Changeset d5b37b6 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:

690ad20

Parents:

571cc2d

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2025-04-11 17:35:09)

git-committer:

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

Message:

Use a new syscall, SYS_KIO_READ, for reading from KIO buffer

Originally, the buffer memory was shared between kernel and
uspace, presumably to avoid the overhead of syscalls.
However, this makes synchronization with kernel impossible,
so it is not possible to ensure it works reliably without
random glitches. Also, relative to everything else /app/kio
does with the data, the syscall overhead is positively tiny.

File:

• uspace/app/kio/kio.c (modified) (7 diffs)

uspace/app/kio/kio.c

@@ -1 +1 @@
 /*
  * Copyright (c) 2006 Ondrej Palkovsky
+ * Copyright (c) 2025 Jiří Zárevúcky
  * All rights reserved.
  *
@@ -34 +35 @@
  */
 
+#include <_bits/decls.h>
+#include <libarch/config.h>
 #include <stdio.h>
 #include <async.h>
@@ -47 +50 @@
 #include <adt/prodcons.h>
 #include <tinput.h>
+#include <uchar.h>
 #include <vfs/vfs.h>
 
@@ -61 +65 @@
 static prodcons_t pc;
 
-/* Pointer to kio area */
-static char32_t *kio = (char32_t *) AS_AREA_ANY;
-static size_t kio_length;
-
 /* Notification mutex */
 static FIBRIL_MUTEX_INITIALIZE(mtx);
 
-static size_t last_notification;
+#define READ_BUFFER_SIZE (PAGE_SIZE / sizeof(char32_t))
+
+static size_t current_at;
+static char32_t read_buffer[READ_BUFFER_SIZE];
 
 /** Klog producer
@@ -151 +154 @@
 static void kio_notification_handler(ipc_call_t *call, void *arg)
 {
+        size_t kio_written = (size_t) ipc_get_arg1(call);
+
         /*
          * Make sure we process only a single notification
@@ -159 +164 @@
         fibril_mutex_lock(&mtx);
 
-        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 + new_chars > kio_length) {
-                size_t split = kio_length - offset;
-
-                producer(split, kio + offset);
-                producer(new_chars - split, kio);
-        } else {
-                producer(new_chars, kio + offset);
+        while (current_at != kio_written) {
+                size_t read = kio_read(read_buffer, READ_BUFFER_SIZE, current_at);
+                if (read == 0)
+                        break;
+
+                current_at += read;
+
+                if (read > READ_BUFFER_SIZE) {
+                        /* We missed some data. */
+                        // TODO: Send a message with the number of lost characters to the consumer.
+                        read = READ_BUFFER_SIZE;
+                }
+
+                producer(read, read_buffer);
         }
 
@@ -189 +186 @@
 int main(int argc, char *argv[])
 {
-        size_t pages;
-        errno_t rc = sysinfo_get_value("kio.pages", &pages);
-        if (rc != EOK) {
-                fprintf(stderr, "%s: Unable to get number of kio pages\n",
-                    NAME);
-                return rc;
-        }
-
-        uintptr_t faddr;
-        rc = sysinfo_get_value("kio.faddr", &faddr);
-        if (rc != EOK) {
-                fprintf(stderr, "%s: Unable to get kio physical address\n",
-                    NAME);
-                return rc;
-        }
-
-        size_t size = pages * PAGE_SIZE;
-        kio_length = size / sizeof(char32_t);
-
-        rc = physmem_map(faddr, pages, AS_AREA_READ | AS_AREA_CACHEABLE,
-            (void *) &kio);
-        if (rc != EOK) {
-                fprintf(stderr, "%s: Unable to map kio\n", NAME);
-                return rc;
-        }
-
         prodcons_initialize(&pc);
-        rc = async_event_subscribe(EVENT_KIO, kio_notification_handler, NULL);
+        errno_t rc = async_event_subscribe(EVENT_KIO, kio_notification_handler, NULL);
         if (rc != EOK) {
                 fprintf(stderr, "%s: Unable to register kio notifications\n",