From e1d5b7e7b40b828253e50e12f27357fef752a927 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sat, 28 Oct 2023 15:15:32 +0200
Subject: [PATCH] kernel: Implement thread stopping and continuing

---
 kernel/src/thread/Thread.cpp | 19 +++++++++++++++++--
 kernel/src/thread/Thread.h   |  4 ++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/kernel/src/thread/Thread.cpp b/kernel/src/thread/Thread.cpp
index 6d092515..c3514560 100644
--- a/kernel/src/thread/Thread.cpp
+++ b/kernel/src/thread/Thread.cpp
@@ -136,6 +136,7 @@ enum class DefaultSignalAction
 {
     Ignore,
     Terminate,
+    Stop,
 };
 
 // FIXME: Implement coredumps for some signals.
@@ -149,9 +150,9 @@ static constexpr DefaultSignalAction default_actions[] = {
     DefaultSignalAction::Ignore,    // SIGCHLD
     DefaultSignalAction::Terminate, // SIGFPE  (dump core)
     DefaultSignalAction::Terminate, // SIGKILL
-    DefaultSignalAction::Terminate, // SIGSTOP (FIXME: Support stopping and continuing)
+    DefaultSignalAction::Stop,      // SIGSTOP
     DefaultSignalAction::Terminate, // SIGSEGV (dump core)
-    DefaultSignalAction::Ignore,    // SIGCONT (FIXME: Support stopping and continuing)
+    DefaultSignalAction::Ignore,    // SIGCONT (Handled separately)
     DefaultSignalAction::Terminate, // SIGPIPE
     DefaultSignalAction::Terminate, // SIGALRM
     DefaultSignalAction::Terminate, // SIGTERM
@@ -193,6 +194,7 @@ void Thread::process_pending_signals(Registers* current_regs)
                 {
                 case DefaultSignalAction::Ignore: return;
                 case DefaultSignalAction::Terminate: exit_and_signal_parent(signo | _SIGBIT);
+                case DefaultSignalAction::Stop: stop();
                 default: return;
                 }
             }
@@ -227,12 +229,25 @@ void Thread::send_signal(int signo)
     if (is_kernel) return;
     if (state == ThreadState::Exited || state == ThreadState::Dying) return;
 
+    if (state == ThreadState::Stopped && signo == SIGCONT)
+    {
+        wake_up();
+        return;
+    }
+
     check(signo > 0 && signo <= NSIG);
     pending_signals.set(signo - 1, true);
 
     if (state == ThreadState::Waiting || state == ThreadState::Sleeping || is_in_kernel(&regs))
     {
+        if (state == ThreadState::Stopped && signo != SIGKILL) return;
         interrupted = true;
         wake_up();
     }
 }
+
+void Thread::stop()
+{
+    state = ThreadState::Stopped;
+    kernel_yield();
+}
diff --git a/kernel/src/thread/Thread.h b/kernel/src/thread/Thread.h
index 8a9829fe..a46ea73d 100644
--- a/kernel/src/thread/Thread.h
+++ b/kernel/src/thread/Thread.h
@@ -26,6 +26,7 @@ enum class ThreadState
     Runnable,
     Sleeping,
     Waiting,
+    Stopped,
     Exited,
     Dying
 };
@@ -152,6 +153,9 @@ struct Thread : public LinkedListNode<Thread>
     Result<u64> push_mem_on_stack(const u8* mem, usize size);
     Result<u64> pop_mem_from_stack(u8* mem, usize size);
 
+    void stop();
+    void resume();
+
     void send_signal(int signo);
 
     static void init();