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Message-ID: <20150604091100.GA19775@gmail.com>
Date: Thu, 4 Jun 2015 11:11:00 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Milos Vyletel <milos@...hat.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Paul Mackerras <paulus@...ba.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Jiri Olsa <jolsa@...nel.org>, Don Zickus <dzickus@...hat.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
"open list:PERFORMANCE EVENT..." <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf tools: avoid possible race condition in copyfile
* Milos Vyletel <milos@...hat.com> wrote:
> Use unique temporary files when copying to buildid dir to prevent races
> in case multiple instances are trying to copy same file. This is done by
>
> - creating template in form <path>/.<filename>.XXXXXX where the suffix is
> used by mkstemp() to create unique file
> - change file mode
> - copy content
> - if successful link temp file to target file
> - unlink temp file
>
> At this point the only file left at target path should be the desired
> one either created by us or other instance if we raced. This should also
> prevent not yet fully copied files to be visible to to other perf
> instances that could try to parse them.
>
> On top of that slow_copyfile no longer needs to deal with file mode when
> creating file since temporary file is already created and mode is set.
>
> Signed-off-by: Milos Vyletel <milos@...hat.com>
Ok, that looks nice!
Assuming it passes testing you can add my ack to it:
Acked-by: Ingo Molnar <mingo@...nel.org>
Is there any other place in tools/perf where we are using file locking or racy
shared access to the same file(s)?
Thanks,
Ingo
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