nptl/sysdeps/pthread/gai_misc.h

   1 /* Copyright (C) 2006, 2007, 2008, 2011 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 /* We define a special synchronization primitive for AIO.  POSIX
  20    conditional variables would be ideal but the pthread_cond_*wait
  21    operations do not return on EINTR.  This is a requirement for
  22    correct aio_suspend and lio_listio implementations.  */
  23
  24 #include <assert.h>
  25 #include <signal.h>
  26 #include <pthreadP.h>
  27 #include <lowlevellock.h>
  28
  29 #define DONT_NEED_GAI_MISC_COND 1
  30
  31 #define GAI_MISC_NOTIFY(waitlist) \
  32   do {                                                                        \
  33     if (*waitlist->counterp > 0 && --*waitlist->counterp == 0)                \
  34       lll_futex_wake (waitlist->counterp, 1, LLL_PRIVATE);                    \
  35   } while (0)
  36
  37 #define GAI_MISC_WAIT(result, futex, timeout, cancel) \
  38   do {                                                                        \
  39     volatile int *futexaddr = &futex;                                         \
  40     int oldval = futex;                                                       \
  41                                                                               \
  42     if (oldval != 0)                                                          \
  43       {                                                                       \
  44         pthread_mutex_unlock (&__gai_requests_mutex);                         \
  45                                                                               \
  46         int oldtype;                                                          \
  47         if (cancel)                                                           \
  48           oldtype = LIBC_CANCEL_ASYNC ();                                     \
  49                                                                               \
  50         int status;                                                           \
  51         do                                                                    \
  52           {                                                                   \
  53             status = lll_futex_timed_wait (futexaddr, oldval, timeout,        \
  54                                            LLL_PRIVATE);                      \
  55             if (status != -EWOULDBLOCK)                                       \
  56               break;                                                          \
  57                                                                               \
  58             oldval = *futexaddr;                                              \
  59           }                                                                   \
  60         while (oldval != 0);                                                  \
  61                                                                               \
  62         if (cancel)                                                           \
  63           LIBC_CANCEL_RESET (oldtype);                                        \
  64                                                                               \
  65         if (status == -EINTR)                                                 \
  66           result = EINTR;                                                     \
  67         else if (status == -ETIMEDOUT)                                        \
  68           result = EAGAIN;                                                    \
  69         else                                                                  \
  70           assert (status == 0 || status == -EWOULDBLOCK);                     \
  71                                                                               \
  72         pthread_mutex_lock (&__gai_requests_mutex);                           \
  73       }                                                                       \
  74   } while (0)
  75
  76
  77 #define gai_start_notify_thread __gai_start_notify_thread
  78 #define gai_create_helper_thread __gai_create_helper_thread
  79
  80 extern inline void
  81 __gai_start_notify_thread (void)
  82 {
  83   sigset_t ss;
  84   sigemptyset (&ss);
  85   INTERNAL_SYSCALL_DECL (err);
  86   INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_SETMASK, &ss, NULL, _NSIG / 8);
  87 }
  88
  89 extern inline int
  90 __gai_create_helper_thread (pthread_t *threadp, void *(*tf) (void *),
  91                             void *arg)
  92 {
  93   pthread_attr_t attr;
  94
  95   /* Make sure the thread is created detached.  */
  96   pthread_attr_init (&attr);
  97   pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
  98
  99   /* The helper thread needs only very little resources.  */
 100   (void) pthread_attr_setstacksize (&attr,
 101                                     __pthread_get_minstack (&attr)
 102                                     + 4 * PTHREAD_STACK_MIN);
 103
 104   /* Block all signals in the helper thread.  To do this thoroughly we
 105      temporarily have to block all signals here.  */
 106   sigset_t ss;
 107   sigset_t oss;
 108   sigfillset (&ss);
 109   INTERNAL_SYSCALL_DECL (err);
 110   INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_SETMASK, &ss, &oss, _NSIG / 8);
 111
 112   int ret = pthread_create (threadp, &attr, tf, arg);
 113
 114   /* Restore the signal mask.  */
 115   INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_SETMASK, &oss, NULL,
 116                     _NSIG / 8);
 117
 118   (void) pthread_attr_destroy (&attr);
 119   return ret;
 120 }
 121
 122 #include_next <gai_misc.h>