1/* Copyright (C) 2002-2016 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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 <http://www.gnu.org/licenses/>. */
18
19#include <errno.h>
20#include <signal.h>
21#include <stdlib.h>
22#include "pthreadP.h"
23#include <atomic.h>
24#include <sysdep.h>
25
26
27int
28pthread_cancel (pthread_t th)
29{
30 volatile struct pthread *pd = (volatile struct pthread *) th;
31
32 /* Make sure the descriptor is valid. */
33 if (INVALID_TD_P (pd))
34 /* Not a valid thread handle. */
35 return ESRCH;
36
37#ifdef SHARED
38 pthread_cancel_init ();
39#endif
40 int result = 0;
41 int oldval;
42 int newval;
43 do
44 {
45 again:
46 oldval = pd->cancelhandling;
47 newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
48
49 /* Avoid doing unnecessary work. The atomic operation can
50 potentially be expensive if the bug has to be locked and
51 remote cache lines have to be invalidated. */
52 if (oldval == newval)
53 break;
54
55 /* If the cancellation is handled asynchronously just send a
56 signal. We avoid this if possible since it's more
57 expensive. */
58 if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
59 {
60 /* Mark the cancellation as "in progress". */
61 if (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling,
62 oldval | CANCELING_BITMASK,
63 oldval))
64 goto again;
65
66#ifdef SIGCANCEL
67 /* The cancellation handler will take care of marking the
68 thread as canceled. */
69 INTERNAL_SYSCALL_DECL (err);
70
71 /* One comment: The PID field in the TCB can temporarily be
72 changed (in fork). But this must not affect this code
73 here. Since this function would have to be called while
74 the thread is executing fork, it would have to happen in
75 a signal handler. But this is no allowed, pthread_cancel
76 is not guaranteed to be async-safe. */
77 int val;
78 val = INTERNAL_SYSCALL (tgkill, err, 3,
79 THREAD_GETMEM (THREAD_SELF, pid), pd->tid,
80 SIGCANCEL);
81
82 if (INTERNAL_SYSCALL_ERROR_P (val, err))
83 result = INTERNAL_SYSCALL_ERRNO (val, err);
84#else
85 /* It should be impossible to get here at all, since
86 pthread_setcanceltype should never have allowed
87 PTHREAD_CANCEL_ASYNCHRONOUS to be set. */
88 abort ();
89#endif
90
91 break;
92 }
93
94 /* A single-threaded process should be able to kill itself, since
95 there is nothing in the POSIX specification that says that it
96 cannot. So we set multiple_threads to true so that cancellation
97 points get executed. */
98 THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
99#ifndef TLS_MULTIPLE_THREADS_IN_TCB
100 __pthread_multiple_threads = *__libc_multiple_threads_ptr = 1;
101#endif
102 }
103 /* Mark the thread as canceled. This has to be done
104 atomically since other bits could be modified as well. */
105 while (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling, newval,
106 oldval));
107
108 return result;
109}
110
111PTHREAD_STATIC_FN_REQUIRE (pthread_create)
112