Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751836AbbBLRL3 (ORCPT ); Thu, 12 Feb 2015 12:11:29 -0500 Received: from mail-qc0-f171.google.com ([209.85.216.171]:64618 "EHLO mail-qc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751625AbbBLRL0 (ORCPT ); Thu, 12 Feb 2015 12:11:26 -0500 From: Vince Weaver X-Google-Original-From: Vince Weaver Date: Thu, 12 Feb 2015 12:14:26 -0500 (EST) To: "Michael Kerrisk (man-pages)" cc: linux-man@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo Subject: [patch] perf_event_open.2: Clarify PERF_EVENT_IOC_REFRESH behavior Message-ID: User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1932 Lines: 50 Currently the PERF_EVENT_IOC_REFRESH ioctl, when applied to a group leader, will refresh all children. Also if a refresh value of 0 is chosen then the refresh becomes infinite (never runs out). Back in 2011 PAPI was relying on these behaviors but I was told that both were unsupported and subject to being removed at any time. (See https://lkml.org/lkml/2011/5/24/337 ) However the behavior has not been changed. This patch updates the manpage to still list the behavior as unsupported, but removes the innacurate description of it only being a problem with 2.6 kernels. Signed-off-by: Vince Weaver diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index 39c8d8c..76136e2 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -2353,6 +2353,12 @@ once the counter reaches 0 is indicated and the underlying event is disabled. +Refreshing an event group leader refreshes all siblings and +refreshing with a parameter of 0 currently enables infinite +refreshes; +these behaviors are unsupported and should not be relied on. +.\" See https://lkml.org/lkml/2011/5/24/337 + Starting with Linux 3.18, .\" commit 179033b3e064d2cd3f5f9945e76b0a0f0fbf4883 .B POLL_HUP @@ -2805,11 +2811,6 @@ Prior to Linux 2.6.35, .B PERF_FORMAT_GROUP did not work with attached processes. -In older Linux 2.6 versions, -refreshing an event group leader refreshed all siblings, -and refreshing with a parameter of 0 enabled infinite refresh. -This behavior is unsupported and should not be relied on. - There is a bug in the kernel code between Linux 2.6.36 and Linux 3.0 that ignores the "watermark" field and acts as if a wakeup_event -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/