ladybird/Kernel/Scheduler.cpp
Andreas Kling cb5021419e Kernel: Move Thread::m_joinee_exit_value into the JoinBlocker
There's no need for this to be a permanent Thread member. Just use a
reference in the JoinBlocker instead.
2019-11-14 21:04:34 +01:00

614 lines
18 KiB
C++

#include <AK/TemporaryChange.h>
#include <Kernel/Arch/i386/PIT.h>
#include <Kernel/Devices/PCSpeaker.h>
#include <Kernel/FileSystem/FileDescription.h>
#include <Kernel/Process.h>
#include <Kernel/RTC.h>
#include <Kernel/Scheduler.h>
SchedulerData* g_scheduler_data;
void Scheduler::init_thread(Thread& thread)
{
g_scheduler_data->m_nonrunnable_threads.append(thread);
}
void Scheduler::update_state_for_thread(Thread& thread)
{
auto& list = g_scheduler_data->thread_list_for_state(thread.state());
if (list.contains(thread))
return;
list.append(thread);
}
//#define LOG_EVERY_CONTEXT_SWITCH
//#define SCHEDULER_DEBUG
//#define SCHEDULER_RUNNABLE_DEBUG
static u32 time_slice_for(ThreadPriority priority)
{
// One time slice unit == 1ms
switch (priority) {
case ThreadPriority::High:
return 50;
case ThreadPriority::Normal:
return 15;
case ThreadPriority::Low:
return 5;
case ThreadPriority::Idle:
return 1;
}
ASSERT_NOT_REACHED();
}
Thread* current;
Thread* g_last_fpu_thread;
Thread* g_finalizer;
static Process* s_colonel_process;
u64 g_uptime;
static u64 s_beep_timeout;
struct TaskRedirectionData {
u16 selector;
TSS32 tss;
};
static TaskRedirectionData s_redirection;
static bool s_active;
bool Scheduler::is_active()
{
return s_active;
}
void Scheduler::beep()
{
PCSpeaker::tone_on(440);
s_beep_timeout = g_uptime + 100;
}
Thread::JoinBlocker::JoinBlocker(Thread& joinee, void*& joinee_exit_value)
: m_joinee(joinee)
, m_joinee_exit_value(joinee_exit_value)
{
ASSERT(m_joinee.m_joiner == nullptr);
m_joinee.m_joiner = current;
current->m_joinee = &joinee;
}
bool Thread::JoinBlocker::should_unblock(Thread& joiner, time_t, long)
{
return !joiner.m_joinee;
}
Thread::FileDescriptionBlocker::FileDescriptionBlocker(const FileDescription& description)
: m_blocked_description(description)
{}
const FileDescription& Thread::FileDescriptionBlocker::blocked_description() const
{
return m_blocked_description;
}
Thread::AcceptBlocker::AcceptBlocker(const FileDescription& description)
: FileDescriptionBlocker(description)
{
}
bool Thread::AcceptBlocker::should_unblock(Thread&, time_t, long)
{
auto& socket = *blocked_description().socket();
return socket.can_accept();
}
Thread::ReceiveBlocker::ReceiveBlocker(const FileDescription& description)
: FileDescriptionBlocker(description)
{
}
bool Thread::ReceiveBlocker::should_unblock(Thread&, time_t now_sec, long now_usec)
{
auto& socket = *blocked_description().socket();
// FIXME: Block until the amount of data wanted is available.
