linux-kernel - Re: [PATCH RESEND] trace_uprobe: support reference counter in fd-based uprobe

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Message-ID: <20180928075219.GH3439@hirez.programming.kicks-ass.net>
Date:   Fri, 28 Sep 2018 09:52:19 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Song Liu <songliubraving@...com>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        "Naveen N . Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH RESEND] trace_uprobe: support reference counter in
 fd-based uprobe

On Fri, Sep 28, 2018 at 07:23:20AM +0000, Song Liu wrote:
> Hi Peter,
> > #ifdef CONFIG_UPROBE_EVENTS
> > +PMU_FORMAT_ATTR(ref_ctr_offset, "config:63-24");
> 
> I guess you meant this part? This is for uprobe only, so I put
> it here. 

Ah,.. right you are.

You seem to have the bitfield backwards, does that mean we should write
the bits in backwards too? Seems a tad loopy if you ask me.

Did you instead mean: "config:24-63" ? Also, why 40 bits? 32 seems like
a much more natural amount.