Changeset af77459 in mainline for uspace/app/kio/kio.c

Timestamp:

2025-04-17T15:14:03Z (5 days ago)

Author:

Jiří Zárevúcky <zarevucky.jiri@…>

Branches:

master

Children:

571cc2d

Parents:

1db4e2ae

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2025-04-11 15:27:51)

git-committer:

Jiří Zárevúcky <zarevucky.jiri@…> (2025-04-17 15:14:03)

Message:

Simplify kio buffer bookkeeping

We only really need to know the number of characters written.
The rest is easily inferred from buffer size.

File:

• uspace/app/kio/kio.c (modified) (2 diffs)

uspace/app/kio/kio.c

@@ -68 +68 @@
 static FIBRIL_MUTEX_INITIALIZE(mtx);
 
+static size_t last_notification;
+
 /** Klog producer
  *
@@ -153 +155 @@
          * at any time to limit the chance of the consumer
          * starving.
-         *
-         * Note: Usually the automatic masking of the kio
-         * notifications on the kernel side does the trick
-         * of limiting the chance of accidentally copying
-         * the same data multiple times. However, due to
-         * the non-blocking architecture of kio notifications,
-         * this possibility cannot be generally avoided.
          */
 
         fibril_mutex_lock(&mtx);
 
-        size_t kio_start = (size_t) ipc_get_arg1(call);
-        size_t kio_len = (size_t) ipc_get_arg2(call);
-        size_t kio_stored = (size_t) ipc_get_arg3(call);
-
-        size_t offset = (kio_start + kio_len - kio_stored) % kio_length;
+        size_t kio_written = (size_t) ipc_get_arg1(call);
+
+        /* This works just fine even when kio_written overflows. */
+        size_t new_chars = kio_written - last_notification;
+        last_notification = kio_written;
+
+        if (new_chars > kio_length) {
+                /* We missed some data. */
+                // TODO: Send a message with the number of lost bytes to the consumer.
+                new_chars = kio_length;
+        }
+
+        size_t offset = (kio_written - new_chars) % kio_length;
 
         /* Copy data from the ring buffer */
-        if (offset + kio_stored >= kio_length) {
+        if (offset + new_chars > kio_length) {
                 size_t split = kio_length - offset;
 
                 producer(split, kio + offset);
-                producer(kio_stored - split, kio);
-        } else
-                producer(kio_stored, kio + offset);
+                producer(new_chars - split, kio);
+        } else {
+                producer(new_chars, kio + offset);
+        }
 
         async_event_unmask(EVENT_KIO);