feat: add conditional compilation variables for schedulers

sched/GNUmakefile

@@ -100,6 +100,17 @@ CFLAGS += -fno-tree-ch
 # Add -fno-stack-protector if the option exists.
 CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
 
+USE_RR =
+USE_PR =
+
+ifeq ($(USE_RR), 1)
+CFLAGS += -DSCHED_ROUND_ROBIN
+else ifeq ($(USE_PR), 1)
+CFLAGS += -DSCHED_PRIORITIES
+else
+CFLAGS += -DSCHED_ROUND_ROBIN
+endif
+
 # Common linker flags
 LDFLAGS := -m elf_i386
 

sched/README.md

@@ -8,10 +8,28 @@ Utilizar el archivo `sched.md` provisto en el repositorio
 
 ## Compilar
 
+Por _default_ se compilará el _scheduler_ en versión **round-robin**.
+
 ```bash
 make
 ```
 
+## Compilación condicional de _schedulers_
+
+Para compilar y probar el kernel y poder probar ambos planificadores, se puede:
+
+- **round-robin**:
+
+```bash
+make <target> USE_RR=1
+```
+
+- **priorities**:
+
+```bash
+make <target> USE_PR=1
+```
+
 ## Pruebas
 
 ```bash

sched/kern/sched.c

@@ -11,13 +11,12 @@ void sched_halt(void);
 void
 sched_yield(void)
 {
-	struct Env *idle;
-
+#ifdef SCHED_ROUND_ROBIN
 	// Implement simple round-robin scheduling.
 	//
 	// Search through 'envs' for an ENV_RUNNABLE environment in
 	// circular fashion starting just after the env this CPU was
-	// last running.  Switch to the first such environment found.
+	// last running. Switch to the first such environment found.
 	//
 	// If no envs are runnable, but the environment previously
 	// running on this CPU is still ENV_RUNNING, it's okay to
@@ -28,8 +27,22 @@ sched_yield(void)
 	// no runnable environments, simply drop through to the code
 	// below to halt the cpu.
 
-	// Your code here
-	// Wihtout scheduler, keep runing the last environment while it exists
+	// Your code here - Round robin
+#endif
+
+#ifdef SCHED_PRIORITIES
+	// Implement simple priorities scheduling.
+	//
+	// Environments now have a "priority" so it must be consider
+	// when the selection is performed.
+	//
+	// Be careful to not fall in "starvation" such that only one
+	// environment is selected and run every time.
+
+	// Your code here - Priorities
+#endif
+
+	// Without scheduler, keep runing the last environment while it exists
 	if (curenv) {
 		env_run(curenv);
 	}