1/* Copyright (C) 2003-2023 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 License as
6 published by the Free Software Foundation; either version 2.1 of the
7 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; see the file COPYING.LIB. If
16 not, see <https://www.gnu.org/licenses/>. */
17
18#include <errno.h>
19#include <setjmp.h>
20#include <signal.h>
21#include <stdbool.h>
22#include <sysdep-cancel.h>
23#include <pthreadP.h>
24#include "kernel-posix-timers.h"
25
26
27/* List of active SIGEV_THREAD timers. */
28struct timer *__timer_active_sigev_thread;
29
30/* Lock for _timer_active_sigev_thread. */
31pthread_mutex_t __timer_active_sigev_thread_lock = PTHREAD_MUTEX_INITIALIZER;
32
33struct thread_start_data
34{
35 void (*thrfunc) (sigval_t);
36 sigval_t sival;
37};
38
39
40/* Helper thread to call the user-provided function. */
41static void *
42timer_sigev_thread (void *arg)
43{
44 signal_unblock_sigtimer ();
45
46 struct thread_start_data *td = (struct thread_start_data *) arg;
47 void (*thrfunc) (sigval_t) = td->thrfunc;
48 sigval_t sival = td->sival;
49
50 /* The TD object was allocated in timer_helper_thread. */
51 free (td);
52
53 /* Call the user-provided function. */
54 thrfunc (sival);
55
56 return NULL;
57}
58
59
60/* Helper function to support starting threads for SIGEV_THREAD. */
61static _Noreturn void *
62timer_helper_thread (void *arg)
63{
64 /* Endless loop of waiting for signals. The loop is only ended when
65 the thread is canceled. */
66 while (1)
67 {
68 siginfo_t si;
69
70 while (__sigwaitinfo (&sigtimer_set, &si) < 0);
71 if (si.si_code == SI_TIMER)
72 {
73 struct timer *tk = (struct timer *) si.si_ptr;
74
75 /* Check the timer is still used and will not go away
76 while we are reading the values here. */
77 __pthread_mutex_lock (&__timer_active_sigev_thread_lock);
78
79 struct timer *runp = __timer_active_sigev_thread;
80 while (runp != NULL)
81 if (runp == tk)
82 break;
83 else
84 runp = runp->next;
85
86 if (runp != NULL)
87 {
88 struct thread_start_data *td = malloc (sizeof (*td));
89
90 /* There is not much we can do if the allocation fails. */
91 if (td != NULL)
92 {
93 /* This is the signal we are waiting for. */
94 td->thrfunc = tk->thrfunc;
95 td->sival = tk->sival;
96
97 pthread_t th;
98 __pthread_create (&th, &tk->attr, timer_sigev_thread, td);
99 }
100 }
101
102 __pthread_mutex_unlock (&__timer_active_sigev_thread_lock);
103 }
104 }
105}
106
107
108/* Control variable for helper thread creation. */
109pthread_once_t __timer_helper_once = PTHREAD_ONCE_INIT;
110
111
112/* TID of the helper thread. */
113pid_t __timer_helper_tid;
114
115
116/* Reset variables so that after a fork a new helper thread gets started. */
117void
118__timer_fork_subprocess (void)
119{
120 __timer_helper_once = PTHREAD_ONCE_INIT;
121 __timer_helper_tid = 0;
122}
123
124
125void
126__timer_start_helper_thread (void)
127{
128 /* The helper thread needs only very little resources
129 and should go away automatically when canceled. */
130 pthread_attr_t attr;
131 __pthread_attr_init (&attr);
132 __pthread_attr_setstacksize (&attr, __pthread_get_minstack (&attr));
133
134 /* Block all signals in the helper thread but SIGSETXID. */
135 sigset_t ss;
136 __sigfillset (&ss);
137 __sigdelset (&ss, SIGSETXID);
138 int res = __pthread_attr_setsigmask_internal (&attr, &ss);
139 if (res != 0)
140 {
141 __pthread_attr_destroy (&attr);
142 return;
143 }
144
145 /* Create the helper thread for this timer. */
146 pthread_t th;
147 res = __pthread_create (&th, &attr, timer_helper_thread, NULL);
148 if (res == 0)
149 /* We managed to start the helper thread. */
150 __timer_helper_tid = ((struct pthread *) th)->tid;
151
152 /* No need for the attribute anymore. */
153 __pthread_attr_destroy (&attr);
154}
155