ladybird/Kernel/WaitQueue.cpp
Tom c4176b0da1 Kernel: Fix Lock race causing infinite spinning between two threads
We need to account for how many shared lock instances the current
thread owns, so that we can properly release such references when
yielding execution.

We also need to release the process lock when donating.
2020-12-16 23:38:17 +01:00

118 lines
4.2 KiB
C++

/*
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* All rights reserved.
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#include <Kernel/Thread.h>
#include <Kernel/WaitQueue.h>
//#define WAITQUEUE_DEBUG
namespace Kernel {
bool WaitQueue::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::Queue);
if (m_wake_requested) {
m_wake_requested = false;
#ifdef WAITQUEUE_DEBUG
dbg() << "WaitQueue @ " << this << ": do not block thread " << *static_cast<Thread*>(data) << ", wake was pending";
#endif
return false;
}
#ifdef WAITQUEUE_DEBUG
dbg() << "WaitQueue @ " << this << ": should block thread " << *static_cast<Thread*>(data);
#endif
return true;
}
void WaitQueue::wake_one()
{
ScopedSpinLock lock(m_lock);
#ifdef WAITQUEUE_DEBUG
dbg() << "WaitQueue @ " << this << ": wake_one";
#endif
bool did_unblock_one = do_unblock_some([&](Thread::Blocker& b, void* data, bool& stop_iterating) {
ASSERT(data);
ASSERT(b.blocker_type() == Thread::Blocker::Type::Queue);
auto& blocker = static_cast<Thread::QueueBlocker&>(b);
#ifdef WAITQUEUE_DEBUG
dbg() << "WaitQueue @ " << this << ": wake_one unblocking " << *static_cast<Thread*>(data);
#endif
if (blocker.unblock()) {
stop_iterating = true;
return true;
}
return false;
});
m_wake_requested = !did_unblock_one;
}
void WaitQueue::wake_n(u32 wake_count)
{
if (wake_count == 0)
return; // should we assert instaed?
ScopedSpinLock lock(m_lock);
#ifdef WAITQUEUE_DEBUG
dbg() << "WaitQueue @ " << this << ": wake_n(" << wake_count << ")";
#endif
bool did_unblock_some = do_unblock_some([&](Thread::Blocker& b, void* data, bool& stop_iterating) {
ASSERT(data);
ASSERT(b.blocker_type() == Thread::Blocker::Type::Queue);
auto& blocker = static_cast<Thread::QueueBlocker&>(b);
#ifdef WAITQUEUE_DEBUG
dbg() << "WaitQueue @ " << this << ": wake_n unblocking " << *static_cast<Thread*>(data);
#endif
ASSERT(wake_count > 0);
if (blocker.unblock()) {
if (--wake_count == 0)
stop_iterating = true;
return true;
}
return false;
});
m_wake_requested = !did_unblock_some;
}
void WaitQueue::wake_all()
{
ScopedSpinLock lock(m_lock);
#ifdef WAITQUEUE_DEBUG
dbg() << "WaitQueue @ " << this << ": wake_all";
#endif
bool did_unblock_any = do_unblock_all([&](Thread::Blocker& b, void* data) {
ASSERT(data);
ASSERT(b.blocker_type() == Thread::Blocker::Type::Queue);
auto& blocker = static_cast<Thread::QueueBlocker&>(b);
#ifdef WAITQUEUE_DEBUG
dbg() << "WaitQueue @ " << this << ": wake_all unblocking " << *static_cast<Thread*>(data);
#endif
return blocker.unblock();
});
m_wake_requested = !did_unblock_any;
}
}