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Subject[tip:perf/urgent] perf: Pass appropriate frame pointer to dump_trace()
Commit-ID:  48b5ba9cc98d676712da29d9931f1c88e5185ff2
Gitweb: http://git.kernel.org/tip/48b5ba9cc98d676712da29d9931f1c88e5185ff2
Author: Frederic Weisbecker <fweisbec@gmail.com>
AuthorDate: Thu, 31 Dec 2009 05:53:02 +0100
Committer: Ingo Molnar <mingo@elte.hu>
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@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1262235183-5320-1-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
---
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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