firmware/export/thread.h

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2002 by Ulf Ralberg
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21 #ifndef THREAD_H
  22 #define THREAD_H
  23
  24 #include "config.h"
  25 #include <inttypes.h>
  26 #include <stddef.h>
  27 #include <stdbool.h>
  28
  29 /* Priority scheduling (when enabled with HAVE_PRIORITY_SCHEDULING) works
  30  * by giving high priority threads more CPU time than lower priority threads
  31  * when they need it. Priority is differential such that the priority
  32  * difference between a lower priority runnable thread and the highest priority
  33  * runnable thread determines the amount of aging necessary for the lower
  34  * priority thread to be scheduled in order to prevent starvation.
  35  *
  36  * If software playback codec pcm buffer is going down to critical, codec
  37  * can gradually raise its own priority to override user interface and
  38  * prevent playback skipping.
  39  */
  40 #define PRIORITY_RESERVED_HIGH   0   /* Reserved */
  41 #define PRIORITY_RESERVED_LOW    32  /* Reserved */
  42 #define HIGHEST_PRIORITY         1   /* The highest possible thread priority */
  43 #define LOWEST_PRIORITY          31  /* The lowest possible thread priority */
  44 /* Realtime range reserved for threads that will not allow threads of lower
  45  * priority to age and run (future expansion) */
  46 #define PRIORITY_REALTIME_1      1
  47 #define PRIORITY_REALTIME_2      2
  48 #define PRIORITY_REALTIME_3      3
  49 #define PRIORITY_REALTIME_4      4
  50 #define PRIORITY_REALTIME        4   /* Lowest realtime range */
  51 #define PRIORITY_BUFFERING       15  /* Codec buffering thread */
  52 #define PRIORITY_USER_INTERFACE  16  /* The main thread */
  53 #define PRIORITY_RECORDING       16  /* Recording thread */
  54 #define PRIORITY_PLAYBACK        16  /* Variable between this and MAX */
  55 #define PRIORITY_PLAYBACK_MAX    5   /* Maximum allowable playback priority */
  56 #define PRIORITY_SYSTEM          18  /* All other firmware threads */
  57 #define PRIORITY_BACKGROUND      20  /* Normal application threads */
  58 #define NUM_PRIORITIES           32
  59 #define PRIORITY_IDLE            32  /* Priority representative of no tasks */
  60
  61 #define IO_PRIORITY_IMMEDIATE    0
  62 #define IO_PRIORITY_BACKGROUND   32
  63
  64 #if CONFIG_CODEC == SWCODEC
  65
  66 #ifdef HAVE_RECORDING
  67 #define BASETHREADS  17
  68 #else
  69 #define BASETHREADS  16
  70 #endif
  71
  72 #else
  73 #define BASETHREADS  11
  74 #endif /* CONFIG_CODE == * */
  75
  76 #ifndef TARGET_EXTRA_THREADS
  77 #define TARGET_EXTRA_THREADS 0
  78 #endif
  79
  80 #define MAXTHREADS (BASETHREADS+TARGET_EXTRA_THREADS)
  81
  82 #define DEFAULT_STACK_SIZE 0x400 /* Bytes */
  83
  84 #ifndef SIMULATOR
  85 /* Need to keep structures inside the header file because debug_menu
  86  * needs them. */
  87 #ifdef CPU_COLDFIRE
  88 struct regs
  89 {
  90     uint32_t macsr; /*     0 - EMAC status register */
  91     uint32_t d[6];  /*  4-24 - d2-d7 */
  92     uint32_t a[5];  /* 28-44 - a2-a6 */
  93     uint32_t sp;    /*    48 - Stack pointer (a7) */
  94     uint32_t start; /*    52 - Thread start address, or NULL when started */
  95 };
  96 #elif CONFIG_CPU == SH7034
  97 struct regs
  98 {
  99     uint32_t r[7];  /*  0-24 - Registers r8 thru r14 */
 100     uint32_t sp;    /*    28 - Stack pointer (r15) */
 101     uint32_t pr;    /*    32 - Procedure register */
 102     uint32_t start; /*    36 - Thread start address, or NULL when started */
 103 };
 104 #elif defined(CPU_ARM)
 105 struct regs
 106 {
 107     uint32_t r[8];  /*  0-28 - Registers r4-r11 */
