semaphore.c

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/* -*- C -*- */
/*
 * Copyright (c) 2012-2020 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 <linux/jiffies.h>  /* timespec_to_jiffies */
#include "lib/semaphore.h"
#include "lib/assert.h"

#define M0_TRACE_SUBSYSTEM M0_TRACE_SUBSYS_M0T1FS
#include "lib/trace.h"

M0_INTERNAL int m0_semaphore_init(struct m0_semaphore *semaphore,
                                  unsigned value)
{
        sema_init(&semaphore->s_sem, value);
        return 0;
}

M0_INTERNAL void m0_semaphore_fini(struct m0_semaphore *semaphore)
{
}

M0_INTERNAL void m0_semaphore_down(struct m0_semaphore *semaphore)
{
        int flag_was_set = 0;

        while (down_interruptible(&semaphore->s_sem) != 0)
                flag_was_set |= test_and_clear_thread_flag(TIF_SIGPENDING);

        if (flag_was_set)
                set_thread_flag(TIF_SIGPENDING);
}

M0_INTERNAL bool m0_semaphore_trydown(struct m0_semaphore *semaphore)
{
        return !down_trylock(&semaphore->s_sem);
}

M0_INTERNAL void m0_semaphore_up(struct m0_semaphore *semaphore)
{
        up(&semaphore->s_sem);
}

M0_INTERNAL unsigned m0_semaphore_value(struct m0_semaphore *semaphore)
{
        return semaphore->s_sem.count;
}

M0_INTERNAL bool m0_semaphore_timeddown(struct m0_semaphore *semaphore,
                                        const m0_time_t abs_timeout)
{
        m0_time_t       nowtime = m0_time_now();
        m0_time_t       abs_timeout_realtime = m0_time_to_realtime(abs_timeout);
        m0_time_t       reltime;
        unsigned long   reljiffies;
        struct timespec ts;

        /* same semantics as user_space semaphore: allow abs_time < now */
        if (abs_timeout_realtime > nowtime)
                reltime = m0_time_sub(abs_timeout_realtime, nowtime);
        else
                reltime = 0;
        ts.tv_sec  = m0_time_seconds(reltime);
        ts.tv_nsec = m0_time_nanoseconds(reltime);
        reljiffies = timespec_to_jiffies(&ts);
        return down_timeout(&semaphore->s_sem, reljiffies) == 0;
}

#undef M0_TRACE_SUBSYSTEM

/*
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 *  c-indentation-style: "K&R"
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 *  fill-column: 80
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 *  End:
 */