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Kernel: Make Thread refcounted

Browse source 
Similar to Process, we need to make Thread refcounted. This will solve
problems that will appear once we schedule threads on more than one
processor. This allows us to hold onto threads without necessarily
holding the scheduler lock for the entire duration.
This commit is contained in:
Tom 2020-09-27 08:53:35 -06:00 • committed by Andreas Kling
parent 079486ed7e
commit 838d9fa251
14 changed files with 136 additions and 90 deletions
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7
Kernel/Syscalls/fork.cpp
View file

@ -36,8 +36,10 @@ namespace Kernel {
pid_t Process::sys$fork(RegisterState& regs)
{
REQUIRE_PROMISE(proc);
Thread* child_first_thread = nullptr;
auto* child = new Process(child_first_thread, m_name, m_uid, m_gid, m_pid, m_is_kernel_process, m_cwd, m_executable, m_tty, this);
RefPtr<Thread> child_first_thread;
auto child = adopt(*new Process(child_first_thread, m_name, m_uid, m_gid, m_pid, m_is_kernel_process, m_cwd, m_executable, m_tty, this));
if (!child_first_thread)
return -ENOMEM;
child->m_root_directory = m_root_directory;
child->m_root_directory_relative_to_global_root = m_root_directory_relative_to_global_root;
child->m_promises = m_promises;
@ -92,6 +94,7 @@ pid_t Process::sys$fork(RegisterState& regs)
{
ScopedSpinLock lock(g_processes_lock);
g_processes->prepend(child);
child->ref(); // This reference will be dropped by Process::reap
}
child_first_thread->set_affinity(Thread::current()->affinity());

51
Kernel/Syscalls/sched.cpp
View file

@ -40,8 +40,12 @@ int Process::sys$donate(pid_t tid)
REQUIRE_PROMISE(stdio);
if (tid < 0)
return -EINVAL;
InterruptDisabler disabler;
auto* thread = Thread::from_tid(tid);
// We don't strictly need to grab the scheduler lock here, but it
// will close a race where we can find the thread but it disappears
// before we call Scheduler::donate_to.
ScopedSpinLock lock(g_scheduler_lock);
auto thread = Thread::from_tid(tid);
if (!thread || thread->pid() != pid())
return -ESRCH;
Scheduler::donate_to(thread, "sys$donate");
@ -55,8 +59,11 @@ int Process::sys$sched_setparam(int pid, Userspace<const struct sched_param*> us
if (!copy_from_user(&desired_param, user_param))
return -EFAULT;
InterruptDisabler disabler;
if (desired_param.sched_priority < THREAD_PRIORITY_MIN || desired_param.sched_priority > THREAD_PRIORITY_MAX)
return -EINVAL;
auto* peer = Thread::current();
ScopedSpinLock lock(g_scheduler_lock);
if (pid != 0)
peer = Thread::from_tid(pid);
@ -66,9 +73,6 @@ int Process::sys$sched_setparam(int pid, Userspace<const struct sched_param*> us
if (!is_superuser() && m_euid != peer->process().m_uid && m_uid != peer->process().m_uid)
return -EPERM;
if (desired_param.sched_priority < THREAD_PRIORITY_MIN || desired_param.sched_priority > THREAD_PRIORITY_MAX)
return -EINVAL;
peer->set_priority((u32)desired_param.sched_priority);
return 0;
}
@ -76,22 +80,27 @@ int Process::sys$sched_setparam(int pid, Userspace<const struct sched_param*> us
int Process::sys$sched_getparam(pid_t pid, Userspace<struct sched_param*> user_param)
{
REQUIRE_PROMISE(proc);
InterruptDisabler disabler;
auto* peer = Thread::current();
if (pid != 0) {
// FIXME: PID/TID BUG
// The entire process is supposed to be affected.
peer = Thread::from_tid(pid);
int priority;
{
auto* peer = Thread::current();
ScopedSpinLock lock(g_scheduler_lock);
if (pid != 0) {
// FIXME: PID/TID BUG
// The entire process is supposed to be affected.
peer = Thread::from_tid(pid);
}
if (!peer)
return -ESRCH;
if (!is_superuser() && m_euid != peer->process().m_uid && m_uid != peer->process().m_uid)
return -EPERM;
priority = (int)peer->priority();
}
if (!peer)
return -ESRCH;
if (!is_superuser() && m_euid != peer->process().m_uid && m_uid != peer->process().m_uid)
return -EPERM;
struct sched_param param {
(int)peer->priority()
priority
};
if (!copy_to_user(user_param, &param))
return -EFAULT;
@ -103,8 +112,8 @@ int Process::sys$set_thread_boost(pid_t tid, int amount)
REQUIRE_PROMISE(proc);
if (amount < 0 || amount > 20)
return -EINVAL;
InterruptDisabler disabler;
auto* thread = Thread::from_tid(tid);
ScopedSpinLock lock(g_scheduler_lock);
auto thread = Thread::from_tid(tid);
if (!thread)
return -ESRCH;
if (thread->state() == Thread::State::Dead || thread->state() == Thread::State::Dying)

