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/** @file
A brief file description
@section license License
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements. See the NOTICE file
distributed with this work for additional information
regarding copyright ownership. The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
#include "ts/ink_config.h"
#include "ts/ink_rwlock.h"
//-------------------------------------------------------------------------
// ink_rwlock_init
//
// Note: This should be called only once.
//-------------------------------------------------------------------------
int
ink_rwlock_init(ink_rwlock *rw)
{
int result;
if ((result = ink_mutex_init(&rw->rw_mutex, NULL)) != 0)
goto Lerror;
ink_cond_init(&rw->rw_condreaders);
ink_cond_init(&rw->rw_condwriters);
rw->rw_nwaitreaders = 0;
rw->rw_nwaitwriters = 0;
// coverity[missing_lock]
rw->rw_refcount = 0;
rw->rw_magic = RW_MAGIC;
return 0;
Lerror:
return result; /* an errno value */
}
//-------------------------------------------------------------------------
// ink_rwlock_destroy
//-------------------------------------------------------------------------
int
ink_rwlock_destroy(ink_rwlock *rw)
{
if (rw->rw_magic != RW_MAGIC)
return EINVAL;
if (rw->rw_refcount != 0 || rw->rw_nwaitreaders != 0 || rw->rw_nwaitwriters != 0)
return EBUSY;
ink_mutex_destroy(&rw->rw_mutex);
ink_cond_destroy(&rw->rw_condreaders);
ink_cond_destroy(&rw->rw_condwriters);
rw->rw_magic = 0;
return 0;
}
//-------------------------------------------------------------------------
// ink_rwlock_rdlock
//-------------------------------------------------------------------------
int
ink_rwlock_rdlock(ink_rwlock *rw)
{
int result;
if (rw->rw_magic != RW_MAGIC)
return EINVAL;
if ((result = ink_mutex_acquire(&rw->rw_mutex)) != 0)
return result;
/* give preference to waiting writers */
while (rw->rw_refcount < 0 || rw->rw_nwaitwriters > 0) {
rw->rw_nwaitreaders++;
ink_cond_wait(&rw->rw_condreaders, &rw->rw_mutex);
rw->rw_nwaitreaders--;
}
rw->rw_refcount++; /* another reader has a read lock */
ink_mutex_release(&rw->rw_mutex);
return 0;
}
//-------------------------------------------------------------------------
// ink_rwlock_wrlock
//-------------------------------------------------------------------------
int
ink_rwlock_wrlock(ink_rwlock *rw)
{
int result;
if (rw->rw_magic != RW_MAGIC)
return EINVAL;
if ((result = ink_mutex_acquire(&rw->rw_mutex)) != 0)
return result;
while (rw->rw_refcount != 0) {
rw->rw_nwaitwriters++;
ink_cond_wait(&rw->rw_condwriters, &rw->rw_mutex);
rw->rw_nwaitwriters--;
}
rw->rw_refcount = -1;
ink_mutex_release(&rw->rw_mutex);
return 0;
}
//-------------------------------------------------------------------------
// ink_rwlock_unlock
//-------------------------------------------------------------------------
int
ink_rwlock_unlock(ink_rwlock *rw)
{
int result;
if (rw->rw_magic != RW_MAGIC)
return EINVAL;
if ((result = ink_mutex_acquire(&rw->rw_mutex)) != 0)
return result;
if (rw->rw_refcount > 0)
rw->rw_refcount--; /* releasing a reader */
else if (rw->rw_refcount == -1)
rw->rw_refcount = 0; /* releasing a reader */
else
ink_release_assert("invalid rw_refcount!");
/* give preference to waiting writers over waiting readers */
if (rw->rw_nwaitwriters > 0) {
if (rw->rw_refcount == 0)
ink_cond_signal(&rw->rw_condwriters);
} else if (rw->rw_nwaitreaders > 0)
ink_cond_broadcast(&rw->rw_condreaders);
ink_mutex_release(&rw->rw_mutex);
return 0;
}
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