From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751854AbcEJNTJ (ORCPT ); Tue, 10 May 2016 09:19:09 -0400 Received: from mga03.intel.com ([134.134.136.65]:9046 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750979AbcEJNTG (ORCPT ); Tue, 10 May 2016 09:19:06 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,604,1455004800"; d="scan'208";a="972574349" From: Alexander Shishkin To: Peter Zijlstra Cc: Thomas Gleixner , x86@kernel.org, Borislav Petkov , Ingo Molnar , linux-kernel@vger.kernel.org, vince@deater.net, eranian@google.com, Arnaldo Carvalho de Melo , Alexander Shishkin Subject: [PATCH 1/2] perf/x86/intel/pt: Generate PMI in the STOP region as well Date: Tue, 10 May 2016 16:18:32 +0300 Message-Id: <1462886313-13660-2-git-send-email-alexander.shishkin@linux.intel.com> X-Mailer: git-send-email 2.8.0.rc3 In-Reply-To: <1462886313-13660-1-git-send-email-alexander.shishkin@linux.intel.com> References: <1462886313-13660-1-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 PT driver always sets the PMI bit one region (page) before the STOP region so that we can wake up the consumer before we run out of room in the buffer and have to disable the event. However, we also need an interrupt in the last output region, so that we actually get to disable the event (if no more room from new data is available at that point), otherwise hardware just quietly refuses to start, but the event is scheduled in and we end up losing trace data till the event gets removed. For a cpu-wide event it is even worse since there may not be any re-scheduling at all and no chance for the ring buffer code to notice that its buffer is filled up and the event needs to be disabled (so that the consumer can re-enable it when it finishes reading the data out). In other words, all the trace data will be lost after the buffer gets filled up. This patch makes PT also generate a PMI when the last output region is full. Reported-by: Markus Metzger Signed-off-by: Alexander Shishkin --- arch/x86/events/intel/pt.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c index 5b648d4a94..a157cf67a9 100644 --- a/arch/x86/events/intel/pt.c +++ b/arch/x86/events/intel/pt.c @@ -861,6 +861,7 @@ static int pt_buffer_reset_markers(struct pt_buffer *buf, /* clear STOP and INT from current entry */ buf->topa_index[buf->stop_pos]->stop = 0; + buf->topa_index[buf->stop_pos]->intr = 0; buf->topa_index[buf->intr_pos]->intr = 0; /* how many pages till the STOP marker */ @@ -885,6 +886,7 @@ static int pt_buffer_reset_markers(struct pt_buffer *buf, buf->intr_pos = idx; buf->topa_index[buf->stop_pos]->stop = 1; + buf->topa_index[buf->stop_pos]->intr = 1; buf->topa_index[buf->intr_pos]->intr = 1; return 0; -- 2.8.1