From 1376aa5f449d13b11bad347e25712d4d845a68a9 Mon Sep 17 00:00:00 2001
From: pjht <pterpstra@pterpstra.com>
Date: Sat, 8 Jun 2024 06:54:53 -0500
Subject: [PATCH] Add suuport for sleeping processes and a syscall to sleep
 waiting for IPC

---
 src/interrupts.rs | 19 +++++++++++++++----
 src/tasking.rs    | 34 ++++++++++++++++++++++++++++++----
 2 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/src/interrupts.rs b/src/interrupts.rs
index 9ee5cb7..4746ef6 100644
--- a/src/interrupts.rs
+++ b/src/interrupts.rs
@@ -1,5 +1,5 @@
 use crate::{
-    bootinfo::BOOTINFO, dbg, print, println, virtual_memory::{ASpaceMutex, AddressSpace, ACTIVE_SPACE, KERNEL_SPACE}, TASKING
+    bootinfo::BOOTINFO, dbg, print, println, tasking::SleepReason, virtual_memory::{ASpaceMutex, AddressSpace, ACTIVE_SPACE, KERNEL_SPACE}, TASKING
 };
 use alloc::{boxed::Box, vec::Vec};
 use core::{arch::asm, ptr::{addr_of, slice_from_raw_parts_mut}, slice, str};
@@ -312,16 +312,20 @@ extern "C" fn syscall_handler() {
             }
         }
         11 => {
+            let pid = regs.rcx as usize;
             if let Some(buffer) = get_buffer(regs.rdx) {
                 assert!(regs.rsi as usize <= buffer.len());
                 let mut tasking = TASKING.lock();
-                if let Some(_queue) = tasking.message_queue_mut(regs.rcx as usize) {
+                if let Some(_queue) = tasking.message_queue_mut(pid) {
                     let len = regs.rsi as usize;
                     let buffer = Box::into_raw(buffer);
                     let new_buffer_key =
-                        tasking.proc_data_buffers_mut(regs.rcx as usize).insert(buffer);
-                    let queue = tasking.message_queue_mut(regs.rcx as usize).unwrap();
+                        tasking.proc_data_buffers_mut(pid).insert(buffer);
+                    let queue = tasking.message_queue_mut(pid).unwrap();
                     queue.push((new_buffer_key, len));
+                    if tasking.proc_sleeping(pid) == Some(SleepReason::WaitingForIPC) {
+                        tasking.wake(pid);
+                    }
                     retval = 0;
                 } else {
                     retval = 1;
@@ -380,9 +384,16 @@ extern "C" fn syscall_handler() {
             let space = tasking.address_spaces_mut().get_mut((regs.rcx - 1) as usize).unwrap();
             space.run(|| unsafe { slice::from_raw_parts_mut(regs.rdx as *mut u8, regs.rsi as usize).fill(0) });
             retval = 0;
+        },
+        18 => {
+            let mut tasking = TASKING.lock();
+            if tasking.current_message_queue_mut().is_empty() {
+                tasking.sleep(SleepReason::WaitingForIPC);
+            }
         }
         _ => (),
     };
+    unsafe { SYSCALL_REGS = regs };
     unsafe {
         asm!(
             "mov rbx, [rip+SYSCALL_REGS+8]",
diff --git a/src/tasking.rs b/src/tasking.rs
index 4746943..572fa16 100644
--- a/src/tasking.rs
+++ b/src/tasking.rs
@@ -1,6 +1,5 @@
 use crate::{
-    gdt, println, qemu_exit,
-    virtual_memory::{ASpaceMutex, AddressSpace, PagingError, KERNEL_SPACE},
+    dbg, gdt, println, qemu_exit, virtual_memory::{ASpaceMutex, AddressSpace, PagingError, KERNEL_SPACE}
 };
 use alloc::{boxed::Box, vec::Vec};
 use core::{arch::asm, ptr::addr_of};
@@ -77,6 +76,11 @@ extern "C" fn task_force_unlock() {
     interrupts::enable();
 }
 
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum SleepReason {
+    WaitingForIPC,
+}
+
 #[derive(Debug)]
 struct Process {
     kernel_stack: Box<[usize], &'static ASpaceMutex>,
@@ -86,6 +90,7 @@ struct Process {
     address_spaces: Slab<AddressSpace>,
     data_buffers: Slab<*mut [u8]>,
     message_queue: SegQueue<(usize, usize)>,
+    sleeping: Option<SleepReason>
 }
 
 unsafe impl Send for Process {}
@@ -129,6 +134,7 @@ impl Tasking {
             address_spaces: Slab::new(),
             data_buffers: Slab::new(),
             message_queue: SegQueue::new(),
+            sleeping: None,
         });
         self.ready_to_run.push(pid);
         Ok(pid)
@@ -149,10 +155,14 @@ impl Tasking {
             self.processes[current_process].address_space = Some(current_address_space);
             let next_process = &self.processes[next_process_pid];
             gdt::set_tss_stack(next_process.kernel_esp_top);
-            self.ready_to_run.push(current_process);
+            if self.processes[current_process].sleeping.is_none() {
+                self.ready_to_run.push(current_process);
+            }
             let kernel_esp = next_process.kernel_esp;
             let previous_process = self.current_process.replace(next_process_pid).unwrap();
             switch_to_asm(&mut (self.processes[previous_process].kernel_esp), kernel_esp);
+        } else if self.processes[current_process].sleeping.is_some() {
+            qemu_exit::exit_qemu();
         }
     }
 
@@ -177,7 +187,7 @@ impl Tasking {
             switch_to_asm_exit(kernel_esp);
             unreachable!()
         } else {
-            println!("Last process exited, exiting QEMU");
+            println!("Last non-sleeping process exited, exiting QEMU");
             qemu_exit::exit_qemu();
         }
     }
@@ -201,4 +211,20 @@ impl Tasking {
     pub fn message_queue_mut(&mut self, pid: usize) -> Option<&mut SegQueue<(usize, usize)>> {
         Some(&mut self.processes.get_mut(pid)?.message_queue)
     }
+
+    pub fn proc_sleeping(&mut self, pid: usize) -> Option<SleepReason> {
+        self.processes[pid].sleeping
+    }
+
+    pub fn sleep(&mut self, reason: SleepReason)  {
+        self.processes[self.current_process.unwrap()].sleeping = Some(reason);
+        self.task_yield();
+    }
+
+    pub fn wake(&mut self, pid: usize) {
+        if self.processes[pid].sleeping.is_some() {
+            self.processes[pid].sleeping = None;
+            self.ready_to_run.push(pid);
+        }
+    }
 }