From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2993269AbcBSOwS (ORCPT ); Fri, 19 Feb 2016 09:52:18 -0500 Received: from casper.infradead.org ([85.118.1.10]:56359 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1426691AbcBSOuJ (ORCPT ); Fri, 19 Feb 2016 09:50:09 -0500 Message-Id: <20160219144132.043429490@infradead.org> User-Agent: quilt/0.61-1 Date: Fri, 19 Feb 2016 15:37:47 +0100 From: Peter Zijlstra To: peterz@infradead.org, mingo@kernel.org, alexander.shishkin@linux.intel.com, eranian@google.com Cc: linux-kernel@vger.kernel.org, vince@deater.net, dvyukov@google.com, andi@firstfloor.org, jolsa@redhat.com, sasha.levin@oracle.com, oleg@redhat.com Subject: [RFC][PATCH 4/7] perf: Fix scaling vs enable_on_exec References: <20160219143743.692339502@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=peterz-perf-more-fixes-4.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oleg reported that enable_on_exec results in weird scale factors. The recent commit 3e349507d12d ("perf: Fix perf_enable_on_exec() event scheduling") caused this by moving task_ctx_sched_out() from before __perf_event_mask_enable() to after it. The overlooked concequence of that change is that task_ctx_sched_out() would update the ctx time fields, and now __perf_event_mask_enable() uses stale time. Fix this by adding an explicit time update. While looking at this, I also found that we need an ctx->is_active check in perf_install_in_context(). XXX: does this actually fix the reported issue? I'm not sure what the reproduction case is. Also an earlier version made Jiri's machine explode -- something I've not managed to reproduce either. Fixes: 3e349507d12d ("perf: Fix perf_enable_on_exec() event scheduling") Reported-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) --- kernel/events/core.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2170,12 +2170,12 @@ perf_install_in_context(struct perf_even raw_spin_unlock_irq(&ctx->lock); return; } - update_context_time(ctx); - /* - * Update cgrp time only if current cgrp matches event->cgrp. - * Must be done before calling add_event_to_ctx(). - */ - update_cgrp_time_from_event(event); + + if (ctx->is_active) { + update_context_time(ctx); + update_cgrp_time_from_event(event); + } + add_event_to_ctx(event, ctx); raw_spin_unlock_irq(&ctx->lock); @@ -3122,6 +3122,12 @@ static void perf_event_enable_on_exec(in cpuctx = __get_cpu_context(ctx); perf_ctx_lock(cpuctx, ctx); + + if (ctx->is_active) { + update_context_time(ctx); + update_cgrp_time_from_cpuctx(cpuctx); + } + list_for_each_entry(event, &ctx->event_list, event_entry) enabled |= event_enable_on_exec(event, ctx);