/*
* Copyright (c) 2017 Advanced Micro Devices, Inc.
* 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;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "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 COPYRIGHT
* OWNER OR CONTRIBUTORS 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.
*
* Authors: Brandon Potter
* Steve Reinhardt
* Alexandru Dutu
*/
#ifndef __FUTEX_MAP_HH__
#define __FUTEX_MAP_HH__
#include <unordered_map>
#include <cpu/thread_context.hh>
/**
* FutexKey class defines an unique identifier for a particular futex in the
* system. The tgid and an address are the unique values needed as the key.
*/
class FutexKey {
public:
uint64_t addr;
uint64_t tgid;
FutexKey(uint64_t addr_in, uint64_t tgid_in)
: addr(addr_in), tgid(tgid_in)
{
}
bool
operator==(const FutexKey &in) const
{
return addr == in.addr && tgid == in.tgid;
}
};
namespace std {
/**
* The unordered_map structure needs the parenthesis operator defined for
* std::hash if a user defined key is used. Our key is is user defined
* so we need to provide the hash functor.
*/
template <>
struct hash<FutexKey>
{
size_t operator()(const FutexKey& in) const
{
size_t hash = 65521;
for (int i = 0; i < sizeof(uint64_t) / sizeof(size_t); i++) {
hash ^= (size_t)(in.addr >> sizeof(size_t) * i) ^
(size_t)(in.tgid >> sizeof(size_t) * i);
}
return hash;
}
};
}
/**
* WaiterState defines internal state of a waiter thread. The state
* includes a pointer to the thread's context and its associated bitmask.
*/
class WaiterState {
public:
ThreadContext* tc;
int bitmask;
/**
* this constructor is used if futex ops with bitset are used
*/
WaiterState(ThreadContext* _tc, int _bitmask)
: tc(_tc), bitmask(_bitmask)
{ }
/**
* if bitset is not defined, just set bitmask to 0xffffffff
*/
WaiterState(ThreadContext* _tc)
: tc(_tc), bitmask(0xffffffff)
{ }
/**
* return true if the bit-wise AND of the wakeup_bitmask given by
* a waking thread and this thread's internal bitmask is non-zero
*/
bool
checkMask(int wakeup_bitmask) const
{
return bitmask & wakeup_bitmask;
}
};
typedef std::list<WaiterState> WaiterList;
/**
* FutexMap class holds a map of all futexes used in the system
*/
class FutexMap : public std::unordered_map<FutexKey, WaiterList>
{
public:
/** Inserts a futex into the map with one waiting TC */
void
suspend(Addr addr, uint64_t tgid, ThreadContext *tc)
{
FutexKey key(addr, tgid);
auto it = find(key);
if (it == end()) {
WaiterList waiterList {WaiterState(tc)};
insert({key, waiterList});
} else {
it->second.push_back(WaiterState(tc));
}
/** Suspend the thread context */
tc->suspend();
}
/** Wakes up at most count waiting threads on a futex */
int
wakeup(Addr addr, uint64_t tgid, int count)
{
FutexKey key(addr, tgid);
auto it = find(key);
if (it == end())
return 0;
int woken_up = 0;
auto &waiterList = it->second;
while (!waiterList.empty() && woken_up < count) {
waiterList.front().tc->activate();
waiterList.pop_front();
woken_up++;
}
if (waiterList.empty())
erase(it);
return woken_up;
}
/**
* inserts a futex into the map with one waiting TC
* associates the waiter with a given bitmask
*/
void
suspend_bitset(Addr addr, uint64_t tgid, ThreadContext *tc,
int bitmask)
{
FutexKey key(addr, tgid);
auto it = find(key);
if (it == end()) {
WaiterList waiterList {WaiterState(tc, bitmask)};
insert({key, waiterList});
} else {
it->second.push_back(WaiterState(tc, bitmask));
}
/** Suspend the thread context */
tc->suspend();
}
/**
* Wakes up all waiters waiting on the addr and associated with the
* given bitset
*/
int
wakeup_bitset(Addr addr, uint64_t tgid, int bitmask)
{
FutexKey key(addr, tgid);
auto it = find(key);
if (it == end())
return 0;
int woken_up = 0;
auto &waiterList = it->second;
auto iter = waiterList.begin();
while (iter != waiterList.end()) {
WaiterState& waiter = *iter;
if (waiter.checkMask(bitmask)) {
waiter.tc->activate();
iter = waiterList.erase(iter);
woken_up++;
} else {
++iter;
}
}
if (waiterList.empty())
erase(it);
return woken_up;
}
/**
* This operation wakes a given number (val) of waiters. If there are
* more threads waiting than woken, they are removed from the wait
* queue of the futex pointed to by addr1 and added to the wait queue
* of the futex pointed to by addr2. The number of waiter moved is
* capped by count2 (misused timeout parameter).
*
* The return value is the number of waiters that are woken or
* requeued.
*/
int
requeue(Addr addr1, uint64_t tgid, int count, int count2, Addr addr2)
{
FutexKey key1(addr1, tgid);
auto it1 = find(key1);
if (it1 == end())
return 0;
int woken_up = 0;
auto &waiterList1 = it1->second;
while (!waiterList1.empty() && woken_up < count) {
waiterList1.front().tc->activate();
waiterList1.pop_front();
woken_up++;
}
WaiterList tmpList;
int requeued = 0;
while (!waiterList1.empty() && requeued < count2) {
auto w = waiterList1.front();
waiterList1.pop_front();
tmpList.push_back(w);
requeued++;
}
FutexKey key2(addr2, tgid);
auto it2 = find(key2);
if (it2 == end() && requeued > 0) {
insert({key2, tmpList});
} else {
it2->second.insert(it2->second.end(),
tmpList.begin(), tmpList.end());
}
if (waiterList1.empty())
erase(it1);
return woken_up + requeued;
}
};
#endif // __FUTEX_MAP_HH__