Re: [PATCH 9/9] tools lib traceevent: Honor operator priority

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Jiri Olsa <jolsa@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
	David Ahern <dsahern@gmail.com>, Minchan Kim <minchan@kernel.org>,
	Joonsoo Kim <js1304@gmail.com>,
	linux-mm@kvack.org, Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 9/9] tools lib traceevent: Honor operator priority
Date: Mon, 13 Apr 2015 10:41:41 -0300	[thread overview]
Message-ID: <20150413134141.GF3200@kernel.org> (raw)
In-Reply-To: <1428298576-9785-10-git-send-email-namhyung@kernel.org>

Em Mon, Apr 06, 2015 at 02:36:16PM +0900, Namhyung Kim escreveu:
> 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)

And this one already went upstream.

- Arnaldo