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 <errno.h>
20#include "pthreadP.h"
21#include <atomic.h>
22
23
24int
25__pthread_setcanceltype (int type, int *oldtype)
26{
27 if (type < PTHREAD_CANCEL_DEFERRED || type > PTHREAD_CANCEL_ASYNCHRONOUS)
28 return EINVAL;
29
30 volatile struct pthread *self = THREAD_SELF;
31
32 int oldval = THREAD_GETMEM (self, cancelhandling);
33 while (1)
34 {
35 int newval = (type == PTHREAD_CANCEL_ASYNCHRONOUS
36 ? oldval | CANCELTYPE_BITMASK
37 : oldval & ~CANCELTYPE_BITMASK);
38
39 /* Store the old value. */
40 if (oldtype != NULL)
41 *oldtype = ((oldval & CANCELTYPE_BITMASK)
42 ? PTHREAD_CANCEL_ASYNCHRONOUS : PTHREAD_CANCEL_DEFERRED);
43
44 /* Avoid doing unnecessary work. The atomic operation can
45 potentially be expensive if the memory has to be locked and
46 remote cache lines have to be invalidated. */
47 if (oldval == newval)
48 break;
49
50 /* Update the cancel handling word. This has to be done
51 atomically since other bits could be modified as well. */
52 int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
53 oldval);
54 if (__glibc_likely (curval == oldval))
55 {
56 if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
57 {
58 THREAD_SETMEM (self, result, PTHREAD_CANCELED);
59 __do_cancel ();
60 }
61
62 break;
63 }
64
65 /* Prepare for the next round. */
66 oldval = curval;
67 }
68
69 return 0;
70}
71strong_alias (__pthread_setcanceltype, pthread_setcanceltype)
72