bool timed_out = now_sec > socket.receive_deadline().tv_sec || (now_sec == socket.receive_deadline().tv_sec && now_usec >= socket.receive_deadline().tv_usec);
if (timed_out || blocked_description().can_read())
return true;
return false;
}
Thread::ConnectBlocker::ConnectBlocker(const FileDescription& description)
: FileDescriptionBlocker(description)
{
}
bool Thread::ConnectBlocker::should_unblock(Thread&, time_t, long)
{
auto& socket = *blocked_description().socket();
return socket.setup_state() == Socket::SetupState::Completed;
}
Thread::WriteBlocker::WriteBlocker(const FileDescription& description)
: FileDescriptionBlocker(description)
{
}
bool Thread::WriteBlocker::should_unblock(Thread&, time_t, long)
{
return blocked_description().can_write();
}
Thread::ReadBlocker::ReadBlocker(const FileDescription& description)
: FileDescriptionBlocker(description)
{
}
bool Thread::ReadBlocker::should_unblock(Thread&, time_t, long)
{
// FIXME: Block until the amount of data wanted is available.
return blocked_description().can_read();
}
Thread::ConditionBlocker::ConditionBlocker(const char* state_string, Function<bool()>&& condition)
: m_block_until_condition(move(condition))
, m_state_string(state_string)
{
ASSERT(m_block_until_condition);
}
bool Thread::ConditionBlocker::should_unblock(Thread&, time_t, long)
{
return m_block_until_condition();
}
Thread::SleepBlocker::SleepBlocker(u64 wakeup_time)
: m_wakeup_time(wakeup_time)
{
}
bool Thread::SleepBlocker::should_unblock(Thread&, time_t, long)
{
return m_wakeup_time <= g_uptime;
}
Thread::SelectBlocker::SelectBlocker(const timeval& tv, bool select_has_timeout, const FDVector& read_fds, const FDVector& write_fds, const FDVector& except_fds)
: m_select_timeout(tv)
, m_select_has_timeout(select_has_timeout)
, m_select_read_fds(read_fds)
, m_select_write_fds(write_fds)
, m_select_exceptional_fds(except_fds)
{
}
bool Thread::SelectBlocker::should_unblock(Thread& thread, time_t now_sec, long now_usec)
{
if (m_select_has_timeout) {
if (now_sec > m_select_timeout.tv_sec || (now_sec == m_select_timeout.tv_sec && now_usec >= m_select_timeout.tv_usec))
return true;
}
auto& process = thread.process();
for (int fd : m_select_read_fds) {
if (process.m_fds[fd].description->can_read())
return true;
}
for (int fd : m_select_write_fds) {
if (process.m_fds[fd].description->can_write())
return true;
}
return false;
}
Thread::WaitBlocker::WaitBlocker(int wait_options, pid_t& waitee_pid)
: m_wait_options(wait_options)
, m_waitee_pid(waitee_pid)
{
}
bool Thread::WaitBlocker::should_unblock(Thread& thread, time_t, long)
{
bool should_unblock = false;
if (m_waitee_pid != -1) {
auto* peer = Process::from_pid(m_waitee_pid);
if (!peer)
return true;
}
thread.process().for_each_child([&](Process& child) {
if (m_waitee_pid != -1 && m_waitee_pid != child.pid())
return IterationDecision::Continue;
bool child_exited = child.is_dead();
bool child_stopped = child.main_thread().state() == Thread::State::Stopped;
bool wait_finished = ((m_wait_options & WEXITED) && child_exited)
|| ((m_wait_options & WSTOPPED) && child_stopped);
if (!wait_finished)
return IterationDecision::Continue;
m_waitee_pid = child.pid();
should_unblock = true;
return IterationDecision::Break;
});
return should_unblock;
}
Thread::SemiPermanentBlocker::SemiPermanentBlocker(Reason reason)
: m_reason(reason)
{}
bool Thread::SemiPermanentBlocker::should_unblock(Thread&, time_t, long)
{
// someone else has to unblock us
return false;
}
// Called by the scheduler on threads that are blocked for some reason.
