From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: Re: Testing tracer wakeup_rt: .. no entries found ..FAILED! Date: Tue, 31 Jul 2012 20:09:38 -0400 Message-ID: <1343779778.27983.73.camel@gandalf.stny.rr.com> References: <20120724090330.GA9830@localhost> <20120724090720.GA10434@localhost> <1343663105.3847.7.camel@fedora> <20120731121759.GA17822@localhost> <5017D19B.5080806@redhat.com> <1343738627.27983.30.camel@gandalf.stny.rr.com> <5017D4AB.3090107@redhat.com> <1343740419.27983.33.camel@gandalf.stny.rr.com> <20120731234336.GA5526@localhost> <1343778699.27983.70.camel@gandalf.stny.rr.com> <20120731235705.GW2422@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: 7bit Cc: Fengguang Wu , Avi Kivity , Steven Rostedt , LKML , "kvm@vger.kernel.org" To: paulmck@linux.vnet.ibm.com Return-path: Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:22603 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756262Ab2HAAJj (ORCPT ); Tue, 31 Jul 2012 20:09:39 -0400 In-Reply-To: <20120731235705.GW2422@linux.vnet.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, 2012-07-31 at 16:57 -0700, Paul E. McKenney wrote: > > What was the next lines? I bet you it was "PASSED". Which means it did > > not fail. This is the second bug you found that has to do with RCU being > > called in 'idle'. The one that Paul posted a patch for. > > Though it needs another patch to actually use it in the right place... Right. Something like this: -- Steve diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 5638104..d915638 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -631,7 +631,12 @@ __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu) memcpy(max_data->comm, tsk->comm, TASK_COMM_LEN); max_data->pid = tsk->pid; - max_data->uid = task_uid(tsk); + /* + * task_uid() calls rcu_read_lock, but this can be called + * outside of RCU state monitoring (irq going back to idle). + */ + RCU_NONIDLE(max_data->uid = task_uid(tsk)); + max_data->nice = tsk->static_prio - 20 - MAX_RT_PRIO; max_data->policy = tsk->policy; max_data->rt_priority = tsk->rt_priority;