1/* Copyright (C) 2002-2020 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 <https://www.gnu.org/licenses/>. */
18
19#include <setjmp.h>
20#include <stdlib.h>
21#include "pthreadP.h"
22#include <futex-internal.h>
23
24
25/* The next two functions are similar to pthread_setcanceltype() but
26 more specialized for the use in the cancelable functions like write().
27 They do not need to check parameters etc. These functions must be
28 AS-safe, with the exception of the actual cancellation, because they
29 are called by wrappers around AS-safe functions like write().*/
30int
31attribute_hidden
32__pthread_enable_asynccancel (void)
33{
34 struct pthread *self = THREAD_SELF;
35 int oldval = THREAD_GETMEM (self, cancelhandling);
36
37 while (1)
38 {
39 int newval = oldval | CANCELTYPE_BITMASK;
40
41 if (newval == oldval)
42 break;
43
44 int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
45 oldval);
46 if (__glibc_likely (curval == oldval))
47 {
48 if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
49 {
50 THREAD_SETMEM (self, result, PTHREAD_CANCELED);
51 __do_cancel ();
52 }
53
54 break;
55 }
56
57 /* Prepare the next round. */
58 oldval = curval;
59 }
60
61 return oldval;
62}
63
64/* See the comment for __pthread_enable_asynccancel regarding
65 the AS-safety of this function. */
66void
67attribute_hidden
68__pthread_disable_asynccancel (int oldtype)
69{
70 /* If asynchronous cancellation was enabled before we do not have
71 anything to do. */
72 if (oldtype & CANCELTYPE_BITMASK)
73 return;
74
75 struct pthread *self = THREAD_SELF;
76 int newval;
77
78 int oldval = THREAD_GETMEM (self, cancelhandling);
79
80 while (1)
81 {
82 newval = oldval & ~CANCELTYPE_BITMASK;
83
84 int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
85 oldval);
86 if (__glibc_likely (curval == oldval))
87 break;
88
89 /* Prepare the next round. */
90 oldval = curval;
91 }
92
93 /* We cannot return when we are being canceled. Upon return the
94 thread might be things which would have to be undone. The
95 following loop should loop until the cancellation signal is
96 delivered. */
97 while (__builtin_expect ((newval & (CANCELING_BITMASK | CANCELED_BITMASK))
98 == CANCELING_BITMASK, 0))
99 {
100 futex_wait_simple ((unsigned int *) &self->cancelhandling, newval,
101 FUTEX_PRIVATE);
102 newval = THREAD_GETMEM (self, cancelhandling);
103 }
104}
105