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/* Copyright (C) 2003-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, see <https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <setjmp.h>
#include <signal.h>
#include <stdbool.h>
#include <sysdep-cancel.h>
#include <nptl/pthreadP.h>
#include "kernel-posix-timers.h"
/* List of active SIGEV_THREAD timers. */
struct timer *__active_timer_sigev_thread;
/* Lock for the __active_timer_sigev_thread. */
pthread_mutex_t __active_timer_sigev_thread_lock = PTHREAD_MUTEX_INITIALIZER;
struct thread_start_data
{
void (*thrfunc) (sigval_t);
sigval_t sival;
};
/* Helper thread to call the user-provided function. */
static void *
timer_sigev_thread (void *arg)
{
__libc_signal_unblock_sigtimer (NULL);
struct thread_start_data *td = (struct thread_start_data *) arg;
void (*thrfunc) (sigval_t) = td->thrfunc;
sigval_t sival = td->sival;
/* The TD object was allocated in timer_helper_thread. */
free (td);
/* Call the user-provided function. */
thrfunc (sival);
return NULL;
}
/* Helper function to support starting threads for SIGEV_THREAD. */
static void *
timer_helper_thread (void *arg)
{
/* Endless loop of waiting for signals. The loop is only ended when
the thread is canceled. */
while (1)
{
siginfo_t si;
while (sigwaitinfo (&sigtimer_set, &si) < 0);
if (si.si_code == SI_TIMER)
{
struct timer *tk = (struct timer *) si.si_ptr;
/* Check the timer is still used and will not go away
while we are reading the values here. */
pthread_mutex_lock (&__active_timer_sigev_thread_lock);
struct timer *runp = __active_timer_sigev_thread;
while (runp != NULL)
if (runp == tk)
break;
else
runp = runp->next;
if (runp != NULL)
{
struct thread_start_data *td = malloc (sizeof (*td));
/* There is not much we can do if the allocation fails. */
if (td != NULL)
{
/* This is the signal we are waiting for. */
td->thrfunc = tk->thrfunc;
td->sival = tk->sival;
pthread_t th;
pthread_create (&th, &tk->attr, timer_sigev_thread, td);
}
}
pthread_mutex_unlock (&__active_timer_sigev_thread_lock);
}
else if (si.si_code == SI_TKILL)
/* The thread is canceled. */
pthread_exit (NULL);
}
}
/* Control variable for helper thread creation. */
pthread_once_t __helper_once attribute_hidden;
/* TID of the helper thread. */
pid_t __helper_tid attribute_hidden;
/* Reset variables so that after a fork a new helper thread gets started. */
static void
reset_helper_control (void)
{
__helper_once = PTHREAD_ONCE_INIT;
__helper_tid = 0;
}
void
attribute_hidden
__start_helper_thread (void)
{
/* The helper thread needs only very little resources
and should go away automatically when canceled. */
pthread_attr_t attr;
(void) pthread_attr_init (&attr);
(void) pthread_attr_setstacksize (&attr, __pthread_get_minstack (&attr));
/* Block all signals in the helper thread but SIGSETXID. */
sigset_t ss;
__sigfillset (&ss);
__sigdelset (&ss, SIGSETXID);
int res = __pthread_attr_setsigmask_internal (&attr, &ss);
if (res != 0)
{
pthread_attr_destroy (&attr);
return;
}
/* Create the helper thread for this timer. */
pthread_t th;
res = pthread_create (&th, &attr, timer_helper_thread, NULL);
if (res == 0)
/* We managed to start the helper thread. */
__helper_tid = ((struct pthread *) th)->tid;
/* No need for the attribute anymore. */
(void) pthread_attr_destroy (&attr);
/* We have to make sure that after fork()ing a new helper thread can
be created. */
pthread_atfork (NULL, NULL, reset_helper_control);
}
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