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/* IBM_PROLOG_BEGIN_TAG */
/* This is an automatically generated prolog. */
/* */
/* $Source: src/kernel/futexmgr.C $ */
/* */
/* OpenPOWER HostBoot Project */
/* */
/* Contributors Listed Below - COPYRIGHT 2011,2016 */
/* [+] International Business Machines Corp. */
/* */
/* */
/* 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. */
/* */
/* IBM_PROLOG_END_TAG */
/**
* @file futexmgr.C
* @brief Definition for kernel side futex management
*/
#include <assert.h>
#include <errno.h>
#include <kernel/task.H>
#include <kernel/cpumgr.H>
#include <kernel/scheduler.H>
#include <kernel/futexmgr.H>
#include <util/singleton.H>
#include <kernel/doorbell.H>
//-----------------------------------------------------------------------------
uint64_t FutexManager::wait(task_t* i_task, uint64_t * i_addr, uint64_t i_val)
{
return Singleton<FutexManager>::instance()._wait(i_task, i_addr, i_val);
}
//-----------------------------------------------------------------------------
uint64_t FutexManager::wake(uint64_t * i_futex1, uint64_t i_count1,
uint64_t * i_futex2, uint64_t i_count2)
{
return Singleton<FutexManager>::instance()._wake(i_futex1, i_count1,
i_futex2, i_count2);
}
//-----------------------------------------------------------------------------
uint64_t FutexManager::_wait(task_t* i_task, uint64_t * i_addr, uint64_t i_val)
{
uint64_t rc = 0;
iv_lock.lock();
if(unlikely(*i_addr != i_val))
{
// some other task has modified the futex
// bail-out retry required.
iv_lock.unlock();
rc = EWOULDBLOCK;
}
else
{
_FutexWait_t * waiter = new _FutexWait_t();
waiter->key = i_addr;
waiter->task = i_task;
// Set blocked state.
i_task->state = TASK_STATE_BLOCK_FUTEX;
i_task->state_info = i_addr;
// Now add the futex/task it to the wait queue
iv_list.insert(waiter);
iv_lock.unlock();
CpuManager::getCurrentCPU()->scheduler->setNextRunnable();
}
return rc;
}
// Wake processes. Any number of processes in excess of count1 are not
// woken up but moved to futex2. the number of processes to move
// is capped by count2.
uint64_t FutexManager::_wake(uint64_t * i_futex1, uint64_t i_count1,
uint64_t * i_futex2, uint64_t i_count2
)
{
uint64_t started = 0;
iv_lock.lock();
// First start up to i_count1 task(s)
while(started < i_count1)
{
_FutexWait_t * waiter = iv_list.find(i_futex1);
if(waiter == NULL)
{
break;
}
task_t * wait_task = waiter->task;
iv_list.erase(waiter);
delete waiter;
// This means we had a waiter in the queue, but that waiter had
// a Null task assigned to it. This should NEVER happen
kassert(wait_task != NULL);
wait_task->cpu->scheduler->addTask(wait_task);
++started;
}
if(i_futex2 && i_count2)
{
uint64_t moved = 0;
// Move up to i_count2 tasks to futex2
while(moved < i_count2)
{
// Note: i_futex2 could be modified by this point due to tasks
// released from i_count1. Userspace has to handle this
// appropriately (currently only in sync_cond_wait).
_FutexWait_t * waiter = iv_list.find(i_futex1);
if(waiter == NULL)
{
break;
}
task_t * wait_task = waiter->task;
iv_list.erase(waiter);
kassert(wait_task != NULL); // should never happen, but...
waiter->key = i_futex2;
wait_task->state_info = i_futex2;
iv_list.insert(waiter);
++moved;
}
}
if(started)
{
doorbell_broadcast();
}
iv_lock.unlock();
return started;
}
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