> I'm not familiar enough with the tty code to decide what the proper fix
> should
> be. I'll try to write a patch if someone could point me in the right
> direction.
Something like this perhaps ?
diff -u --new-file --recursive --exclude-from /usr/src/exclude
linux.vanilla-2.6.23rc1-mm1/drivers/char/tty_io.c
linux-2.6.23rc1-mm1/drivers/char/tty_io.c
--- linux.vanilla-2.6.23rc1-mm1/drivers/char/tty_io.c 2007-07-26
15:02:57.000000000 +0100
+++ linux-2.6.23rc1-mm1/drivers/char/tty_io.c 2007-08-08 11:39:29.791433672
+0100
@@ -369,25 +369,50 @@
}
/**
- * tty_buffer_flush - flush full tty buffers
+ * __tty_buffer_flush - flush full tty buffers
* @tty: tty to flush
*
- * flush all the buffers containing receive data
+ * flush all the buffers containing receive data. Caller must
+ * hold the buffer lock and must have ensured no parallel flush to
+ * ldisc is running.
*
* Locking: none
*/
-static void tty_buffer_flush(struct tty_struct *tty)
+static void __tty_buffer_flush(struct tty_struct *tty)
{
struct tty_buffer *thead;
- unsigned long flags;
- spin_lock_irqsave(&tty->buf.lock, flags);
while((thead = tty->buf.head) != NULL) {
tty->buf.head = thead->next;
tty_buffer_free(tty, thead);
}
tty->buf.tail = NULL;
+}
+
+/**
+ * tty_buffer_flush - flush full tty buffers
+ * @tty: tty to flush
+ *
+ * flush all the buffers containing receive data. If the buffer is
+ * being processed by flush_to_ldisc then we defer the processing
+ * to that function
+ *
+ * Locking: none
+ */
+
+static void tty_buffer_flush(struct tty_struct *tty)
+{
+ unsigned long flags;
+ spin_lock_irqsave(&tty->buf.lock, flags);
+
+ /* If the data is being pushed to the tty layer then we can't
+ process it here. Instead set a flag and the flush_to_ldisc
+ path will process the flush request before it exits */
+ if (tty->buf.flushing)
+ tty->buf.flushpending = 1;
+ else
+ __tty_buffer_flush(tty);
spin_unlock_irqrestore(&tty->buf.lock, flags);
}
@@ -3594,6 +3619,7 @@
return;
spin_lock_irqsave(&tty->buf.lock, flags);
+ tty->buf.flushing = 1; /* So we know for tty_flush_buffers */
head = tty->buf.head;
if (head != NULL) {
tty->buf.head = NULL;
@@ -3607,6 +3633,11 @@
tty_buffer_free(tty, tbuf);
continue;
}
+ /* Ldisc or user is trying to flush the buffers
+ we are feeding to the ldisc, stop feeding the
+ line discipline as we want to empty the queue */
+ if (tty->buf.flushpending)
+ break;
if (!tty->receive_room) {
schedule_delayed_work(&tty->buf.work, 1);
break;
@@ -3620,8 +3651,16 @@
disc->receive_buf(tty, char_buf, flag_buf, count);
spin_lock_irqsave(&tty->buf.lock, flags);
}
+ /* Restore the queue head */
tty->buf.head = head;
+ /* We may have a deferred request to flush the input buffer,
+ if so do it now under the lock and empty the queue */
+ if (tty->buf.flushpending) {
+ __tty_buffer_flush(tty);
+ tty->buf.flushpending = 0;
+ }
}
+ tty->buf.flushing = 0;
spin_unlock_irqrestore(&tty->buf.lock, flags);
tty_ldisc_deref(disc);
diff -u --new-file --recursive --exclude-from /usr/src/exclude
linux.vanilla-2.6.23rc1-mm1/include/linux/tty.h
linux-2.6.23rc1-mm1/include/linux/tty.h
--- linux.vanilla-2.6.23rc1-mm1/include/linux/tty.h 2007-07-26
15:02:04.000000000 +0100
+++ linux-2.6.23rc1-mm1/include/linux/tty.h 2007-08-08 11:44:32.000000000
+0100
@@ -80,13 +73,10 @@
struct tty_buffer *tail; /* Active buffer */
struct tty_buffer *free; /* Free queue head */
int memory_used; /* Buffer space used excluding free
queue */
+ unsigned int flushing:1; /* flush_to_ldisc active */
+ unsigned int flushpending:1; /* A request to clear the queue is
pending */
};
/*
- * The pty uses char_buf and flag_buf as a contiguous buffer
- */
-#define PTY_BUF_SIZE 4*TTY_FLIPBUF_SIZE
-
-/*
* When a break, frame error, or parity error happens, these codes are
* stuffed into the flags buffer.
*/
-
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