From nobody Wed Dec 31 15:01:06 2025 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2D46C0018A for ; Thu, 2 Nov 2023 15:33:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1376812AbjKBPdZ (ORCPT ); Thu, 2 Nov 2023 11:33:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53246 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347613AbjKBPdH (ORCPT ); Thu, 2 Nov 2023 11:33:07 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A2D0C137 for ; Thu, 2 Nov 2023 08:32:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-Id:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=zYnYxbpqthdvjZXSbX3mfTIRB+RNguvN2goMXYp9Xns=; b=cxJLDQdGkB8ClhyhktXpUFBuAg S0Bzic4TiexMyJAqSvdRRhZIsHSgJkNnIyjJ1NPV3+s8AYBlYUkUwUN52YkM0TG1OsBS/5BE98dLa L5AYvGDBuRSTNMWjHiaMkIjI4D5C2itdmbpTaWCIxiRzdhx9PUdna+HAr5siNLbxVEX2tLpdqZilY /E8U61ux02QKGPF8pwMxWogLE5rG2PDt08aiC5OxKDVCRG4L3M6qTAGJt6/QZhsWc+Enj3LOG/CVZ 0Iz3PJwqOz25KYowq8Fe2BPHQYLIf61IR+RhpClDTdl3feTGbF3vE77hrZJVKuzPTiaeJZrVDQOoj 0U6hjr7g==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1qyZgU-0005PB-TJ; Thu, 02 Nov 2023 15:32:39 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 0) id 3BC543004AB; Thu, 2 Nov 2023 16:32:39 +0100 (CET) Message-Id: <20231102152017.847792675@infradead.org> User-Agent: quilt/0.65 Date: Thu, 02 Nov 2023 16:09:20 +0100 From: Peter Zijlstra To: mingo@kernel.org Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, acme@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, irogers@google.com, adrian.hunter@intel.com Subject: [PATCH 01/13] perf: Simplify perf_event_alloc() error path References: <20231102150919.719936610@infradead.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The error cleanup sequence in perf_event_alloc() is a subset of the existing _free_event() function (it must of course be). Split this out into __free_event() and simplify the error path. Signed-off-by: Peter Zijlstra (Intel) --- include/linux/perf_event.h | 1=20 kernel/events/core.c | 129 ++++++++++++++++++++++------------------= ----- 2 files changed, 66 insertions(+), 64 deletions(-) --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -634,6 +634,7 @@ struct swevent_hlist { #define PERF_ATTACH_ITRACE 0x10 #define PERF_ATTACH_SCHED_CB 0x20 #define PERF_ATTACH_CHILD 0x40 +#define PERF_ATTACH_EXCLUSIVE 0x80 =20 struct bpf_prog; struct perf_cgroup; --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5094,6 +5094,8 @@ static int exclusive_event_init(struct p return -EBUSY; } =20 + event->attach_state |=3D PERF_ATTACH_EXCLUSIVE; + return 0; } =20 @@ -5101,14 +5103,13 @@ static void exclusive_event_destroy(stru { struct pmu *pmu =3D event->pmu; =20 - if (!is_exclusive_pmu(pmu)) - return; - /* see comment in exclusive_event_init() */ if (event->attach_state & PERF_ATTACH_TASK) atomic_dec(&pmu->exclusive_cnt); else atomic_inc(&pmu->exclusive_cnt); + + event->attach_state &=3D ~PERF_ATTACH_EXCLUSIVE; } =20 static bool exclusive_event_match(struct perf_event *e1, struct perf_event= *e2) @@ -5143,38 +5144,22 @@ static bool exclusive_event_installable( static void perf_addr_filters_splice(struct perf_event *event, struct list_head *head); =20 -static void _free_event(struct perf_event *event) +/* vs perf_event_alloc() error */ +static void __free_event(struct perf_event *event) { - irq_work_sync(&event->pending_irq); - - unaccount_event(event); - - security_perf_event_free(event); - - if (event->rb) { - /* - * Can happen when we close an event with re-directed output. - * - * Since we have a 0 refcount, perf_mmap_close() will skip - * over us; possibly making our ring_buffer_put() the last. - */ - mutex_lock(&event->mmap_mutex); - ring_buffer_attach(event, NULL); - mutex_unlock(&event->mmap_mutex); - } - - if (is_cgroup_event(event)) - perf_detach_cgroup(event); - if (!event->parent) { if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) put_callchain_buffers(); } =20 - perf_event_free_bpf_prog(event); - perf_addr_filters_splice(event, NULL); kfree(event->addr_filter_ranges); =20 + if (event->attach_state & PERF_ATTACH_EXCLUSIVE) + exclusive_event_destroy(event); + + if (is_cgroup_event(event)) + perf_detach_cgroup(event); + if (event->destroy) event->destroy(event); =20 @@ -5185,22 +5170,56 @@ static void _free_event(struct perf_even if (event->hw.target) put_task_struct(event->hw.target); =20 - if (event->pmu_ctx) + if (event->pmu_ctx) { + /* + * put_pmu_ctx() needs an event->ctx reference, because of + * epc->ctx. + */ + WARN_ON_ONCE(!event->ctx); + WARN_ON_ONCE(event->pmu_ctx->ctx !