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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: Adrian 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: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Adrian Hunter 2018-09-20 16:00:45 +03:00 committed by Arnaldo Carvalho de Melo
parent ff645daf30
commit 4d60e5e36a
1 changed files with 30 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
tools/perf/util/thread-stack.c
View File

@ -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);
}