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 1.30 2008/03/01 06:21:28 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/sysctl.h>
  46 #include <sys/ktr.h>
  47 #include <sys/kthread.h>
  48 #include <machine/cpu.h>
  49 #include <sys/lock.h>
  50 #include <sys/caps.h>
  51 #include <sys/spinlock.h>
  52
  53 #include <sys/thread2.h>
  54 #include <sys/spinlock2.h>
  55
  56 #include <vm/vm.h>
  57 #include <vm/vm_param.h>
  58 #include <vm/vm_kern.h>
  59 #include <vm/vm_object.h>
  60 #include <vm/vm_page.h>
  61 #include <vm/vm_map.h>
  62 #include <vm/vm_pager.h>
  63 #include <vm/vm_extern.h>
  64 #include <vm/vm_zone.h>
  65
  66 #include <machine/stdarg.h>
  67 #include <machine/smp.h>
  68
  69 #else
  70
  71 #include <sys/stdint.h>
  72 #include <libcaps/thread.h>
  73 #include <sys/thread.h>
  74 #include <sys/msgport.h>
  75 #include <sys/errno.h>
  76 #include <libcaps/globaldata.h>
  77 #include <machine/cpufunc.h>
  78 #include <sys/thread2.h>
  79 #include <sys/msgport2.h>
  80 #include <stdio.h>
  81 #include <stdlib.h>
  82 #include <string.h>
  83 #include <machine/lock.h>
  84 #include <machine/cpu.h>
  85
  86 #endif
  87
  88 #ifndef LWKT_NUM_POOL_TOKENS
  89 #define LWKT_NUM_POOL_TOKENS    1024    /* power of 2 */
  90 #endif
  91 #define LWKT_MASK_POOL_TOKENS   (LWKT_NUM_POOL_TOKENS - 1)
  92
  93 #ifdef INVARIANTS
  94 static int token_debug = 0;
  95 #endif
  96
  97 static lwkt_token       pool_tokens[LWKT_NUM_POOL_TOKENS];
  98
  99 #define TOKEN_STRING    "REF=%p TOK=%p TD=%p"
 100 #define CONTENDED_STRING        "REF=%p TOK=%p TD=%p (contention started)"
 101 #define UNCONTENDED_STRING      "REF=%p TOK=%p TD=%p (contention stopped)"
 102 #if !defined(KTR_TOKENS)
 103 #define KTR_TOKENS      KTR_ALL
 104 #endif
 105
 106 KTR_INFO_MASTER(tokens);
 107 KTR_INFO(KTR_TOKENS, tokens, try, 0, TOKEN_STRING, sizeof(void *) * 3);
 108 KTR_INFO(KTR_TOKENS, tokens, get, 1, TOKEN_STRING, sizeof(void *) * 3);
 109 KTR_INFO(KTR_TOKENS, tokens, release, 2, TOKEN_STRING, sizeof(void *) * 3);
 110 #if 0
 111 KTR_INFO(KTR_TOKENS, tokens, remote, 3, TOKEN_STRING, sizeof(void *) * 3);
 112 KTR_INFO(KTR_TOKENS, tokens, reqremote, 4, TOKEN_STRING, sizeof(void *) * 3);
 113 KTR_INFO(KTR_TOKENS, tokens, reqfail, 5, TOKEN_STRING, sizeof(void *) * 3);
 114 KTR_INFO(KTR_TOKENS, tokens, drain, 6, TOKEN_STRING, sizeof(void *) * 3);
 115 KTR_INFO(KTR_TOKENS, tokens, contention_start, 7, CONTENDED_STRING, sizeof(void *) * 3);
 116 KTR_INFO(KTR_TOKENS, tokens, contention_stop, 7, UNCONTENDED_STRING, sizeof(void *) * 3);
 117 #endif
 118
 119 #define logtoken(name, ref)                                             \
 120         KTR_LOG(tokens_ ## name, ref, ref->tr_tok, curthread)
 121
 122 #ifdef _KERNEL
 123
 124 #ifdef INVARIANTS
 125 SYSCTL_INT(_lwkt, OID_AUTO, token_debug, CTLFLAG_RW, &token_debug, 0, "");
 126 #endif
 127
 128 #endif
 129
 130 /*
 131  * Obtain all the tokens required by the specified thread on the current
 132  * cpu, return 0 on failure and non-zero on success.
