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Date:   Wed, 17 Apr 2019 10:54:23 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Phil Auld <pauld@redhat.com>
Cc:     Slavomir Kaslev <kaslevs@vmware.com>,
        linux-trace-devel@vger.kernel.org, ykaradzhov@vmware.com,
        jbacik@fb.com, tstoyanov@vmware.com, slavomir.kaslev@gmail.com
Subject: Re: [PATCH v4 1/2] trace-cmd: Optimize how pid filters are
 expressed
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On Wed, 17 Apr 2019 09:58:58 -0400
Phil Auld <pauld@redhat.com> wrote:

> FILTER write /sys/kernel/debug/tracing/events/sched/sched_switch/filter (len 142) value "(common_pid<21420||common_pid>21425)&&(common_pid<21265||common_pid>21418)||(next_pid<21420||next_pid>21425)&&(next_pid<21265||next_pid>21418)"
> 
> 
> The latter is correct given precendce of && before || but I wonder if () don't make sense? I always have to look
> that one up :)

Yes, as the one who wrote the parsing code (and was lectured by
Al Viro about it), I know for a fact that && has a higher precedence
than the || and it should work. I was about to comment about that, but
then remembered my "lesson" :-)

-- Steve


> 
> If I were writing that in code I'd probably put in the extra ()s, but since it's generated and no
> one actually sees it, probably okay and simpler as is.