 393     /*
 394      * Guard check and stack check (if in the same stack page).  We must
 395      * also wait for any action pending on remote cpus which we do by
 396      * checking the magic number and yielding in a loop.
 397      */
 398     ref = _ref;
 399 #ifdef INVARIANTS
 400     if ((((intptr_t)ref ^ (intptr_t)&_ref) & ~(intptr_t)PAGE_MASK) == 0)
 401         KKASSERT((char *)ref > (char *)&_ref);
 402     KKASSERT(ref->tr_magic == LWKT_TOKREF_MAGIC1 ||
 403              ref->tr_magic == LWKT_TOKREF_MAGIC2);
 404 #endif
 405     /*
 406      * Locate and unlink the token.  Interlock with the token's cpureq
 407      * to give the token away before we release it from our thread list,
 408      * which allows us to avoid using a critical section.
 409      */
 410     gd = mycpu;
 411     td = gd->gd_curthread;
 412     for (pref = &td->td_toks; (ref = *pref) != _ref; pref = &ref->tr_next) {
 413         KKASSERT(ref != NULL);
 414     }
 415     tok = ref->tr_tok;
 416     KKASSERT(tok->t_cpu == gd);
 417     tok->t_cpu = tok->t_reqcpu; /* we do not own 'tok' after this */
 418     *pref = ref->tr_next;       /* note: also removes giveaway interlock */
 419
 420     /*
 421      * If we had gotten the token opportunistically and it still happens to
 422      * be queued to a target cpu, we have to wait for the target cpu
 423      * to finish processing it.  This does not happen very often and does
 424      * not need to be optimal.
 425      */
 426     while (ref->tr_magic == LWKT_TOKREF_MAGIC2) {
 427 #if defined(MAKE_TOKENS_SPIN)
 428         crit_enter();
 429 #ifdef SMP
 430         lwkt_process_ipiq();
 431 #endif
 432         splz();
 433         crit_exit();
 434 #elif defined(MAKE_TOKENS_YIELD)
 435         lwkt_yield();
 436 #else
 437 #error MAKE_TOKENS_XXX ?
 438 #endif
 439     }
 440 }
 441
 442 /*
 443  * Pool tokens are used to provide a type-stable serializing token
 444  * pointer that does not race against disappearing data structures.
 445  *
 446  * This routine is called in early boot just after we setup the BSP's
 447  * globaldata structure.
 448  */
 449 void
 450 lwkt_token_pool_init(void)
 451 {
 452     int i;
 453
 454     for (i = 0; i < LWKT_NUM_POOL_TOKENS; ++i)
 455         lwkt_token_init(&pool_tokens[i]);
 456 }
 457
 458 lwkt_token_t
 459 lwkt_token_pool_get(void *ptraddr)
 460 {
 461     int i;
 462
 463     i = ((int)(intptr_t)ptraddr >> 2) ^ ((int)(intptr_t)ptraddr >> 12);
 464     return(&pool_tokens[i & LWKT_MASK_POOL_TOKENS]);
 465 }
 466
 467 #ifdef SMP
 468
 469 /*
 470  * This is the receiving side of a remote IPI requesting a token.  If we
 471  * cannot immediately hand the token off to another cpu we queue it.
 472  *
 473  * NOTE!  we 'own' the ref structure, but we only 'own' the token if
 474  * t_cpu == mycpu.
 475  */
 476 static void
 477 lwkt_reqtoken_remote(void *data)
 478 {
 479     lwkt_tokref_t ref = data;
 480     globaldata_t gd = mycpu;
 481     lwkt_token_t tok = ref->tr_tok;
 482
 483     /*
 484      * We do not have to queue the token if we can give it away
 485      * immediately.  Otherwise we queue it to our globaldata structure.
 486      */
 487     KKASSERT(ref->tr_magic == LWKT_TOKREF_MAGIC2);
 488     if (lwkt_oktogiveaway_token(tok)) {
 489         if (tok->t_cpu == gd)
 490             tok->t_cpu = ref->tr_reqgd;
 491         cpu_mb1();
 492         ref->tr_magic = LWKT_TOKREF_MAGIC1;
 493     } else {
 494         ref->tr_gdreqnext = gd->gd_tokreqbase;
 495         gd->gd_tokreqbase = ref;
 496     }
 497 }
 498
 499 /*
 500  * Must be called from a critical section.  Satisfy all remote token
 501  * requests that are pending on our globaldata structure.  The request
 502  * does not have to be satisfied with a successful change of ownership
 503  * but we do have to acknowledge that we have completed processing the
 504  * request by setting the magic number back to MAGIC1.
 505  *
 506  * NOTE!  we 'own' the ref structure, but we only 'own' the token if
 507  * t_cpu == mycpu.
 508  */
 509 void
 510 lwkt_drain_token_requests(void)
 511 {
 512     globaldata_t gd = mycpu;
 513     lwkt_tokref_t ref;
 514
 515     while ((ref = gd->gd_tokreqbase) != NULL) {
 516         gd->gd_tokreqbase = ref->tr_gdreqnext;
 517         KKASSERT(ref->tr_magic == LWKT_TOKREF_MAGIC2);
 518         if (ref->tr_tok->t_cpu == gd)
 519             ref->tr_tok->t_cpu = ref->tr_reqgd;
 520         cpu_mb1();
 521         ref->tr_magic = LWKT_TOKREF_MAGIC1;
 522     }
 523 }
 524
 525 #endif
 526
 527 /*
 528  * Initialize the owner and release-to cpu to the current cpu
 529  * and reset the generation count.
 530  */
 531 void
 532 lwkt_token_init(lwkt_token_t tok)
 533 {
 534     tok->t_cpu = tok->t_reqcpu = mycpu;
 535 }
 536
 537 void
 538 lwkt_token_uninit(lwkt_token_t tok)
 539 {
 540     /* empty */
 541 }