Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758848AbZDCOrp (ORCPT ); Fri, 3 Apr 2009 10:47:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765684AbZDCOqC (ORCPT ); Fri, 3 Apr 2009 10:46:02 -0400 Received: from mga09.intel.com ([134.134.136.24]:17417 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932717AbZDCOqA (ORCPT ); Fri, 3 Apr 2009 10:46:00 -0400 Content-Type: multipart/mixed; boundary="===============0328690642==" MIME-Version: 1.0 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.39,319,1235980800"; d="scan'208";a="503328302" Message-Id: <20090403144551.919636000@intel.com> References: <20090403144332.799740000@intel.com> User-Agent: quilt/0.46-1 Date: Fri, 03 Apr 2009 16:43:36 +0200 From: markus.t.metzger@intel.com To: mingo@elte.hu, tglx@linutronix.de, hpa@zytor.com Cc: markus.t.metzger@gmail.com, roland@redhat.com, eranian@googlemail.com, oleg@redhat.com, juan.villacis@intel.com, ak@linux.jf.intel.com, linux-kernel@vger.kernel.org, Markus Metzger Subject: [patch 04/20] x86, bts: wait until traced task has been scheduled out Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3459 Lines: 115 --===============0328690642== MIME-Version: 1.0 Content-Disposition: inline; filename=tip.master.ds.wait_task_inactive.patch In order to stop branch tracing for a running task, we need to first clear the branch tracing control bits before we may free the tracing buffer. If the traced task is running, the cpu might still trace that task after the branch trace control bits have cleared. Wait until the traced task has been scheduled out before proceeding. A similar problem affects the task debug store context. We first remove the context, then we need to wait until the task has been scheduled out before we can free the context memory. Reviewed-by: Oleg Nesterov Signed-off-by: Markus Metzger --- arch/x86/kernel/ds.c | 23 19 + 4 - 0 ! 1 file changed, 19 insertions(+), 4 deletions(-) Index: b/arch/x86/kernel/ds.c =================================================================== --- a/arch/x86/kernel/ds.c +++ b/arch/x86/kernel/ds.c @@ -299,6 +299,7 @@ static inline struct ds_context *ds_get_ static inline void ds_put_context(struct ds_context *context) { + struct task_struct *task; unsigned long irq; if (!context) @@ -313,14 +314,20 @@ static inline void ds_put_context(struct *(context->this) = NULL; - if (context->task) - clear_tsk_thread_flag(context->task, TIF_DS_AREA_MSR); + task = context->task; + + if (task) + clear_tsk_thread_flag(task, TIF_DS_AREA_MSR); - if (!context->task || (context->task == current)) + if (!task || (task == current)) wrmsrl(MSR_IA32_DS_AREA, 0); spin_unlock_irqrestore(&ds_lock, irq); + /* The context might still be in use for context switching. */ + if (task && (task != current)) + wait_task_context_switch(task); + kfree(context); } @@ -781,15 +788,23 @@ struct pebs_tracer *ds_request_pebs(stru void ds_release_bts(struct bts_tracer *tracer) { + struct task_struct *task; + if (!tracer) return; + task = tracer->ds.context->task; + ds_suspend_bts(tracer); WARN_ON_ONCE(tracer->ds.context->bts_master != tracer); tracer->ds.context->bts_master = NULL; - put_tracer(tracer->ds.context->task); + /* Make sure tracing stopped and the tracer is not in use. */ + if (task && (task != current)) + wait_task_context_switch(task); + + put_tracer(task); ds_put_context(tracer->ds.context); kfree(tracer); -- --===============0328690642== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline --------------------------------------------------------------------- Intel GmbH Dornacher Strasse 1 85622 Feldkirchen/Muenchen Germany Sitz der Gesellschaft: Feldkirchen bei Muenchen Geschaeftsfuehrer: Douglas Lusk, Peter Gleissner, Hannes Schwaderer Registergericht: Muenchen HRB 47456 Ust.-IdNr. VAT Registration No.: DE129385895 Citibank Frankfurt (BLZ 502 109 00) 600119052 This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies. --===============0328690642==-- -- 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/