semaphore.c

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/* -*- C -*- */
/*
 * Copyright (c) 2013-2020 Seagate Technology LLC and/or its Affiliates
 *
 * Licensed 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.
 *
 * For any questions about this software or licensing,
 * please email opensource@seagate.com or cortx-questions@seagate.com.
 *
 */


#include "lib/semaphore.h"
#include "lib/assert.h"
#include "lib/errno.h"
#include "lib/types.h"      /* INT_MAX */
#include "lib/arith.h"      /* min_check */

M0_INTERNAL int m0_semaphore_init(struct m0_semaphore *semaphore,
                                  unsigned value)
{
        int rc;
        int err;

        rc = sem_init(&semaphore->s_sem, 0, value);
        err = rc == 0 ? 0 : errno;
        M0_ASSERT_INFO(rc == 0, "rc=%d errno=%d", rc, err);
        return -err;
}

M0_INTERNAL void m0_semaphore_fini(struct m0_semaphore *semaphore)
{
        int rc;

        rc = sem_destroy(&semaphore->s_sem);
        M0_ASSERT_INFO(rc == 0, "rc=%d errno=%d", rc, errno);
}

M0_INTERNAL void m0_semaphore_down(struct m0_semaphore *semaphore)
{
        int rc;

        do
                rc = sem_wait(&semaphore->s_sem);
        while (rc == -1 && errno == EINTR);
        M0_ASSERT_INFO(rc == 0, "rc=%d errno=%d", rc, errno);
}

M0_INTERNAL void m0_semaphore_up(struct m0_semaphore *semaphore)
{
        int rc;

        rc = sem_post(&semaphore->s_sem);
        M0_ASSERT_INFO(rc == 0, "rc=%d errno=%d", rc, errno);
}

M0_INTERNAL bool m0_semaphore_trydown(struct m0_semaphore *semaphore)
{
        int rc;

        do
                rc = sem_trywait(&semaphore->s_sem);
        while (rc == -1 && errno == EINTR);
        M0_ASSERT_INFO(rc == 0 || (rc == -1 && errno == EAGAIN),
                       "rc=%d errno=%d", rc, errno);
        errno = 0;
        return rc == 0;
}

M0_INTERNAL unsigned m0_semaphore_value(struct m0_semaphore *semaphore)
{
        int rc;
        int result;

        rc = sem_getvalue(&semaphore->s_sem, &result);
        M0_ASSERT_INFO(rc == 0, "rc=%d errno=%d", rc, errno);
        M0_POST(result >= 0);
        return result;
}

M0_INTERNAL bool m0_semaphore_timeddown(struct m0_semaphore *semaphore,
                                        const m0_time_t abs_timeout)
{
        m0_time_t       abs_timeout_realtime = m0_time_to_realtime(abs_timeout);
        struct timespec ts = {
                        .tv_sec  = m0_time_seconds(abs_timeout_realtime),
                        .tv_nsec = m0_time_nanoseconds(abs_timeout_realtime)
        };
        int             rc;

        /*
         * Workaround for sem_timedwait(3) on Centos >= 7.2, which returns
         * -ETIMEDOUT immediately if tv_sec is greater than
         * gettimeofday(2) + INT_MAX.
         *
         *  For more information refer to:
         *    https://bugzilla.redhat.com/show_bug.cgi?id=1412082
         *    https://jts.seagate.com/browse/CASTOR-1990
         *    `git blame` these lines and read commit message
         *    doc/workarounds.md
         *
         *  It should be reverted when glibc is fixed in future RedHat releases.
         */
        ts.tv_sec = min_check(ts.tv_sec, (time_t)(INT_MAX - 1));
        /* ----- end of workaround ----- */

        do
                rc = sem_timedwait(&semaphore->s_sem, &ts);
        while (rc == -1 && errno == EINTR);
        M0_ASSERT_INFO(rc == 0 || (rc == -1 && errno == ETIMEDOUT),
                       "rc=%d errno=%d", rc, errno);
        if (rc == -1 && errno == ETIMEDOUT)
                errno = 0;
        return rc == 0;
}

/*
 *  Local variables:
 *  c-indentation-style: "K&R"
 *  c-basic-offset: 8
 *  tab-width: 8
 *  fill-column: 80
 *  scroll-step: 1
 *  End:
 */