mirror of
https://github.com/LadybirdBrowser/ladybird.git
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b3a1671f1a
Passing this flag to recv() temporarily puts the file descriptor into non-blocking mode. Also implement LocalSocket::recv() as a simple forwarding to read().
456 lines
15 KiB
C++
456 lines
15 KiB
C++
#include "Scheduler.h"
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#include "Process.h"
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#include "RTC.h"
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#include "i8253.h"
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#include <AK/TemporaryChange.h>
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#include <Kernel/Alarm.h>
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#include <Kernel/FileSystem/FileDescriptor.h>
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#include <Kernel/Devices/PCSpeaker.h>
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//#define LOG_EVERY_CONTEXT_SWITCH
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//#define SCHEDULER_DEBUG
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static dword time_slice_for(Process::Priority priority)
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{
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// One time slice unit == 1ms
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switch (priority) {
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case Process::HighPriority:
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return 50;
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case Process::NormalPriority:
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return 15;
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case Process::LowPriority:
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return 5;
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case Process::IdlePriority:
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return 1;
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}
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ASSERT_NOT_REACHED();
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}
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Thread* current;
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Thread* g_last_fpu_thread;
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Thread* g_finalizer;
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static Process* s_colonel_process;
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qword g_uptime;
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static qword s_beep_timeout;
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struct TaskRedirectionData {
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word selector;
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TSS32 tss;
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};
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static TaskRedirectionData s_redirection;
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static bool s_active;
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bool Scheduler::is_active()
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{
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return s_active;
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}
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void Scheduler::beep()
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{
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PCSpeaker::tone_on(440);
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s_beep_timeout = g_uptime + 100;
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}
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bool Scheduler::pick_next()
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{
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ASSERT_INTERRUPTS_DISABLED();
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ASSERT(!s_active);
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TemporaryChange<bool> change(s_active, true);
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ASSERT(s_active);
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if (!current) {
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// XXX: The first ever context_switch() goes to the idle process.
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// This to setup a reliable place we can return to.
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return context_switch(s_colonel_process->main_thread());
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}
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struct timeval now;
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kgettimeofday(now);
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auto now_sec = now.tv_sec;
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auto now_usec = now.tv_usec;
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// Check and unblock threads whose wait conditions have been met.
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Thread::for_each_nonrunnable([&] (Thread& thread) {
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auto& process = thread.process();
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if (thread.state() == Thread::BlockedSleep) {
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if (thread.wakeup_time() <= g_uptime)
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thread.unblock();
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return IterationDecision::Continue;
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}
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if (thread.state() == Thread::BlockedWait) {
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process.for_each_child([&] (Process& child) {
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if (!child.is_dead())
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return true;
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if (thread.waitee_pid() == -1 || thread.waitee_pid() == child.pid()) {
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thread.m_waitee_pid = child.pid();
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thread.unblock();
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return false;
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}
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return true;
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});
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return IterationDecision::Continue;
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}
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if (thread.state() == Thread::BlockedRead) {
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ASSERT(thread.m_blocked_descriptor);
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// FIXME: Block until the amount of data wanted is available.
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if (thread.m_blocked_descriptor->can_read())
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thread.unblock();
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return IterationDecision::Continue;
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}
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if (thread.state() == Thread::BlockedWrite) {
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ASSERT(thread.m_blocked_descriptor != -1);
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if (thread.m_blocked_descriptor->can_write())
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thread.unblock();
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return IterationDecision::Continue;
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}
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if (thread.state() == Thread::BlockedConnect) {
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auto& descriptor = *thread.m_blocked_descriptor;
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auto& socket = *descriptor.socket();
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if (socket.is_connected())
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thread.unblock();
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return IterationDecision::Continue;
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}
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if (thread.state() == Thread::BlockedReceive) {
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auto& descriptor = *thread.m_blocked_descriptor;
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auto& socket = *descriptor.socket();
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// FIXME: Block until the amount of data wanted is available.
