sysdeps/nptl/gai_misc.h

   1 /* Copyright (C) 2006-2024 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 /* We define a special synchronization primitive for AIO.  POSIX
  19    conditional variables would be ideal but the pthread_cond_*wait
  20    operations do not return on EINTR.  This is a requirement for
  21    correct aio_suspend and lio_listio implementations.  */
  22
  23 #include <assert.h>
  24 #include <signal.h>
  25 #include <pthreadP.h>
  26 #include <futex-internal.h>
  27
  28 #define DONT_NEED_GAI_MISC_COND 1
  29
  30 #define GAI_MISC_NOTIFY(waitlist) \
  31   do {                                                                        \
  32     if (*waitlist->counterp > 0 && --*waitlist->counterp == 0)                \
  33       futex_wake ((unsigned int *) waitlist->counterp, 1, FUTEX_PRIVATE);     \
  34   } while (0)
  35
  36 #define GAI_MISC_WAIT(result, futex, timeout, cancel) \
  37   do {                                                                        \
  38     volatile unsigned int *futexaddr = &futex;                                \
  39     unsigned int oldval = futex;                                              \
  40                                                                               \
  41     if (oldval != 0)                                                          \
  42       {                                                                       \
  43         __pthread_mutex_unlock (&__gai_requests_mutex);                       \
  44                                                                               \
  45         int status;                                                           \
  46         do                                                                    \
  47           {                                                                   \
  48             if (cancel)                                                       \
  49               status = __futex_abstimed_wait_cancelable64 (                   \
  50                 (unsigned int *) futexaddr, oldval, CLOCK_MONOTONIC, timeout, \
  51                 FUTEX_PRIVATE);                                               \
  52             else                                                              \
  53               status = __futex_abstimed_wait64 ((unsigned int *) futexaddr,   \
  54                 oldval, CLOCK_REALTIME, timeout, FUTEX_PRIVATE);              \
  55             if (status != EAGAIN)                                             \
  56               break;                                                          \
  57                                                                               \
  58             oldval = *futexaddr;                                              \
  59           }                                                                   \
  60         while (oldval != 0);                                                  \
  61                                                                               \
  62         if (status == EINTR)                                                  \
  63           result = EINTR;                                                     \
  64         else if (status == ETIMEDOUT)                                         \
  65           result = EAGAIN;                                                    \
  66         else if (status == EOVERFLOW)                                         \
  67           result = EOVERFLOW;                                                 \
  68         else                                                                  \
  69           assert (status == 0 || status == EAGAIN);                           \
  70                                                                               \
  71         __pthread_mutex_lock (&__gai_requests_mutex);                         \
  72       }                                                                       \
  73   } while (0)
  74
  75
  76 #define gai_start_notify_thread __gai_start_notify_thread
  77 #define gai_create_helper_thread __gai_create_helper_thread
  78
  79 extern inline void
  80 __gai_start_notify_thread (void)
  81 {
  82   sigset_t ss;
  83   sigemptyset (&ss);
  84   (void) __pthread_sigmask (SIG_SETMASK, &ss, NULL);
  85 }
  86
  87 extern inline int
  88 __gai_create_helper_thread (pthread_t *threadp, void *(*tf) (void *),
  89                             void *arg)
  90 {
  91   pthread_attr_t attr;
  92
  93   /* Make sure the thread is created detached.  */
  94   __pthread_attr_init (&attr);
  95   __pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
  96
  97   /* The helper thread needs only very little resources.  */
  98   (void) __pthread_attr_setstacksize (&attr,
  99                                       __pthread_get_minstack (&attr)
 100                                       + 4 * PTHREAD_STACK_MIN);
 101
 102   /* Block all signals in the helper thread.  To do this thoroughly we
 103      temporarily have to block all signals here.  */
 104   sigset_t ss;
 105   sigset_t oss;
 106   sigfillset (&ss);
 107   (void) __pthread_sigmask (SIG_SETMASK, &ss, &oss);
 108
 109   int ret = __pthread_create (threadp, &attr, tf, arg);
 110
 111   /* Restore the signal mask.  */
 112   (void) __pthread_sigmask (SIG_SETMASK, &oss, NULL);
 113
 114   (void) __pthread_attr_destroy (&attr);
 115   return ret;
 116 }
 117
 118 #include_next <gai_misc.h>