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Kernel: Stop swallowing thread unblocks while process is stopped

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This easily led to kernel deadlocks if the stopped thread held an
important global mutex (like the disk cache lock) while blocking.
Resolve this by ensuring stopped threads have a chance to return to the
userland boundary before actually stopping.
This commit is contained in:
Idan Horowitz 2024-02-09 21:13:41 +02:00 • committed by Andreas Kling
parent 458e990b7b
commit e38ccebfc8
4 changed files with 24 additions and 23 deletions
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14
Kernel/Tasks/Thread.cpp
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@ -314,8 +314,8 @@ void Thread::unblock_from_blocker(Blocker& blocker)
SpinlockLocker block_lock(m_block_lock);
if (m_blocker != &blocker)
return;
if (!should_be_stopped() && !is_stopped())
unblock();
VERIFY(!is_stopped());
unblock();
};
if (Processor::current_in_irq() != 0) {
Processor::deferred_call_queue([do_unblock = move(do_unblock), self = try_make_weak_ptr().release_value_but_fixme_should_propagate_errors()]() {
@ -1273,14 +1273,8 @@ void Thread::set_state(State new_state, u8 stop_signal)
m_stop_state = previous_state != Thread::State::Running ? previous_state : Thread::State::Runnable;
auto& process = this->process();
if (!process.set_stopped(true)) {
process.for_each_thread([&](auto& thread) {
if (&thread == this)
return;
if (thread.is_stopped())
return;
dbgln_if(THREAD_DEBUG, "Stopping peer thread {}", thread);
thread.set_state(Thread::State::Stopped, stop_signal);
});
// Note that we don't explicitly stop peer threads, we let them stop on their own the next time they
// enter/exit a syscall, or once their current time slice runs out.
process.unblock_waiters(Thread::WaitBlocker::UnblockFlags::Stopped, stop_signal);
// Tell the parent process (if any) about this change.
if (auto parent = Process::from_pid_ignoring_jails(process.ppid())) {