 108     uint32_t sp;    /*    32 - Stack pointer (r13) */
 109     uint32_t lr;    /*    36 - r14 (lr) */
 110     uint32_t start; /*    40 - Thread start address, or NULL when started */
 111 };
 112 #elif defined(CPU_MIPS)
 113 struct regs
 114 {
 115     uint32_t r[9];  /* 0-32 - Registers s0-s7, fp */
 116     uint32_t sp;    /*   36 - Stack pointer */
 117     uint32_t ra;    /*   40 - Return address */
 118     uint32_t start; /*   44 - Thread start address, or NULL when started */
 119 };
 120 #endif /* CONFIG_CPU */
 121 #else
 122 struct regs
 123 {
 124     void *t;             /* Simulator OS thread */
 125     void *s;             /* Semaphore for blocking and wakeup */
 126     void (*start)(void); /* Start function */
 127 };
 128 #endif /* !SIMULATOR */
 129
 130 /* NOTE: The use of the word "queue" may also refer to a linked list of
 131    threads being maintained that are normally dealt with in FIFO order
 132    and not necessarily kernel event_queue */
 133 enum
 134 {
 135     /* States without a timeout must be first */
 136     STATE_KILLED = 0,    /* Thread is killed (default) */
 137     STATE_RUNNING,       /* Thread is currently running */
 138     STATE_BLOCKED,       /* Thread is indefinitely blocked on a queue */
 139     /* These states involve adding the thread to the tmo list */
 140     STATE_SLEEPING,      /* Thread is sleeping with a timeout */
 141     STATE_BLOCKED_W_TMO, /* Thread is blocked on a queue with a timeout */
 142     /* Miscellaneous states */
 143     STATE_FROZEN,        /* Thread is suspended and will not run until
 144                             thread_thaw is called with its ID */
 145     THREAD_NUM_STATES,
 146     TIMEOUT_STATE_FIRST = STATE_SLEEPING,
 147 };
 148
 149 #if NUM_CORES > 1
 150 /* Pointer value for name field to indicate thread is being killed. Using
 151  * an alternate STATE_* won't work since that would interfere with operation
 152  * while the thread is still running. */
 153 #define THREAD_DESTRUCT ((const char *)~(intptr_t)0)
 154 #endif
 155
 156 /* Link information for lists thread is in */
 157 struct thread_entry; /* forward */
 158 struct thread_list
 159 {
 160     struct thread_entry *prev; /* Previous thread in a list */
 161     struct thread_entry *next; /* Next thread in a list */
 162 };
 163
 164 /* Small objects for core-wise mutual exclusion */
 165 #if CONFIG_CORELOCK == SW_CORELOCK
 166 /* No reliable atomic instruction available - use Peterson's algorithm */
 167 struct corelock
 168 {
 169     volatile unsigned char myl[NUM_CORES];
 170     volatile unsigned char turn;
 171 } __attribute__((packed));
 172
 173 void corelock_init(struct corelock *cl);
 174 void corelock_lock(struct corelock *cl);
 175 int corelock_try_lock(struct corelock *cl);
 176 void corelock_unlock(struct corelock *cl);
 177 #elif CONFIG_CORELOCK == CORELOCK_SWAP
 178 /* Use native atomic swap/exchange instruction */
 179 struct corelock
 180 {
 181     volatile unsigned char locked;
 182 } __attribute__((packed));
 183
 184 #define corelock_init(cl) \
 185     ({ (cl)->locked = 0; })
 186 #define corelock_lock(cl) \
 187     ({ while (test_and_set(&(cl)->locked, 1)); })
 188 #define corelock_try_lock(cl) \
 189     ({ test_and_set(&(cl)->locked, 1) ? 0 : 1; })
 190 #define corelock_unlock(cl) \
 191     ({ (cl)->locked = 0; })
 192 #else
 193 /* No atomic corelock op needed or just none defined */
 194 #define corelock_init(cl)
 195 #define corelock_lock(cl)
 196 #define corelock_try_lock(cl)
 197 #define corelock_unlock(cl)
 198 #endif /* core locking selection */
 199
 200 #ifdef HAVE_PRIORITY_SCHEDULING
 201 struct blocker
 202 {
 203     struct thread_entry *thread;   /* thread blocking other threads
