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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2E67C433FE for ; Thu, 20 Oct 2022 16:34:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230157AbiJTQeA (ORCPT ); Thu, 20 Oct 2022 12:34:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230111AbiJTQd7 (ORCPT ); Thu, 20 Oct 2022 12:33:59 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A88681D8F20; Thu, 20 Oct 2022 09:33:57 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 9378DB826C8; Thu, 20 Oct 2022 16:33:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 57611C433D6; Thu, 20 Oct 2022 16:33:53 +0000 (UTC) Date: Thu, 20 Oct 2022 12:33:57 -0400 From: Steven Rostedt To: "Paul E. McKenney" Cc: LKML , Linux Trace Kernel , Masami Hiramatsu , Andrew Morton , Mathieu Desnoyers , Joel Fernandes , Tom Zanussi Subject: Re: [PATCH] tracing: Add trace_trigger kernel command line option Message-ID: <20221020123357.0f90e823@gandalf.local.home> In-Reply-To: <20221020155900.GM5600@paulmck-ThinkPad-P17-Gen-1> References: <20221019200137.70343645@gandalf.local.home> <20221019200745.0152fc51@gandalf.local.home> <20221020155900.GM5600@paulmck-ThinkPad-P17-Gen-1> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org On Thu, 20 Oct 2022 08:59:00 -0700 "Paul E. McKenney" wrote: > On Wed, Oct 19, 2022 at 08:07:45PM -0400, Steven Rostedt wrote: > > On Wed, 19 Oct 2022 20:01:37 -0400 > > Steven Rostedt wrote: > > > > > @@ -90,6 +90,10 @@ int unregister_tracepoint_module_notifier(struct notifier_block *nb) > > > #ifdef CONFIG_TRACEPOINTS > > > static inline void tracepoint_synchronize_unregister(void) > > > { > > > + /* Early updates do not need synchronization */ > > > + if (early_boot_irqs_disabled) > > > + return; > > > + > > > synchronize_srcu(&tracepoint_srcu); > > > synchronize_rcu(); > > > > I wonder if this check should be just moved to the RCU synchronization > > code? That is, if early_boot_irqs_disabled is set, do nothing, as there > > should be nothing to synchronize against. > > There already is a similar check, but it follows the lockdep check. > > Does the following patch help? Not sure if it would. I added this: diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index c03fd7037add..79ac31a6a87b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2748,9 +2748,12 @@ void trace_buffered_event_disable(void) disable_trace_buffered_event, NULL, 1); preempt_enable(); + if (!irqs_disabled()) + printk("IRQS DISABLED!! before %s:%d\n", __func__, __LINE__); /* Wait for all current users to finish */ - if (!early_boot_irqs_disabled) - synchronize_rcu(); + synchronize_rcu(); + if (!irqs_disabled()) + printk("IRQS DISABLED!! after %s:%d\n", __func__, __LINE__); for_each_tracing_cpu(cpu) { free_page((unsigned long)per_cpu(trace_buffered_event, cpu)); Which produced this: [ 0.972867] ftrace: allocating 47021 entries in 184 pages [ 0.978285] ftrace section at ffffffffacef74c0 sorted properly [ 0.991153] ftrace: allocated 184 pages with 4 groups [ 0.996163] Dynamic Preempt: full [ 0.999354] rcu: Preemptible hierarchical RCU implementation. [ 1.005020] rcu: RCU restricting CPUs from NR_CPUS=128 to nr_cpu_ids=8. [ 1.011680] Tasks-RCU CPU stall warnings timeout set to 120000 (rcu_task_stall_timeout). [ 1.019813] Trampoline variant of Tasks RCU enabled. [ 1.024831] Rude variant of Tasks RCU enabled. [ 1.029330] Tracing variant of Tasks RCU enabled. [ 1.034089] rcu: RCU calculated value of scheduler-enlistment delay is 100 jiffies. [ 1.041699] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=8 [ 1.052607] IRQS DISABLED!! after trace_buffered_event_disable:2756 [ 1.058712] NR_IRQS: 8448, nr_irqs: 488, preallocated irqs: 16 [ 1.064670] NO_HZ: Full dynticks CPUs: 3. [ 1.068501] rcu: Offload RCU callbacks from CPUs: 3. [ 1.073519] rcu: srcu_init: Setting srcu_struct sizes based on contention. [ 1.080400] ------------[ cut here ]------------ [ 1.084938] Interrupts were enabled early [ 1.088919] WARNING: CPU: 0 PID: 0 at init/main.c:1061 start_kernel+0x36f/0x4e8 [ 1.096184] Modules linked in: [ 1.099213] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.1.0-rc1-test+ #468 [ 1.106047] Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016 [ 1.114960] RIP: 0010:start_kernel+0x36f/0x4e8 [ 1.119373] Code: 48 27 53 e8 fd 7b 03 00 e8 55 72 e5 fe e8 6b 05 03 00 ff 15 2a f9 89 ff 0f ba e0 09 73 0e 48 c7 c7 98 25 31 ac e8 01 5b df fe <0f> 0b c6 05 c7 2c af ff 00 e8 ba 36 47 fe ff 15 14 f9 89 ff e8 56 [ 1.138057] RSP: 0000:ffffffffac603f30 EFLAGS: 00010286 [ 1.143248] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 1.150343] RDX: 0000000000000002 RSI: 00000000ffffdfff RDI: 0000000000000001 [ 1.157438] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffffac603dd8 [ 1.164537] R10: 0000000000000003 R11: ffffffffac734168 R12: 000000000000180a [ 1.171633] R13: 00000000010fecf0 R14: 0000000000000000 R15: 00000000d44e3018 [ 1.178730] FS: 0000000000000000(0000) GS:ffff93ee1aa00000(0000) knlGS:0000000000000000 [ 1.186778] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1.192489] CR2: ffff93ee1edff000 CR3: 000000002e60a001 CR4: 00000000000606f0 [ 1.199584] Call Trace: [ 1.202009] So I'm not sure how just updating srcu will do anything to prevent this. -- Steve > > Thanx, Paul > > ------------------------------------------------------------------------ > > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > index ca4b5dcec675b..356ef70d5442c 100644 > --- a/kernel/rcu/srcutree.c > +++ b/kernel/rcu/srcutree.c > @@ -1267,14 +1267,15 @@ static void __synchronize_srcu(struct srcu_struct *ssp, bool do_norm) > { > struct rcu_synchronize rcu; > > + if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) > + return; > + > RCU_LOCKDEP_WARN(lockdep_is_held(ssp) || > lock_is_held(&rcu_bh_lock_map) || > lock_is_held(&rcu_lock_map) || > lock_is_held(&rcu_sched_lock_map), > "Illegal synchronize_srcu() in same-type SRCU (or in RCU) read-side critical section"); > > - if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) > - return; > might_sleep(); > check_init_srcu_struct(ssp); > init_completion(&rcu.completion);