// Make a decision as to whether to unblock them or not.
void Thread::consider_unblock(time_t now_sec, long now_usec)
{
switch (state()) {
case Thread::Invalid:
case Thread::Runnable:
case Thread::Running:
case Thread::Dead:
case Thread::Stopped:
/* don't know, don't care */
return;
case Thread::Blocked:
ASSERT(m_blocker != nullptr);
if (m_blocker->should_unblock(*this, now_sec, now_usec))
unblock();
return;
case Thread::Skip1SchedulerPass:
set_state(Thread::Skip0SchedulerPasses);
return;
case Thread::Skip0SchedulerPasses:
set_state(Thread::Runnable);
return;
case Thread::Dying:
ASSERT(g_finalizer);
if (g_finalizer->is_blocked())
g_finalizer->unblock();
return;
}
}
bool Scheduler::pick_next()
{
ASSERT_INTERRUPTS_DISABLED();
ASSERT(!s_active);
TemporaryChange<bool> change(s_active, true);
ASSERT(s_active);
if (!current) {
// XXX: The first ever context_switch() goes to the idle process.
// This to setup a reliable place we can return to.
return context_switch(s_colonel_process->main_thread());
}
struct timeval now;
kgettimeofday(now);
auto now_sec = now.tv_sec;
auto now_usec = now.tv_usec;
// Check and unblock threads whose wait conditions have been met.
Scheduler::for_each_nonrunnable([&](Thread& thread) {
thread.consider_unblock(now_sec, now_usec);
return IterationDecision::Continue;
});
Process::for_each([&](Process& process) {
if (process.is_dead()) {
if (current != &process.main_thread() && (!process.ppid() || !Process::from_pid(process.ppid()))) {
auto name = process.name();
auto pid = process.pid();
auto exit_status = Process::reap(process);
dbgprintf("reaped unparented process %s(%u), exit status: %u\n", name.characters(), pid, exit_status);
}
return IterationDecision::Continue;
}
if (process.m_alarm_deadline && g_uptime > process.m_alarm_deadline) {
process.m_alarm_deadline = 0;
process.send_signal(SIGALRM, nullptr);
}
return IterationDecision::Continue;
});
// Dispatch any pending signals.
// FIXME: Do we really need this to be a separate pass over the process list?
Thread::for_each_living([](Thread& thread) -> IterationDecision {
if (!thread.has_unmasked_pending_signals())
return IterationDecision::Continue;
// FIXME: It would be nice if the Scheduler didn't have to worry about who is "current"
// For now, avoid dispatching signals to "current" and do it in a scheduling pass
// while some other process is interrupted. Otherwise a mess will be made.
if (&thread == current)
return IterationDecision::Continue;
// We know how to interrupt blocked processes, but if they are just executing
// at some random point in the kernel, let them continue. They'll be in userspace
// sooner or later and we can deliver the signal then.
// FIXME: Maybe we could check when returning from a syscall if there's a pending
// signal and dispatch it then and there? Would that be doable without the
// syscall effectively being "interrupted" despite having completed?
if (thread.in_kernel() && !thread.is_blocked() && !thread.is_stopped())
return IterationDecision::Continue;
// NOTE: dispatch_one_pending_signal() may unblock the process.
bool was_blocked = thread.is_blocked();
if (thread.dispatch_one_pending_signal() == ShouldUnblockThread::No)
return IterationDecision::Continue;
if (was_blocked) {
dbgprintf("Unblock %s(%u) due to signal\n", thread.process().name().characters(), thread.pid());
ASSERT(thread.m_blocker != nullptr);
thread.m_blocker->set_interrupted_by_signal();
thread.unblock();
}
return IterationDecision::Continue;
});
#ifdef SCHEDULER_RUNNABLE_DEBUG
dbgprintf("Non-runnables:\n");
Scheduler::for_each_nonrunnable([](Thread& thread) -> IterationDecision {
auto& process = thread.process();
dbgprintf("[K%x] %-12s %s(%u:%u) @ %w:%x\n", &process, thread.state_string(), process.name().characters(), process.pid(), thread.tid(), thread.tss().cs, thread.tss().eip);
return IterationDecision::Continue;
});
dbgprintf("Runnables:\n");
Scheduler::for_each_runnable([](Thread& thread) -> IterationDecision {
auto& process = thread.process();
dbgprintf("[K%x] %-12s %s(%u:%u) @ %w:%x\n", &process, thread.state_string(), process.name().characters(), process.pid(), thread.tid(), thread.tss().cs, thread.tss().eip);
return IterationDecision::Continue;
});
#endif
auto& runnable_list = g_scheduler_data->m_runnable_threads;
if (runnable_list.is_empty())
return context_switch(s_colonel_process->main_thread());
auto* previous_head = runnable_list.first();
for (;;) {
// Move head to tail.