 204                                       (aka. object owner) */
 205     int priority;                  /* highest priority waiter */
 206     struct thread_entry * (*wakeup_protocol)(struct thread_entry *thread);
 207 };
 208
 209 /* Choices of wakeup protocol */
 210
 211 /* For transfer of object ownership by one thread to another thread by
 212  * the owning thread itself (mutexes) */
 213 struct thread_entry *
 214     wakeup_priority_protocol_transfer(struct thread_entry *thread);
 215
 216 /* For release by owner where ownership doesn't change - other threads,
 217  * interrupts, timeouts, etc. (mutex timeout, queues) */
 218 struct thread_entry *
 219     wakeup_priority_protocol_release(struct thread_entry *thread);
 220
 221
 222 struct priority_distribution
 223 {
 224     uint8_t  hist[NUM_PRIORITIES]; /* Histogram: Frequency for each priority */
 225     uint32_t mask;                 /* Bitmask of hist entries that are not zero */
 226 };
 227
 228 #endif /* HAVE_PRIORITY_SCHEDULING */
 229
 230 /* Information kept in each thread slot
 231  * members are arranged according to size - largest first - in order
 232  * to ensure both alignment and packing at the same time.
 233  */
 234 struct thread_entry
 235 {
 236     struct regs context;       /* Register context at switch -
 237                                   _must_ be first member */
 238     uintptr_t *stack;          /* Pointer to top of stack */
 239     const char *name;          /* Thread name */
 240     long tmo_tick;             /* Tick when thread should be woken from
 241                                   timeout -
 242                                   states: STATE_SLEEPING/STATE_BLOCKED_W_TMO */
 243     struct thread_list l;      /* Links for blocked/waking/running -
 244                                   circular linkage in both directions */
 245     struct thread_list tmo;    /* Links for timeout list -
 246                                   Circular in reverse direction, NULL-terminated in
 247                                   forward direction -
 248                                   states: STATE_SLEEPING/STATE_BLOCKED_W_TMO */
 249     struct thread_entry **bqp; /* Pointer to list variable in kernel
 250                                   object where thread is blocked - used
 251                                   for implicit unblock and explicit wake
 252                                   states: STATE_BLOCKED/STATE_BLOCKED_W_TMO  */
 253 #if NUM_CORES > 1
 254     struct corelock *obj_cl;   /* Object corelock where thead is blocked -
 255                                   states: STATE_BLOCKED/STATE_BLOCKED_W_TMO */
 256     struct corelock waiter_cl; /* Corelock for thread_wait */
 257     struct corelock slot_cl;   /* Corelock to lock thread slot */
 258     unsigned char core;        /* The core to which thread belongs */
 259 #endif
 260     struct thread_entry *queue; /* List of threads waiting for thread to be
 261                                   removed */
 262 #ifdef HAVE_WAKEUP_EXT_CB
 263     void (*wakeup_ext_cb)(struct thread_entry *thread); /* Callback that
 264                                   performs special steps needed when being
 265                                   forced off of an object's wait queue that
 266                                   go beyond the standard wait queue removal
 267                                   and priority disinheritance */
 268     /* Only enabled when using queue_send for now */
 269 #endif
 270 #if defined(HAVE_EXTENDED_MESSAGING_AND_NAME) || NUM_CORES > 1
 271     intptr_t retval;           /* Return value from a blocked operation/
 272                                   misc. use */
