2 files changed, 55 insertions, 9 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index c502024..da55fa3 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1,3 +1,4 @@
+#include <asm/interrupt.h>
 #include <asm/system.h>
 #include <errno.h>
 #include <kernel/con.h>
@@ -241,8 +242,13 @@ void reschedule(void) {
       }
     }
 
-    /* if not, then halt the machine */
-    __asm__ ("hlt");
+    /* if not, then halt the machine (temporarily re-enabling interrupts) */
+    __asm__ volatile (
+        "pushf\n"
+        "sti\n"
+        "hlt\n"
+        "popf\n"
+        );
   }
 }
 
@@ -258,6 +264,45 @@ void wake_up(struct task_struct **task) {
   *task = NULL;
 }
 
+void sleep_on(struct task_struct **waiting) {
+  struct task_struct *t;
+
+  if(waiting == NULL)
+    return;
+
+  t = *waiting;
+  *waiting = ctask;
+  ctask->state = TSTATE_UNINTERRUPTIBLE;
+  reschedule();
+
+  *waiting = t;
+  if(t)
+    t->state = TSTATE_RUNNING;
+}
+
+void interruptible_sleep_on(struct task_struct **waiting) {
+  struct task_struct *t;
+
+  if(waiting == NULL)
+    return;
+
+  t = *waiting;
+  *waiting = ctask;
+  while(1) {
+    ctask->state = TSTATE_INTERRUPTIBLE;
+    reschedule();
+
+    if(*waiting == NULL || *waiting == ctask)
+      break;
+
+    (*waiting)->state = TSTATE_RUNNING;
+  }
+
+  *waiting = NULL;
+  if(t)
+    t->state = TSTATE_RUNNING;
+}
+
 void sighandler_default(uint32_t sig) {
   switch(sig) {
     case SIGKILL:
diff --git a/kernel/serial.c b/kernel/serial.c
index 911f02c..f5610f5 100644
--- a/kernel/serial.c
+++ b/kernel/serial.c
@@ -97,18 +97,19 @@ ssize_t rsread(void *buf, size_t len) {
     return 0;
 
   while(n--) {
-    if(rxread == rxwrite) {
-      /* put the current task to sleep */
-      waiting_task = ctask;
-      ctask->state = TSTATE_INTERRUPTIBLE;
-      reschedule();
-    }
+    /* check if the buffer's empty and if so, go to sleep */
+    cli();
+    if(rxread == rxwrite)
+      interruptible_sleep_on(&waiting_task);
+
     /* check again to see if anything was read, or we were interrupted */
     if(rxread == rxwrite) {
-      waiting_task = NULL;
+      sti();
       return -EINTR;
     }
 
+    sti();
+
     *b++ = rxbuf[rxread];
     rxread = rxread + 1 % sizeof(rxbuf);
   }