28
Kernel/Syscalls/thread.cpp
View file

@ -102,8 +102,7 @@ void Process::sys$exit_thread(Userspace<void*> exit_value)
int Process::sys$detach_thread(pid_t tid)
{
REQUIRE_PROMISE(thread);
InterruptDisabler disabler;
auto* thread = Thread::from_tid(tid);
auto thread = Thread::from_tid(tid);
if (!thread || thread->pid() != pid())
return -ESRCH;
@ -118,8 +117,7 @@ int Process::sys$join_thread(pid_t tid, Userspace<void**> exit_value)
{
REQUIRE_PROMISE(thread);
InterruptDisabler disabler;
auto* thread = Thread::from_tid(tid);
auto thread = Thread::from_tid(tid);
if (!thread || thread->pid() != pid())
return -ESRCH;
@ -134,20 +132,14 @@ int Process::sys$join_thread(pid_t tid, Userspace<void**> exit_value)
KResult try_join_result(KSuccess);
auto result = current_thread->block<Thread::JoinBlocker>(nullptr, *thread, try_join_result, joinee_exit_value);
if (result == Thread::BlockResult::NotBlocked) {
ASSERT_INTERRUPTS_DISABLED();
if (try_join_result.is_error())
return try_join_result.error();
break;
}
if (result == Thread::BlockResult::InterruptedByDeath) {
ASSERT_INTERRUPTS_DISABLED();
break;
}
if (result == Thread::BlockResult::InterruptedByDeath)
return 0; // we're not going to return back to user mode
}
// NOTE: 'thread' is very possibly deleted at this point. Clear it just to be safe.
thread = nullptr;
if (exit_value && !copy_to_user(exit_value, &joinee_exit_value))
return -EFAULT;
return 0;
@ -164,8 +156,7 @@ int Process::sys$set_thread_name(pid_t tid, Userspace<const char*> user_name, si
if (name.length() > max_thread_name_size)
return -EINVAL;
InterruptDisabler disabler;
auto* thread = Thread::from_tid(tid);
auto thread = Thread::from_tid(tid);
if (!thread || thread->pid() != pid())
return -ESRCH;
@ -179,15 +170,16 @@ int Process::sys$get_thread_name(pid_t tid, Userspace<char*> buffer, size_t buff
if (buffer_size == 0)
return -EINVAL;
InterruptDisabler disabler;
auto* thread = Thread::from_tid(tid);
auto thread = Thread::from_tid(tid);
if (!thread || thread->pid() != pid())
return -ESRCH;
if (thread->name().length() + 1 > (size_t)buffer_size)
// We must make a temporary copy here to avoid a race with sys$set_thread_name
auto thread_name = thread->name();
if (thread_name.length() + 1 > (size_t)buffer_size)
return -ENAMETOOLONG;
if (!copy_to_user(buffer, thread->name().characters(), thread->name().length() + 1))
if (!copy_to_user(buffer, thread_name.characters(), thread_name.length() + 1))
return -EFAULT;
return 0;
}

4
Kernel/Syscalls/waitid.cpp
View file

@ -68,7 +68,9 @@ KResultOr<siginfo_t> Process::do_waitid(idtype_t idtype, int id, int options)
return reap(*waitee_process);
} else {
// FIXME: PID/TID BUG
auto* waitee_thread = Thread::from_tid(waitee_pid.value());
// Make sure to hold the scheduler lock so that we operate on a consistent state
ScopedSpinLock scheduler_lock(g_scheduler_lock);
auto waitee_thread = Thread::from_tid(waitee_pid.value());
if (!waitee_thread)
return KResult(-ECHILD);
ASSERT((options & WNOHANG) || waitee_thread->state() == Thread::State::Stopped);