perf tools: Fix comment for sort__* compare functions

In commit 2f15bd8c6c6e ("perf tools: Fix "Command" sort_entry's cmp and
collapse function") we switched from pointer to string comparison.

But failed to remove related comments. Removing them and adding another
one to warn before pointer comparison in here.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180206181813.10943-18-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
index 2da4d0456a0354e0f83a9959b423ca63e3611257..e8514f651865239578a622e8632d214b6ab6c3b2 100644 (file)
--- a/tools/perf/util/sort.c
+++ b/tools/perf/util/sort.c
@@ -111,17 +111,20 @@ struct sort_entry sort_thread = {
 
 /* --sort comm */
 
+/*
+ * We can't use pointer comparison in functions below,
+ * because it gives different results based on pointer
+ * values, which could break some sorting assumptions.
+ */
 static int64_t
 sort__comm_cmp(struct hist_entry *left, struct hist_entry *right)
 {
-       /* Compare the addr that should be unique among comm */
        return strcmp(comm__str(right->comm), comm__str(left->comm));
 }
 
 static int64_t
 sort__comm_collapse(struct hist_entry *left, struct hist_entry *right)
 {
-       /* Compare the addr that should be unique among comm */
        return strcmp(comm__str(right->comm), comm__str(left->comm));
 }