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8f861542dd
Since the FUTEX_WAIT operation takes a relative timeout, the pthread_cond_timedwait and other timed function implementations have to get a relative timeout from the absolute timeout parameter it gets before it makes the futex syscall. This value is then converted back into an absolute timeout within the kernel. This is a waste and has hence been improved upon by a FUTEX_WAIT_BITSET operation (OR'd with FUTEX_CLOCK_REALTIME to make the kernel use the realtime clock instead of the default monotonic clock). This was implemented only in the x86 and sh assembly code and not in the C code. This patch implements support for FUTEX_WAIT_BITSET whenever available (since linux-2.6.29) for s390 and powerpc.
128 lines
3.3 KiB
C
128 lines
3.3 KiB
C
/* Copyright (C) 2006-2012 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Jakub Jelinek <jakub@redhat.com>, 2006.
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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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#include <errno.h>
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#include <sysdep.h>
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#include <lowlevellock.h>
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#include <sys/time.h>
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#include <pthreadP.h>
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int
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__lll_robust_lock_wait (int *futex, int private)
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{
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int oldval = *futex;
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int tid = THREAD_GETMEM (THREAD_SELF, tid);
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/* If the futex changed meanwhile try locking again. */
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if (oldval == 0)
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goto try;
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do
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{
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if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
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return oldval;
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int newval = oldval | FUTEX_WAITERS;
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if (oldval != newval
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&& atomic_compare_and_exchange_bool_acq (futex, newval, oldval))
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continue;
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lll_futex_wait (futex, newval, private);
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try:
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;
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}
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while ((oldval = atomic_compare_and_exchange_val_acq (futex,
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tid | FUTEX_WAITERS,
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0)) != 0);
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return 0;
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}
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int
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__lll_robust_timedlock_wait (int *futex, const struct timespec *abstime,
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int private)
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{
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/* Reject invalid timeouts. */
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if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
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return EINVAL;
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int tid = THREAD_GETMEM (THREAD_SELF, tid);
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int oldval = *futex;
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/* If the futex changed meanwhile try locking again. */
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if (oldval == 0)
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goto try;
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/* Work around the fact that the kernel rejects negative timeout values
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despite them being valid. */
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if (__builtin_expect (abstime->tv_sec < 0, 0))
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return ETIMEDOUT;
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do
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{
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#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
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|| !defined lll_futex_timed_wait_bitset)
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struct timeval tv;
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struct timespec rt;
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/* Get the current time. */
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(void) __gettimeofday (&tv, NULL);
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/* Compute relative timeout. */
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rt.tv_sec = abstime->tv_sec - tv.tv_sec;
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rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
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if (rt.tv_nsec < 0)
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{
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rt.tv_nsec += 1000000000;
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--rt.tv_sec;
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}
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/* Already timed out? */
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if (rt.tv_sec < 0)
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return ETIMEDOUT;
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#endif
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/* Wait. */
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if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
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return oldval;
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int newval = oldval | FUTEX_WAITERS;
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if (oldval != newval
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&& atomic_compare_and_exchange_bool_acq (futex, newval, oldval))
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continue;
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#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
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|| !defined lll_futex_timed_wait_bitset)
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lll_futex_timed_wait (futex, newval, &rt, private);
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#else
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lll_futex_timed_wait_bitset (futex, newval, abstime,
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FUTEX_CLOCK_REALTIME, private);
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#endif
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try:
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;
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}
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while ((oldval = atomic_compare_and_exchange_val_acq (futex,
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tid | FUTEX_WAITERS,
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0)) != 0);
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return 0;
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}
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