nptl/sysdeps/unix/sysv/linux/timer_routines.c

   1 /* Copyright (C) 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
   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 License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    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; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <setjmp.h>
  22 #include <signal.h>
  23 #include <stdbool.h>
  24 #include <sysdep.h>
  25 #include <kernel-features.h>
  26 #include <nptl/pthreadP.h>
  27 #include "kernel-posix-timers.h"
  28
  29
  30 /* List of active SIGEV_THREAD timers.  */
  31 struct timer *__active_timer_sigev_thread;
  32 /* Lock for the __active_timer_sigev_thread.  */
  33 pthread_mutex_t __active_timer_sigev_thread_lock = PTHREAD_MUTEX_INITIALIZER;
  34
  35
  36 struct thread_start_data
  37 {
  38   void (*thrfunc) (sigval_t);
  39   sigval_t sival;
  40 };
  41
  42
  43 #ifdef __NR_timer_create
  44 /* Helper thread to call the user-provided function.  */
  45 static void *
  46 timer_sigev_thread (void *arg)
  47 {
  48   /* The parent thread has all signals blocked.  This is a bit
  49      surprising for user code, although valid.  We unblock all
  50      signals.  */
  51   sigset_t ss;
  52   sigemptyset (&ss);
  53   INTERNAL_SYSCALL_DECL (err);
  54   INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_SETMASK, &ss, NULL, _NSIG / 8);
  55
  56   struct thread_start_data *td = (struct thread_start_data *) arg;
  57
  58   void (*thrfunc) (sigval_t) = td->thrfunc;
  59   sigval_t sival = td->sival;
  60
  61   /* The TD object was allocated in timer_helper_thread.  */
  62   free (td);
  63
  64   /* Call the user-provided function.  */
  65   thrfunc (sival);
  66
  67   return NULL;
  68 }
  69
  70
  71 /* Helper function to support starting threads for SIGEV_THREAD.  */
  72 static void *
  73 timer_helper_thread (void *arg)
  74 {
  75   /* Wait for the SIGTIMER signal, allowing the setXid signal, and
  76      none else.  */
  77   sigset_t ss;
  78   sigemptyset (&ss);
  79   __sigaddset (&ss, SIGTIMER);
  80
  81   /* Endless loop of waiting for signals.  The loop is only ended when
  82      the thread is canceled.  */
  83   while (1)
  84     {
  85       siginfo_t si;
  86
  87       /* sigwaitinfo cannot be used here, since it deletes
  88          SIGCANCEL == SIGTIMER from the set.  */
  89
  90       int oldtype = LIBC_CANCEL_ASYNC ();
  91
  92       /* XXX The size argument hopefully will have to be changed to the
  93          real size of the user-level sigset_t.  */
  94       int result = INLINE_SYSCALL (rt_sigtimedwait, 4, &ss, &si, NULL,
  95                                    _NSIG / 8);
  96
  97       LIBC_CANCEL_RESET (oldtype);
  98
  99       if (result > 0)
 100         {
 101           if (si.si_code == SI_TIMER)
 102             {
 103               struct timer *tk = (struct timer *) si.si_ptr;
 104
 105               /* Check the timer is still used and will not go away
 106                  while we are reading the values here.  */
 107               pthread_mutex_lock (&__active_timer_sigev_thread_lock);
 108
 109               struct timer *runp = __active_timer_sigev_thread;
 110               while (runp != NULL)
 111                 if (runp == tk)
 112                   break;
 113                 else
 114                   runp = runp->next;
 115
 116               if (runp != NULL)
 117                 {
 118                   struct thread_start_data *td = malloc (sizeof (*td));
 119
 120                   /* There is not much we can do if the allocation fails.  */
 121                   if (td != NULL)
 122                     {
 123                       /* This is the signal we are waiting for.  */
 124                       td->thrfunc = tk->thrfunc;
 125                       td->sival = tk->sival;
 126
 127                       pthread_t th;
 128                       (void) pthread_create (&th, &tk->attr,
 129                                              timer_sigev_thread, td);
 130                     }
 131                 }
 132
 133               pthread_mutex_unlock (&__active_timer_sigev_thread_lock);
 134             }
 135           else if (si.si_code == SI_TKILL)
 136             /* The thread is canceled.  */
 137             pthread_exit (NULL);
 138         }
 139     }
 140 }
 141
 142
 143 /* Control variable for helper thread creation.  */
 144 pthread_once_t __helper_once attribute_hidden;
 145
 146
 147 /* TID of the helper thread.  */
 148 pid_t __helper_tid attribute_hidden;
 149
 150
 151 /* Reset variables so that after a fork a new helper thread gets started.  */
 152 static void
 153 reset_helper_control (void)
 154 {
 155   __helper_once = PTHREAD_ONCE_INIT;
 156   __helper_tid = 0;
 157 }
 158
 159
 160 void
 161 attribute_hidden
 162 __start_helper_thread (void)
 163 {
 164   /* The helper thread needs only very little resources
 165      and should go away automatically when canceled.  */
 166   pthread_attr_t attr;
 167   (void) pthread_attr_init (&attr);
 168   (void) pthread_attr_setstacksize (&attr, PTHREAD_STACK_MIN);
 169
 170   /* Block all signals in the helper thread but SIGSETXID.  To do this
 171      thoroughly we temporarily have to block all signals here.  The
 172      helper can lose wakeups if SIGCANCEL is not blocked throughout,
 173      but sigfillset omits it SIGSETXID.  So, we add SIGCANCEL back
 174      explicitly here.  */
 175   sigset_t ss;
 176   sigset_t oss;
 177   sigfillset (&ss);
 178   __sigaddset (&ss, SIGCANCEL);
 179   INTERNAL_SYSCALL_DECL (err);
 180   INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_SETMASK, &ss, &oss, _NSIG / 8);
 181
 182   /* Create the helper thread for this timer.  */
 183   pthread_t th;
 184   int res = pthread_create (&th, &attr, timer_helper_thread, NULL);
 185   if (res == 0)
 186     /* We managed to start the helper thread.  */
 187     __helper_tid = ((struct pthread *) th)->tid;
 188
 189   /* Restore the signal mask.  */
 190   INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_SETMASK, &oss, NULL,
 191                     _NSIG / 8);
 192
 193   /* No need for the attribute anymore.  */
 194   (void) pthread_attr_destroy (&attr);
 195
 196   /* We have to make sure that after fork()ing a new helper thread can
 197      be created.  */
 198   pthread_atfork (NULL, NULL, reset_helper_control);
 199 }
 200 #endif
 201
 202 #ifndef __ASSUME_POSIX_TIMERS
 203 # include <nptl/sysdeps/pthread/timer_routines.c>
 204 #endif