runnable_list.append(*runnable_list.first());
auto* thread = runnable_list.first();
if (!thread->process().is_being_inspected() && (thread->state() == Thread::Runnable || thread->state() == Thread::Running)) {
#ifdef SCHEDULER_DEBUG
dbgprintf("switch to %s(%u:%u) @ %w:%x\n", thread->process().name().characters(), thread->process().pid(), thread->tid(), thread->tss().cs, thread->tss().eip);
#endif
return context_switch(*thread);
}
if (thread == previous_head) {
// Back at process_head, nothing wants to run. Send in the colonel!
return context_switch(s_colonel_process->main_thread());
}
}
}
bool Scheduler::donate_to(Thread* beneficiary, const char* reason)
{
InterruptDisabler disabler;
if (!Thread::is_thread(beneficiary))
return false;
(void)reason;
unsigned ticks_left = current->ticks_left();
if (!beneficiary || beneficiary->state() != Thread::Runnable || ticks_left <= 1)
return yield();
unsigned ticks_to_donate = min(ticks_left - 1, time_slice_for(beneficiary->priority()));
#ifdef SCHEDULER_DEBUG
dbgprintf("%s(%u:%u) donating %u ticks to %s(%u:%u), reason=%s\n", current->process().name().characters(), current->pid(), current->tid(), ticks_to_donate, beneficiary->process().name().characters(), beneficiary->pid(), beneficiary->tid(), reason);
#endif
context_switch(*beneficiary);
beneficiary->set_ticks_left(ticks_to_donate);
switch_now();
return false;
}
bool Scheduler::yield()
{
InterruptDisabler disabler;
ASSERT(current);
// dbgprintf("%s(%u:%u) yield()\n", current->process().name().characters(), current->pid(), current->tid());
if (!pick_next())
return false;
// dbgprintf("yield() jumping to new process: sel=%x, %s(%u:%u)\n", current->far_ptr().selector, current->process().name().characters(), current->pid(), current->tid());
switch_now();
return true;
}
void Scheduler::pick_next_and_switch_now()
{
bool someone_wants_to_run = pick_next();
ASSERT(someone_wants_to_run);
switch_now();
}
void Scheduler::switch_now()
{
Descriptor& descriptor = get_gdt_entry(current->selector());
descriptor.type = 9;
flush_gdt();
asm("sti\n"
"ljmp *(%%eax)\n" ::"a"(&current->far_ptr()));
}
bool Scheduler::context_switch(Thread& thread)
{
thread.set_ticks_left(time_slice_for(thread.priority()));
thread.did_schedule();
if (current == &thread)
return false;
if (current) {
// If the last process hasn't blocked (still marked as running),
// mark it as runnable for the next round.
