Re: [PATCH v13 1/8] perf tools: Drop redundant evsel->overwrite indicator

[Wangnan (F)]

On 2016/7/6 18:53, Jiri Olsa wrote:

On Mon, Jul 04, 2016 at 06:20:02AM +0000, Wang Nan wrote:

SNIP

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 0fea724..3abe519 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1359,6 +1359,9 @@ static int __perf_evsel__open(struct perf_evsel *evsel, 
struct cpu_map *cpus,
        int pid = -1, err;
        enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;

+ if (perf_missing_features.write_backward && evsel->attr.write_backward)

+               return -EINVAL;
+
        if (evsel->system_wide)
                nthreads = 1;
        else
@@ -1389,11 +1392,6 @@ fallback_missing_features:
        if (perf_missing_features.lbr_flags)
                evsel->attr.branch_sample_type &= ~(PERF_SAMPLE_BRANCH_NO_FLAGS 
|
                                     PERF_SAMPLE_BRANCH_NO_CYCLES);
-       if (perf_missing_features.write_backward) {
-               if (evsel->overwrite)
-                       return -EINVAL;
-               evsel->attr.write_backward = false;
-       }

so we don't change the attr.write_backward anymore?
based on the kernel support..

We don't need fallback here. If evsel->attr.write_backward is selected
and it is missing, we should fail.

we do it for other features, why not here? also changelog
did not mentioned it at all ;-)

thanks,
jirka