Really make it safe to call printf() from any context.

[pintos-anon] / src / devices / intq.h

diff --git a/src/devices/intq.h b/src/devices/intq.h
index 161d7eb5a161780c79749483a278a608a35a3c0b..2b3edeafea24f51c8c01ec441145ee1bc56d6347 100644 (file)
--- a/src/devices/intq.h
+++ b/src/devices/intq.h
@@ -7,23 +7,14 @@
 /* An "interrupt queue", a circular buffer shared between
    kernel threads and external interrupt handlers.
 
-   A kernel thread that touches an interrupt queue must bracket
-   its accesses with calls to intq_lock() and intq_unlock().
-   These functions take a lock associated with the queue (which
-   locks out other kernel threads) and disable interrupts (which
-   locks out interrupt handlers).
-
-   An external interrupt handler that touches an interrupt queue
-   need not take any special precautions.  Interrupts are
-   disabled in an external interrupt handler, so other code will
-   not interfere.  The interrupt cannot occur during an update to
-   the interrupt queue by a kernel thread because kernel threads
-   disable interrupts while touching interrupt queues.
+   These functions can be called from kernel threads or from
+   external interrupt handlers.  Except for intq_init(),
+   interrupts must be off in either case.
 
    Incidentally, this has the structure of a "monitor".  Normally
    we'd use locks and condition variables from threads/synch.h to
-   implement a monitor.  Unfortunately, those are intended only
-   to protect kernel threads from one another, not from interrupt
+   implement a monitor, but those are intended only to protect
+   kernel threads from one another, not from interrupt
    handlers. */
 
 /* Queue buffer size, in bytes. */
@@ -32,11 +23,8 @@
 /* A circular queue of bytes. */
 struct intq
   {
-    /* Mutual exclusion. */
-    enum intr_level old_level;  /* Excludes interrupt handlers. */
-    struct lock lock;           /* Excludes kernel threads. */
-
     /* Waiting threads. */
+    struct lock lock;           /* Only one thread may wait at once. */
     struct thread *not_full;    /* Thread waiting for not-full condition. */
     struct thread *not_empty;   /* Thread waiting for not-empty condition. */
 
@@ -47,8 +35,6 @@ struct intq
   };
 
 void intq_init (struct intq *, const char *);
-void intq_lock (struct intq *);
-void intq_unlock (struct intq *);
 bool intq_empty (const struct intq *);
 bool intq_full (const struct intq *);
 uint8_t intq_getc (struct intq *);