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 X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3301C742D7 for ; Sat, 13 Jul 2019 11:12:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A3AC620848 for ; Sat, 13 Jul 2019 11:12:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="FYxhmluX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727914AbfGMLMg (ORCPT ); Sat, 13 Jul 2019 07:12:36 -0400 Received: from terminus.zytor.com ([198.137.202.136]:41005 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726474AbfGMLMg (ORCPT ); Sat, 13 Jul 2019 07:12:36 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id x6DBCJLN3842035 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Sat, 13 Jul 2019 04:12:19 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 terminus.zytor.com x6DBCJLN3842035 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2019061801; t=1563016340; bh=8P1Xx6tgO+zT9lTIq+5BV5iWKojj++eBEI9j+VPGaBQ=; h=Date:From:Cc:Reply-To:In-Reply-To:References:To:Subject:From; b=FYxhmluXHhqF2Rknt7Z6vMBTx+UyKMGh1AVebGXh8Ii22P2RXsoK+2/sf6fnNwlMz fMB0x+QEGP+c6duyihUEntHtGd2RrRtbPe12ZThIDJf0Fbq5wOurCy+rZCPxieJDr/ UY0JIMW4HQLJc8rMh2Y1VtfmW/Up1M9CEN4yTQkqndXRM5paQqsWtgNatN8l4pU9NE EM4iNoL9U9hhavOkCeA1rGA9oeScco1gIVxjpNQ0CxLS86jQbfhm6e3pRr4VL4TEiA u1sPYTdSrqt69n4GW6LHgsyBN9oI/UnfdC7vSqv6cD+RQvAoWzDbUg5W/dqGSpEOfS D4JBzSyl3p7tQ== Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id x6DBCJAX3842032; Sat, 13 Jul 2019 04:12:19 -0700 Date: Sat, 13 Jul 2019 04:12:19 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Alexander Shishkin Message-ID: Cc: linux-kernel@vger.kernel.org, alexander.shishkin@linux.intel.com, tglx@linutronix.de, hpa@zytor.com, torvalds@linux-foundation.org, stable@vger.kernel.org, jolsa@redhat.com, vincent.weaver@maine.edu, acme@redhat.com, peterz@infradead.org, mingo@kernel.org, eranian@google.com Reply-To: linux-kernel@vger.kernel.org, alexander.shishkin@linux.intel.com, tglx@linutronix.de, hpa@zytor.com, torvalds@linux-foundation.org, stable@vger.kernel.org, jolsa@redhat.com, vincent.weaver@maine.edu, acme@redhat.com, peterz@infradead.org, mingo@kernel.org, eranian@google.com In-Reply-To: <20190701110755.24646-1-alexander.shishkin@linux.intel.com> References: <20190701110755.24646-1-alexander.shishkin@linux.intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/urgent] perf/core: Fix exclusive events' grouping Git-Commit-ID: 8a58ddae23796c733c5dfbd717538d89d036c5bd X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 8a58ddae23796c733c5dfbd717538d89d036c5bd Gitweb: https://git.kernel.org/tip/8a58ddae23796c733c5dfbd717538d89d036c5bd Author: Alexander Shishkin AuthorDate: Mon, 1 Jul 2019 14:07:55 +0300 Committer: Ingo Molnar CommitDate: Sat, 13 Jul 2019 11:21:28 +0200 perf/core: Fix exclusive events' grouping So far, we tried to disallow grouping exclusive events for the fear of complications they would cause with moving between contexts. Specifically, moving a software group to a hardware context would violate the exclusivity rules if both groups contain matching exclusive events. This attempt was, however, unsuccessful: the check that we have in the perf_event_open() syscall is both wrong (looks at wrong PMU) and insufficient (group leader may still be exclusive), as can be illustrated by running: $ perf record -e '{intel_pt//,cycles}' uname $ perf record -e '{cycles,intel_pt//}' uname ultimately successfully. Furthermore, we are completely free to trigger the exclusivity violation by: perf -e '{cycles,intel_pt//}' -e '{intel_pt//,instructions}' even though the helpful perf record will not allow that, the ABI will. The warning later in the perf_event_open() path will also not trigger, because