From 63938e1acd892fed9caa15f26b7b00c0becba2c5 Mon Sep 17 00:00:00 2001
From: Ruslan Isaev <ubijca16@gmail.com>
Date: Wed, 3 Sep 2025 16:35:07 +0300
Subject: [PATCH] syscalls: fix nanosleep, thanks to gemini, sorry for that

---
 src/tasking/syscalls.c |  7 ++--
 src/tasking/task.c     | 75 ++++++++++++++++++++++++++++--------------
 2 files changed, 55 insertions(+), 27 deletions(-)

diff --git a/src/tasking/syscalls.c b/src/tasking/syscalls.c
index 4bb3da1..b85a95e 100644
--- a/src/tasking/syscalls.c
+++ b/src/tasking/syscalls.c
@@ -315,10 +315,11 @@ uint32_t sys_nanosleep(TrapFrame *tf)
     //debug_log("waiting for 0x%X ms\n", ms);
     size_t start_time = timer_ticks;
 
+    scheduler_lock();
     current->wake_up_time = timer_ticks + ms;
-    //debug_log("setting wake up time to %X (current time is %X)\n", current->wake_up_time, timer_ticks);
-    
-    //TODO: find a way to call the scheduler from here without fucking shit up
+    current->state = Waiting;
+    schedule();
+    scheduler_unlock();
     
     return 0;
 }
diff --git a/src/tasking/task.c b/src/tasking/task.c
index f0c8d68..e4d960c 100644
--- a/src/tasking/task.c
+++ b/src/tasking/task.c
@@ -103,23 +103,33 @@ void scheduler_unlock()
 void schedule() {
     scheduler_lock();
 
-    Process* prev = NULL;
+    // Step 1: Iterate through all processes to wake up any that are due.
     Process* p = queue;
+    while (p) {
+        if (p->state == Waiting && timer_ticks >= p->wake_up_time) {
+            p->state = Ready;
+        }
+        p = p->next;
+    }
+
+    // Step 2: Clean up any terminated processes.
+    Process* prev = NULL;
+    p = queue;
     while (p) {
         if (p->state == Terminated) {
             Process* next_proc = p->next;
-            // Unlink from the queue
             if (prev) {
                 prev->next = next_proc;
             } else {
                 queue = next_proc;
             }
 
-            // If the terminated process is the current one, we must not switch to it.
+            // If we are terminating the currently running process, we must find a new one.
             if (p == current) {
                 current = NULL;
             }
 
+            // Free the terminated process's resources.
             destroy_page_dir(p->pagedir);
             free_page((void*)virt_to_phys(p->kstack));
             free_page((void*)virt_to_phys(p));
@@ -131,36 +141,53 @@ void schedule() {
         }
     }
 
-    // If 'current' was terminated or this is the first run, find a new process.
-    if (!current || current->state != Ready) {
-        current = queue; // Start search from the beginning
+    // If there are no processes left, we have a problem.
+    if (!queue) {
+        scheduler_unlock();
+        // Ideally, you would panic the kernel here.
+        // For now, we just return and hope an interrupt happens.
+        return;
     }
 
-    if(current->wake_up_time > timer_ticks)
-    {
-        current = queue;
+    // Step 3: Find the next process to run using a round-robin algorithm.
+    Process* start_search = NULL;
+    if (current && current->state == Ready) {
+        // If the current process is still ready, start searching from the next one.
+        start_search = current->next;
+    } else {
+        // If the current process is not ready (e.g., it's Waiting or was Terminated),
+        // start the search from the beginning of the queue.
+        start_search = queue;
     }
 
-    // Find the next ready process to run
-    Process* next = current ? current->next : NULL;
-    if (!next) next = queue;
+    // Ensure start_search is not NULL (handles wrapping around).
+    if (!start_search) {
+        start_search = queue;
+    }
 
-    // Iterate through the list to find a process that is ready to run
-    Process* start_node = next;
-    while (next && next->state != Ready) {
-        next = next->next;
-        if (!next) next = queue; // Wrap around
-        if (next == start_node) { // Full circle, no ready process
+    // Find the first available 'Ready' process.
+    Process* next = start_search;
+    do {
+        if (next->state == Ready) {
+            // We found a process to run.
+            // If it's not the same one we're already running, switch to it.
+            if (next != current) {
+                tss.esp0 = next->kstack_top;
+                switchProcess(next); // This will update 'current' and switch contexts.
+            }
+            // If next == current, we don't need to switch. Just continue execution.
             scheduler_unlock();
             return;
         }
-    }
-
-    if (next && next != current) {
-        tss.esp0 = next->kstack_top;
-        switchProcess(next);
-    }
+        next = next->next;
+        if (!next) {
+            next = queue; // Wrap around to the beginning of the list.
+        }
+    } while (next != start_search);
 
+    // If we get here, it means no process is in the 'Ready' state.
+    // This can happen if all tasks are waiting for I/O or sleeping.
+    // We just unlock and wait for the next interrupt to change a process's state.
     scheduler_unlock();
 }