1/* Copyright (C) 2006-2022 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18/* We define a special synchronization primitive for AIO. POSIX
19 conditional variables would be ideal but the pthread_cond_*wait
20 operations do not return on EINTR. This is a requirement for
21 correct aio_suspend and lio_listio implementations. */
22
23#include <assert.h>
24#include <signal.h>
25#include <pthreadP.h>
26#include <futex-internal.h>
27
28#define DONT_NEED_GAI_MISC_COND 1
29
30#define GAI_MISC_NOTIFY(waitlist) \
31 do { \
32 if (*waitlist->counterp > 0 && --*waitlist->counterp == 0) \
33 futex_wake ((unsigned int *) waitlist->counterp, 1, FUTEX_PRIVATE); \
34 } while (0)
35
36#define GAI_MISC_WAIT(result, futex, timeout, cancel) \
37 do { \
38 volatile unsigned int *futexaddr = &futex; \
39 unsigned int oldval = futex; \
40 \
41 if (oldval != 0) \
42 { \
43 __pthread_mutex_unlock (&__gai_requests_mutex); \
44 \
45 int status; \
46 do \
47 { \
48 if (cancel) \
49 status = __futex_abstimed_wait_cancelable64 ( \
50 (unsigned int *) futexaddr, oldval, CLOCK_MONOTONIC, timeout, \
51 FUTEX_PRIVATE); \
52 else \
53 status = __futex_abstimed_wait64 ((unsigned int *) futexaddr, \
54 oldval, CLOCK_REALTIME, timeout, FUTEX_PRIVATE); \
55 if (status != EAGAIN) \
56 break; \
57 \
58 oldval = *futexaddr; \
59 } \
60 while (oldval != 0); \
61 \
62 if (status == EINTR) \
63 result = EINTR; \
64 else if (status == ETIMEDOUT) \
65 result = EAGAIN; \
66 else if (status == EOVERFLOW) \
67 result = EOVERFLOW; \
68 else \
69 assert (status == 0 || status == EAGAIN); \
70 \
71 __pthread_mutex_lock (&__gai_requests_mutex); \
72 } \
73 } while (0)
74
75
76#define gai_start_notify_thread __gai_start_notify_thread
77#define gai_create_helper_thread __gai_create_helper_thread
78
79extern inline void
80__gai_start_notify_thread (void)
81{
82 sigset_t ss;
83 sigemptyset (&ss);
84 int sigerr __attribute__ ((unused));
85 sigerr = __pthread_sigmask (SIG_SETMASK, &ss, NULL);
86 assert_perror (sigerr);
87}
88
89extern inline int
90__gai_create_helper_thread (pthread_t *threadp, void *(*tf) (void *),
91 void *arg)
92{
93 pthread_attr_t attr;
94
95 /* Make sure the thread is created detached. */
96 __pthread_attr_init (&attr);
97 __pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
98
99 /* The helper thread needs only very little resources. */
100 (void) __pthread_attr_setstacksize (&attr,
101 __pthread_get_minstack (&attr)
102 + 4 * PTHREAD_STACK_MIN);
103
104 /* Block all signals in the helper thread. To do this thoroughly we
105 temporarily have to block all signals here. */
106 sigset_t ss;
107 sigset_t oss;
108 sigfillset (&ss);
109 int sigerr __attribute__ ((unused));
110 sigerr = __pthread_sigmask (SIG_SETMASK, &ss, &oss);
111 assert_perror (sigerr);
112
113 int ret = __pthread_create (threadp, &attr, tf, arg);
114
115 /* Restore the signal mask. */
116 sigerr = __pthread_sigmask (SIG_SETMASK, &oss, NULL);
117 assert_perror (sigerr);
118
119 (void) __pthread_attr_destroy (&attr);
120 return ret;
121}
122
123#include_next <gai_misc.h>
124

source code of glibc/sysdeps/nptl/gai_misc.h