Commit 4d60e5e3 authored by Adrian Hunter's avatar Adrian Hunter Committed by Arnaldo Carvalho de Melo
Browse files

perf tools: Improve thread_stack__event() for trace begin / end 



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.

Previously, the Intel PT decoder would indicate begin / end by a branch
from / to zero. That hides useful information, in particular when a
trace ends with a call. Before remedying that, enhance the thread stack
so that it does not expect to see the 'return' for a 'call' that ends
the trace.

Committer notes:

Added this:

                return thread_stack__push(thread->ts, ret_addr,
-                                         flags && PERF_IP_FLAG_TRACE_END);
+                                         flags & PERF_IP_FLAG_TRACE_END);

To fix problem spotted by:

debian:9:            clang version 3.8.1-24 (tags/RELEASE_381/final)
debian:experimental: clang version 6.0.1-6 (tags/RELEASE_601/final)

Signed-off-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20180920130048.31432-4-adrian.hunter@intel.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent ff645daf

tools/perf/util/thread-stack.c

+30 −5
Original line number Diff line number Diff line
@@ -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);

	}

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