From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757290AbbEVPb3 (ORCPT ); Fri, 22 May 2015 11:31:29 -0400 Received: from mga02.intel.com ([134.134.136.20]:55126 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757018AbbEVPb0 (ORCPT ); Fri, 22 May 2015 11:31:26 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,476,1427785200"; d="scan'208";a="714302063" From: Alexander Shishkin To: Peter Zijlstra , Ingo Molnar Cc: linux-kernel@vger.kernel.org, Paul Mackerras , adrian.hunter@intel.com, x86@kernel.org, hpa@zytor.com, acme@infradead.org, Alexander Shishkin Subject: [PATCH v1 5/7] perf/x86/intel/pt: Document pt_buffer_reset_offsets() Date: Fri, 22 May 2015 18:30:24 +0300 Message-Id: <1432308626-18845-6-git-send-email-alexander.shishkin@linux.intel.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1432308626-18845-1-git-send-email-alexander.shishkin@linux.intel.com> References: <1432308626-18845-1-git-send-email-alexander.shishkin@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently, the description of pt_buffer_reset_offsets() lacks information about its calling constraints and ordering with regards to other buffer management functions. Add a clarification about when this function has to be called. Signed-off-by: Alexander Shishkin --- arch/x86/kernel/cpu/perf_event_intel_pt.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c index b2746eafa0..40ba5e4312 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_pt.c +++ b/arch/x86/kernel/cpu/perf_event_intel_pt.c @@ -705,7 +705,14 @@ static void pt_buffer_setup_topa_index(struct pt_buffer *buf) * @head: Write pointer (aux_head) from AUX buffer. * * Find the ToPA table and entry corresponding to given @head and set buffer's - * "current" pointers accordingly. + * "current" pointers accordingly. This is done after we have obtained the + * current aux_head position from a successful call to perf_aux_output_begin() + * to make sure the hardware is writing to the right place. + * + * This function modifies buf::{cur,cur_idx,output_off} that will be programmed + * into PT msrs when the tracing is enabled and buf::head and buf::data_size, + * which are used to determine INT and STOP markers' locations by a subsequent + * call to pt_buffer_reset_markers(). */ static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head) { -- 2.1.4