From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 24 Mar 2009 12:18:16 +0000 (+0100)
Subject: perf_counter: fix perf_poll()
X-Git-Tag: v2.6.31-rc1~383^2~437
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c7138f37f905bb7987b1f9f5a8ee73667db39f25;p=pandora-kernel.git

perf_counter: fix perf_poll()

Impact: fix kerneltop 100% CPU usage

Only return a poll event when there's actually been one, poll_wait()
doesn't actually wait for the waitq you pass it, it only enqueues
you on it.

Only once all FDs have been iterated and none of thm returned a
poll-event will it schedule().

Also make it return POLL_HUP when there's not mmap() area to read from.

Further, fix a silly bug in the write code.

Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Orig-LKML-Reference: <1237897096.24918.181.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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