Resolved

risc_v/src/syscall.rs

@@ -9,8 +9,6 @@ use crate::{block::block_op,
             page::{virt_to_phys, Table},
             process::{delete_process, get_by_pid, set_sleeping, set_waiting}};
 
-use crate::process::{PROCESS_LIST_MUTEX, PROCESS_LIST, Process};
-
 /// do_syscall is called from trap.rs to invoke a system call. No discernment is
 /// made here whether this is a U-mode, S-mode, or M-mode system call.
 /// Since we can't do anything unless we dereference the passed pointer,
@@ -43,6 +41,7 @@ pub unsafe fn do_syscall(mepc: usize, frame: *mut TrapFrame) -> usize {
 			set_sleeping((*frame).pid as u16, (*frame).regs[10]);
 			0
 		},
+<<<<<<< HEAD
 		11 => {
 			// Add process to the scheduler. This is obviously insecure and
 			// we wouldn't do this realistically.
@@ -62,6 +61,8 @@ pub unsafe fn do_syscall(mepc: usize, frame: *mut TrapFrame) -> usize {
 			}
 			mepc + 4
 		},
+=======
+>>>>>>> parent of fe5a909... Create a system call to add a process to prevent data race with the process list.
 		63 => {
 			// Read system call
 			// This is an asynchronous call. This will get the
@@ -207,6 +208,7 @@ pub fn syscall_sleep(duration: usize)
 }
 
 pub fn syscall_add_process(process: Process) -> bool {
+	// Thid doesn't quite work since we move process which causes it to drop :(
 	1 == do_make_syscall(11, &process as *const Process as usize, 0, 0, 0, 0, 0)
 }
 // These system call numbers come from libgloss so that we can use newlib

risc_v/src/test.rs

@@ -13,9 +13,11 @@ use crate::{cpu::{build_satp,
                       ProcessData,
                       ProcessState,
                       NEXT_PID,
+					  PROCESS_LIST,
+					  PROCESS_LIST_MUTEX,
                       STACK_ADDR,
                       STACK_PAGES},
-            syscall::{syscall_add_process, syscall_fs_read}};
+            syscall::syscall_fs_read};
 
 /// Test block will load raw binaries into memory to execute them. This function
 /// will load ELF files and try to execute them.
@@ -185,14 +187,32 @@ pub fn test_elf() {
 	// now. Since we don't reuse PIDs, this means that we can only spawn
 	// 65534 processes.
 	satp_fence_asid(my_pid as usize);
-
-	// We will get a data race if we don't use the add process system call. This
-	// test process is being ran as a kernel process, which then competes with
-	// the scheduler due to the context switch timer. When we use a system call,
-	// it goes into an interrupt context so that the scheduler can safely
-	// receive our new process without preemption.
-	if !syscall_add_process(my_proc) {
-		println!("Could not add process to the process list.");
+	// I took a different tact here than in process.rs. In there I created
+	// the process while holding onto the process list. It might
+	// matter since this is asynchronous--it is being ran as a kernel process.
+	unsafe {
+		PROCESS_LIST_MUTEX.spin_lock();
+	}
+	if let Some(mut pl) = unsafe { PROCESS_LIST.take() } {
+		// As soon as we push this process on the list, it'll be
+		// schedule-able.
+		println!(
+		         "Added user process to the scheduler...get ready \
+		          for take-off!"
+		);
+		pl.push_back(my_proc);
+		unsafe {
+			PROCESS_LIST.replace(pl);
+		}
+	}
+	else {
+		println!("Unable to spawn process.");
+		// Since my_proc couldn't enter the process list, it
+		// will be dropped and all of the associated allocations
+		// will be deallocated through the process' Drop trait.
+	}
+	unsafe {
+		PROCESS_LIST_MUTEX.unlock();
 	}
 	println!();
 }