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https://github.com/RGBCube/serenity
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cbaa3465a8
We should consider whether the selected Thread is within the same jail or not. Therefore let's make it clear to callers with jail semantics if a called method checks if the desired Thread object is within the same jail. As for Thread::for_each_* methods, currently nothing in the kernel codebase needs iteration with consideration for jails, so the old Thread::for_each* were simply renamed to include "ignoring_jails" suffix in their names.
561 lines
20 KiB
C++
561 lines
20 KiB
C++
/*
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* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/BuiltinWrappers.h>
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#include <AK/ScopeGuard.h>
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#include <AK/Singleton.h>
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#include <AK/Time.h>
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#include <Kernel/Arch/TrapFrame.h>
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#include <Kernel/Debug.h>
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#include <Kernel/Interrupts/InterruptDisabler.h>
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#include <Kernel/Library/Panic.h>
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#include <Kernel/Sections.h>
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#include <Kernel/Tasks/PerformanceManager.h>
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#include <Kernel/Tasks/Process.h>
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#include <Kernel/Tasks/Scheduler.h>
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#include <Kernel/Time/TimeManagement.h>
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#include <Kernel/kstdio.h>
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namespace Kernel {
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RecursiveSpinlock<LockRank::None> g_scheduler_lock {};
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static u32 time_slice_for(Thread const& thread)
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{
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// One time slice unit == 4ms (assuming 250 ticks/second)
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if (thread.is_idle_thread())
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return 1;
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return 2;
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}
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READONLY_AFTER_INIT Thread* g_finalizer;
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READONLY_AFTER_INIT WaitQueue* g_finalizer_wait_queue;
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Atomic<bool> g_finalizer_has_work { false };
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READONLY_AFTER_INIT static Process* s_colonel_process;
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struct ThreadReadyQueue {
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IntrusiveList<&Thread::m_ready_queue_node> thread_list;
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};
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struct ThreadReadyQueues {
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u32 mask {};
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static constexpr size_t count = sizeof(mask) * 8;
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Array<ThreadReadyQueue, count> queues;
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};
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static Singleton<SpinlockProtected<ThreadReadyQueues, LockRank::None>> g_ready_queues;
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static SpinlockProtected<TotalTimeScheduled, LockRank::None> g_total_time_scheduled {};
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static void dump_thread_list(bool = false);
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static inline u32 thread_priority_to_priority_index(u32 thread_priority)
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{
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// Converts the priority in the range of THREAD_PRIORITY_MIN...THREAD_PRIORITY_MAX
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// to a index into g_ready_queues where 0 is the highest priority bucket
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VERIFY(thread_priority >= THREAD_PRIORITY_MIN && thread_priority <= THREAD_PRIORITY_MAX);
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constexpr u32 thread_priority_count = THREAD_PRIORITY_MAX - THREAD_PRIORITY_MIN + 1;
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static_assert(thread_priority_count > 0);
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auto priority_bucket = ((thread_priority_count - (thread_priority - THREAD_PRIORITY_MIN)) / thread_priority_count) * (ThreadReadyQueues::count - 1);
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VERIFY(priority_bucket < ThreadReadyQueues::count);
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return priority_bucket;
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}
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Thread& Scheduler::pull_next_runnable_thread()
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{
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auto affinity_mask = 1u << Processor::current_id();
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return g_ready_queues->with([&](auto& ready_queues) -> Thread& {
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auto priority_mask = ready_queues.mask;
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while (priority_mask != 0) {
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auto priority = bit_scan_forward(priority_mask);
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VERIFY(priority > 0);
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auto& ready_queue = ready_queues.queues[--priority];
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for (auto& thread : ready_queue.thread_list) {
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VERIFY(thread.m_runnable_priority == (int)priority);
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if (thread.is_active())
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continue;
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if (!(thread.affinity() & affinity_mask))
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continue;
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thread.m_runnable_priority = -1;
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ready_queue.thread_list.remove(thread);
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if (ready_queue.thread_list.is_empty())
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ready_queues.mask &= ~(1u << priority);
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// Mark it as active because we are using this thread. This is similar
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// to comparing it with Processor::current_thread, but when there are
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// multiple processors there's no easy way to check whether the thread
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// is actually still needed. This prevents accidental finalization when
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// a thread is no longer in Running state, but running on another core.
