panic: don't print redundant backtraces on oops

When an oops causes a panic and panic prints another backtrace it's pretty
common to have the original oops data be scrolled away on a 80x50 screen.

The second backtrace is quite redundant and not needed anyways.

So don't print the panic backtrace when oops_in_progress is true.

[akpm@linux-foundation.org: add comment]
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kernel/panic.c

@@ -94,7 +94,11 @@ void panic(const char *fmt, ...)
 	va_end(args);
 	printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
 #ifdef CONFIG_DEBUG_BUGVERBOSE
-	dump_stack();
+	/*
+	 * Avoid nested stack-dumping if a panic occurs during oops processing
+	 */
+	if (!oops_in_progress)
+		dump_stack();
 #endif
 
 	/*