linux-kernel - Re: [PATCH v5 06/10] Uprobes: Support SDT markers having reference count (semaphore)

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Message-Id: <42dbe9a2-9795-0269-1a90-a5a71fcbe970@linux.ibm.com>
Date:   Wed, 4 Jul 2018 11:37:13 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     oleg@...hat.com, rostedt@...dmis.org, mhiramat@...nel.org,
        peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, linux-kernel@...r.kernel.org, corbet@....net,
        linux-doc@...r.kernel.org, ananth@...ux.vnet.ibm.com,
        alexis.berlemont@...il.com, naveen.n.rao@...ux.vnet.ibm.com,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
        linux@...linux.org.uk, ralf@...ux-mips.org, paul.burton@...s.com,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: Re: [PATCH v5 06/10] Uprobes: Support SDT markers having reference
 count (semaphore)

Hi Srikar,

On 07/02/2018 09:31 PM, Srikar Dronamraju wrote:

> 2. ref_ctr_offset is necessarily a consumer property, its not a uprobe
> property at all.


Sorry to ask this after agreeing :P

Initially, I thought this point is right. But after thinking more on this,
it seems wrong to me. Ex a python SDT probe:

    Provider: python
    Name: function__entry
    Location: 0x0000000000140de4, Base: 0x00000000001ddfb0, Semaphore: 0x0000000000268320

Here, "Semaphore" field is what we are referring to as reference counter.
Basically reference counter's job is to gate invocation of uprobe and
thus ref_ctr_offset becomes a uprobe property, not the consumer property.
No? Am I missing anything?

Thanks,
Ravi