Commit 06d65bda authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
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perf events, x86/stacktrace: Fix performance/softlockup by providing a special... 


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: default avatarFrederic 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: default avatarIngo Molnar <mingo@elte.hu>
parent 61c1917f

arch/x86/include/asm/stacktrace.h

+6 −0
Original line number Diff line number Diff line
@@ -22,6 +22,12 @@ print_context_stack(struct thread_info *tinfo, 
		    const struct stacktrace_ops *ops, void *data,

		    unsigned long *end, int *graph);



extern 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);



/* Generic stack tracer with callbacks */



struct stacktrace_ops {

arch/x86/kernel/cpu/perf_event.c

+1 −1
Original line number Diff line number Diff line
@@ -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"

arch/x86/kernel/dumpstack.c

+26 −2
Original line number Diff line number Diff line
@@ -109,6 +109,30 @@ print_context_stack(struct thread_info *tinfo, 
	}

	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

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