Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751427AbbLIO71 (ORCPT ); Wed, 9 Dec 2015 09:59:27 -0500 Received: from mga14.intel.com ([192.55.52.115]:44122 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750910AbbLIO7Z convert rfc822-to-8bit (ORCPT ); Wed, 9 Dec 2015 09:59:25 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,404,1444719600"; d="scan'208";a="10276860" From: "Liang, Kan" To: Peter Zijlstra , "linux-kernel@vger.kernel.org" , "hpa@zytor.com" , "torvalds@linux-foundation.org" , "acme@kernel.org" , "mingo@kernel.org" , "paulus@samba.org" , "tglx@linutronix.de" CC: "linux-tip-commits@vger.kernel.org" Subject: RE: [tip:perf/core] perf: Add pmu specific data for perf task context Thread-Topic: [tip:perf/core] perf: Add pmu specific data for perf task context Thread-Index: AQHQS56FtwqUg90vnEyKXKxk9n6Q0J7Dm10AgADvnyA= Date: Wed, 9 Dec 2015 14:59:21 +0000 Message-ID: <37D7C6CF3E00A74B8858931C1DB2F077019AAE28@SHSMSX103.ccr.corp.intel.com> References: <1415156173-10035-6-git-send-email-kan.liang@intel.com> <20151209083402.GK6356@twins.programming.kicks-ass.net> In-Reply-To: <20151209083402.GK6356@twins.programming.kicks-ass.net> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-titus-metadata-40: eyJDYXRlZ29yeUxhYmVscyI6IiIsIk1ldGFkYXRhIjp7Im5zIjoiaHR0cDpcL1wvd3d3LnRpdHVzLmNvbVwvbnNcL0ludGVsIiwiaWQiOiI5MWI0OTUzOC00NTQxLTQ3NzItOTkyMC1kYWQ2OGE3MDA5MmIiLCJwcm9wcyI6W3sibiI6IkludGVsRGF0YUNsYXNzaWZpY2F0aW9uIiwidmFscyI6W3sidmFsdWUiOiJDVFBfSUMifV19XX0sIlN1YmplY3RMYWJlbHMiOltdLCJUTUNWZXJzaW9uIjoiMTUuNC4xMC4xOSIsIlRydXN0ZWRMYWJlbEhhc2giOiJuYTRwTjQ0UHFncUo1MnFEb1FvaVUzenpQWmgxK1FXTE13XC9xTjJGRFZhST0ifQ== x-inteldataclassification: CTP_IC x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2977 Lines: 114 > > On Wed, Feb 18, 2015 at 09:15:06AM -0800, tip-bot for Yan, Zheng wrote: > > +find_get_context(struct pmu *pmu, struct task_struct *task, > > + struct perf_event *event) > > { > > struct perf_event_context *ctx, *clone_ctx = NULL; > > struct perf_cpu_context *cpuctx; > > + void *task_ctx_data = NULL; > > unsigned long flags; > > int ctxn, err; > > + int cpu = event->cpu; > > > > if (!task) { > > /* Must be root to operate on a CPU event: */ @@ - > 3342,11 +3354,24 > > @@ find_get_context(struct pmu *pmu, struct task_struct *task, int cpu) > > if (ctxn < 0) > > goto errout; > > > > + if (event->attach_state & PERF_ATTACH_TASK_DATA) { > > + task_ctx_data = kzalloc(pmu->task_ctx_size, GFP_KERNEL); > > + if (!task_ctx_data) { > > + err = -ENOMEM; > > + goto errout; > > + } > > + } > > + > > retry: > > ctx = perf_lock_task_context(task, ctxn, &flags); > > if (ctx) { > > clone_ctx = unclone_ctx(ctx); > > ++ctx->pin_count; > > + > > + if (task_ctx_data && !ctx->task_ctx_data) { > > + ctx->task_ctx_data = task_ctx_data; > > + task_ctx_data = NULL; > > + } > > raw_spin_unlock_irqrestore(&ctx->lock, flags); > > > > if (clone_ctx) > > @@ -3357,6 +3382,11 @@ retry: > > if (!ctx) > > goto errout; > > > > + if (task_ctx_data) { > > + ctx->task_ctx_data = task_ctx_data; > > + task_ctx_data = NULL; > > + } > > + > > err = 0; > > mutex_lock(&task->perf_event_mutex); > > /* > > @@ -3383,9 +3413,11 @@ retry: > > } > > } > > > > + kfree(task_ctx_data); > > return ctx; > > > > errout: > > + kfree(task_ctx_data); > > return ERR_PTR(err); > > } > > > diff --git a/kernel/events/core.c b/kernel/events/core.c index > 36babfd..97aa610 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -3508,11 +3515,6 @@ retry: > if (!ctx) > goto errout; > > - if (task_ctx_data) { > - ctx->task_ctx_data = task_ctx_data; > - task_ctx_data = NULL; > - } > - > err = 0; > mutex_lock(&task->perf_event_mutex); > /* > @@ -3526,6 +3528,10 @@ retry: > else { > get_ctx(ctx); > ++ctx->pin_count; > + if (task_ctx_data) { > + ctx->task_ctx_data = task_ctx_data; > + task_ctx_data = NULL; > + } > rcu_assign_pointer(task->perf_event_ctxp[ctxn], > ctx); > } > mutex_unlock(&task->perf_event_mutex); > > > Does that make sense? No point in setting task_ctx_data if we're going to > free the ctx and try again. The task_ctx_data will be checked before use. So it wouldn't crash the system if it's NULL. The problem is that LBR stack info will not be save/store on context switch anymore. The user probably get wrong call stack information. May I know why you want to do that? Thanks, Kan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/