if (current->state() == Thread::Running)
current->set_state(Thread::Runnable);
#ifdef LOG_EVERY_CONTEXT_SWITCH
dbgprintf("Scheduler: %s(%u:%u) -> %s(%u:%u) %w:%x\n",
current->process().name().characters(), current->process().pid(), current->tid(),
thread.process().name().characters(), thread.process().pid(), thread.tid(),
thread.tss().cs, thread.tss().eip);
#endif
}
current = &thread;
thread.set_state(Thread::Running);
if (!thread.selector()) {
thread.set_selector(gdt_alloc_entry());
auto& descriptor = get_gdt_entry(thread.selector());
descriptor.set_base(&thread.tss());
descriptor.set_limit(0xffff);
descriptor.dpl = 0;
descriptor.segment_present = 1;
descriptor.granularity = 1;
descriptor.zero = 0;
descriptor.operation_size = 1;
descriptor.descriptor_type = 0;
}
if (!thread.thread_specific_data().is_null()) {
auto& descriptor = thread_specific_descriptor();
descriptor.set_base(thread.thread_specific_data().as_ptr());
descriptor.set_limit(sizeof(ThreadSpecificData*));
}
auto& descriptor = get_gdt_entry(thread.selector());
descriptor.type = 11; // Busy TSS
flush_gdt();
return true;
}
static void initialize_redirection()
{
auto& descriptor = get_gdt_entry(s_redirection.selector);
descriptor.set_base(&s_redirection.tss);
descriptor.set_limit(0xffff);
descriptor.dpl = 0;
descriptor.segment_present = 1;
descriptor.granularity = 1;
descriptor.zero = 0;
descriptor.operation_size = 1;
descriptor.descriptor_type = 0;
descriptor.type = 9;
flush_gdt();
}
void Scheduler::prepare_for_iret_to_new_process()
{
auto& descriptor = get_gdt_entry(s_redirection.selector);
descriptor.type = 9;
s_redirection.tss.backlink = current->selector();
load_task_register(s_redirection.selector);
}
void Scheduler::prepare_to_modify_tss(Thread& thread)
{
// This ensures that a currently running process modifying its own TSS
// in order to yield() and end up somewhere else doesn't just end up
// right after the yield().
if (current == &thread)
load_task_register(s_redirection.selector);
}
Process* Scheduler::colonel()
{
return s_colonel_process;
}
void Scheduler::initialize()
{
g_scheduler_data = new SchedulerData;
s_redirection.selector = gdt_alloc_entry();
initialize_redirection();
s_colonel_process = Process::create_kernel_process("colonel", nullptr);
// Make sure the colonel uses a smallish time slice.
s_colonel_process->main_thread().set_priority(ThreadPriority::Idle);
load_task_register(s_redirection.selector);
}
void Scheduler::timer_tick(RegisterDump& regs)
{
if (!current)
return;
++g_uptime;
if (s_beep_timeout && g_uptime > s_beep_timeout) {
PCSpeaker::tone_off();
s_beep_timeout = 0;
}
if (current->tick())
return;
auto& outgoing_tss = current->tss();
if (!pick_next())
return;
outgoing_tss.gs = regs.gs;
outgoing_tss.fs = regs.fs;
outgoing_tss.es = regs.es;
outgoing_tss.ds = regs.ds;
outgoing_tss.edi = regs.edi;
outgoing_tss.esi = regs.esi;
outgoing_tss.ebp = regs.ebp;
outgoing_tss.ebx = regs.ebx;
outgoing_tss.edx = regs.edx;
outgoing_tss.ecx = regs.ecx;
outgoing_tss.eax = regs.eax;
outgoing_tss.eip = regs.eip;
outgoing_tss.cs = regs.cs;
outgoing_tss.eflags = regs.eflags;
// Compute process stack pointer.
// Add 16 for CS, EIP, EFLAGS, exception code (interrupt mechanic)
outgoing_tss.esp = regs.esp + 16;
outgoing_tss.ss = regs.ss;
if ((outgoing_tss.cs & 3) != 0) {
outgoing_tss.ss = regs.ss_if_crossRing;
outgoing_tss.esp = regs.esp_if_crossRing;
}
prepare_for_iret_to_new_process();
// Set the NT (nested task) flag.
asm(
"pushf\n"
"orl $0x00004000, (%esp)\n"
"popf\n");
}
static bool s_should_stop_idling = false;
void Scheduler::stop_idling()
{
if (current != &s_colonel_process->main_thread())
return;
s_should_stop_idling = true;
}
void Scheduler::idle_loop()
{
for (;;) {
asm("hlt");
if (s_should_stop_idling) {
s_should_stop_idling = false;
yield();
}
}
}