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 D4BB1C433EF for ; Thu, 14 Oct 2021 14:57:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD8C8611C8 for ; Thu, 14 Oct 2021 14:57:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230467AbhJNO7l (ORCPT ); Thu, 14 Oct 2021 10:59:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:42916 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232520AbhJNO6n (ORCPT ); Thu, 14 Oct 2021 10:58:43 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 355A7611C8; Thu, 14 Oct 2021 14:56:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1634223398; bh=GCt2C3RDvSbqWnxistKcpoIX6m1JQokV/m2AZecj7q8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1YiogPrEUFRoOpNe1eNd54fBcUC9s/Yu40H8SLSkKSb2R6EeiVkUQnNmwP33sTVXP 8eXo6lz/zkNdsveteDxV451wSBMdtEALnUUsV8ouil9LpQzEBATJ0NJBH0iF828R3R r3x2HUrEEO8JDw04nCbME8fiiDRDtL6j6Rml5CAU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Anand K Mistry , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 4.9 25/25] perf/x86: Reset destroy callback on event init failure Date: Thu, 14 Oct 2021 16:53:56 +0200 Message-Id: <20211014145208.383562223@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20211014145207.575041491@linuxfoundation.org> References: <20211014145207.575041491@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Anand K Mistry [ Upstream commit 02d029a41dc986e2d5a77ecca45803857b346829 ] perf_init_event tries multiple init callbacks and does not reset the event state between tries. When x86_pmu_event_init runs, it unconditionally sets the destroy callback to hw_perf_event_destroy. On the next init attempt after x86_pmu_event_init, in perf_try_init_event, if the pmu's capabilities includes PERF_PMU_CAP_NO_EXCLUDE, the destroy callback will be run. However, if the next init didn't set the destroy callback, hw_perf_event_destroy will be run (since the callback wasn't reset). Looking at other pmu init functions, the common pattern is to only set the destroy callback on a successful init. Resetting the callback on failure tries to replicate that pattern. This was discovered after commit f11dd0d80555 ("perf/x86/amd/ibs: Extend PERF_PMU_CAP_NO_EXCLUDE to IBS Op") when the second (and only second) run of the perf tool after a reboot results in 0 samples being generated. The extra run of hw_perf_event_destroy results in active_events having an extra decrement on each perf run. The second run has active_events == 0 and every subsequent run has active_events < 0. When active_events == 0, the NMI handler will early-out and not record any samples. Signed-off-by: Anand K Mistry Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20210929170405.1.I078b98ee7727f9ae9d6df8262bad7e325e40faf0@changeid Signed-off-by: Sasha Levin --- arch/x86/events/core.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index c26cca506f64..c20df6a3540c 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2075,6 +2075,7 @@ static int x86_pmu_event_init(struct perf_event *event) if (err) { if (event->destroy) event->destroy(event); + event->destroy = NULL; } if (ACCESS_ONCE(x86_pmu.attr_rdpmc)) -- 2.33.0