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>
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 8aaa119..c56bc28 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -109,6 +109,30 @@
}
return bp;
}
+EXPORT_SYMBOL_GPL(print_context_stack);
+
+unsigned long
+print_context_stack_bp(struct thread_info *tinfo,
+ unsigned long *stack, unsigned long bp,
+ const struct stacktrace_ops *ops, void *data,
+ unsigned long *end, int *graph)
+{
+ struct stack_frame *frame = (struct stack_frame *)bp;
+ unsigned long *ret_addr = &frame->return_address;
+
+ while (valid_stack_ptr(tinfo, ret_addr, sizeof(*ret_addr), end)) {
+ unsigned long addr = *ret_addr;
+
+ if (__kernel_text_address(addr)) {
+ ops->address(data, addr, 1);
+ frame = frame->next_frame;
+ ret_addr = &frame->return_address;
+ print_ftrace_graph_addr(addr, data, ops, tinfo, graph);
+ }
+ }
+ return (unsigned long)frame;
+}
+EXPORT_SYMBOL_GPL(print_context_stack_bp);
static void
@@ -143,8 +167,8 @@
static const struct stacktrace_ops print_trace_ops = {
.warning = print_trace_warning,
.warning_symbol = print_trace_warning_symbol,
- .stack = print_trace_stack,
- .address = print_trace_address,
+ .stack = print_trace_stack,
+ .address = print_trace_address,
.walk_stack = print_context_stack,
};