Hi Steve,
On Mon, Apr 06, 2015 at 10:45:04AM -0400, Steven Rostedt wrote:
> On Mon, 6 Apr 2015 14:36:16 +0900
> Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> > 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)
>
> Nice catch. One nit.
>
> >
> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> > Signed-off-by: Namhyung Kim <namhyung@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 6d31b6419d37..604bea5c3fb0 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;
> > +
> > + /* swap ops according to the priority */
>
> This isn't really a swap. Better term to use is "rotate".
You're right!
>
> But other than that,
>
> Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Thanks for the review
Namhyung
>
> > + 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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