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// We need to mark it active here so that this thread won't be
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// scheduled on another core if it were to be queued before actually
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// switching to it.
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// FIXME: Figure out a better way maybe?
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thread.set_active(true);
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return thread;
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}
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priority_mask &= ~(1u << priority);
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}
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auto* idle_thread = Processor::idle_thread();
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idle_thread->set_active(true);
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return *idle_thread;
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});
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}
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Thread* Scheduler::peek_next_runnable_thread()
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{
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auto affinity_mask = 1u << Processor::current_id();
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return g_ready_queues->with([&](auto& ready_queues) -> Thread* {
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auto priority_mask = ready_queues.mask;
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while (priority_mask != 0) {
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auto priority = bit_scan_forward(priority_mask);
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VERIFY(priority > 0);
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auto& ready_queue = ready_queues.queues[--priority];
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for (auto& thread : ready_queue.thread_list) {
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VERIFY(thread.m_runnable_priority == (int)priority);
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if (thread.is_active())
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continue;
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if (!(thread.affinity() & affinity_mask))
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continue;
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return &thread;
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}
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priority_mask &= ~(1u << priority);
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}
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// Unlike in pull_next_runnable_thread() we don't want to fall back to
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// the idle thread. We just want to see if we have any other thread ready
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// to be scheduled.
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return nullptr;
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});
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}
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bool Scheduler::dequeue_runnable_thread(Thread& thread, bool check_affinity)
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{
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if (thread.is_idle_thread())
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return true;
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return g_ready_queues->with([&](auto& ready_queues) {
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auto priority = thread.m_runnable_priority;
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if (priority < 0) {
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VERIFY(!thread.m_ready_queue_node.is_in_list());
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return false;
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}
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if (check_affinity && !(thread.affinity() & (1 << Processor::current_id())))
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return false;
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VERIFY(ready_queues.mask & (1u << priority));
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auto& ready_queue = ready_queues.queues[priority];
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thread.m_runnable_priority = -1;
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ready_queue.thread_list.remove(thread);
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if (ready_queue.thread_list.is_empty())
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ready_queues.mask &= ~(1u << priority);
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return true;
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});
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}
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void Scheduler::enqueue_runnable_thread(Thread& thread)
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{
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VERIFY(g_scheduler_lock.is_locked_by_current_processor());
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if (thread.is_idle_thread())
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return;
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auto priority = thread_priority_to_priority_index(thread.priority());
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g_ready_queues->with([&](auto& ready_queues) {
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VERIFY(thread.m_runnable_priority < 0);
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thread.m_runnable_priority = (int)priority;
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VERIFY(!thread.m_ready_queue_node.is_in_list());
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auto& ready_queue = ready_queues.queues[priority];
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bool was_empty = ready_queue.thread_list.is_empty();
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ready_queue.thread_list.append(thread);
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if (was_empty)
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ready_queues.mask |= (1u << priority);
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});
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}
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UNMAP_AFTER_INIT void Scheduler::start()
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{
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VERIFY_INTERRUPTS_DISABLED();
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// We need to acquire our scheduler lock, which will be released
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// by the idle thread once control transferred there
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g_scheduler_lock.lock();
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auto& processor = Processor::current();
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VERIFY(processor.is_initialized());
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auto& idle_thread = *Processor::idle_thread();
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VERIFY(processor.current_thread() == &idle_thread);
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idle_thread.set_ticks_left(time_slice_for(idle_thread));
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idle_thread.did_schedule();
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idle_thread.set_initialized(true);
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processor.init_context(idle_thread, false);
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idle_thread.set_state(Thread::State::Running);
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VERIFY(idle_thread.affinity() == (1u << processor.id()));
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processor.initialize_context_switching(idle_thread);
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VERIFY_NOT_REACHED();
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}
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void Scheduler::pick_next()
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{
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VERIFY_INTERRUPTS_DISABLED();
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// Set the in_scheduler flag before acquiring the spinlock. This
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// prevents a recursive call into Scheduler::invoke_async upon
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// leaving the scheduler lock.
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ScopedCritical critical;
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Processor::set_current_in_scheduler(true);
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ScopeGuard guard(
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[]() {
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// We may be on a different processor after we got switched
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// back to this thread!
