[tip:perf/core] tools lib traceevent: Honor operator priority

[tip-bot for Namhyung Kim]

Commit-ID:  3201f0dc42f7fad9387afc4692cea3d0c730cba2
Gitweb:     http://git.kernel.org/tip/3201f0dc42f7fad9387afc4692cea3d0c730cba2
Author:     Namhyung Kim <namhyung@xxxxxxxxxx>
AuthorDate: Mon, 6 Apr 2015 14:36:16 +0900
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Wed, 8 Apr 2015 09:07:09 -0300

tools lib traceevent: Honor operator priority

Currently it ignores operator priority and just sets processed args as a
right operand.  But it could result in priority inversion in case that
the right operand is also a operator arg and its priority is lower.

For example, following print format is from new kmem events.

  "page=%p", REC->pfn != -1UL ? (((struct page *)(0xffffea0000000000UL)) + (REC->pfn)) : ((void *)0)

But this was treated as below:

  REC->pfn != ((null - 1UL) ? ((struct page *)0xffffea0000000000UL + REC->pfn) : (void *) 0)

In this case, the right arg was '?' operator which has lower priority.
But it just sets the whole arg so making the output confusing - page was
always 0 or 1 since that's the result of logical operation.

With this patch, it can handle it properly like following:

  ((REC->pfn != (null - 1UL)) ? ((struct page *)0xffffea0000000000UL + REC->pfn) : (void *) 0)

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Joonsoo Kim <js1304@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Link: http://lkml.kernel.org/r/1428298576-9785-10-git-send-email-namhyung@xxxxxxxxxx
[ Replaced 'swap' with 'rotate' in a comment as requested by Steve and agreed by Namhyung ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/lib/traceevent/event-parse.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index 6d31b64..12a7e2a 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -1939,7 +1939,22 @@ process_op(struct event_format *event, struct print_arg *arg, char **tok)
 			goto out_warn_free;
 
 		type = process_arg_token(event, right, tok, type);
-		arg->op.right = right;
+
+		if (right->type == PRINT_OP &&
+		    get_op_prio(arg->op.op) < get_op_prio(right->op.op)) {
+			struct print_arg tmp;
+
+			/* rotate ops according to the priority */
+			arg->op.right = right->op.left;
+
+			tmp = *arg;
+			*arg = *right;
+			*right = tmp;
+
+			arg->op.left = right;
+		} else {
+			arg->op.right = right;
+		}
 
 	} else if (strcmp(token, "[") == 0) {
 
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