[PATCH] unnecessary removal of guest console characters

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

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Hi all,
currently when max_capacity is set in xenconsoled and the buffer if 
completely filled then some characters in the buffer are discarded (even 
though the rate limitation makes this unlikely to happen).
A better way to handle this scenario would be to stop reading from the 
ring until the buffer has some free space.
I am attaching a simple patch that does exactly this.
Best Regards,

Stefano Stabellini

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

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diff -r 082d3886fded tools/console/daemon/io.c
--- a/tools/console/daemon/io.c	Fri Apr 11 09:14:03 2008 +0100
+++ b/tools/console/daemon/io.c	Fri Apr 11 14:12:51 2008 +0100
@@ -200,21 +200,6 @@ static void buffer_append(struct domain 
 			      "on domain %d: %d (%s)\n",
 			      dom->domid, errno, strerror(errno));
 	}
-
-	if (buffer->max_capacity &&
-	    buffer->size > buffer->max_capacity) {
-		/* Discard the middle of the data. */
-
-		size_t over = buffer->size - buffer->max_capacity;
-		char *maxpos = buffer->data + buffer->max_capacity;
-
-		memmove(maxpos - over, maxpos, over);
-		buffer->data = realloc(buffer->data, buffer->max_capacity);
-		buffer->size = buffer->capacity = buffer->max_capacity;
-
-		if (buffer->consumed > buffer->max_capacity - over)
-			buffer->consumed = buffer->max_capacity - over;
-	}
 }
 
 static bool buffer_empty(struct buffer *buffer)
@@ -228,6 +213,11 @@ static void buffer_advance(struct buffer
 	if (buffer->consumed == buffer->size) {
 		buffer->consumed = 0;
 		buffer->size = 0;
+		if (buffer->max_capacity &&
+		    buffer->capacity > buffer->max_capacity) {
+			buffer->data = realloc(buffer->data, buffer->max_capacity);
+			buffer->capacity = buffer->max_capacity;
+		}
 	}
 }
 
@@ -1005,9 +995,12 @@ void handle_io(void)
 				    d->next_period < next_timeout)
 					next_timeout = d->next_period;
 			} else if (d->xce_handle != -1) {
-				int evtchn_fd = xc_evtchn_fd(d->xce_handle);
-				FD_SET(evtchn_fd, &readfds);
-				max_fd = MAX(evtchn_fd, max_fd);
+				if (!d->buffer.max_capacity ||
+				    d->buffer.size < d->buffer.max_capacity) {
+					int evtchn_fd = xc_evtchn_fd(d->xce_handle);
+					FD_SET(evtchn_fd, &readfds);
+					max_fd = MAX(evtchn_fd, max_fd);
+				}
 			}
 
 			if (d->master_fd != -1) {

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