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bool timed_out = now_sec > socket.receive_deadline().tv_sec || (now_sec == socket.receive_deadline().tv_sec && now_usec >= socket.receive_deadline().tv_usec);
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if (timed_out || descriptor.can_read()) {
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thread.unblock();
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return IterationDecision::Continue;
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}
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return IterationDecision::Continue;
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}
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if (thread.state() == Thread::BlockedSelect) {
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if (thread.m_select_has_timeout) {
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if (now_sec > thread.m_select_timeout.tv_sec || (now_sec == thread.m_select_timeout.tv_sec && now_usec >= thread.m_select_timeout.tv_usec)) {
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thread.unblock();
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return IterationDecision::Continue;
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}
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}
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for (int fd : thread.m_select_read_fds) {
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if (process.m_fds[fd].descriptor->can_read()) {
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thread.unblock();
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return IterationDecision::Continue;
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}
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}
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for (int fd : thread.m_select_write_fds) {
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if (process.m_fds[fd].descriptor->can_write()) {
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thread.unblock();
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return IterationDecision::Continue;
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}
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}
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return IterationDecision::Continue;
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}
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if (thread.state() == Thread::BlockedSnoozing) {
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if (thread.m_snoozing_alarm->is_ringing()) {
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thread.m_snoozing_alarm = nullptr;
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thread.unblock();
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}
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return IterationDecision::Continue;
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}
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if (thread.state() == Thread::Skip1SchedulerPass) {
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thread.set_state(Thread::Skip0SchedulerPasses);
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return IterationDecision::Continue;
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}
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if (thread.state() == Thread::Skip0SchedulerPasses) {
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thread.set_state(Thread::Runnable);
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return IterationDecision::Continue;
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}
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if (thread.state() == Thread::Dying) {
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ASSERT(g_finalizer);
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if (g_finalizer->state() == Thread::BlockedLurking)
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g_finalizer->unblock();
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return IterationDecision::Continue;
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}
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return IterationDecision::Continue;
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});
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Process::for_each([&] (Process& process) {
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if (process.is_dead()) {
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if (current != &process.main_thread() && (!process.ppid() || !Process::from_pid(process.ppid()))) {
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auto name = process.name();
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auto pid = process.pid();
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auto exit_status = Process::reap(process);
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dbgprintf("reaped unparented process %s(%u), exit status: %u\n", name.characters(), pid, exit_status);
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}
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}
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return true;
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});
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// Dispatch any pending signals.
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// FIXME: Do we really need this to be a separate pass over the process list?
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Thread::for_each_living([] (Thread& thread) {
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if (!thread.has_unmasked_pending_signals())
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return true;
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// FIXME: It would be nice if the Scheduler didn't have to worry about who is "current"
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// For now, avoid dispatching signals to "current" and do it in a scheduling pass
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// while some other process is interrupted. Otherwise a mess will be made.
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if (&thread == current)
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return true;
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// We know how to interrupt blocked processes, but if they are just executing
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// at some random point in the kernel, let them continue. They'll be in userspace
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// sooner or later and we can deliver the signal then.
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// FIXME: Maybe we could check when returning from a syscall if there's a pending
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// signal and dispatch it then and there? Would that be doable without the
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// syscall effectively being "interrupted" despite having completed?
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if (thread.in_kernel() && !thread.is_blocked() && !thread.is_stopped())
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return true;
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// NOTE: dispatch_one_pending_signal() may unblock the process.
