Re: [tip:perf/core] perf: Use read() instead of lseek() in trace_event_read.c:skip()

From: Pekka Enberg
Date: Thu May 20 2010 - 09:39:46 EST


On Thu, May 20, 2010 at 3:54 PM, tip-bot for Tom Zanussi
<tzanussi@xxxxxxxxx> wrote:
> Commit-ID:  cbb5cf7ff6b298beacfe23db3386335b0b9c0a2d
> Gitweb:     http://git.kernel.org/tip/cbb5cf7ff6b298beacfe23db3386335b0b9c0a2d
> Author:     Tom Zanussi <tzanussi@xxxxxxxxx>
> AuthorDate: Tue, 4 May 2010 23:02:10 -0500
> Committer:  Frederic Weisbecker <fweisbec@xxxxxxxxx>
> CommitDate: Thu, 20 May 2010 08:37:17 +0200
>
> perf: Use read() instead of lseek() in trace_event_read.c:skip()
>
> This is a small fix for a problem affecting live-mode, introduced
> recently:
>
> root@tropicana:~# perf trace rwtop
> perf trace started with Perl
> script /root/libexec/perf-core/scripts/perl/rwtop.pl
>
>  Fatal: did not read header event
>
> commit d00a47cce569a3e660a8c9de5d57af28d6a9f0f7 added a skip()
> function to skip over e.g. header_page, but this doesn't work for
> live mode.  This patch re-implements skip() to use read() instead of
> lseek() to fix that.

Out of curiosity: why doesn't lseek() work and why can't we fix that?
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