rt/aio_notify.c

   1 /* Notify initiator of AIO request.
   2    Copyright (C) 1997-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   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 #include <errno.h>
  20 #include <pthreadP.h>
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include <aio_misc.h>
  24 #include <signal.h>
  25
  26 #if !PTHREAD_IN_LIBC
  27 # define __pthread_attr_init pthread_attr_init
  28 # define __pthread_attr_setdetachstate pthread_attr_setdetachstate
  29 #endif
  30
  31 #ifndef aio_start_notify_thread
  32 # define aio_start_notify_thread() do { } while (0)
  33 #endif
  34
  35 struct notify_func
  36   {
  37     void (*func) (sigval_t);
  38     sigval_t value;
  39   };
  40
  41 static void *
  42 notify_func_wrapper (void *arg)
  43 {
  44   aio_start_notify_thread ();
  45   struct notify_func *const n = arg;
  46   void (*func) (sigval_t) = n->func;
  47   sigval_t value = n->value;
  48   free (n);
  49   (*func) (value);
  50   return NULL;
  51 }
  52
  53
  54 int
  55 __aio_notify_only (struct sigevent *sigev)
  56 {
  57   int result = 0;
  58
  59   /* Send the signal to notify about finished processing of the request.  */
  60   if (__glibc_unlikely (sigev->sigev_notify == SIGEV_THREAD))
  61     {
  62       /* We have to start a thread.  */
  63       pthread_t tid;
  64       pthread_attr_t attr, *pattr;
  65
  66       pattr = (pthread_attr_t *) sigev->sigev_notify_attributes;
  67       if (pattr == NULL)
  68         {
  69           __pthread_attr_init (&attr);
  70           __pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
  71           pattr = &attr;
  72         }
  73
  74       /* SIGEV may be freed as soon as we return, so we cannot let the
  75          notification thread use that pointer.  Even though a sigval_t is
  76          only one word and the same size as a void *, we cannot just pass
  77          the value through pthread_create as the argument and have the new
  78          thread run the user's function directly, because on some machines
  79          the calling convention for a union like sigval_t is different from
  80          that for a pointer type like void *.  */
  81       struct notify_func *nf = malloc (sizeof *nf);
  82       if (nf == NULL)
  83         result = -1;
  84       else
  85         {
  86           nf->func = sigev->sigev_notify_function;
  87           nf->value = sigev->sigev_value;
  88           if (__pthread_create (&tid, pattr, notify_func_wrapper, nf) < 0)
  89             {
  90               free (nf);
  91               result = -1;
  92             }
  93         }
  94     }
  95   else if (sigev->sigev_notify == SIGEV_SIGNAL)
  96     {
  97       /* We have to send a signal.  */
  98 #if _POSIX_REALTIME_SIGNALS > 0
  99       /* Note that the standard gives us the option of using a plain
 100          non-queuing signal here when SA_SIGINFO is not set for the signal.  */
 101       if (__aio_sigqueue (sigev->sigev_signo, sigev->sigev_value, getpid ())
 102           < 0)
 103         result = -1;
 104 #else
 105       /* There are no queued signals on this system at all.  */
 106       result = raise (sigev->sigev_signo);
 107 #endif
 108     }
 109
 110   return result;
 111 }
 112
 113
 114 void
 115 __aio_notify (struct requestlist *req)
 116 {
 117   struct waitlist *waitlist;
 118   struct aiocb *aiocbp = &req->aiocbp->aiocb;
 119
 120   if (__aio_notify_only (&aiocbp->aio_sigevent) != 0)
 121     {
 122       /* XXX What shall we do if already an error is set by
 123          read/write/fsync?  */
 124       aiocbp->__error_code = errno;
 125       aiocbp->__return_value = -1;
 126     }
 127
 128   /* Now also notify possibly waiting threads.  */
 129   waitlist = req->waiting;
 130   while (waitlist != NULL)
 131     {
 132       struct waitlist *next = waitlist->next;
 133
 134       if (waitlist->sigevp == NULL)
 135         {
 136           if (waitlist->result != NULL && aiocbp->__return_value == -1)
 137             *waitlist->result = -1;
 138
 139 #ifdef DONT_NEED_AIO_MISC_COND
 140           AIO_MISC_NOTIFY (waitlist);
 141 #else
 142           /* Decrement the counter.  */
 143           --*waitlist->counterp;
 144
 145           pthread_cond_signal (waitlist->cond);
 146 #endif
 147         }
 148       else
 149         /* This is part of an asynchronous `lio_listio' operation.  If
 150            this request is the last one, send the signal.  */
 151         if (--*waitlist->counterp == 0)
 152           {
 153             __aio_notify_only (waitlist->sigevp);
 154             /* This is tricky.  See lio_listio.c for the reason why
 155                this works.  */
 156             free ((void *) waitlist->counterp);
 157           }
 158
 159       waitlist = next;
 160     }
 161 }