Setup critical section management for parts that must not be interrupted.

2 files changed, 19 insertions, 10 deletions

diff --git a/src/kernel/include/idt.h b/src/kernel/include/idt.h
index 2cccfa5..45cc3e3 100644
--- a/src/kernel/include/idt.h
+++ b/src/kernel/include/idt.h
@@ -75,14 +75,13 @@ void idt_set_ex_handler(int number, isr_handler_t func);	//Set exception handler
 void idt_set_irq_handler(int number, isr_handler_t func);	//Set IRQ handler
 
 // Warning about IRQ handlers :
-// IRQ handlers must not call yield(), because that may not return ! Therefore they cannot
-// use mutexes, memory allocation and most usefull things. Basically the only thing they
-// can do is wake up another thread, so it is a good idea to have a thread that waits for
-// the IRQ and does something when it happens, and the IRQ handler only wakes up that thread
-// when the IRQ happens.
-// Remark on resume_thread : if the second argument is set to true, yield() is called in the
-// function, so it may never return in some circumstances
-// IRQ handlers are never preemptible
+// IRQ handlers may run on the kernel0 stack, which is reset each time the scheduler
+// is entered. Therefore IRQ handler routines may not call yield(), which makes them
+// unable to use mutexes, memory allocation and most usefull things. Basically the only
+// thing they can do is wake up another thread, so it is a good idea to have a thread
+// that waits for the IRQ and does something when it happens, and the IRQ handler only
+// wakes up that thread when the IRQ happens. They may also communicate via atomical
+// or lock free data structures.
 
 void dbg_dump_registers(registers_t*);
 
diff --git a/src/kernel/include/thread.h b/src/kernel/include/thread.h
index fa7dc6f..127b0d7 100644
--- a/src/kernel/include/thread.h
+++ b/src/kernel/include/thread.h
@@ -9,7 +9,7 @@
 #define T_STATE_PAUSED	 	2
 #define T_STATE_FINISHED	3
 
-#define KPROC_STACK_SIZE 0x8000	// 8Kb
+#define KPROC_STACK_SIZE 0x2000	// 8Kb
 
 #define TASK_SWITCH_FREQUENCY	100		// in herz
 
@@ -25,6 +25,7 @@ typedef struct thread {
 
 	uint32_t state;
 	uint64_t last_ran;
+	int critical_level;
 
 	region_info_t *stack_region;
 
@@ -46,7 +47,16 @@ void pause();
 void exit();
 void usleep(int usecs);
 
-bool resume_thread(thread_t *thread, bool run_at_once); // true if thrad was paused, false if was running
+bool resume_thread(thread_t *thread);
 void kill_thread(thread_t *thread);
 
+// Kernel critical sections
+#define CL_EXCL			3	// No interruptions accepted, context switching not allowed
+#define CL_NOINT 		2	// No interruptions accepted, timer context switching disabled (manual switch allowed)
+#define CL_NOSWITCH 	1	// Interruptions accepted, timer context switching disabled (manual switch allowed)
+#define CL_USER  		0	// Anything can happen
+
+int enter_critical(int level);
+void exit_critical(int prev_level);
+
 /* vim: set ts=4 sw=4 tw=0 noet :*/