HelenOS sources

root/uspace/srv/logger/logs.c

DEFINITIONS

1. find_log_by_name_and_parent_no_list_lock
2. create_dest
3. create_log_no_locking
4. find_or_create_log_and_lock
5. find_log_by_name_and_lock
6. find_log_by_id_and_lock
7. get_actual_log_level
8. shall_log_message
9. log_unlock
10. log_release
11. write_to_log
12. registered_logs_init
13. register_log
14. unregister_logs

/*
 * Copyright (c) 2012 Vojtech Horky
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup logger
 * @{
 */
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <str.h>
#include "logger.h"

static FIBRIL_MUTEX_INITIALIZE(log_list_guard);
static LIST_INITIALIZE(log_list);

static logger_log_t *find_log_by_name_and_parent_no_list_lock(const char *name, logger_log_t *parent)
{
        list_foreach(log_list, link, logger_log_t, log) {
                if ((parent == log->parent) && (str_cmp(log->name, name) == 0))
                        return log;
        }

        return NULL;
}

static errno_t create_dest(const char *name, logger_dest_t **dest)
{
        logger_dest_t *result = malloc(sizeof(logger_dest_t));
        if (result == NULL)
                return ENOMEM;
        if (asprintf(&result->filename, "/log/%s", name) < 0) {
                free(result);
                return ENOMEM;
        }
        result->logfile = NULL;
        fibril_mutex_initialize(&result->guard);
        *dest = result;
        return EOK;
}

static logger_log_t *create_log_no_locking(const char *name, logger_log_t *parent)
{
        logger_log_t *result = calloc(1, sizeof(logger_log_t));
        if (result == NULL)
                return NULL;

        result->name = str_dup(name);
        if (result->name == NULL)
                goto error;

        /*
         * Notice that we create new dest as the last
         * operation that can fail and thus there is no code
         * to deallocate dest.
         */
        if (parent == NULL) {
                result->full_name = str_dup(name);
                if (result->full_name == NULL)
                        goto error;
                errno_t rc = create_dest(name, &result->dest);
                if (rc != EOK)
                        goto error;
        } else {
                if (asprintf(&result->full_name, "%s/%s",
                    parent->full_name, name) < 0)
                        goto error;
                result->dest = parent->dest;
        }

        /* Following initializations cannot fail. */
        result->logged_level = LOG_LEVEL_USE_DEFAULT;
        fibril_mutex_initialize(&result->guard);
        link_initialize(&result->link);
        result->parent = parent;

        return result;

error:
        free(result->name);
        free(result->full_name);
        free(result);
        return NULL;

}

logger_log_t *find_or_create_log_and_lock(const char *name, sysarg_t parent_id)
{
        logger_log_t *result = NULL;
        logger_log_t *parent = (logger_log_t *) parent_id;

        fibril_mutex_lock(&log_list_guard);

        result = find_log_by_name_and_parent_no_list_lock(name, parent);
        if (result == NULL) {
                result = create_log_no_locking(name, parent);
                if (result == NULL)
                        goto leave;
                list_append(&result->link, &log_list);
                if (result->parent != NULL) {
                        fibril_mutex_lock(&result->parent->guard);
                        result->parent->ref_counter++;
                        fibril_mutex_unlock(&result->parent->guard);
                }
        }

        fibril_mutex_lock(&result->guard);

leave:
        fibril_mutex_unlock(&log_list_guard);

        return result;
}

logger_log_t *find_log_by_name_and_lock(const char *name)
{
        logger_log_t *result = NULL;

        fibril_mutex_lock(&log_list_guard);
        list_foreach(log_list, link, logger_log_t, log) {
                if (str_cmp(log->full_name, name) == 0) {
                        fibril_mutex_lock(&log->guard);
                        result = log;
                        break;
                }
        }
        fibril_mutex_unlock(&log_list_guard);

        return result;
}

logger_log_t *find_log_by_id_and_lock(sysarg_t id)
{
        logger_log_t *result = NULL;

        fibril_mutex_lock(&log_list_guard);
        list_foreach(log_list, link, logger_log_t, log) {
                if ((sysarg_t) log == id) {
                        fibril_mutex_lock(&log->guard);
                        result = log;
                        break;
                }
        }
        fibril_mutex_unlock(&log_list_guard);

        return result;
}

static log_level_t get_actual_log_level(logger_log_t *log)
{
        /* Find recursively proper log level. */
        if (log->logged_level == LOG_LEVEL_USE_DEFAULT) {
                if (log->parent == NULL)
                        return get_default_logging_level();
                else
                        return get_actual_log_level(log->parent);
        }
        return log->logged_level;
}

bool shall_log_message(logger_log_t *log, log_level_t level)
{
        fibril_mutex_lock(&log_list_guard);
        bool result = level <= get_actual_log_level(log);
        fibril_mutex_unlock(&log_list_guard);
        return result;
}

void log_unlock(logger_log_t *log)
{
        assert(fibril_mutex_is_locked(&log->guard));
        fibril_mutex_unlock(&log->guard);
}