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VERIFY(Processor::current_in_scheduler());
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Processor::set_current_in_scheduler(false);
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});
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SpinlockLocker lock(g_scheduler_lock);
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if constexpr (SCHEDULER_RUNNABLE_DEBUG) {
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dump_thread_list();
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}
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auto& thread_to_schedule = pull_next_runnable_thread();
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if constexpr (SCHEDULER_DEBUG) {
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dbgln("Scheduler[{}]: Switch to {} @ {:p}",
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Processor::current_id(),
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thread_to_schedule,
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thread_to_schedule.regs().ip());
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}
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// We need to leave our first critical section before switching context,
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// but since we're still holding the scheduler lock we're still in a critical section
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critical.leave();
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thread_to_schedule.set_ticks_left(time_slice_for(thread_to_schedule));
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context_switch(&thread_to_schedule);
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}
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void Scheduler::yield()
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{
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InterruptDisabler disabler;
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auto const* current_thread = Thread::current();
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dbgln_if(SCHEDULER_DEBUG, "Scheduler[{}]: yielding thread {} in_irq={}", Processor::current_id(), *current_thread, Processor::current_in_irq());
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VERIFY(current_thread != nullptr);
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if (Processor::current_in_irq() || Processor::in_critical()) {
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// If we're handling an IRQ we can't switch context, or we're in
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// a critical section where we don't want to switch contexts, then
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// delay until exiting the trap or critical section
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Processor::current().invoke_scheduler_async();
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return;
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}
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Scheduler::pick_next();
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}
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void Scheduler::context_switch(Thread* thread)
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{
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thread->did_schedule();
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auto* from_thread = Thread::current();
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VERIFY(from_thread);
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if (from_thread == thread)
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return;
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// If the last process hasn't blocked (still marked as running),
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// mark it as runnable for the next round.
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if (from_thread->state() == Thread::State::Running)
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from_thread->set_state(Thread::State::Runnable);
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#ifdef LOG_EVERY_CONTEXT_SWITCH
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auto const msg = "Scheduler[{}]: {} -> {} [prio={}] {:p}";
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dbgln(msg,
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Processor::current_id(), from_thread->tid().value(),
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thread->tid().value(), thread->priority(), thread->regs().ip());
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#endif
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auto& proc = Processor::current();
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if (!thread->is_initialized()) {
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proc.init_context(*thread, false);
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thread->set_initialized(true);
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}
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thread->set_state(Thread::State::Running);
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PerformanceManager::add_context_switch_perf_event(*from_thread, *thread);
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proc.switch_context(from_thread, thread);
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// NOTE: from_thread at this point reflects the thread we were
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// switched from, and thread reflects Thread::current()
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enter_current(*from_thread);
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VERIFY(thread == Thread::current());
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{
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SpinlockLocker lock(thread->get_lock());
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thread->dispatch_one_pending_signal();
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}
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}
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void Scheduler::enter_current(Thread& prev_thread)
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{
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VERIFY(g_scheduler_lock.is_locked_by_current_processor());
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// We already recorded the scheduled time when entering the trap, so this merely accounts for the kernel time since then
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auto scheduler_time = TimeManagement::scheduler_current_time();
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prev_thread.update_time_scheduled(scheduler_time, true, true);
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auto* current_thread = Thread::current();
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current_thread->update_time_scheduled(scheduler_time, true, false);
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// NOTE: When doing an exec(), we will context switch from and to the same thread!
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// In that case, we must not mark the previous thread as inactive.
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if (&prev_thread != current_thread)
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prev_thread.set_active(false);
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if (prev_thread.state() == Thread::State::Dying) {
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// If the thread we switched from is marked as dying, then notify
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// the finalizer. Note that as soon as we leave the scheduler lock
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// the finalizer may free from_thread!
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notify_finalizer();
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}
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}
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void Scheduler::leave_on_first_switch(InterruptsState previous_interrupts_state)
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{
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// This is called when a thread is switched into for the first time.
