simplify the stacktrace code

Simplify the stacktrace code:

 - remove the unused task argument to save_stack_trace, it's always
   current
 - remove the all_contexts flag, it's alwasy 0

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andi Kleen <ak@suse.de>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 7065a68..c1e308a 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -257,9 +257,8 @@
 	trace->entries = stack_trace + nr_stack_trace_entries;
 
 	trace->skip = 3;
-	trace->all_contexts = 0;
 
-	save_stack_trace(trace, NULL);
+	save_stack_trace(trace);
 
 	trace->max_entries = trace->nr_entries;