 273 #endif
 274 #ifdef HAVE_PRIORITY_SCHEDULING
 275     /* Priority summary of owned objects that support inheritance */
 276     struct blocker *blocker;   /* Pointer to blocker when this thread is blocked
 277                                   on an object that supports PIP -
 278                                   states: STATE_BLOCKED/STATE_BLOCKED_W_TMO  */
 279     struct priority_distribution pdist; /* Priority summary of owned objects
 280                                   that have blocked threads and thread's own
 281                                   base priority */
 282     int skip_count;            /* Number of times skipped if higher priority
 283                                   thread was running */
 284     unsigned char base_priority; /* Base priority (set explicitly during
 285                                   creation or thread_set_priority) */
 286     unsigned char priority;    /* Scheduled priority (higher of base or
 287                                   all threads blocked by this one) */
 288 #endif
 289     uint16_t id;               /* Current slot id */
 290     unsigned short stack_size; /* Size of stack in bytes */
 291     unsigned char state;       /* Thread slot state (STATE_*) */
 292 #ifdef HAVE_SCHEDULER_BOOSTCTRL
 293     unsigned char cpu_boost;   /* CPU frequency boost flag */
 294 #endif
 295 #ifdef HAVE_IO_PRIORITY
 296     unsigned char io_priority;
 297 #endif
 298 };
 299
 300 /*** Macros for internal use ***/
 301 /* Thread ID, 16 bits = |VVVVVVVV|SSSSSSSS| */
 302 #define THREAD_ID_VERSION_SHIFT      8
 303 #define THREAD_ID_VERSION_MASK  0xff00
 304 #define THREAD_ID_SLOT_MASK     0x00ff
 305 #define THREAD_ID_INIT(n)       ((1u << THREAD_ID_VERSION_SHIFT) | (n))
 306
 307 /* Specify current thread in a function taking an ID. */
 308 #define THREAD_ID_CURRENT ((unsigned int)-1)
 309
 310 #if NUM_CORES > 1
 311 /* Operations to be performed just before stopping a thread and starting
 312    a new one if specified before calling switch_thread */
 313 enum
 314 {
 315     TBOP_CLEAR = 0,       /* No operation to do */
 316     TBOP_UNLOCK_CORELOCK, /* Unlock a corelock variable */
 317     TBOP_SWITCH_CORE,     /* Call the core switch preparation routine */
 318 };
 319
 320 struct thread_blk_ops
 321 {
 322     struct corelock *cl_p;    /* pointer to corelock */
 323     unsigned char    flags;   /* TBOP_* flags */
 324 };
 325 #endif /* NUM_CORES > 1 */
 326
 327 /* Information kept for each core
 328  * Members are arranged for the same reason as in thread_entry
 329  */
 330 struct core_entry
 331 {
 332     /* "Active" lists - core is constantly active on these and are never
 333        locked and interrupts do not access them */
 334     struct thread_entry *running;  /* threads that are running (RTR) */
 335     struct thread_entry *timeout;  /* threads that are on a timeout before
 336                                       running again */
 337     struct thread_entry *block_task; /* Task going off running list */
 338 #ifdef HAVE_PRIORITY_SCHEDULING
 339     struct priority_distribution rtr; /* Summary of running and ready-to-run
 340                                          threads */
 341 #endif
 342     long next_tmo_check;           /* soonest time to check tmo threads */
 343 #if NUM_CORES > 1
 344     struct thread_blk_ops blk_ops; /* operations to perform when
 345                                       blocking a thread */
 346     struct corelock rtr_cl;        /* Lock for rtr list */
 347 #endif /* NUM_CORES */
 348 };
 349
 350 #ifdef HAVE_PRIORITY_SCHEDULING
 351 #define IF_PRIO(...)    __VA_ARGS__
 352 #define IFN_PRIO(...)
 353 #else
 354 #define IF_PRIO(...)