/** Decreases reference counter on the log and destroy the log if
 * necessary.
 *
 * Precondition: log is locked.
 *
 * @param log Log to release from using by the caller.
 */
void log_release(logger_log_t *log)
{
        assert(fibril_mutex_is_locked(&log->guard));
        assert(log->ref_counter > 0);

        /* We are definitely not the last ones. */
        if (log->ref_counter > 1) {
                log->ref_counter--;
                fibril_mutex_unlock(&log->guard);
                return;
        }

        /*
         * To prevent deadlock, we need to get the list lock first.
         * Deadlock scenario:
         * Us: LOCKED(log), want to LOCK(list)
         * Someone else calls find_log_by_name_and_lock(log->fullname) ->
         *   LOCKED(list), wants to LOCK(log)
         */
        fibril_mutex_unlock(&log->guard);

        /* Ensuring correct locking order. */
        fibril_mutex_lock(&log_list_guard);
        /*
         * The reference must be still valid because we have not decreased
         * the reference counter.
         */
        fibril_mutex_lock(&log->guard);
        assert(log->ref_counter > 0);
        log->ref_counter--;

        if (log->ref_counter > 0) {
                /*
                 * Meanwhile, someone else increased the ref counter.
                 * No big deal, we just return immediatelly.
                 */
                fibril_mutex_unlock(&log->guard);
                fibril_mutex_unlock(&log_list_guard);
                return;
        }

        /*
         * Here we are on a destroy path. We need to
         * - remove ourselves from the list
         * - decrease reference of the parent (if not top-level log)
         *   - we must do that after we relaase list lock to prevent
         *     deadlock with ourselves
         * - destroy dest (if top-level log)
         */
        assert(log->ref_counter == 0);

        list_remove(&log->link);
        fibril_mutex_unlock(&log_list_guard);
        fibril_mutex_unlock(&log->guard);

        if (log->parent == NULL) {
                /*
                 * Due to lazy file opening in write_to_log(),
                 * it is possible that no file was actually opened.
                 */
                if (log->dest->logfile != NULL) {
                        fclose(log->dest->logfile);
                }
                free(log->dest->filename);
                free(log->dest);
        } else {
                fibril_mutex_lock(&log->parent->guard);
                log_release(log->parent);
        }

        logger_log("Destroyed log %s.\n", log->full_name);

        free(log->name);
        free(log->full_name);

        free(log);
}

void write_to_log(logger_log_t *log, log_level_t level, const char *message)
{
        assert(fibril_mutex_is_locked(&log->guard));
        assert(log->dest != NULL);
        fibril_mutex_lock(&log->dest->guard);
        if (log->dest->logfile == NULL)
                log->dest->logfile = fopen(log->dest->filename, "a");

        if (log->dest->logfile != NULL) {
                fprintf(log->dest->logfile, "[%s] %s: %s\n",
                    log->full_name, log_level_str(level),
                    (const char *) message);
                fflush(log->dest->logfile);
        }

        fibril_mutex_unlock(&log->dest->guard);
}

void registered_logs_init(logger_registered_logs_t *logs)
{
        logs->logs_count = 0;
}

bool register_log(logger_registered_logs_t *logs, logger_log_t *new_log)
{
        if (logs->logs_count >= MAX_REFERENCED_LOGS_PER_CLIENT) {
                return false;
        }

        assert(fibril_mutex_is_locked(&new_log->guard));
        new_log->ref_counter++;

        logs->logs[logs->logs_count] = new_log;
        logs->logs_count++;

        return true;
}

void unregister_logs(logger_registered_logs_t *logs)
{
        for (size_t i = 0; i < logs->logs_count; i++) {
                logger_log_t *log = logs->logs[i];
                fibril_mutex_lock(&log->guard);
                log_release(log);
        }
}

/**
 * @}
 */