AsidManager.cc

/*
 * Copyright (c) 2008-2014, Pedigree Developers
 *
 * Please see the CONTRIB file in the root of the source tree for a full
 * list of contributors.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "AsidManager.h"
#include "pedigree/kernel/Log.h"
#include "pedigree/kernel/panic.h"

AsidManager AsidManager::m_Instance;

AsidManager &AsidManager::instance()
{
    return m_Instance;
}

AsidManager::AsidManager()
{
}

AsidManager::~AsidManager()
{
}

AsidManager::Asid AsidManager::obtainAsid()
{
    // Our algorithm is a linear search of multiple levels.
    // Firstly we search for an ASID with a contention of zero.
    // if that's not found, we search for one with <= 1,
    // etc. The reason for the less than is that an asid could be given back
    // while we are searching, and this covers all eventualities.

    for (int i = 0; i < 10; i++)
    {
        for (int j = 0; j < NUM_ASID; j++)
        {
            if (m_Asids[j] <= i)
            {
                // Lock it.
                m_Mutex.acquire();
                // Is it still valid?
                if (m_Asids[j] <= 1)
                {
                    // Success! If this ASID is contended, clear the TLB.
                    if (m_Asids[j] > 0)
                        bulldoze(j);
                    m_Asids[j]++;
                    m_Mutex.release();
                    return j;
                }
                // No? Then release the lock and keep searching.
                m_Mutex.release();
            }
        }
    }
    // If we got here then we didn't find any asid with less than a contention
    // of 10. This is really really bad. Panic here.
    panic("Too many processes running, not enough ASIDs!");
}

void AsidManager::returnAsid(AsidManager::Asid asid)
{
    // Grab the lock.
    m_Mutex.acquire();
    // Sanity check...
    if (m_Asids[asid] == 0)
        ERROR("returnAsid called on an ASID that hasn't been allocated!");
    m_Asids[asid]--;
    // Release the lock.
    m_Mutex.release();
}

void AsidManager::bulldoze(AsidManager::Asid asid)
{
    // TODO:: implement
}