 355 #define IFN_PRIO(...)   __VA_ARGS__
 356 #endif
 357
 358 /* Macros generate better code than an inline function is this case */
 359 #if (defined (CPU_PP) || defined (CPU_ARM))
 360 /* atomic */
 361 #if CONFIG_CORELOCK == SW_CORELOCK
 362 #define test_and_set(a, v, cl) \
 363     xchg8((a), (v), (cl))
 364 /* atomic */
 365 #define xchg8(a, v, cl) \
 366 ({  uint32_t o;            \
 367     corelock_lock(cl);     \
 368     o = *(uint8_t *)(a);   \
 369     *(uint8_t *)(a) = (v); \
 370     corelock_unlock(cl);   \
 371     o; })
 372 #define xchg32(a, v, cl) \
 373 ({  uint32_t o;             \
 374     corelock_lock(cl);      \
 375     o = *(uint32_t *)(a);   \
 376     *(uint32_t *)(a) = (v); \
 377     corelock_unlock(cl);    \
 378     o; })
 379 #define xchgptr(a, v, cl) \
 380 ({  typeof (*(a)) o;     \
 381     corelock_lock(cl);   \
 382     o = *(a);            \
 383     *(a) = (v);          \
 384     corelock_unlock(cl); \
 385     o; })
 386 #elif CONFIG_CORELOCK == CORELOCK_SWAP
 387 /* atomic */
 388 #define test_and_set(a, v, ...) \
 389     xchg8((a), (v))
 390 #define xchg8(a, v, ...) \
 391 ({  uint32_t o;                \
 392     asm volatile(              \
 393         "swpb %0, %1, [%2]"    \
 394         : "=&r"(o)             \
 395         : "r"(v),              \
 396           "r"((uint8_t*)(a))); \
 397     o; })
 398 /* atomic */
 399 #define xchg32(a, v, ...) \
 400 ({  uint32_t o;                 \
 401     asm volatile(               \
 402         "swp %0, %1, [%2]"      \
 403         : "=&r"(o)              \
 404         : "r"((uint32_t)(v)),   \
 405           "r"((uint32_t*)(a))); \
 406     o; })
 407 /* atomic */
 408 #define xchgptr(a, v, ...) \
 409 ({  typeof (*(a)) o;        \
 410     asm volatile(           \
 411         "swp %0, %1, [%2]"  \
 412         : "=&r"(o)          \
 413         : "r"(v), "r"(a));  \
 414     o; })
 415 #endif /* locking selection */
 416 #elif defined (CPU_COLDFIRE)
 417 /* atomic */
 418 /* one branch will be optimized away if v is a constant expression */
 419 #define test_and_set(a, v, ...) \
 420 ({  uint32_t o = 0;                \
 421     if (v) {                       \
 422         asm volatile (             \
 423             "bset.b #0, (%0)"      \
 424             : : "a"((uint8_t*)(a)) \
 425             : "cc");               \
 426     } else {                       \
 427         asm volatile (             \
 428             "bclr.b #0, (%0)"      \
 429             : : "a"((uint8_t*)(a)) \
 430             : "cc");               \
 431     }                              \
 432     asm volatile ("sne.b %0"       \
 433         : "+d"(o));                \
 434     o; })
 435 #elif CONFIG_CPU == SH7034
 436 /* atomic */
 437 #define test_and_set(a, v, ...) \
 438 ({  uint32_t o;                 \
 439     asm volatile (              \
 440         "tas.b  @%2     \n"     \
 441         "mov    #-1, %0 \n"     \
 442         "negc   %0, %0  \n"     \
 443         : "=r"(o)               \
 444         : "M"((uint32_t)(v)),   /* Value of_v must be 1 */ \
 445           "r"((uint8_t *)(a))); \
 446     o; })
 447 #endif /* CONFIG_CPU == */
 448
 449 /* defaults for no asm version */
 450 #ifndef test_and_set
 451 /* not atomic */
 452 #define test_and_set(a, v, ...) \
 453 ({  uint32_t o = *(uint8_t *)(a); \
 454     *(uint8_t *)(a) = (v);        \
 455     o; })
 456 #endif /* test_and_set */
 457 #ifndef xchg8
 458 /* not atomic */
 459 #define xchg8(a, v, ...) \
 460 ({  uint32_t o = *(uint8_t *)(a); \
 461     *(uint8_t *)(a) = (v);        \
 462     o; })
 463 #endif /* xchg8 */
 464 #ifndef xchg32
 465 /* not atomic */
 466 #define xchg32(a, v, ...) \
 467 ({  uint32_t o = *(uint32_t *)(a); \
 468     *(uint32_t *)(a) = (v);        \
