xen/debug: make debugtrace more clever regarding repeating entries

In case debugtrace is writing to memory and the last entry is repeated
don't fill up the trace buffer, but modify the count prefix to "x-y "
style instead.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 41ec13ce52f2da285240762ac52055ed51ded785..f41b689847dde64478b79479669f2a7d4b969231 100644 (file)
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -1225,13 +1225,26 @@ void debugtrace_dump(void)
     watchdog_enable();
 }
 
+static void debugtrace_add_to_buf(char *buf)
+{
+    char *p;
+
+    for ( p = buf; *p != '\0'; p++ )
+    {
+        debugtrace_buf[debugtrace_prd++] = *p;
+        /* Always leave a nul byte at the end of the buffer. */
+        if ( debugtrace_prd == (debugtrace_bytes - 1) )
+            debugtrace_prd = 0;
+    }
+}
+
 void debugtrace_printk(const char *fmt, ...)
 {
-    static char    buf[1024];
-    static u32 count;
+    static char buf[1024], last_buf[1024];
+    static unsigned int count, last_count, last_prd;
 
+    char          cntbuf[24];
     va_list       args;
-    char         *p;
     unsigned long flags;
 
     if ( debugtrace_bytes == 0 )
@@ -1243,25 +1256,32 @@ void debugtrace_printk(const char *fmt, ...)
 
     ASSERT(debugtrace_buf[debugtrace_bytes - 1] == 0);
 
-    snprintf(buf, sizeof(buf), "%u ", ++count);
-
     va_start(args, fmt);
-    (void)vsnprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), fmt, args);
+    vsnprintf(buf, sizeof(buf), fmt, args);
     va_end(args);
 
     if ( debugtrace_send_to_console )
     {
+        snprintf(cntbuf, sizeof(cntbuf), "%u ", ++count);
+        serial_puts(sercon_handle, cntbuf);
         serial_puts(sercon_handle, buf);
     }
     else
     {
-        for ( p = buf; *p != '\0'; p++ )
+        if ( strcmp(buf, last_buf) )
+        {
+            last_prd = debugtrace_prd;
+            last_count = ++count;
+            safe_strcpy(last_buf, buf);
+            snprintf(cntbuf, sizeof(cntbuf), "%u ", count);
+        }
+        else
         {
-            debugtrace_buf[debugtrace_prd++] = *p;            
-            /* Always leave a nul byte at the end of the buffer. */
-            if ( debugtrace_prd == (debugtrace_bytes - 1) )
-                debugtrace_prd = 0;
+            debugtrace_prd = last_prd;
+            snprintf(cntbuf, sizeof(cntbuf), "%u-%u ", last_count, ++count);
         }
+        debugtrace_add_to_buf(cntbuf);
+        debugtrace_add_to_buf(buf);
     }
 
     spin_unlock_irqrestore(&debugtrace_lock, flags);