 133  *
 134  * The preemption code will not allow a target thread holding spinlocks to
 135  * preempt the current thread so we do not have to implement this for UP.
 136  * The only reason why we implement this for UP is that we want to detect
 137  * stale tokens (lwkt_token_is_stale).
 138  *
 139  * lwkt_getalltokens is called by the LWKT scheduler to acquire all
 140  * tokens that the thread had aquired prior to going to sleep.
 141  *
 142  * Called from a critical section.
 143  */
 144 int
 145 lwkt_getalltokens(thread_t td)
 146 {
 147     lwkt_tokref_t refs;
 148 #ifdef SMP
 149     lwkt_tokref_t undo;
 150 #endif
 151     lwkt_token_t tok;
 152
 153     for (refs = td->td_toks; refs; refs = refs->tr_next) {
 154         KKASSERT(refs->tr_state == 0);
 155         tok = refs->tr_tok;
 156         if (tok->t_owner != td) {
 157 #ifdef SMP
 158             if (spin_trylock_wr(&tok->t_spinlock) == 0) {
 159                 /*
 160                  * Release the partial list of tokens obtained and return
 161                  * failure.
 162                  */
 163                 for (undo = td->td_toks; undo != refs; undo = undo->tr_next) {
 164                     tok = undo->tr_tok;
 165                     undo->tr_state = 0;
 166                     if (--tok->t_count == 0) {
 167                         tok->t_owner = NULL;
 168                         spin_unlock_wr(&tok->t_spinlock);
 169                     }
 170                 }
 171                 return (FALSE);
 172             }
 173 #endif
 174             KKASSERT(tok->t_owner == NULL && tok->t_count == 0);
 175             tok->t_owner = td;
 176
 177             /*
 178              * Detect the situation where the token was acquired by
 179              * another thread while the token was released from the
 180              * current thread due to a blocking condition.
 181              * In this case we set t_lastowner to NULL to mark the
 182              * token as stale from the point of view of BOTH threads.
 183              * See lwkt_token_is_stale().
 184              */
 185             if (tok->t_lastowner != tok->t_owner)
 186                 tok->t_lastowner = NULL;
 187         }
 188         ++tok->t_count;
 189         refs->tr_state = 1;
 190     }
 191     return (TRUE);
 192 }
 193
 194 /*
 195  * Release all tokens owned by the specified thread on the current cpu.
 196  *
 197  * Called from a critical section.
 198  */
 199 void
 200 lwkt_relalltokens(thread_t td)
 201 {
 202     lwkt_tokref_t refs;
 203     lwkt_token_t tok;
 204
 205     for (refs = td->td_toks; refs; refs = refs->tr_next) {
 206         if (refs->tr_state) {
 207             refs->tr_state = 0;
 208             tok = refs->tr_tok;
 209             KKASSERT(tok->t_owner == td && tok->t_count > 0);
 210             if (--tok->t_count == 0) {
 211                 tok->t_owner = NULL;
 212 #ifdef SMP
 213                 spin_unlock_wr(&tok->t_spinlock);
 214 #endif
 215             }
 216         }
 217     }
 218 }
 219
 220 /*
 221  * Token acquisition helper function.  Note that get/trytokenref do not
 222  * reset t_lastowner if the token is already held.  Only lwkt_token_is_stale()
 223  * is allowed to do that.