 469     o; })
 470 #endif /* xchg32 */
 471 #ifndef xchgptr
 472 /* not atomic */
 473 #define xchgptr(a, v, ...) \
 474 ({  typeof (*(a)) o = *(a); \
 475     *(a) = (v);             \
 476     o; })
 477 #endif /* xchgptr */
 478
 479 void core_idle(void);
 480 void core_wake(IF_COP_VOID(unsigned int core));
 481
 482 /* Initialize the scheduler */
 483 void init_threads(void) INIT_ATTR;
 484
 485 /* Allocate a thread in the scheduler */
 486 #define CREATE_THREAD_FROZEN   0x00000001 /* Thread is frozen at create time */
 487 unsigned int create_thread(void (*function)(void),
 488                            void* stack, size_t stack_size,
 489                            unsigned flags, const char *name
 490                            IF_PRIO(, int priority)
 491                            IF_COP(, unsigned int core));
 492
 493 /* Set and clear the CPU frequency boost flag for the calling thread */
 494 #ifdef HAVE_SCHEDULER_BOOSTCTRL
 495 void trigger_cpu_boost(void);
 496 void cancel_cpu_boost(void);
 497 #else
 498 #define trigger_cpu_boost()
 499 #define cancel_cpu_boost()
 500 #endif
 501 /* Return thread entry from id */
 502 struct thread_entry *thread_id_entry(unsigned int thread_id);
 503 /* Make a frozed thread runnable (when started with CREATE_THREAD_FROZEN).
 504  * Has no effect on a thread not frozen. */
 505 void thread_thaw(unsigned int thread_id);
 506 /* Wait for a thread to exit */
 507 void thread_wait(unsigned int thread_id);
 508 /* Exit the current thread */
 509 void thread_exit(void);
 510 #if defined(DEBUG) || defined(ROCKBOX_HAS_LOGF)
 511 #define ALLOW_REMOVE_THREAD
 512 /* Remove a thread from the scheduler */
 513 void remove_thread(unsigned int thread_id);
 514 #endif
 515
 516 /* Switch to next runnable thread */
 517 void switch_thread(void);
 518 /* Blocks a thread for at least the specified number of ticks (0 = wait until
 519  * next tick) */
 520 void sleep_thread(int ticks);
 521 /* Indefinitely blocks the current thread on a thread queue */
 522 void block_thread(struct thread_entry *current);
 523 /* Blocks the current thread on a thread queue until explicitely woken or
 524  * the timeout is reached */
 525 void block_thread_w_tmo(struct thread_entry *current, int timeout);
 526
 527 /* Return bit flags for thread wakeup */
 528 #define THREAD_NONE     0x0 /* No thread woken up (exclusive) */
 529 #define THREAD_OK       0x1 /* A thread was woken up */
 530 #define THREAD_SWITCH   0x2 /* Task switch recommended (one or more of
 531                                higher priority than current were woken) */
 532
 533 /* A convenience function for waking an entire queue of threads. */
 534 unsigned int thread_queue_wake(struct thread_entry **list);
 535
 536 /* Wakeup a thread at the head of a list */
 537 unsigned int wakeup_thread(struct thread_entry **list);
 538
 539 #ifdef HAVE_PRIORITY_SCHEDULING
 540 int thread_set_priority(unsigned int thread_id, int priority);
 541 int thread_get_priority(unsigned int thread_id);
 542 #endif /* HAVE_PRIORITY_SCHEDULING */
 543 #ifdef HAVE_IO_PRIORITY
 544 void thread_set_io_priority(unsigned int thread_id, int io_priority);
 545 int thread_get_io_priority(unsigned int thread_id);
 546 #endif /* HAVE_IO_PRIORITY */
 547 #if NUM_CORES > 1
 548 unsigned int switch_core(unsigned int new_core);
 549 #endif
 550 unsigned int thread_get_current(void);
 551
 552 /* Debugging info - only! */
 553 int thread_stack_usage(const struct thread_entry *thread);
 554 #if NUM_CORES > 1
 555 int idle_stack_usage(unsigned int core);
 556 #endif
 557 void thread_get_name(char *buffer, int size,
 558                      struct thread_entry *thread);
 559 #ifdef RB_PROFILE
 560 void profile_thread(void);
 561 #endif
 562
 563 #endif /* THREAD_H */