=3D event->ctx); put_pmu_ctx(event->pmu_ctx); + } =20 /* - * perf_event_free_task() relies on put_ctx() being 'last', in particular - * all task references must be cleaned up. + * perf_event_free_task() relies on put_ctx() being 'last', in + * particular all task references must be cleaned up. */ if (event->ctx) put_ctx(event->ctx); =20 - exclusive_event_destroy(event); - module_put(event->pmu->module); + if (event->pmu) + module_put(event->pmu->module); =20 call_rcu(&event->rcu_head, free_event_rcu); } =20 +/* vs perf_event_alloc() success */ +static void _free_event(struct perf_event *event) +{ + irq_work_sync(&event->pending_irq); + + unaccount_event(event); + + security_perf_event_free(event); + + if (event->rb) { + /* + * Can happen when we close an event with re-directed output. + * + * Since we have a 0 refcount, perf_mmap_close() will skip + * over us; possibly making our ring_buffer_put() the last. + */ + mutex_lock(&event->mmap_mutex); + ring_buffer_attach(event, NULL); + mutex_unlock(&event->mmap_mutex); + } + + perf_event_free_bpf_prog(event); + perf_addr_filters_splice(event, NULL); + + __free_event(event); +} + /* * Used to free events which have a known refcount of 1, such as in error = paths * where the event isn't exposed yet and inherited events. @@ -11591,8 +11610,10 @@ static int perf_try_init_event(struct pm event->destroy(event); } =20 - if (ret) + if (ret) { + event->pmu =3D NULL; module_put(pmu->module); + } =20 return ret; } @@ -11918,7 +11939,7 @@ perf_event_alloc(struct perf_event_attr * See perf_output_read(). */ if (attr->inherit && (attr->sample_type & PERF_SAMPLE_READ)) - goto err_ns; + goto err; =20 if (!has_branch_stack(event)) event->attr.branch_sample_type =3D 0; @@ -11926,7 +11947,7 @@ perf_event_alloc(struct perf_event_attr pmu =3D perf_init_event(event); if (IS_ERR(pmu)) { err =3D PTR_ERR(pmu); - goto err_ns; + goto err; } =20 /* @@ -11936,24 +11957,24 @@ perf_event_alloc(struct perf_event_attr */ if (pmu->task_ctx_nr =3D=3D perf_invalid_context && (task || cgroup_fd != =3D -1)) { err =3D -EINVAL; - goto err_pmu; + goto err; } =20 if (event->attr.aux_output && !(pmu->capabilities & PERF_PMU_CAP_AUX_OUTPUT)) { err =3D -EOPNOTSUPP; - goto err_pmu; + goto err; } =20 if (cgroup_fd !=3D -1) { err =3D perf_cgroup_connect(cgroup_fd, event, attr, group_leader); if (err) - goto err_pmu; + goto err; } =20 err =3D exclusive_event_init(event); if (err) - goto err_pmu; + goto err; =20 if (has_addr_filter(event)) { event->addr_filter_ranges =3D kcalloc(pmu->nr_addr_filters, @@ -11961,7 +11982,7 @@ perf_event_alloc(struct perf_event_attr GFP_KERNEL); if (!event->addr_filter_ranges) { err =3D -ENOMEM; - goto err_per_task; + goto err; } =20 /* @@ -11986,41 +12007,21 @@ perf_event_alloc(struct perf_event_attr if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) { err =3D get_callchain_buffers(attr->sample_max_stack); if (err) - goto err_addr_filters; + goto err; } } =20 err =3D security_perf_event_alloc(event); if (err) - goto err_callchain_buffer; + goto err; =20 /* symmetric to unaccount_event() in _free_event() */ account_event(event); =20 return event; =20 -err_callchain_buffer: - if (!event->parent) { - if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) - put_callchain_buffers(); - } -err_addr_filters: - kfree(event->addr_filter_ranges); - -err_per_task: - exclusive_event_destroy(event); - -err_pmu: - if (is_cgroup_event(event)) - perf_detach_cgroup(event); - if (event->destroy) - event->destroy(event); - module_put(pmu->module); -err_ns: - if (event->hw.target) - put_task_struct(event->hw.target); - call_rcu(&event->rcu_head, free_event_rcu); - +err: + __free_event(event); return ERR_PTR(err); }