nptl/descr.h

   1 /* Copyright (C) 2002-2020 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _DESCR_H
  20 #define _DESCR_H        1
  21
  22 #include <limits.h>
  23 #include <sched.h>
  24 #include <setjmp.h>
  25 #include <stdbool.h>
  26 #include <sys/types.h>
  27 #include <hp-timing.h>
  28 #include <list_t.h>
  29 #include <lowlevellock.h>
  30 #include <pthreaddef.h>
  31 #include <dl-sysdep.h>
  32 #include <thread_db.h>
  33 #include <tls.h>
  34 #include <unwind.h>
  35 #include <bits/types/res_state.h>
  36 #include <kernel-features.h>
  37
  38 #ifndef TCB_ALIGNMENT
  39 # define TCB_ALIGNMENT  sizeof (double)
  40 #endif
  41
  42
  43 /* We keep thread specific data in a special data structure, a two-level
  44    array.  The top-level array contains pointers to dynamically allocated
  45    arrays of a certain number of data pointers.  So we can implement a
  46    sparse array.  Each dynamic second-level array has
  47         PTHREAD_KEY_2NDLEVEL_SIZE
  48    entries.  This value shouldn't be too large.  */
  49 #define PTHREAD_KEY_2NDLEVEL_SIZE       32
  50
  51 /* We need to address PTHREAD_KEYS_MAX key with PTHREAD_KEY_2NDLEVEL_SIZE
  52    keys in each subarray.  */
  53 #define PTHREAD_KEY_1STLEVEL_SIZE \
  54   ((PTHREAD_KEYS_MAX + PTHREAD_KEY_2NDLEVEL_SIZE - 1) \
  55    / PTHREAD_KEY_2NDLEVEL_SIZE)
  56
  57
  58
  59
  60 /* Internal version of the buffer to store cancellation handler
  61    information.  */
  62 struct pthread_unwind_buf
  63 {
  64   struct
  65   {
  66     __jmp_buf jmp_buf;
  67     int mask_was_saved;
  68   } cancel_jmp_buf[1];
  69
  70   union
  71   {
  72     /* This is the placeholder of the public version.  */
  73     void *pad[4];
  74
  75     struct
  76     {
  77       /* Pointer to the previous cleanup buffer.  */
  78       struct pthread_unwind_buf *prev;
  79
  80       /* Backward compatibility: state of the old-style cleanup
  81          handler at the time of the previous new-style cleanup handler
  82          installment.  */
  83       struct _pthread_cleanup_buffer *cleanup;
  84
  85       /* Cancellation type before the push call.  */
  86       int canceltype;
  87     } data;
  88   } priv;
  89 };
  90
  91
  92 /* Opcodes and data types for communication with the signal handler to
  93    change user/group IDs.  */
  94 struct xid_command
  95 {
  96   int syscall_no;
  97   long int id[3];
  98   volatile int cntr;
  99   volatile int error; /* -1: no call yet, 0: success seen, >0: error seen.  */
 100 };
 101
 102
 103 /* Data structure used by the kernel to find robust futexes.  */
 104 struct robust_list_head
 105 {
 106   void *list;
 107   long int futex_offset;
 108   void *list_op_pending;
 109 };
 110
 111
 112 /* Data strcture used to handle thread priority protection.  */
 113 struct priority_protection_data
 114 {
 115   int priomax;
 116   unsigned int priomap[];
 117 };
 118
 119
 120 /* Thread descriptor data structure.  */
 121 struct pthread
 122 {
 123   union
 124   {
 125 #if !TLS_DTV_AT_TP
 126     /* This overlaps the TCB as used for TLS without threads (see tls.h).  */
 127     tcbhead_t header;
 128 #else
 129     struct
 130     {
 131       /* multiple_threads is enabled either when the process has spawned at
 132          least one thread or when a single-threaded process cancels itself.
 133          This enables additional code to introduce locking before doing some
 134          compare_and_exchange operations and also enable cancellation points.
 135          The concepts of multiple threads and cancellation points ideally
 136          should be separate, since it is not necessary for multiple threads to
 137          have been created for cancellation points to be enabled, as is the
 138          case is when single-threaded process cancels itself.
