[tip:perf/urgent] perf: Pass appropriate frame pointer to dump_trace()

[tip-bot for Frederic Weisbecker]

Commit-ID:  48b5ba9cc98d676712da29d9931f1c88e5185ff2
Gitweb:     http://git.kernel.org/tip/48b5ba9cc98d676712da29d9931f1c88e5185ff2
Author:     Frederic Weisbecker <fweisbec@xxxxxxxxx>
AuthorDate: Thu, 31 Dec 2009 05:53:02 +0100
Committer:  Ingo Molnar <mingo@xxxxxxx>
CommitDate: Thu, 31 Dec 2009 13:11:31 +0100

perf: Pass appropriate frame pointer to dump_trace()

Pass the frame pointer from the regs of the interrupted path
to dump_trace() while processing the stack trace.

Currently, dump_trace() takes the current bp and starts the
callchain from dump_trace() itself. This is wasteful because
we need to walk through the entire NMI/DEBUG stack before
retrieving the interrupted point.

We can fix that by just using the frame pointer from the
captured regs. It points exactly where we want to start.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
LKML-Reference: <1262235183-5320-1-git-send-regression-fweisbec@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
---
 arch/x86/kernel/cpu/perf_event.c |    2 +-
 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 c223b7e..d616c06 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -2347,7 +2347,7 @@ perf_callchain_kernel(struct pt_regs *regs, struct perf_callchain_entry *entry)
 	callchain_store(entry, PERF_CONTEXT_KERNEL);
 	callchain_store(entry, regs->ip);
 
-	dump_trace(NULL, regs, NULL, 0, &backtrace_ops, entry);
+	dump_trace(NULL, regs, NULL, regs->bp, &backtrace_ops, entry);
 }
 
 /*
--
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