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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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49
Kernel/Scheduler.cpp
View file

@ -62,19 +62,6 @@ void Scheduler::init_thread(Thread& thread)
g_scheduler_data->m_nonrunnable_threads.append(thread);
}
void Scheduler::update_state_for_thread(Thread& thread)
{
ASSERT_INTERRUPTS_DISABLED();
ASSERT(g_scheduler_data);
ASSERT(g_scheduler_lock.own_lock());
auto& list = g_scheduler_data->thread_list_for_state(thread.state());
if (list.contains(thread))
return;
list.append(thread);
}
static u32 time_slice_for(const Thread& thread)
{
// One time slice unit == 1ms
@ -104,7 +91,7 @@ Thread::JoinBlocker::JoinBlocker(Thread& joinee, void*& joinee_exit_value)
current_thread->m_joinee = &joinee;
}
bool Thread::JoinBlocker::should_unblock(Thread& joiner, time_t, long)
bool Thread::JoinBlocker::should_unblock(Thread& joiner)
{
return !joiner.m_joinee;
}
@ -124,7 +111,7 @@ Thread::AcceptBlocker::AcceptBlocker(const FileDescription& description)
{
}
bool Thread::AcceptBlocker::should_unblock(Thread&, time_t, long)
bool Thread::AcceptBlocker::should_unblock(Thread&)
{
auto& socket = *blocked_description().socket();
return socket.can_accept();
@ -135,7 +122,7 @@ Thread::ConnectBlocker::ConnectBlocker(const FileDescription& description)
{
}
bool Thread::ConnectBlocker::should_unblock(Thread&, time_t, long)
bool Thread::ConnectBlocker::should_unblock(Thread&)
{
auto& socket = *blocked_description().socket();
return socket.setup_state() == Socket::SetupState::Completed;
@ -157,12 +144,17 @@ Thread::WriteBlocker::WriteBlocker(const FileDescription& description)
}
}
bool Thread::WriteBlocker::should_unblock(Thread&, time_t now_sec, long now_usec)
bool Thread::WriteBlocker::should_unblock(Thread& thread, time_t now_sec, long now_usec)
{
if (m_deadline.has_value()) {
bool timed_out = now_sec > m_deadline.value().tv_sec || (now_sec == m_deadline.value().tv_sec && now_usec >= m_deadline.value().tv_usec);
return timed_out || blocked_description().can_write();
}
return should_unblock(thread);
}
bool Thread::WriteBlocker::should_unblock(Thread&)
{
return blocked_description().can_write();
}
@ -182,12 +174,17 @@ Thread::ReadBlocker::ReadBlocker(const FileDescription& description)
}
}
bool Thread::ReadBlocker::should_unblock(Thread&, time_t now_sec, long now_usec)
bool Thread::ReadBlocker::should_unblock(Thread& thread, time_t now_sec, long now_usec)
{
if (m_deadline.has_value()) {
bool timed_out = now_sec > m_deadline.value().tv_sec || (now_sec == m_deadline.value().tv_sec && now_usec >= m_deadline.value().tv_usec);
return timed_out || blocked_description().can_read();
}
return should_unblock(thread);
}
bool Thread::ReadBlocker::should_unblock(Thread&)
{
return blocked_description().can_read();
}
@ -198,7 +195,7 @@ Thread::ConditionBlocker::ConditionBlocker(const char* state_string, Function<bo
ASSERT(m_block_until_condition);
}
bool Thread::ConditionBlocker::should_unblock(Thread&, time_t, long)
bool Thread::ConditionBlocker::should_unblock(Thread&)
{
return m_block_until_condition();
}
@ -208,7 +205,7 @@ Thread::SleepBlocker::SleepBlocker(u64 wakeup_time)
{
}
bool Thread::SleepBlocker::should_unblock(Thread&, time_t, long)
bool Thread::SleepBlocker::should_unblock(Thread&)
{
return m_wakeup_time <= g_uptime;
}
@ -228,7 +225,11 @@ bool Thread::SelectBlocker::should_unblock(Thread& thread, time_t now_sec, long
if (now_sec > m_select_timeout.tv_sec || (now_sec == m_select_timeout.tv_sec && now_usec * 1000 >= m_select_timeout.tv_nsec))
return true;
}
return should_unblock(thread);
}
bool Thread::SelectBlocker::should_unblock(Thread& thread)
{
auto& process = thread.process();
for (int fd : m_select_read_fds) {
if (!process.m_fds[fd])
@ -252,7 +253,7 @@ Thread::WaitBlocker::WaitBlocker(int wait_options, pid_t& waitee_pid)
{
}
bool Thread::WaitBlocker::should_unblock(Thread& thread, time_t, long)
bool Thread::WaitBlocker::should_unblock(Thread& thread)
{
bool should_unblock = m_wait_options & WNOHANG;
if (m_waitee_pid != -1) {
@ -294,7 +295,7 @@ Thread::SemiPermanentBlocker::SemiPermanentBlocker(Reason reason)
{
}
bool Thread::SemiPermanentBlocker::should_unblock(Thread&, time_t, long)
bool Thread::SemiPermanentBlocker::should_unblock(Thread&)
{
// someone else has to unblock us
return false;
@ -304,6 +305,7 @@ bool Thread::SemiPermanentBlocker::should_unblock(Thread&, time_t, long)
// Make a decision as to whether to unblock them or not.
void Thread::consider_unblock(time_t now_sec, long now_usec)
{
ScopedSpinLock lock(m_lock);
switch (state()) {
case Thread::Invalid:
case Thread::Runnable:
@ -403,6 +405,7 @@ bool Scheduler::pick_next()
// Dispatch any pending signals.
Thread::for_each_living([&](Thread& thread) -> IterationDecision {
ScopedSpinLock lock(thread.get_lock());
if (!thread.has_unmasked_pending_signals())
return IterationDecision::Continue;
// NOTE: dispatch_one_pending_signal() may unblock the process.
@ -427,6 +430,8 @@ bool Scheduler::pick_next()
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)
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);
return IterationDecision::Continue;
});