linux-kernel - Re: perf script: rwtop: SIGALRM and pipe read race

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Date:	Mon, 17 Sep 2012 09:16:19 -0600
From:	David Ahern <dsahern@...il.com>
To:	Andrew Jones <drjones@...hat.com>, acme@...stprotocols.net
CC:	linux-kernel@...r.kernel.org, a.p.zijlstra@...llo.nl,
	paulus@...ba.org, mingo@...hat.com, tzanussi@...il.com
Subject: Re: perf script: rwtop: SIGALRM and pipe read race

On 9/17/12 8:55 AM, David Ahern wrote:
> 2. the rwtop.pl script is not handling negative return values ($ret < 0)
> properly -- the '$ret > 0' check is succeeding even though $ret is
> negative (e.g., -EAGAIN) leading to astronomical read values

I think perl is treating $ret as an unsigned integer.

Again, I know little about perl, but this change to 
./scripts/perl/rwtop.pl makes it behave properly:

     my $n = sprintf("%d", $ret);

     if ($n > 0) {
     ...

David
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