perf events, x86/stacktrace: Fix performance/softlockup by providing a special frame pointer-only stack walker

It's just wasteful for stacktrace users like perf to walk
through every entries on the stack whereas these only accept
reliable ones, ie: that the frame pointer validates.

Since perf requires pure reliable stacktraces, it needs a stack
walker based on frame pointers-only to optimize the stacktrace
processing.

This might solve some near-lockup scenarios that can be triggered
by call-graph tracing timer events.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1261024834-5336-2-git-send-regression-fweisbec@gmail.com>
[ v2: fix for modular builds and small detail tidyup ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index d3802ee5a416..c223b7e895d9 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -2336,7 +2336,7 @@ static const struct stacktrace_ops backtrace_ops = {
         .warning_symbol         = backtrace_warning_symbol,
         .stack                  = backtrace_stack,
         .address                = backtrace_address,
-        .walk_stack             = print_context_stack,
+        .walk_stack             = print_context_stack_bp,
 };
 
 #include "../dumpstack.h"