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a2f0363f81
This adds new functions for futex operations, starting with wait, abstimed_wait, reltimed_wait, wake. They add documentation and error checking according to the current draft of the Linux kernel futex manpage. Waiting with absolute or relative timeouts is split into separate functions. This allows for removing a few cases of code duplication in pthreads code, which uses absolute timeouts; also, it allows us to put platform-specific code to go from an absolute to a relative timeout into the platform-specific futex abstractions.. Futex operations that can be canceled are also split out into separate functions suffixed by "_cancelable". There are separate versions for both Linux and NaCl; while they currently differ only slightly, my expectation is that the separate versions of lowlevellock-futex.h will eventually be merged into futex-internal.h when we get to move the lll_ functions over to the new futex API.
122 lines
3.8 KiB
C
122 lines
3.8 KiB
C
/* Copyright (C) 2006-2015 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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/* We define a special synchronization primitive for AIO. POSIX
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conditional variables would be ideal but the pthread_cond_*wait
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operations do not return on EINTR. This is a requirement for
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correct aio_suspend and lio_listio implementations. */
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#include <assert.h>
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#include <signal.h>
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#include <nptl/pthreadP.h>
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#include <futex-internal.h>
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#define DONT_NEED_GAI_MISC_COND 1
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#define GAI_MISC_NOTIFY(waitlist) \
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do { \
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if (*waitlist->counterp > 0 && --*waitlist->counterp == 0) \
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futex_wake ((unsigned int *) waitlist->counterp, 1, FUTEX_PRIVATE); \
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} while (0)
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#define GAI_MISC_WAIT(result, futex, timeout, cancel) \
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do { \
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volatile unsigned int *futexaddr = &futex; \
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unsigned int oldval = futex; \
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\
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if (oldval != 0) \
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{ \
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pthread_mutex_unlock (&__gai_requests_mutex); \
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\
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int oldtype; \
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if (cancel) \
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oldtype = LIBC_CANCEL_ASYNC (); \
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\
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int status; \
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do \
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{ \
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status = futex_reltimed_wait ((unsigned int *) futexaddr, oldval, \
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timeout, FUTEX_PRIVATE); \
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if (status != EAGAIN) \
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break; \
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\
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oldval = *futexaddr; \
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} \
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while (oldval != 0); \
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\
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if (cancel) \
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LIBC_CANCEL_RESET (oldtype); \
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\
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if (status == EINTR) \
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result = EINTR; \
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else if (status == ETIMEDOUT) \
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result = EAGAIN; \
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else \
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assert (status == 0 || status == EAGAIN); \
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\
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pthread_mutex_lock (&__gai_requests_mutex); \
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} \
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} while (0)
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#define gai_start_notify_thread __gai_start_notify_thread
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#define gai_create_helper_thread __gai_create_helper_thread
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extern inline void
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__gai_start_notify_thread (void)
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{
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sigset_t ss;
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sigemptyset (&ss);
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int sigerr = pthread_sigmask (SIG_SETMASK, &ss, NULL);
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assert_perror (sigerr);
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}
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extern inline int
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__gai_create_helper_thread (pthread_t *threadp, void *(*tf) (void *),
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void *arg)
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{
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pthread_attr_t attr;
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/* Make sure the thread is created detached. */
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pthread_attr_init (&attr);
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pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
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/* The helper thread needs only very little resources. */
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(void) pthread_attr_setstacksize (&attr,
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__pthread_get_minstack (&attr)
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+ 4 * PTHREAD_STACK_MIN);
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/* Block all signals in the helper thread. To do this thoroughly we
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temporarily have to block all signals here. */
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sigset_t ss;
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sigset_t oss;
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sigfillset (&ss);
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int sigerr = pthread_sigmask (SIG_SETMASK, &ss, &oss);
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assert_perror (sigerr);
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int ret = pthread_create (threadp, &attr, tf, arg);
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/* Restore the signal mask. */
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sigerr = pthread_sigmask (SIG_SETMASK, &oss, NULL);
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assert_perror (sigerr);
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(void) pthread_attr_destroy (&attr);
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return ret;
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}
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#include_next <gai_misc.h>
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