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Kernel: Fix a few Thread::block related races

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We need to have a Thread lock to protect threading related
operations, such as Thread::m_blocker which is used in
Thread::block.

Also, if a Thread::Blocker indicates that it should be
unblocking immediately, don't actually block the Thread
and instead return immediately in Thread::block.
This commit is contained in:
Tom 2020-08-02 16:59:01 -06:00 • committed by Andreas Kling
parent df3c8267d4
commit c813bb7355
7 changed files with 109 additions and 46 deletions
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34
Kernel/Thread.cpp
View file

@ -114,6 +114,7 @@ Thread::~Thread()
void Thread::unblock()
{
ASSERT(m_lock.own_lock());
m_blocker = nullptr;
if (Thread::current() == this) {
if (m_should_die)
@ -144,6 +145,7 @@ void Thread::set_should_die()
m_should_die = true;
if (is_blocked()) {
ScopedSpinLock lock(m_lock);
ASSERT(m_blocker != nullptr);
// We're blocked in the kernel.
m_blocker->set_interrupted_by_death();
@ -264,6 +266,7 @@ void Thread::finalize()
set_state(Thread::State::Dead);
if (m_joiner) {
ScopedSpinLock lock(m_joiner->m_lock);
ASSERT(m_joiner->m_joinee == this);
static_cast<JoinBlocker*>(m_joiner->m_blocker)->set_joinee_exit_value(m_exit_value);
static_cast<JoinBlocker*>(m_joiner->m_blocker)->set_interrupted_by_death();
@ -468,9 +471,11 @@ ShouldUnblockThread Thread::dispatch_signal(u8 signal)
set_state(m_stop_state);
m_stop_state = State::Invalid;
// make sure SemiPermanentBlocker is unblocked
if (m_state != Thread::Runnable && m_state != Thread::Running
&& m_blocker && m_blocker->is_reason_signal())
unblock();
if (m_state != Thread::Runnable && m_state != Thread::Running) {
ScopedSpinLock lock(m_lock);
if (m_blocker && m_blocker->is_reason_signal())
unblock();
}
}
else {
@ -482,6 +487,7 @@ ShouldUnblockThread Thread::dispatch_signal(u8 signal)
if (!thread_tracer->has_pending_signal(signal)) {
m_stop_signal = signal;
// make sure SemiPermanentBlocker is unblocked
ScopedSpinLock lock(m_lock);
if (m_blocker && m_blocker->is_reason_signal())
unblock();
set_state(Stopped);
@ -697,13 +703,15 @@ void Thread::set_state(State new_state)
m_stop_state = m_state;
}
auto previous_state = m_state;
m_state = new_state;
#ifdef THREAD_DEBUG
dbg() << "Set Thread " << *this << " state to " << state_string();
#endif
if (m_process->pid() != 0) {
Scheduler::update_state_for_thread(*this);
update_state_for_thread(previous_state);
ASSERT(g_scheduler_data->has_thread(*this));
}
if (m_state == Dying && this != Thread::current() && is_finalizable()) {
@ -713,6 +721,24 @@ void Thread::set_state(State new_state)
}
}
void Thread::update_state_for_thread(Thread::State previous_state)
{
ASSERT_INTERRUPTS_DISABLED();
ASSERT(g_scheduler_data);
ASSERT(g_scheduler_lock.own_lock());
auto& previous_list = g_scheduler_data->thread_list_for_state(previous_state);
auto& list = g_scheduler_data->thread_list_for_state(state());
if (&previous_list != &list) {
previous_list.remove(*this);
}
if (list.contains(*this))
return;
list.append(*this);
}
String Thread::backtrace()
{
return backtrace_impl();