 224  *
 225  * NOTE: On failure, this function doesn't remove the token from the
 226  * thread's token list, so that you have to perform that yourself:
 227  *
 228  *      td->td_toks = ref->tr_next;
 229  */
 230 static __inline
 231 int
 232 _lwkt_trytokref2(lwkt_tokref_t ref, thread_t td)
 233 {
 234 #ifndef SMP
 235     lwkt_tokref_t scan;
 236     thread_t itd;
 237 #endif
 238     lwkt_token_t tok;
 239
 240     KKASSERT(mycpu->gd_intr_nesting_level == 0);
 241     KKASSERT(ref->tr_state == 0);
 242     tok = ref->tr_tok;
 243
 244     /*
 245      * Link the tokref to the thread's list
 246      */
 247     ref->tr_next = td->td_toks;
 248     cpu_ccfence();
 249
 250     /*
 251      * Once td_toks is set to a non NULL value, we can't preempt
 252      * another thread anymore (the scheduler takes care that this
 253      * won't happen). Additionally, we can't get preempted by
 254      * another thread that wants to access the same token (tok).
 255      */
 256     td->td_toks = ref;
 257
 258     if (tok->t_owner != td) {
 259 #ifdef SMP
 260         /*
 261          * Gain ownership of the token's spinlock, SMP version.
 262          */
 263         if (spin_trylock_wr(&tok->t_spinlock) == 0) {
 264             return (FALSE);
 265         }
 266 #else
 267         /*
 268          * Gain ownership of the token, UP version.   All we have to do
 269          * is check the token if we are preempting someone owning the
 270          * same token, in which case we fail to acquire the token.
 271          */
 272         itd = td;
 273         while ((itd = itd->td_preempted) != NULL) {
 274             for (scan = itd->td_toks; scan; scan = scan->tr_next) {
 275                 if (scan->tr_tok == tok) {
 276                     return (FALSE);
 277                 }
 278             }
 279         }
 280 #endif
 281         KKASSERT(tok->t_owner == NULL && tok->t_count == 0);
 282         tok->t_owner = td;
 283         tok->t_lastowner = td;
 284     }
 285     ++tok->t_count;
 286     ref->tr_state = 1;
 287
 288     return (TRUE);
 289 }
 290
 291 static __inline
 292 int
 293 _lwkt_trytokref(lwkt_tokref_t ref)
 294 {
 295     thread_t td = curthread;
 296
 297     if (_lwkt_trytokref2(ref, td) == FALSE) {
 298         /*
 299          * Cleanup. Remove the token from the thread's list.
 300          */
 301         td->td_toks = ref->tr_next;
 302         return (FALSE);
 303     }
 304
 305     return (TRUE);
 306 }
 307
 308 /*
 309  * Acquire a serializing token.  This routine can block.
 310  *
 311  * We track ownership and a per-owner counter.  Tokens are
 312  * released when a thread switches out and reacquired when a thread
 313  * switches back in.
 314  */
 315 static __inline
 316 void
 317 _lwkt_gettokref(lwkt_tokref_t ref)
 318 {
 319   if (_lwkt_trytokref2(ref, curthread) == FALSE) {
 320         /*
 321          * Give up running if we can't acquire the token right now. But as we
 322          * have linked in the tokref to the thread's list (_lwkt_trytokref2),
 323          * the scheduler now takes care to acquire the token (by calling
 324          * lwkt_getalltokens) before resuming execution. As such, when we
 325          * return from lwkt_yield(), the token is acquired.
