linux-kernel - Re: [PATCH v2 02/40] tracing: Add support to detect and avoid duplicates

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Message-ID: <20170906143243.381a38df@gandalf.local.home>
Date:   Wed, 6 Sep 2017 14:32:43 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc:     tglx@...utronix.de, mhiramat@...nel.org, namhyung@...nel.org,
        vedang.patel@...el.com, bigeasy@...utronix.de,
        joel.opensrc@...il.com, joelaf@...gle.com,
        mathieu.desnoyers@...icios.com, baohong.liu@...el.com,
        linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH v2 02/40] tracing: Add support to detect and avoid
 duplicates

On Tue,  5 Sep 2017 16:57:14 -0500
Tom Zanussi <tom.zanussi@...ux.intel.com> wrote:

> From: Vedang Patel <vedang.patel@...el.com>
> 
> A duplicate in the tracing_map hash table is when 2 different entries
> have the same key and, as a result, the key_hash. This is possible due
> to a race condition in the algorithm. This race condition is inherent to
> the algorithm and not a bug. This was fine because, until now, we were
> only interested in the sum of all the values related to a particular
> key (the duplicates are dealt with in tracing_map_sort_entries()). But,
> with the inclusion of variables[1], we are interested in individual
> values. So, it will not be clear what value to choose when
> there are duplicates. So, the duplicates need to be removed.
> 


> [1] - https://lkml.org/lkml/2017/6/26/751

FYI, something like this should have:

Link: http://lkml.kernel.org/r/cover.1498510759.git.tom.zanussi@linux.intel.com

And avoid any non kernel.org archiving system.

-- Steve

> 
> Signed-off-by: Vedang Patel <vedang.patel@...el.com>
> ---
>