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 | |
27 | int |
28 | pthread_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 | |
111 | PTHREAD_STATIC_FN_REQUIRE (pthread_create) |
112 | |