 326          */
 327         lwkt_yield();
 328   }
 329 }
 330
 331 void
 332 lwkt_gettoken(lwkt_tokref_t ref, lwkt_token_t tok)
 333 {
 334     lwkt_tokref_init(ref, tok);
 335     logtoken(get, ref);
 336     _lwkt_gettokref(ref);
 337 }
 338
 339 void
 340 lwkt_gettokref(lwkt_tokref_t ref)
 341 {
 342     logtoken(get, ref);
 343     _lwkt_gettokref(ref);
 344 }
 345
 346 int
 347 lwkt_trytoken(lwkt_tokref_t ref, lwkt_token_t tok)
 348 {
 349     lwkt_tokref_init(ref, tok);
 350     logtoken(try, ref);
 351     return(_lwkt_trytokref(ref));
 352 }
 353
 354 int
 355 lwkt_trytokref(lwkt_tokref_t ref)
 356 {
 357     logtoken(try, ref);
 358     return(_lwkt_trytokref(ref));
 359 }
 360
 361 /*
 362  * Release a serializing token
 363  */
 364 void
 365 lwkt_reltoken(lwkt_tokref_t ref)
 366 {
 367     struct lwkt_tokref **scanp;
 368     lwkt_token_t tok;
 369     thread_t td;
 370
 371     td = curthread;
 372     tok = ref->tr_tok;
 373
 374     KKASSERT(tok->t_owner == td && ref->tr_state == 1 && tok->t_count > 0);
 375
 376     ref->tr_state = 0;
 377
 378     /*
 379      * Fix-up the count now to avoid racing a preemption which may occur
 380      * after the token has been removed from td_toks.
 381      */
 382     if (--tok->t_count == 0) {
 383         tok->t_owner = NULL;
 384         tok->t_lastowner = NULL;
 385 #ifdef SMP
 386         spin_unlock_wr(&tok->t_spinlock);
 387 #endif
 388      }
 389
 390     /*
 391      * Remove ref from thread's token list.
 392      *
 393      * After removing the token from the thread's list, it's unsafe
 394      * on a UP machine to modify the token, because we might get
 395      * preempted by another thread that wants to acquire the same token.
 396      * This thread now thinks that it can acquire the token, because it's
 397      * no longer in our thread's list. Bang!
 398      *
 399      * SMP: Do not modify token after spin_unlock_wr.
 400      */
 401     for (scanp = &td->td_toks; *scanp != ref; scanp = &((*scanp)->tr_next))
 402         ;
 403     *scanp = ref->tr_next;
 404
 405     logtoken(release, ref);
 406 }
 407
 408 /*
 409  * Pool tokens are used to provide a type-stable serializing token
 410  * pointer that does not race against disappearing data structures.
 411  *
 412  * This routine is called in early boot just after we setup the BSP's
 413  * globaldata structure.
 414  */
 415 void
 416 lwkt_token_pool_init(void)
 417 {
 418     int i;
 419
 420     for (i = 0; i < LWKT_NUM_POOL_TOKENS; ++i)
 421         lwkt_token_init(&pool_tokens[i]);
 422 }
 423
 424 lwkt_token_t
 425 lwkt_token_pool_get(void *ptraddr)
 426 {
 427     int i;
 428
 429     i = ((int)(intptr_t)ptraddr >> 2) ^ ((int)(intptr_t)ptraddr >> 12);
 430     return(&pool_tokens[i & LWKT_MASK_POOL_TOKENS]);
 431 }
 432
 433 /*
 434  * Initialize the owner and release-to cpu to the current cpu
 435  * and reset the generation count.
 436  */
 437 void
 438 lwkt_token_init(lwkt_token_t tok)
 439 {
 440 #ifdef SMP
 441     spin_init(&tok->t_spinlock);
 442 #endif
 443     tok->t_owner = NULL;
 444     tok->t_lastowner = NULL;
 445     tok->t_count = 0;
 446 }
 447
 448 void
 449 lwkt_token_uninit(lwkt_token_t tok)
 450 {
 451     /* empty */
 452 }
 453
 454 int
 455 lwkt_token_is_stale(lwkt_tokref_t ref)
 456 {
 457     lwkt_token_t tok = ref->tr_tok;
 458
 459     KKASSERT(tok->t_owner == curthread && ref->tr_state == 1 &&
 460              tok->t_count > 0);
 461
 462     /* Token is not stale */
 463     if (tok->t_lastowner == tok->t_owner)
 464         return (FALSE);
 465
 466     /*
 467      * The token is stale. Reset to not stale so that the next call to
 468      * lwkt_token_is_stale will return "not stale" unless the token
 469      * was acquired in-between by another thread.
 470      */
 471     tok->t_lastowner = tok->t_owner;
 472     return (TRUE);
 473 }