rt/aio_notify.c

   1 /* Notify initiator of AIO request.
   2    Copyright (C) 1997-2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <errno.h>
  21 #include <pthreadP.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24 #include <aio_misc.h>
  25 #include <signal.h>
  26
  27 #if !PTHREAD_IN_LIBC
  28 # define __pthread_attr_init pthread_attr_init
  29 # define __pthread_attr_setdetachstate pthread_attr_setdetachstate
  30 #endif
  31
  32 #ifndef aio_start_notify_thread
  33 # define aio_start_notify_thread() do { } while (0)
  34 #endif
  35
  36 struct notify_func
  37   {
  38     void (*func) (sigval_t);
  39     sigval_t value;
  40   };
  41
  42 static void *
  43 notify_func_wrapper (void *arg)
  44 {
  45   aio_start_notify_thread ();
  46   struct notify_func *const n = arg;
  47   void (*func) (sigval_t) = n->func;
  48   sigval_t value = n->value;
  49   free (n);
  50   (*func) (value);
  51   return NULL;
  52 }
  53
  54
  55 int
  56 __aio_notify_only (struct sigevent *sigev)
  57 {
  58   int result = 0;
  59
  60   /* Send the signal to notify about finished processing of the request.  */
  61   if (__glibc_unlikely (sigev->sigev_notify == SIGEV_THREAD))
  62     {
  63       /* We have to start a thread.  */
  64       pthread_t tid;
  65       pthread_attr_t attr, *pattr;
  66
  67       pattr = (pthread_attr_t *) sigev->sigev_notify_attributes;
  68       if (pattr == NULL)
  69         {
  70           __pthread_attr_init (&attr);
  71           __pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
  72           pattr = &attr;
  73         }
  74
  75       /* SIGEV may be freed as soon as we return, so we cannot let the
  76          notification thread use that pointer.  Even though a sigval_t is
  77          only one word and the same size as a void *, we cannot just pass
  78          the value through pthread_create as the argument and have the new
  79          thread run the user's function directly, because on some machines
  80          the calling convention for a union like sigval_t is different from
  81          that for a pointer type like void *.  */
  82       struct notify_func *nf = malloc (sizeof *nf);
  83       if (nf == NULL)
  84         result = -1;
  85       else
  86         {
  87           nf->func = sigev->sigev_notify_function;
  88           nf->value = sigev->sigev_value;
  89           if (__pthread_create (&tid, pattr, notify_func_wrapper, nf) < 0)
  90             {
  91               free (nf);
  92               result = -1;
  93             }
  94         }
  95     }
  96   else if (sigev->sigev_notify == SIGEV_SIGNAL)
  97     {
  98       /* We have to send a signal.  */
  99 #if _POSIX_REALTIME_SIGNALS > 0
 100       /* Note that the standard gives us the option of using a plain
 101          non-queuing signal here when SA_SIGINFO is not set for the signal.  */
 102       if (__aio_sigqueue (sigev->sigev_signo, sigev->sigev_value, getpid ())
 103           < 0)
 104         result = -1;
 105 #else
 106       /* There are no queued signals on this system at all.  */
 107       result = raise (sigev->sigev_signo);
 108 #endif
 109     }
 110
 111   return result;
 112 }
 113
 114
 115 void
 116 __aio_notify (struct requestlist *req)
 117 {
 118   struct waitlist *waitlist;
 119   struct aiocb *aiocbp = &req->aiocbp->aiocb;
 120
 121   if (__aio_notify_only (&aiocbp->aio_sigevent) != 0)
 122     {
 123       /* XXX What shall we do if already an error is set by
 124          read/write/fsync?  */
 125       aiocbp->__error_code = errno;
 126       aiocbp->__return_value = -1;
 127     }
 128
 129   /* Now also notify possibly waiting threads.  */
 130   waitlist = req->waiting;
 131   while (waitlist != NULL)
 132     {
 133       struct waitlist *next = waitlist->next;
 134
 135       if (waitlist->sigevp == NULL)
 136         {
 137           if (waitlist->result != NULL && aiocbp->__return_value == -1)
 138             *waitlist->result = -1;
 139
 140 #ifdef DONT_NEED_AIO_MISC_COND
 141           AIO_MISC_NOTIFY (waitlist);
 142 #else
 143           /* Decrement the counter.  */
 144           --*waitlist->counterp;
 145
 146           pthread_cond_signal (waitlist->cond);
 147 #endif
 148         }
 149       else
 150         /* This is part of an asynchronous `lio_listio' operation.  If
 151            this request is the last one, send the signal.  */
 152         if (--*waitlist->counterp == 0)
 153           {
 154             __aio_notify_only (waitlist->sigevp);
 155             /* This is tricky.  See lio_listio.c for the reason why
 156                this works.  */
 157             free ((void *) waitlist->counterp);
 158           }
 159
 160       waitlist = next;
 161     }
 162 }