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bool was_blocked = thread.is_blocked();
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if (thread.dispatch_one_pending_signal() == ShouldUnblockThread::No)
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return true;
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if (was_blocked) {
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dbgprintf("Unblock %s(%u) due to signal\n", thread.process().name().characters(), thread.pid());
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thread.m_was_interrupted_while_blocked = true;
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thread.unblock();
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}
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return true;
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});
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#ifdef SCHEDULER_DEBUG
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dbgprintf("Non-runnables:\n");
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for (auto* thread = g_nonrunnable_threads->head(); thread; thread = thread->next()) {
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auto* process = &thread->process();
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dbgprintf("[K%x] % 12s %s(%u:%u) @ %w:%x\n", process, to_string(thread->state()), process->name().characters(), process->pid(), thread->tid(), thread->tss().cs, thread->tss().eip);
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}
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dbgprintf("Runnables:\n");
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for (auto* thread = g_runnable_threads->head(); thread; thread = thread->next()) {
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auto* process = &thread->process();
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dbgprintf("[K%x] % 12s %s(%u:%u) @ %w:%x\n", process, to_string(thread->state()), process->name().characters(), process->pid(), thread->tid(), thread->tss().cs, thread->tss().eip);
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}
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#endif
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if (g_runnable_threads->is_empty())
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return context_switch(s_colonel_process->main_thread());
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auto* previous_head = g_runnable_threads->head();
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for (;;) {
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// Move head to tail.
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g_runnable_threads->append(g_runnable_threads->remove_head());
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auto* thread = g_runnable_threads->head();
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if (!thread->process().is_being_inspected() && (thread->state() == Thread::Runnable || thread->state() == Thread::Running)) {
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#ifdef SCHEDULER_DEBUG
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kprintf("switch to %s(%u:%u) @ %w:%x\n", thread->process().name().characters(), thread->process().pid(), thread->tid(), thread->tss().cs, thread->tss().eip);
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#endif
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return context_switch(*thread);
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}
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if (thread == previous_head) {
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// Back at process_head, nothing wants to run. Send in the colonel!
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return context_switch(s_colonel_process->main_thread());
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}
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}
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}
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bool Scheduler::donate_to(Thread* beneficiary, const char* reason)
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{
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InterruptDisabler disabler;
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if (!Thread::is_thread(beneficiary))
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return false;
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(void)reason;
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unsigned ticks_left = current->ticks_left();
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if (!beneficiary || beneficiary->state() != Thread::Runnable || ticks_left <= 1)
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return yield();
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unsigned ticks_to_donate = min(ticks_left - 1, time_slice_for(beneficiary->process().priority()));
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#ifdef SCHEDULER_DEBUG
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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);
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#endif
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context_switch(*beneficiary);
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beneficiary->set_ticks_left(ticks_to_donate);
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switch_now();
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return false;
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}
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bool Scheduler::yield()
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{
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InterruptDisabler disabler;
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ASSERT(current);
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// dbgprintf("%s(%u:%u) yield()\n", current->process().name().characters(), current->pid(), current->tid());
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if (!pick_next())
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return false;
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// dbgprintf("yield() jumping to new process: sel=%x, %s(%u:%u)\n", current->far_ptr().selector, current->process().name().characters(), current->pid(), current->tid());
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switch_now();
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return true;
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}
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void Scheduler::pick_next_and_switch_now()
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{
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bool someone_wants_to_run = pick_next();
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ASSERT(someone_wants_to_run);
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switch_now();
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}
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void Scheduler::switch_now()
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{
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Descriptor& descriptor = get_gdt_entry(current->selector());
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descriptor.type = 9;
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flush_gdt();
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asm("sti\n"
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"ljmp *(%%eax)\n"
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::"a"(¤t->far_ptr())
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);
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}
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bool Scheduler::context_switch(Thread& thread)
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{
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thread.set_ticks_left(time_slice_for(thread.process().priority()));
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thread.did_schedule();
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if (current == &thread)
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return false;
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if (current) {
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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 (current->state() == Thread::Running)
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current->set_state(Thread::Runnable);
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#ifdef LOG_EVERY_CONTEXT_SWITCH
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dbgprintf("Scheduler: %s(%u:%u) -> %s(%u:%u) %w:%x\n",
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current->process().name().characters(), current->process().pid(), current->tid(),
