From 0bd861c19f480643f158063209434a2bbd6ebc59 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Sat, 8 Oct 2022 22:03:46 -0300
Subject: [PATCH] process removal: remove a few bugs and race conditions

---
 src/sys/sched/scheduler.c  |  7 -------
 src/sys/syscalls/exit.c    | 12 ++++++++++--
 src/sys/syscalls/waitpid.c | 16 ++++++++--------
 3 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/src/sys/sched/scheduler.c b/src/sys/sched/scheduler.c
index 3b6b84b3..39ee3893 100644
--- a/src/sys/sched/scheduler.c
+++ b/src/sys/sched/scheduler.c
@@ -362,13 +362,6 @@ void sched_dequeue(){
 	
 	timer_resume();
 
-	thread_t* curthread = arch_getcls()->thread;
-	
-	// context and thread destruction will happen in the waitpid()	
-	// the pointer to this thread will reside in proc->threads
-
-	curthread->proc->threads = curthread;
-
 	// for safety
 
 
diff --git a/src/sys/syscalls/exit.c b/src/sys/syscalls/exit.c
index c61de29f..ed199222 100644
--- a/src/sys/syscalls/exit.c
+++ b/src/sys/syscalls/exit.c
@@ -4,6 +4,7 @@
 #include <stdbool.h>
 #include <kernel/event.h>
 #include <kernel/alloc.h>
+#include <arch/interrupt.h>
 
 void syscall_exit(int status){
 	proc_t* proc = arch_getcls()->thread->proc;
@@ -44,10 +45,17 @@ void syscall_exit(int status){
 	}	
 
 	spinlock_release(&init->lock);
-	spinlock_release(&proc->lock);
-
 	event_signal(&proc->parent->childevent, true);
 
+        // context and thread destruction will happen in the waitpid()
+        // the pointer to this thread will reside in proc->threads
+
+        proc->threads = arch_getcls()->thread;
+	
+	arch_interrupt_disable();
+
+	spinlock_release(&proc->lock);
+
 	sched_dequeue();
 	
 	__builtin_unreachable();
diff --git a/src/sys/syscalls/waitpid.c b/src/sys/syscalls/waitpid.c
index 7a122da2..d98d2f59 100644
--- a/src/sys/syscalls/waitpid.c
+++ b/src/sys/syscalls/waitpid.c
@@ -38,25 +38,24 @@ syscallret syscall_waitpid(pid_t pid, int *status, int options){
 	proc_t* proc = arch_getcls()->thread->proc;
 
 	bool loop = true;
-
-
+	
 	proc_t* child;
 	proc_t* sibling;
 
 	while(1){
-		
-		child = proc->child;
-		sibling = NULL;
 
 		// now find the child
 		
 		spinlock_acquire(&proc->lock);
-			
+		child = proc->child;
+		sibling = NULL;
+
 		while(child){
 			if(pid > 0 && child->pid != pid)
 			       continue;	
 
 			if(child->state == PROC_STATE_ZOMBIE){
+				loop = false;
 				break;
 			}
 
@@ -90,6 +89,9 @@ syscallret syscall_waitpid(pid_t pid, int *status, int options){
 		sibling->sibling = child->sibling;
 		spinlock_release(&sibling->lock);
 	}
+	else{
+		proc->child = child->sibling;
+	}
 
 	*status = child->status; // XXX safer way of doing this
 	
@@ -98,7 +100,6 @@ syscallret syscall_waitpid(pid_t pid, int *status, int options){
 	thread_t* thread = child->threads;
 
 	// TODO free ctx
-	
 	free(thread->regs);
 	free(thread->kernelstackbase);
 	free(thread);	
@@ -106,7 +107,6 @@ syscallret syscall_waitpid(pid_t pid, int *status, int options){
 
 	retv.ret = child->pid;
 	retv.errno = 0;
-	
 	return retv;