 139
 140          Since enabling multiple_threads enables additional code in
 141          cancellation points and compare_and_exchange operations, there is a
 142          potential for an unneeded performance hit when it is enabled in a
 143          single-threaded, self-canceling process.  This is OK though, since a
 144          single-threaded process will enable async cancellation only when it
 145          looks to cancel itself and is hence going to end anyway.  */
 146       int multiple_threads;
 147       int gscope_flag;
 148     } header;
 149 #endif
 150
 151     /* This extra padding has no special purpose, and this structure layout
 152        is private and subject to change without affecting the official ABI.
 153        We just have it here in case it might be convenient for some
 154        implementation-specific instrumentation hack or suchlike.  */
 155     void *__padding[24];
 156   };
 157
 158   /* This descriptor's link on the `stack_used' or `__stack_user' list.  */
 159   list_t list;
 160
 161   /* Thread ID - which is also a 'is this thread descriptor (and
 162      therefore stack) used' flag.  */
 163   pid_t tid;
 164
 165   /* Ununsed.  */
 166   pid_t pid_ununsed;
 167
 168   /* List of robust mutexes the thread is holding.  */
 169 #if __PTHREAD_MUTEX_HAVE_PREV
 170   void *robust_prev;
 171   struct robust_list_head robust_head;
 172
 173   /* The list above is strange.  It is basically a double linked list
 174      but the pointer to the next/previous element of the list points
 175      in the middle of the object, the __next element.  Whenever
 176      casting to __pthread_list_t we need to adjust the pointer
 177      first.
 178      These operations are effectively concurrent code in that the thread
 179      can get killed at any point in time and the kernel takes over.  Thus,
 180      the __next elements are a kind of concurrent list and we need to
 181      enforce using compiler barriers that the individual operations happen
 182      in such a way that the kernel always sees a consistent list.  The
 183      backward links (ie, the __prev elements) are not used by the kernel.
 184      FIXME We should use relaxed MO atomic operations here and signal fences
 185      because this kind of concurrency is similar to synchronizing with a
 186      signal handler.  */
 187 # define QUEUE_PTR_ADJUST (offsetof (__pthread_list_t, __next))
 188
 189 # define ENQUEUE_MUTEX_BOTH(mutex, val)                                       \
 190   do {                                                                        \
 191     __pthread_list_t *next = (__pthread_list_t *)                             \
 192       ((((uintptr_t) THREAD_GETMEM (THREAD_SELF, robust_head.list)) & ~1ul)   \
 193        - QUEUE_PTR_ADJUST);                                                   \
 194     next->__prev = (void *) &mutex->__data.__list.__next;                     \
 195     mutex->__data.__list.__next = THREAD_GETMEM (THREAD_SELF,                 \
 196                                                  robust_head.list);           \
 197     mutex->__data.__list.__prev = (void *) &THREAD_SELF->robust_head;         \
 198     /* Ensure that the new list entry is ready before we insert it.  */       \
 199     __asm ("" ::: "memory");                                                  \
 200     THREAD_SETMEM (THREAD_SELF, robust_head.list,                             \
 201                    (void *) (((uintptr_t) &mutex->__data.__list.__next)       \
 202                              | val));                                         \
 203   } while (0)
 204 # define DEQUEUE_MUTEX(mutex) \
 205   do {                                                                        \
 206     __pthread_list_t *next = (__pthread_list_t *)                             \
 207       ((char *) (((uintptr_t) mutex->__data.__list.__next) & ~1ul)            \
 208        - QUEUE_PTR_ADJUST);                                                   \
 209     next->__prev = mutex->__data.__list.__prev;                               \
 210     __pthread_list_t *prev = (__pthread_list_t *)                             \
 211       ((char *) (((uintptr_t) mutex->__data.__list.__prev) & ~1ul)            \
 212        - QUEUE_PTR_ADJUST);                                                   \
