linux-kernel - Re: [PATCH 0/7] Uprobes: Support SDT markers having reference count (semaphore)

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Message-ID: <20180620123750.79811466@gandalf.local.home>
Date:   Wed, 20 Jun 2018 12:37:50 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc:     oleg@...hat.com, srikar@...ux.vnet.ibm.com, 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
Subject: Re: [PATCH 0/7] Uprobes: Support SDT markers having reference count
 (semaphore)

On Wed,  6 Jun 2018 14:03:37 +0530
Ravi Bangoria <ravi.bangoria@...ux.ibm.com> wrote:

> Why RFC again:
> 
> This series is different from earlier versions[1]. Earlier series
> implemented this feature in trace_uprobe while this has implemented
> the logic in core uprobe. Few reasons for this:
>  1. One of the major reason was the deadlock between uprobe_lock and
>  mm->mmap inside trace_uprobe_mmap(). That deadlock was not easy to fix
>  because mm->mmap is not in control of trace_uprobe_mmap() and it has
>  to take uprobe_lock to loop over trace_uprobe list. More details can
>  be found at[2]. With this new approach, there are no deadlocks found
>  so far.
>  2. Many of the core uprobe function and data-structures needs to be
>  exported to make earlier implementation simple. With this new approach,
>  reference counter logic is been implemented in core uprobe and thus
>  no need to export anything.


A quick scan of the patches, I don't see anything controversial with
them. Unless others have any qualms about it, I say repost as non RFC,
and we can start doing a more thorough review.

Thanks,

-- Steve