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

diff --git a/src/devices/intq.h b/src/devices/intq.h
index 161d7eb5a161780c79749483a278a608a35a3c0b..2312b129e1fd984240bc5813d56da9760eb9bd3b 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.
-
-   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
+   Interrupt queue functions can be called from kernel threads or
+   from external interrupt handlers.  Except for intq_init(),
+   interrupts must be off in either case.
+
+   The interrupt queue has the structure of a "monitor".  Locks
+   and condition variables from threads/synch.h cannot be used in
+   this case, as they normally would, because they can only
+   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. */
 
@@ -46,9 +34,7 @@ struct intq
     int tail;                   /* Old data is read here. */
   };
 
-void intq_init (struct intq *, const char *);
-void intq_lock (struct intq *);
-void intq_unlock (struct intq *);
+void intq_init (struct intq *);
 bool intq_empty (const struct intq *);
 bool intq_full (const struct intq *);
 uint8_t intq_getc (struct intq *);