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8ba6ad703c
900778283a ("htl: make pthread_spin_lock really spin") made
pthread_spin_lock really spin and not block, but the current users of
__pthread_spin_lock were assuming that it blocks, i.e. they use it as a
lightweight mutex fitting in just one int.
__pthread_spin_wait provides that support back.
56 lines
1.7 KiB
C
56 lines
1.7 KiB
C
/* Try to acquire a rwlock for reading. Generic version.
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Copyright (C) 2002-2020 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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<https://www.gnu.org/licenses/>. */
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#include <pthread.h>
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#include <assert.h>
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#include <pt-internal.h>
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/* Try to acquire RWLOCK. */
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int
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pthread_rwlock_tryrdlock (struct __pthread_rwlock *rwlock)
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{
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__pthread_spin_wait (&rwlock->__lock);
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if (__pthread_spin_trylock (&rwlock->__held) == 0)
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/* Successfully acquired the lock. */
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{
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assert (rwlock->__readerqueue == 0);
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assert (rwlock->__writerqueue == 0);
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assert (rwlock->__readers == 0);
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rwlock->__readers = 1;
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__pthread_spin_unlock (&rwlock->__lock);
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return 0;
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}
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else
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/* Lock is held, but is held by a reader? */
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if (rwlock->__readers > 0)
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{
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assert (rwlock->__readerqueue == 0);
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rwlock->__readers++;
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__pthread_spin_unlock (&rwlock->__lock);
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return 0;
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}
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/* The lock is busy. */
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__pthread_spin_unlock (&rwlock->__lock);
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return EBUSY;
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}
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