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// At this point, enter_current has already be called, but because
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// Scheduler::context_switch is not in the call stack we need to
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// clean up and release locks manually here
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g_scheduler_lock.unlock(previous_interrupts_state);
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VERIFY(Processor::current_in_scheduler());
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Processor::set_current_in_scheduler(false);
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}
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void Scheduler::prepare_after_exec()
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{
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// This is called after exec() when doing a context "switch" into
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// the new process. This is called from Processor::assume_context
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VERIFY(g_scheduler_lock.is_locked_by_current_processor());
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VERIFY(!Processor::current_in_scheduler());
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Processor::set_current_in_scheduler(true);
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}
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void Scheduler::prepare_for_idle_loop()
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{
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// This is called when the CPU finished setting up the idle loop
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// and is about to run it. We need to acquire the scheduler lock
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VERIFY(!g_scheduler_lock.is_locked_by_current_processor());
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g_scheduler_lock.lock();
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VERIFY(!Processor::current_in_scheduler());
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Processor::set_current_in_scheduler(true);
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}
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Process* Scheduler::colonel()
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{
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VERIFY(s_colonel_process);
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return s_colonel_process;
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}
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UNMAP_AFTER_INIT void Scheduler::initialize()
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{
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VERIFY(Processor::is_initialized()); // sanity check
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VERIFY(TimeManagement::is_initialized());
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g_finalizer_wait_queue = new WaitQueue;
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g_finalizer_has_work.store(false, AK::MemoryOrder::memory_order_release);
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auto [colonel_process, idle_thread] = MUST(Process::create_kernel_process("colonel"sv, idle_loop, nullptr, 1, Process::RegisterProcess::No));
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s_colonel_process = &colonel_process.leak_ref();
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idle_thread->set_priority(THREAD_PRIORITY_MIN);
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idle_thread->set_name("Idle Task #0"sv);
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set_idle_thread(idle_thread);
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}
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UNMAP_AFTER_INIT void Scheduler::set_idle_thread(Thread* idle_thread)
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{
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idle_thread->set_idle_thread();
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Processor::current().set_idle_thread(*idle_thread);
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Processor::set_current_thread(*idle_thread);
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}
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UNMAP_AFTER_INIT Thread* Scheduler::create_ap_idle_thread(u32 cpu)
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{
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VERIFY(cpu != 0);
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// This function is called on the bsp, but creates an idle thread for another AP
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VERIFY(Processor::is_bootstrap_processor());
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VERIFY(s_colonel_process);
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Thread* idle_thread = MUST(s_colonel_process->create_kernel_thread(idle_loop, nullptr, THREAD_PRIORITY_MIN, MUST(KString::formatted("idle thread #{}", cpu))->view(), 1 << cpu, false));
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VERIFY(idle_thread);
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return idle_thread;
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}
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void Scheduler::add_time_scheduled(u64 time_to_add, bool is_kernel)
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{
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g_total_time_scheduled.with([&](auto& total_time_scheduled) {
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total_time_scheduled.total += time_to_add;
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if (is_kernel)
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total_time_scheduled.total_kernel += time_to_add;
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});
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}
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void Scheduler::timer_tick(RegisterState const& regs)
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{
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VERIFY_INTERRUPTS_DISABLED();
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VERIFY(Processor::current_in_irq());
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auto* current_thread = Processor::current_thread();
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if (!current_thread)
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return;
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// Sanity checks
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VERIFY(current_thread->current_trap());
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VERIFY(current_thread->current_trap()->regs == ®s);
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if (current_thread->process().is_kernel_process()) {
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// Because the previous mode when entering/exiting kernel threads never changes
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// we never update the time scheduled. So we need to update it manually on the
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// timer interrupt
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current_thread->update_time_scheduled(TimeManagement::scheduler_current_time(), true, false);
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}
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if (current_thread->previous_mode() == ExecutionMode::User && current_thread->should_die() && !current_thread->is_blocked()) {
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SpinlockLocker scheduler_lock(g_scheduler_lock);
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dbgln_if(SCHEDULER_DEBUG, "Scheduler[{}]: Terminating user mode thread {}", Processor::current_id(), *current_thread);
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current_thread->set_state(Thread::State::Dying);
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Processor::current().invoke_scheduler_async();
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return;
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}
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if (current_thread->tick())
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return;
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if (!current_thread->is_idle_thread() && !peek_next_runnable_thread()) {
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// If no other thread is ready to be scheduled we don't need to
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// switch to the idle thread. Just give the current thread another
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// time slice and let it run!
