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Subject[PATCH 3/6] perf tools: Improve thread_stack__event() for trace begin / end
Date
thread_stack__event() is used to create call stacks, by keeping track of
calls and returns. Improve the handling of trace begin / end to allow for a
trace that ends in a call.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
tools/perf/util/thread-stack.c | 35 +++++++++++++++++++++++++++++-----
1 file changed, 30 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c
index dd17d6a38d3a..cea28b9074c1 100644
--- a/tools/perf/util/thread-stack.c
+++ b/tools/perf/util/thread-stack.c
@@ -36,6 +36,7 @@
* @branch_count: the branch count when the entry was created
* @cp: call path
* @no_call: a 'call' was not seen
+ * @trace_end: a 'call' but trace ended
*/
struct thread_stack_entry {
u64 ret_addr;
@@ -44,6 +45,7 @@ struct thread_stack_entry {
u64 branch_count;
struct call_path *cp;
bool no_call;
+ bool trace_end;
};

/**
@@ -112,7 +114,8 @@ static struct thread_stack *thread_stack__new(struct thread *thread,
return ts;
}

-static int thread_stack__push(struct thread_stack *ts, u64 ret_addr)
+static int thread_stack__push(struct thread_stack *ts, u64 ret_addr,
+ bool trace_end)
{
int err = 0;

@@ -124,6 +127,7 @@ static int thread_stack__push(struct thread_stack *ts, u64 ret_addr)
}
}

+ ts->stack[ts->cnt].trace_end = trace_end;
ts->stack[ts->cnt++].ret_addr = ret_addr;

return err;
@@ -150,6 +154,18 @@ static void thread_stack__pop(struct thread_stack *ts, u64 ret_addr)
}
}

+static void thread_stack__pop_trace_end(struct thread_stack *ts)
+{
+ size_t i;
+
+ for (i = ts->cnt; i; ) {
+ if (ts->stack[--i].trace_end)
+ ts->cnt = i;
+ else
+ return;
+ }
+}
+
static bool thread_stack__in_kernel(struct thread_stack *ts)
{
if (!ts->cnt)
@@ -254,10 +270,19 @@ int thread_stack__event(struct thread *thread, u32 flags, u64 from_ip,
ret_addr = from_ip + insn_len;
if (ret_addr == to_ip)
return 0; /* Zero-length calls are excluded */
- return thread_stack__push(thread->ts, ret_addr);
- } else if (flags & PERF_IP_FLAG_RETURN) {
- if (!from_ip)
- return 0;
+ return thread_stack__push(thread->ts, ret_addr,
+ flags && PERF_IP_FLAG_TRACE_END);
+ } else if (flags & PERF_IP_FLAG_TRACE_BEGIN) {
+ /*
+ * If the caller did not change the trace number (which would
+ * have flushed the stack) then try to make sense of the stack.
+ * Possibly, tracing began after returning to the current
+ * address, so try to pop that. Also, do not expect a call made
+ * when the trace ended, to return, so pop that.
+ */
+ thread_stack__pop(thread->ts, to_ip);
+ thread_stack__pop_trace_end(thread->ts);
+ } else if ((flags & PERF_IP_FLAG_RETURN) && from_ip) {
thread_stack__pop(thread->ts, to_ip);
}

--
2.17.1
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