 213     prev->__next = mutex->__data.__list.__next;                               \
 214     /* Ensure that we remove the entry from the list before we change the     \
 215        __next pointer of the entry, which is read by the kernel.  */          \
 216     __asm ("" ::: "memory");                                                  \
 217     mutex->__data.__list.__prev = NULL;                                       \
 218     mutex->__data.__list.__next = NULL;                                       \
 219   } while (0)
 220 #else
 221   union
 222   {
 223     __pthread_slist_t robust_list;
 224     struct robust_list_head robust_head;
 225   };
 226
 227 # define ENQUEUE_MUTEX_BOTH(mutex, val)                                       \
 228   do {                                                                        \
 229     mutex->__data.__list.__next                                               \
 230       = THREAD_GETMEM (THREAD_SELF, robust_list.__next);                      \
 231     /* Ensure that the new list entry is ready before we insert it.  */       \
 232     __asm ("" ::: "memory");                                                  \
 233     THREAD_SETMEM (THREAD_SELF, robust_list.__next,                           \
 234                    (void *) (((uintptr_t) &mutex->__data.__list) | val));     \
 235   } while (0)
 236 # define DEQUEUE_MUTEX(mutex) \
 237   do {                                                                        \
 238     __pthread_slist_t *runp = (__pthread_slist_t *)                           \
 239       (((uintptr_t) THREAD_GETMEM (THREAD_SELF, robust_list.__next)) & ~1ul); \
 240     if (runp == &mutex->__data.__list)                                        \
 241       THREAD_SETMEM (THREAD_SELF, robust_list.__next, runp->__next);          \
 242     else                                                                      \
 243       {                                                                       \
 244         __pthread_slist_t *next = (__pthread_slist_t *)               \
 245           (((uintptr_t) runp->__next) & ~1ul);                                \
 246         while (next != &mutex->__data.__list)                                 \
 247           {                                                                   \
 248             runp = next;                                                      \
 249             next = (__pthread_slist_t *) (((uintptr_t) runp->__next) & ~1ul); \
 250           }                                                                   \
 251                                                                               \
 252         runp->__next = next->__next;                                          \
 253         /* Ensure that we remove the entry from the list before we change the \
 254            __next pointer of the entry, which is read by the kernel.  */      \
 255             __asm ("" ::: "memory");                                          \
 256         mutex->__data.__list.__next = NULL;                                   \
 257       }                                                                       \
 258   } while (0)
 259 #endif
 260 #define ENQUEUE_MUTEX(mutex) ENQUEUE_MUTEX_BOTH (mutex, 0)
 261 #define ENQUEUE_MUTEX_PI(mutex) ENQUEUE_MUTEX_BOTH (mutex, 1)
 262
 263   /* List of cleanup buffers.  */
 264   struct _pthread_cleanup_buffer *cleanup;
 265
 266   /* Unwind information.  */
 267   struct pthread_unwind_buf *cleanup_jmp_buf;
 268 #define HAVE_CLEANUP_JMP_BUF
 269
 270   /* Flags determining processing of cancellation.  */
 271   int cancelhandling;
 272   /* Bit set if cancellation is disabled.  */
 273 #define CANCELSTATE_BIT         0
 274 #define CANCELSTATE_BITMASK     (0x01 << CANCELSTATE_BIT)
 275   /* Bit set if asynchronous cancellation mode is selected.  */
 276 #define CANCELTYPE_BIT          1
 277 #define CANCELTYPE_BITMASK      (0x01 << CANCELTYPE_BIT)
 278   /* Bit set if canceling has been initiated.  */
 279 #define CANCELING_BIT           2
 280 #define CANCELING_BITMASK       (0x01 << CANCELING_BIT)
 281   /* Bit set if canceled.  */
 282 #define CANCELED_BIT            3
 283 #define CANCELED_BITMASK        (0x01 << CANCELED_BIT)
 284   /* Bit set if thread is exiting.  */
 285 #define EXITING_BIT             4
 286 #define EXITING_BITMASK         (0x01 << EXITING_BIT)
 287   /* Bit set if thread terminated and TCB is freed.  */