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current_thread->set_ticks_left(time_slice_for(*current_thread));
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current_thread->did_schedule();
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dbgln_if(SCHEDULER_DEBUG, "Scheduler[{}]: No other threads ready, give {} another timeslice", Processor::current_id(), *current_thread);
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return;
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}
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VERIFY_INTERRUPTS_DISABLED();
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VERIFY(Processor::current_in_irq());
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Processor::current().invoke_scheduler_async();
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}
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void Scheduler::invoke_async()
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{
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VERIFY_INTERRUPTS_DISABLED();
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VERIFY(!Processor::current_in_irq());
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// Since this function is called when leaving critical sections (such
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// as a Spinlock), we need to check if we're not already doing this
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// to prevent recursion
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if (!Processor::current_in_scheduler())
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pick_next();
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}
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void Scheduler::notify_finalizer()
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{
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if (!g_finalizer_has_work.exchange(true, AK::MemoryOrder::memory_order_acq_rel))
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g_finalizer_wait_queue->wake_all();
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}
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void Scheduler::idle_loop(void*)
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{
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auto& proc = Processor::current();
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dbgln("Scheduler[{}]: idle loop running", proc.id());
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VERIFY(Processor::are_interrupts_enabled());
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|
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|
for (;;) {
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proc.idle_begin();
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|
proc.wait_for_interrupt();
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|
proc.idle_end();
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VERIFY_INTERRUPTS_ENABLED();
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|
yield();
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|
}
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|
}
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|
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void Scheduler::dump_scheduler_state(bool with_stack_traces)
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|
{
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dump_thread_list(with_stack_traces);
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}
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|
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bool Scheduler::is_initialized()
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|
{
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// The scheduler is initialized iff the idle thread exists
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return Processor::idle_thread() != nullptr;
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|
}
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|
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|
TotalTimeScheduled Scheduler::get_total_time_scheduled()
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|
{
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|
return g_total_time_scheduled.with([&](auto& total_time_scheduled) { return total_time_scheduled; });
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|
}
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|
|
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void dump_thread_list(bool with_stack_traces)
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|
{
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|
dbgln("Scheduler thread list for processor {}:", Processor::current_id());
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|
|
|
auto get_eip = [](Thread& thread) -> u32 {
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|
if (!thread.current_trap())
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|
return thread.regs().ip();
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|
return thread.get_register_dump_from_stack().ip();
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|
};
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|
|
|
Thread::for_each_ignoring_jails([&](Thread& thread) {
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|
auto color = thread.process().is_kernel_process() ? "\x1b[34;1m"sv : "\x1b[33;1m"sv;
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|
switch (thread.state()) {
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|
case Thread::State::Dying:
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|
dmesgln(" {}{:30}\x1b[0m @ {:08x} is {:14} (Finalizable: {}, nsched: {})",
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|
color,
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|
thread,
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|
get_eip(thread),
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|
thread.state_string(),
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|
thread.is_finalizable(),
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|
thread.times_scheduled());
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|
break;
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|
default:
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|
dmesgln(" {}{:30}\x1b[0m @ {:08x} is {:14} (Pr:{:2}, nsched: {})",
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|
color,
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|
thread,
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|
get_eip(thread),
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|
thread.state_string(),
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|
thread.priority(),
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|
thread.times_scheduled());
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|
break;
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|
}
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|
if (thread.state() == Thread::State::Blocked && thread.blocking_mutex()) {
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|
dmesgln(" Blocking on Mutex {:#x} ({})", thread.blocking_mutex(), thread.blocking_mutex()->name());
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|
}
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|
if (thread.state() == Thread::State::Blocked && thread.blocker()) {
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|
dmesgln(" Blocking on Blocker {:#x}", thread.blocker());
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|
}
|
|
#if LOCK_DEBUG
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|
thread.for_each_held_lock([](auto const& entry) {
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|
dmesgln(" Holding lock {:#x} ({}) at {}", entry.lock, entry.lock->name(), entry.lock_location);
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|
});
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|
#endif
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|
if (with_stack_traces) {
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|
auto trace_or_error = thread.backtrace();
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|
if (!trace_or_error.is_error()) {
|
|
auto trace = trace_or_error.release_value();
|
|
dbgln("Backtrace:");
|
|
kernelputstr(trace->characters(), trace->length());
|
|
}
|
|
}
|
|
return IterationDecision::Continue;
|
|
});
|
|
}
|
|
|
|
}
|