[Xen-changelog] [xen staging] xen/debug: make debugtrace more clever regarding repeating entries

[patchbot@xxxxxxx]

commit fc5021c29a59630a12de89fd33f4a00b99299e13
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Mon Mar 18 11:40:32 2019 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Mar 18 11:40:32 2019 +0100

    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@xxxxxxxx>
    Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 xen/drivers/char/console.c | 42 +++++++++++++++++++++++++++++++-----------
 1 file changed, 31 insertions(+), 11 deletions(-)

diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 41ec13ce52..f41b689847 100644
--- 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);
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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