 288 #define TERMINATED_BIT          5
 289 #define TERMINATED_BITMASK      (0x01 << TERMINATED_BIT)
 290   /* Bit set if thread is supposed to change XID.  */
 291 #define SETXID_BIT              6
 292 #define SETXID_BITMASK          (0x01 << SETXID_BIT)
 293   /* Mask for the rest.  Helps the compiler to optimize.  */
 294 #define CANCEL_RESTMASK         0xffffff80
 295
 296 #define CANCEL_ENABLED_AND_CANCELED(value) \
 297   (((value) & (CANCELSTATE_BITMASK | CANCELED_BITMASK | EXITING_BITMASK       \
 298                | CANCEL_RESTMASK | TERMINATED_BITMASK)) == CANCELED_BITMASK)
 299 #define CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS(value) \
 300   (((value) & (CANCELSTATE_BITMASK | CANCELTYPE_BITMASK | CANCELED_BITMASK    \
 301                | EXITING_BITMASK | CANCEL_RESTMASK | TERMINATED_BITMASK))     \
 302    == (CANCELTYPE_BITMASK | CANCELED_BITMASK))
 303
 304   /* Flags.  Including those copied from the thread attribute.  */
 305   int flags;
 306
 307   /* We allocate one block of references here.  This should be enough
 308      to avoid allocating any memory dynamically for most applications.  */
 309   struct pthread_key_data
 310   {
 311     /* Sequence number.  We use uintptr_t to not require padding on
 312        32- and 64-bit machines.  On 64-bit machines it helps to avoid
 313        wrapping, too.  */
 314     uintptr_t seq;
 315
 316     /* Data pointer.  */
 317     void *data;
 318   } specific_1stblock[PTHREAD_KEY_2NDLEVEL_SIZE];
 319
 320   /* Two-level array for the thread-specific data.  */
 321   struct pthread_key_data *specific[PTHREAD_KEY_1STLEVEL_SIZE];
 322
 323   /* Flag which is set when specific data is set.  */
 324   bool specific_used;
 325
 326   /* True if events must be reported.  */
 327   bool report_events;
 328
 329   /* True if the user provided the stack.  */
 330   bool user_stack;
 331
 332   /* True if thread must stop at startup time.  */
 333   bool stopped_start;
 334
 335   /* The parent's cancel handling at the time of the pthread_create
 336      call.  This might be needed to undo the effects of a cancellation.  */
 337   int parent_cancelhandling;
 338
 339   /* Lock to synchronize access to the descriptor.  */
 340   int lock;
 341
 342   /* Lock for synchronizing setxid calls.  */
 343   unsigned int setxid_futex;
 344
 345 #if HP_TIMING_INLINE
 346   hp_timing_t cpuclock_offset_ununsed;
 347 #endif
 348
 349   /* If the thread waits to join another one the ID of the latter is
 350      stored here.
 351
 352      In case a thread is detached this field contains a pointer of the
 353      TCB if the thread itself.  This is something which cannot happen
 354      in normal operation.  */
 355   struct pthread *joinid;
 356   /* Check whether a thread is detached.  */
 357 #define IS_DETACHED(pd) ((pd)->joinid == (pd))
 358
 359   /* The result of the thread function.  */
 360   void *result;
 361
 362   /* Scheduling parameters for the new thread.  */
 363   struct sched_param schedparam;
 364   int schedpolicy;
 365
 366   /* Start position of the code to be executed and the argument passed
 367      to the function.  */
 368   void *(*start_routine) (void *);
 369   void *arg;
 370
 371   /* Debug state.  */
 372   td_eventbuf_t eventbuf;
 373   /* Next descriptor with a pending event.  */
 374   struct pthread *nextevent;
 375
 376   /* Machine-specific unwind info.  */
 377   struct _Unwind_Exception exc;
 378
 379   /* If nonzero, pointer to the area allocated for the stack and guard. */
 380   void *stackblock;
 381   /* Size of the stackblock area including the guard.  */
 382   size_t stackblock_size;
 383   /* Size of the included guard area.  */
 384   size_t guardsize;
 385   /* This is what the user specified and what we will report.  */
 386   size_t reported_guardsize;
 387
 388   /* Thread Priority Protection data.  */
 389   struct priority_protection_data *tpp;
 390
 391   /* Resolver state.  */
 392   struct __res_state res;
 393
 394   /* Indicates whether is a C11 thread created by thrd_creat.  */
 395   bool c11;
 396
 397   /* This member must be last.  */
 398   char end_padding[];
 399
 400 #define PTHREAD_STRUCT_END_PADDING \
 401   (sizeof (struct pthread) - offsetof (struct pthread, end_padding))
 402 } __attribute ((aligned (TCB_ALIGNMENT)));
 403
 404
 405 #endif  /* descr.h */