1 | /* Copyright (C) 2003-2020 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 |
17 | not, see <https://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <errno.h> |
20 | #include <setjmp.h> |
21 | #include <signal.h> |
22 | #include <stdbool.h> |
23 | #include <sysdep-cancel.h> |
24 | #include <nptl/pthreadP.h> |
25 | #include "kernel-posix-timers.h" |
26 | |
27 | |
28 | /* List of active SIGEV_THREAD timers. */ |
29 | struct timer *__active_timer_sigev_thread; |
30 | /* Lock for the __active_timer_sigev_thread. */ |
31 | pthread_mutex_t __active_timer_sigev_thread_lock = PTHREAD_MUTEX_INITIALIZER; |
32 | |
33 | |
34 | struct thread_start_data |
35 | { |
36 | void (*thrfunc) (sigval_t); |
37 | sigval_t sival; |
38 | }; |
39 | |
40 | |
41 | /* Helper thread to call the user-provided function. */ |
42 | static void * |
43 | timer_sigev_thread (void *arg) |
44 | { |
45 | /* The parent thread has all signals blocked. This is a bit |
46 | surprising for user code, although valid. We unblock all |
47 | signals. */ |
48 | sigset_t ss; |
49 | sigemptyset (&ss); |
50 | INTERNAL_SYSCALL_DECL (err); |
51 | INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_SETMASK, &ss, NULL, _NSIG / 8); |
52 | |
53 | struct thread_start_data *td = (struct thread_start_data *) arg; |
54 | |
55 | void (*thrfunc) (sigval_t) = td->thrfunc; |
56 | sigval_t sival = td->sival; |
57 | |
58 | /* The TD object was allocated in timer_helper_thread. */ |
59 | free (td); |
60 | |
61 | /* Call the user-provided function. */ |
62 | thrfunc (sival); |
63 | |
64 | return NULL; |
65 | } |
66 | |
67 | |
68 | /* Helper function to support starting threads for SIGEV_THREAD. */ |
69 | static void * |
70 | timer_helper_thread (void *arg) |
71 | { |
72 | /* Wait for the SIGTIMER signal, allowing the setXid signal, and |
73 | none else. */ |
74 | sigset_t ss; |
75 | sigemptyset (&ss); |
76 | __sigaddset (&ss, SIGTIMER); |
77 | |
78 | /* Endless loop of waiting for signals. The loop is only ended when |
79 | the thread is canceled. */ |
80 | while (1) |
81 | { |
82 | siginfo_t si; |
83 | |
84 | /* sigwaitinfo cannot be used here, since it deletes |
85 | SIGCANCEL == SIGTIMER from the set. */ |
86 | |
87 | /* XXX The size argument hopefully will have to be changed to the |
88 | real size of the user-level sigset_t. */ |
89 | int result = SYSCALL_CANCEL (rt_sigtimedwait, &ss, &si, NULL, _NSIG / 8); |
90 | |
91 | if (result > 0) |
92 | { |
93 | if (si.si_code == SI_TIMER) |
94 | { |
95 | struct timer *tk = (struct timer *) si.si_ptr; |
96 | |
97 | /* Check the timer is still used and will not go away |
98 | while we are reading the values here. */ |
99 | pthread_mutex_lock (&__active_timer_sigev_thread_lock); |
100 | |
101 | struct timer *runp = __active_timer_sigev_thread; |
102 | while (runp != NULL) |
103 | if (runp == tk) |
104 | break; |
105 | else |
106 | runp = runp->next; |
107 | |
108 | if (runp != NULL) |
109 | { |
110 | struct thread_start_data *td = malloc (sizeof (*td)); |
111 | |
112 | /* There is not much we can do if the allocation fails. */ |
113 | if (td != NULL) |
114 | { |
115 | /* This is the signal we are waiting for. */ |
116 | td->thrfunc = tk->thrfunc; |
117 | td->sival = tk->sival; |
118 | |
119 | pthread_t th; |
120 | (void) pthread_create (&th, &tk->attr, |
121 | timer_sigev_thread, td); |
122 | } |
123 | } |
124 | |
125 | pthread_mutex_unlock (&__active_timer_sigev_thread_lock); |
126 | } |
127 | else if (si.si_code == SI_TKILL) |
128 | /* The thread is canceled. */ |
129 | pthread_exit (NULL); |
130 | } |
131 | } |
132 | } |
133 | |
134 | |
135 | /* Control variable for helper thread creation. */ |
136 | pthread_once_t __helper_once attribute_hidden; |
137 | |
138 | |
139 | /* TID of the helper thread. */ |
140 | pid_t __helper_tid attribute_hidden; |
141 | |
142 | |
143 | /* Reset variables so that after a fork a new helper thread gets started. */ |
144 | static void |
145 | reset_helper_control (void) |
146 | { |
147 | __helper_once = PTHREAD_ONCE_INIT; |
148 | __helper_tid = 0; |
149 | } |
150 | |
151 | |
152 | void |
153 | attribute_hidden |
154 | __start_helper_thread (void) |
155 | { |
156 | /* The helper thread needs only very little resources |
157 | and should go away automatically when canceled. */ |
158 | pthread_attr_t attr; |
159 | (void) pthread_attr_init (&attr); |
160 | (void) pthread_attr_setstacksize (&attr, __pthread_get_minstack (&attr)); |
161 | |
162 | /* Block all signals in the helper thread but SIGSETXID. To do this |
163 | thoroughly we temporarily have to block all signals here. The |
164 | helper can lose wakeups if SIGCANCEL is not blocked throughout, |
165 | but sigfillset omits it SIGSETXID. So, we add SIGCANCEL back |
166 | explicitly here. */ |
167 | sigset_t ss; |
168 | sigset_t oss; |
169 | sigfillset (&ss); |
170 | __sigaddset (&ss, SIGCANCEL); |
171 | INTERNAL_SYSCALL_DECL (err); |
172 | INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_SETMASK, &ss, &oss, _NSIG / 8); |
173 | |
174 | /* Create the helper thread for this timer. */ |
175 | pthread_t th; |
176 | int res = pthread_create (&th, &attr, timer_helper_thread, NULL); |
177 | if (res == 0) |
178 | /* We managed to start the helper thread. */ |
179 | __helper_tid = ((struct pthread *) th)->tid; |
180 | |
181 | /* Restore the signal mask. */ |
182 | INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_SETMASK, &oss, NULL, |
183 | _NSIG / 8); |
184 | |
185 | /* No need for the attribute anymore. */ |
186 | (void) pthread_attr_destroy (&attr); |
187 | |
188 | /* We have to make sure that after fork()ing a new helper thread can |
189 | be created. */ |
190 | pthread_atfork (NULL, NULL, reset_helper_control); |
191 | } |
192 | |