[Xen-changelog] [xen staging] xen: fix debugtrace clearing

[patchbot@xxxxxxx]

commit 36b312064b9b94e891c993bd1c70e784a23cfb49
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Mon Sep 9 14:34:37 2019 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Sep 9 14:34:37 2019 +0200

    xen: fix debugtrace clearing
    
    After dumping the debugtrace buffer it is cleared. This results in some
    entries not being printed in case the buffer is dumped again before
    having wrapped.
    
    While at it remove the trailing zero byte in the buffer as it is no
    longer needed. Commit b5e6e1ee8da59f introduced passing the number of
    chars to be printed in the related interfaces, so the trailing 0 byte
    is no longer required.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/drivers/char/console.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index f49c6f29a8..3783618c17 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -1173,6 +1173,7 @@ static char        *debugtrace_buf; /* Debug-trace buffer 
*/
 static unsigned int debugtrace_prd; /* Producer index     */
 static unsigned int debugtrace_kilobytes = 128, debugtrace_bytes;
 static unsigned int debugtrace_used;
+static bool debugtrace_buf_empty = true;
 static DEFINE_SPINLOCK(debugtrace_lock);
 integer_param("debugtrace", debugtrace_kilobytes);
 
@@ -1184,16 +1185,17 @@ static void debugtrace_dump_worker(void)
     printk("debugtrace_dump() starting\n");
 
     /* Print oldest portion of the ring. */
-    ASSERT(debugtrace_buf[debugtrace_bytes - 1] == 0);
     if ( debugtrace_buf[debugtrace_prd] != '\0' )
         console_serial_puts(&debugtrace_buf[debugtrace_prd],
-                            debugtrace_bytes - debugtrace_prd - 1);
+                            debugtrace_bytes - debugtrace_prd);
 
     /* Print youngest portion of the ring. */
     debugtrace_buf[debugtrace_prd] = '\0';
     console_serial_puts(&debugtrace_buf[0], debugtrace_prd);
 
     memset(debugtrace_buf, '\0', debugtrace_bytes);
+    debugtrace_prd = 0;
+    debugtrace_buf_empty = true;
 
     printk("debugtrace_dump() finished\n");
 }
@@ -1241,8 +1243,7 @@ static void debugtrace_add_to_buf(char *buf)
     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) )
+        if ( debugtrace_prd == debugtrace_bytes )
             debugtrace_prd = 0;
     }
 }
@@ -1264,8 +1265,6 @@ void debugtrace_printk(const char *fmt, ...)
 
     spin_lock_irqsave(&debugtrace_lock, flags);
 
-    ASSERT(debugtrace_buf[debugtrace_bytes - 1] == 0);
-
     va_start(args, fmt);
     nr = vscnprintf(buf, sizeof(buf), fmt, args);
     va_end(args);
@@ -1279,8 +1278,9 @@ void debugtrace_printk(const char *fmt, ...)
     }
     else
     {
-        if ( strcmp(buf, last_buf) )
+        if ( debugtrace_buf_empty || strcmp(buf, last_buf) )
         {
+            debugtrace_buf_empty = false;
             last_prd = debugtrace_prd;
             last_count = ++count;
             safe_strcpy(last_buf, buf);
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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