From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7601FC433F5 for ; Tue, 5 Oct 2021 13:52:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F446611F2 for ; Tue, 5 Oct 2021 13:52:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236154AbhJENyW (ORCPT ); Tue, 5 Oct 2021 09:54:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:33172 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235139AbhJENxX (ORCPT ); Tue, 5 Oct 2021 09:53:23 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7D0BC61A56; Tue, 5 Oct 2021 13:51:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1633441893; bh=HMRab5a0PXOH864n7eniAn3IyhBdZDy/3/p7pynA8Rk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=myPP8NbdBl08rBX3fUGpW50+WKZoek51vQZCtVyfjbYTqMNnWSBVGh/0EakQmfCak 0uzJVKuaps5Pi3f8OFgislcn5A3M7+XnGqN7DM2HnbiWtjr7kyd1N+RTatC5e9XbKK nqg5I51H4Pw4N0jgKwp5bBNR1lQAppljaIMmBmrf+hhfxsbpV+7JJE2giMPBpnATCk RPWruBk2AdHchwiCryi1WwRlX6FzJmwJB3aOWeiv+xYcoZgml/mAyZ5nsH5HgeKJpk mSn1Y6LnI37fIIyAXZ2OFTXkTcFWSa98OQR9ugYup//+KwsZ+KY5aO/PD6BHzqPX1b SaHLIzzis7aWg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Song Liu , Peter Zijlstra , Lucian Grijincu , Sasha Levin , mingo@redhat.com, acme@kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH AUTOSEL 5.14 37/40] perf/core: fix userpage->time_enabled of inactive events Date: Tue, 5 Oct 2021 09:50:16 -0400 Message-Id: <20211005135020.214291-37-sashal@kernel.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20211005135020.214291-1-sashal@kernel.org> References: <20211005135020.214291-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Song Liu [ Upstream commit f792565326825ed806626da50c6f9a928f1079c1 ] Users of rdpmc rely on the mmapped user page to calculate accurate time_enabled. Currently, userpage->time_enabled is only updated when the event is added to the pmu. As a result, inactive event (due to counter multiplexing) does not have accurate userpage->time_enabled. This can be reproduced with something like: /* open 20 task perf_event "cycles", to create multiplexing */ fd = perf_event_open(); /* open task perf_event "cycles" */ userpage = mmap(fd); /* use mmap and rdmpc */ while (true) { time_enabled_mmap = xxx; /* use logic in perf_event_mmap_page */ time_enabled_read = read(fd).time_enabled; if (time_enabled_mmap > time_enabled_read) BUG(); } Fix this by updating userpage for inactive events in merge_sched_in. Suggested-by: Peter Zijlstra (Intel) Reported-and-tested-by: Lucian Grijincu Signed-off-by: Song Liu Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20210929194313.2398474-1-songliubraving@fb.com Signed-off-by: Sasha Levin --- include/linux/perf_event.h | 4 +++- kernel/events/core.c | 34 ++++++++++++++++++++++++++++++---- 2 files changed, 33 insertions(+), 5 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 2d510ad750ed..4aa52f7a48c1 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -683,7 +683,9 @@ struct perf_event { /* * timestamp shadows the actual context timing but it can * be safely used in NMI interrupt context. It reflects the - * context time as it was when the event was last scheduled in. + * context time as it was when the event was last scheduled in, + * or when ctx_sched_in failed to schedule the event because we + * run out of PMC. * * ctx_time already accounts for ctx->timestamp. Therefore to * compute ctx_time for a sample, simply add perf_clock(). diff --git a/kernel/events/core.c b/kernel/events/core.c index e5c4aca620c5..22c5b1622c22 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3707,6 +3707,29 @@ static noinline int visit_groups_merge(struct perf_cpu_context *cpuctx, return 0; } +static inline bool event_update_userpage(struct perf_event *event) +{ + if (likely(!atomic_read(&event->mmap_count))) + return false; + + perf_event_update_time(event); + perf_set_shadow_time(event, event->ctx); + perf_event_update_userpage(event); + + return true; +} + +static inline void group_update_userpage(struct perf_event *group_event) +{ + struct perf_event *event; + + if (!event_update_userpage(group_event)) + return; + + for_each_sibling_event(event, group_event) + event_update_userpage(event); +} + static int merge_sched_in(struct perf_event *event, void *data) { struct perf_event_context *ctx = event->ctx; @@ -3725,14 +3748,15 @@ static int merge_sched_in(struct perf_event *event, void *data) } if (event->state == PERF_EVENT_STATE_INACTIVE) { + *can_add_hw = 0; if (event->attr.pinned) { perf_cgroup_event_disable(event, ctx); perf_event_set_state(event, PERF_EVENT_STATE_ERROR); + } else { + ctx->rotate_necessary = 1; + perf_mux_hrtimer_restart(cpuctx); + group_update_userpage(event); } - - *can_add_hw = 0; - ctx->rotate_necessary = 1; - perf_mux_hrtimer_restart(cpuctx); } return 0; @@ -6311,6 +6335,8 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma) ring_buffer_attach(event, rb); + perf_event_update_time(event); + perf_set_shadow_time(event, event->ctx); perf_event_init_userpage(event); perf_event_update_userpage(event); } else { -- 2.33.0