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/*
* Copyright (c) 2020, The SerenityOS developers.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. 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.
*
* 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 HOLDER 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.
*/
#include <Kernel/FutexQueue.h>
#include <Kernel/Thread.h>
//#define FUTEXQUEUE_DEBUG
namespace Kernel {
bool FutexQueue::should_add_blocker(Thread::Blocker& b, void* data)
{
ASSERT(data != nullptr); // Thread that is requesting to be blocked
ASSERT(m_lock.is_locked());
ASSERT(b.blocker_type() == Thread::Blocker::Type::Futex);
#ifdef FUTEXQUEUE_DEBUG
dbg() << "FutexQueue @ " << this << ": should block thread " << *static_cast<Thread*>(data);
#endif
return true;
}
u32 FutexQueue::wake_n_requeue(u32 wake_count, const Function<FutexQueue*()>& get_target_queue, u32 requeue_count, bool& is_empty, bool& is_empty_target)
{
is_empty_target = false;
ScopedSpinLock lock(m_lock);
#ifdef FUTEXQUEUE_DEBUG
dbg() << "FutexQueue @ " << this << ": wake_n_requeue(" << wake_count << ", " << requeue_count << ")";
#endif
u32 did_wake = 0, did_requeue = 0;
do_unblock([&](Thread::Blocker& b, void* data, bool& stop_iterating) {
ASSERT(data);
ASSERT(b.blocker_type() == Thread::Blocker::Type::Futex);
auto& blocker = static_cast<Thread::FutexBlocker&>(b);
#ifdef FUTEXQUEUE_DEBUG
dbg() << "FutexQueue @ " << this << ": wake_n_requeue unblocking " << *static_cast<Thread*>(data);
#endif
ASSERT(did_wake < wake_count);
if (blocker.unblock()) {
if (++did_wake >= wake_count)
stop_iterating = true;
return true;
}
return false;
});
is_empty = is_empty_locked();
if (requeue_count > 0) {
auto blockers_to_requeue = do_take_blockers(requeue_count);
if (!blockers_to_requeue.is_empty()) {
if (auto* target_futex_queue = get_target_queue()) {
#ifdef FUTEXQUEUE_DEBUG
dbg() << "FutexQueue @ " << this << ": wake_n_requeue requeueing " << blockers_to_requeue.size() << " blockers to " << target_futex_queue;
#endif
// While still holding m_lock, notify each blocker
for (auto& info : blockers_to_requeue) {
ASSERT(info.blocker->blocker_type() == Thread::Blocker::Type::Futex);
auto& blocker = *static_cast<Thread::FutexBlocker*>(info.blocker);
blocker.begin_requeue();
}
lock.unlock();
did_requeue = blockers_to_requeue.size();
ScopedSpinLock target_lock(target_futex_queue->m_lock);
// Now that we have the lock of the target, append the blockers
// and notify them that they completed the move
for (auto& info : blockers_to_requeue) {
ASSERT(info.blocker->blocker_type() == Thread::Blocker::Type::Futex);
auto& blocker = *static_cast<Thread::FutexBlocker*>(info.blocker);
blocker.finish_requeue(*target_futex_queue);
}
target_futex_queue->do_append_blockers(move(blockers_to_requeue));
is_empty_target = target_futex_queue->is_empty_locked();
} else {
#ifdef FUTEXQUEUE_DEBUG
dbg() << "FutexQueue @ " << this << ": wake_n_requeue could not get target queue to requeueing " << blockers_to_requeue.size() << " blockers";
#endif
do_append_blockers(move(blockers_to_requeue));
}
}
}
return did_wake + did_requeue;
}
u32 FutexQueue::wake_n(u32 wake_count, const Optional<u32>& bitset, bool& is_empty)
{
if (wake_count == 0)
return 0; // should we assert instaed?
ScopedSpinLock lock(m_lock);
#ifdef FUTEXQUEUE_DEBUG
dbg() << "FutexQueue @ " << this << ": wake_n(" << wake_count << ")";
#endif
u32 did_wake = 0;
do_unblock([&](Thread::Blocker& b, void* data, bool& stop_iterating) {
ASSERT(data);
ASSERT(b.blocker_type() == Thread::Blocker::Type::Futex);
auto& blocker = static_cast<Thread::FutexBlocker&>(b);
#ifdef FUTEXQUEUE_DEBUG
dbg() << "FutexQueue @ " << this << ": wake_n unblocking " << *static_cast<Thread*>(data);
#endif
ASSERT(did_wake < wake_count);
if (bitset.has_value() ? blocker.unblock_bitset(bitset.value()) : blocker.unblock()) {
if (++did_wake >= wake_count)
stop_iterating = true;
return true;
}
return false;
});
is_empty = is_empty_locked();
return did_wake;
}
u32 FutexQueue::wake_all(bool& is_empty)
{
ScopedSpinLock lock(m_lock);
#ifdef FUTEXQUEUE_DEBUG
dbg() << "FutexQueue @ " << this << ": wake_all";
#endif
u32 did_wake = 0;
do_unblock([&](Thread::Blocker& b, void* data, bool&) {
ASSERT(data);
ASSERT(b.blocker_type() == Thread::Blocker::Type::Futex);
auto& blocker = static_cast<Thread::FutexBlocker&>(b);
#ifdef FUTEXQUEUE_DEBUG
dbg() << "FutexQueue @ " << this << ": wake_all unblocking " << *static_cast<Thread*>(data);
#endif
if (blocker.unblock(true)) {
did_wake++;
return true;
}
return false;
});
is_empty = is_empty_locked();
return did_wake;
}
}
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