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Kernel: Fix some issues related to fixes and block conditions

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Fix some problems with join blocks where the joining thread block
condition was added twice, which lead to a crash when trying to
unblock that condition a second time.

Deferred block condition evaluation by File objects were also not
properly keeping the File object alive, which lead to some random
crashes and corruption problems.

Other problems were caused by the fact that the Queued state didn't
handle signals/interruptions consistently. To solve these issues we
remove this state entirely, along with Thread::wait_on and change
the WaitQueue into a BlockCondition instead.

Also, deliver signals even if there isn't going to be a context switch
to another thread.

Fixes #4336 and #4330
This commit is contained in:
Tom 2020-12-07 21:29:41 -07:00 • committed by Andreas Kling
parent 0918d8b1f8
commit da5cc34ebb
22 changed files with 474 additions and 434 deletions
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28
Kernel/Scheduler.cpp
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@ -140,9 +140,7 @@ bool Scheduler::pick_next()
#ifdef SCHEDULER_RUNNABLE_DEBUG
dbg() << "Scheduler[" << Processor::current().id() << "]: Non-runnables:";
Scheduler::for_each_nonrunnable([&](Thread& thread) -> IterationDecision {
if (thread.state() == Thread::Queued)
dbg() << " " << String::format("%-12s", thread.state_string()) << " " << thread << " @ " << String::format("%w", thread.tss().cs) << ":" << String::format("%x", thread.tss().eip) << " Reason: " << (thread.wait_reason() ? thread.wait_reason() : "none");
else if (thread.state() == Thread::Dying)
if (thread.state() == Thread::Dying)
dbg() << " " << String::format("%-12s", thread.state_string()) << " " << thread << " @ " << String::format("%w", thread.tss().cs) << ":" << String::format("%x", thread.tss().eip) << " Finalizable: " << thread.is_finalizable();
else
dbg() << " " << String::format("%-12s", thread.state_string()) << " " << thread << " @ " << String::format("%w", thread.tss().cs) << ":" << String::format("%x", thread.tss().eip);
@ -324,14 +322,6 @@ bool Scheduler::context_switch(Thread* thread)
thread->did_schedule();
auto from_thread = Thread::current();
// Check if we have any signals we should deliver (even if we don't
// end up switching to another thread)
if (from_thread && from_thread->state() == Thread::Running && from_thread->pending_signals_for_state()) {
ScopedSpinLock lock(from_thread->get_lock());
from_thread->dispatch_one_pending_signal();
}
if (from_thread == thread)
return false;
@ -364,21 +354,31 @@ bool Scheduler::context_switch(Thread* thread)
// NOTE: from_thread at this point reflects the thread we were
// switched from, and thread reflects Thread::current()
enter_current(*from_thread);
enter_current(*from_thread, false);
ASSERT(thread == Thread::current());
return true;
}
void Scheduler::enter_current(Thread& prev_thread)
void Scheduler::enter_current(Thread& prev_thread, bool is_first)
{
ASSERT(g_scheduler_lock.is_locked());
ASSERT(g_scheduler_lock.own_lock());
prev_thread.set_active(false);
if (prev_thread.state() == Thread::Dying) {
// If the thread we switched from is marked as dying, then notify
// the finalizer. Note that as soon as we leave the scheduler lock
// the finalizer may free from_thread!
notify_finalizer();
} else if (!is_first) {
// Check if we have any signals we should deliver (even if we don't
// end up switching to another thread).
auto current_thread = Thread::current();
if (!current_thread->is_in_block()) {
ScopedSpinLock lock(current_thread->get_lock());
if (current_thread->state() == Thread::Running && current_thread->pending_signals_for_state()) {
current_thread->dispatch_one_pending_signal();
}
}
}
}