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thread.process().name().characters(), thread.process().pid(), thread.tid(),
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thread.tss().cs, thread.tss().eip);
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#endif
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}
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current = &thread;
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thread.set_state(Thread::Running);
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if (!thread.selector()) {
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thread.set_selector(gdt_alloc_entry());
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auto& descriptor = get_gdt_entry(thread.selector());
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descriptor.set_base(&thread.tss());
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descriptor.set_limit(0xffff);
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descriptor.dpl = 0;
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descriptor.segment_present = 1;
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descriptor.granularity = 1;
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descriptor.zero = 0;
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descriptor.operation_size = 1;
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descriptor.descriptor_type = 0;
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}
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auto& descriptor = get_gdt_entry(thread.selector());
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descriptor.type = 11; // Busy TSS
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flush_gdt();
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return true;
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}
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static void initialize_redirection()
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{
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auto& descriptor = get_gdt_entry(s_redirection.selector);
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descriptor.set_base(&s_redirection.tss);
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descriptor.set_limit(0xffff);
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descriptor.dpl = 0;
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descriptor.segment_present = 1;
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descriptor.granularity = 1;
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descriptor.zero = 0;
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descriptor.operation_size = 1;
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descriptor.descriptor_type = 0;
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descriptor.type = 9;
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flush_gdt();
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}
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void Scheduler::prepare_for_iret_to_new_process()
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{
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auto& descriptor = get_gdt_entry(s_redirection.selector);
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descriptor.type = 9;
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s_redirection.tss.backlink = current->selector();
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load_task_register(s_redirection.selector);
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}
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void Scheduler::prepare_to_modify_tss(Thread& thread)
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{
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// This ensures that a currently running process modifying its own TSS
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// in order to yield() and end up somewhere else doesn't just end up
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// right after the yield().
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if (current == &thread)
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load_task_register(s_redirection.selector);
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}
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Process* Scheduler::colonel()
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{
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return s_colonel_process;
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}
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void Scheduler::initialize()
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{
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s_redirection.selector = gdt_alloc_entry();
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initialize_redirection();
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s_colonel_process = Process::create_kernel_process("colonel", nullptr);
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// Make sure the colonel uses a smallish time slice.
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s_colonel_process->set_priority(Process::IdlePriority);
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load_task_register(s_redirection.selector);
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}
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void Scheduler::timer_tick(RegisterDump& regs)
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{
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if (!current)
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return;
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++g_uptime;
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if (s_beep_timeout && g_uptime > s_beep_timeout) {
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PCSpeaker::tone_off();
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s_beep_timeout = 0;
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}
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if (current->tick())
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return;
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current->tss().gs = regs.gs;
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current->tss().fs = regs.fs;
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current->tss().es = regs.es;
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current->tss().ds = regs.ds;
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current->tss().edi = regs.edi;
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current->tss().esi = regs.esi;
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current->tss().ebp = regs.ebp;
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current->tss().ebx = regs.ebx;
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current->tss().edx = regs.edx;
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current->tss().ecx = regs.ecx;
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current->tss().eax = regs.eax;
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current->tss().eip = regs.eip;
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current->tss().cs = regs.cs;
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current->tss().eflags = regs.eflags;
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// Compute process stack pointer.
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// Add 12 for CS, EIP, EFLAGS (interrupt mechanic)
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current->tss().esp = regs.esp + 12;
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current->tss().ss = regs.ss;
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if ((current->tss().cs & 3) != 0) {
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current->tss().ss = regs.ss_if_crossRing;
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current->tss().esp = regs.esp_if_crossRing;
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}
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if (!pick_next())
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return;
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prepare_for_iret_to_new_process();
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// Set the NT (nested task) flag.
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asm(
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"pushf\n"
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"orl $0x00004000, (%esp)\n"
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"popf\n"
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);
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}
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