it's also wrong. Fix all this by validating the original group before moving, getting rid of broken safeguards and placing a useful one to perf_install_in_context(). Signed-off-by: Alexander Shishkin Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: mathieu.poirier@linaro.org Cc: will.deacon@arm.com Fixes: bed5b25ad9c8a ("perf: Add a pmu capability for "exclusive" events") Link: https://lkml.kernel.org/r/20190701110755.24646-1-alexander.shishkin@linux.intel.com Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 5 +++++ kernel/events/core.c | 34 ++++++++++++++++++++++------------ 2 files changed, 27 insertions(+), 12 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 16e38c286d46..e8ad3c590a23 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1055,6 +1055,11 @@ static inline int in_software_context(struct perf_event *event) return event->ctx->pmu->task_ctx_nr == perf_sw_context; } +static inline int is_exclusive_pmu(struct pmu *pmu) +{ + return pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE; +} + extern struct static_key perf_swevent_enabled[PERF_COUNT_SW_MAX]; extern void ___perf_sw_event(u32, u64, struct pt_regs *, u64); diff --git a/kernel/events/core.c b/kernel/events/core.c index 5dd19bedbf64..eea9d52b010c 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2553,6 +2553,9 @@ unlock: return ret; } +static bool exclusive_event_installable(struct perf_event *event, + struct perf_event_context *ctx); + /* * Attach a performance event to a context. * @@ -2567,6 +2570,8 @@ perf_install_in_context(struct perf_event_context *ctx, lockdep_assert_held(&ctx->mutex); + WARN_ON_ONCE(!exclusive_event_installable(event, ctx)); + if (event->cpu != -1) event->cpu = cpu; @@ -4360,7 +4365,7 @@ static int exclusive_event_init(struct perf_event *event) { struct pmu *pmu = event->pmu; - if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE)) + if (!is_exclusive_pmu(pmu)) return 0; /* @@ -4391,7 +4396,7 @@ static void exclusive_event_destroy(struct perf_event *event) { struct pmu *pmu = event->pmu; - if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE)) + if (!is_exclusive_pmu(pmu)) return; /* see comment in exclusive_event_init() */ @@ -4411,14 +4416,15 @@ static bool exclusive_event_match(struct perf_event *e1, struct perf_event *e2) return false; } -/* Called under the same ctx::mutex as perf_install_in_context() */ static bool exclusive_event_installable(struct perf_event *event, struct perf_event_context *ctx) { struct perf_event *iter_event; struct pmu *pmu = event->pmu; - if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE)) + lockdep_assert_held(&ctx->mutex); + + if (!is_exclusive_pmu(pmu)) return true; list_for_each_entry(iter_event, &ctx->event_list, event_entry) { @@ -10947,11 +10953,6 @@ SYSCALL_DEFINE5(perf_event_open, goto err_alloc; } - if ((pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE) && group_leader) { - err = -EBUSY; - goto err_context; - } - /* * Look up the group leader (we will attach this event to it): */ @@ -11039,6 +11040,18 @@ SYSCALL_DEFINE5(perf_event_open, move_group = 0; } } + + /* + * Failure to create exclusive events returns -EBUSY. + */ + err = -EBUSY; + if (!exclusive_event_installable(group_leader, ctx)) + goto err_locked; + + for_each_sibling_event(sibling, group_leader) { + if (!exclusive_event_installable(sibling, ctx)) + goto err_locked; + } } else { mutex_lock(&ctx->mutex); } @@ -11075,9 +11088,6 @@ SYSCALL_DEFINE5(perf_event_open, * because we need to serialize with concurrent event creation. */ if (!exclusive_event_installable(event, ctx)) { - /* exclusive and group stuff are assumed mutually exclusive */ - WARN_ON_ONCE(move_group); - err = -EBUSY; goto err_locked; }