From: Ran Rozenstein <ranro@mellanox.com>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "mingo@kernel.org" <mingo@kernel.org>,
"jiangshanlai@gmail.com" <jiangshanlai@gmail.com>,
"dipankar@in.ibm.com" <dipankar@in.ibm.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"mathieu.desnoyers@efficios.com" <mathieu.desnoyers@efficios.com>,
"josh@joshtriplett.org" <josh@joshtriplett.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"peterz@infradead.org" <peterz@infradead.org>,
"rostedt@goodmis.org" <rostedt@goodmis.org>,
"dhowells@redhat.com" <dhowells@redhat.com>,
"edumazet@google.com" <edumazet@google.com>,
"fweisbec@gmail.com" <fweisbec@gmail.com>,
"oleg@redhat.com" <oleg@redhat.com>,
"joel@joelfernandes.org" <joel@joelfernandes.org>,
Maor Gottlieb <maorg@mellanox.com>,
Tariq Toukan <tariqt@mellanox.com>,
Eran Ben Elisha <eranbe@mellanox.com>,
Leon Romanovsky <leonro@mellanox.com>
Subject: RE: [PATCH tip/core/rcu 02/19] rcu: Defer reporting RCU-preempt quiescent states when disabled
Date: Mon, 29 Oct 2018 11:24:42 +0000 [thread overview]
Message-ID: <AM4PR0501MB27691ECD1B0ECB0531B16F20C5F30@AM4PR0501MB2769.eurprd05.prod.outlook.com> (raw)
In-Reply-To: <20180829222047.319-2-paulmck@linux.vnet.ibm.com>
Hi Paul and all,
> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-
> owner@vger.kernel.org] On Behalf Of Paul E. McKenney
> Sent: Thursday, August 30, 2018 01:21
> To: linux-kernel@vger.kernel.org
> Cc: mingo@kernel.org; jiangshanlai@gmail.com; dipankar@in.ibm.com;
> akpm@linux-foundation.org; mathieu.desnoyers@efficios.com;
> josh@joshtriplett.org; tglx@linutronix.de; peterz@infradead.org;
> rostedt@goodmis.org; dhowells@redhat.com; edumazet@google.com;
> fweisbec@gmail.com; oleg@redhat.com; joel@joelfernandes.org; Paul E.
> McKenney <paulmck@linux.vnet.ibm.com>
> Subject: [PATCH tip/core/rcu 02/19] rcu: Defer reporting RCU-preempt
> quiescent states when disabled
>
> This commit defers reporting of RCU-preempt quiescent states at
> rcu_read_unlock_special() time when any of interrupts, softirq, or
> preemption are disabled. These deferred quiescent states are reported at a
> later RCU_SOFTIRQ, context switch, idle entry, or CPU-hotplug offline
> operation. Of course, if another RCU read-side critical section has started in
> the meantime, the reporting of the quiescent state will be further deferred.
>
> This also means that disabling preemption, interrupts, and/or softirqs will act
> as an RCU-preempt read-side critical section.
> This is enforced by checking preempt_count() as needed.
>
> Some special cases must be handled on an ad-hoc basis, for example,
> context switch is a quiescent state even though both the scheduler and
> do_exit() disable preemption. In these cases, additional calls to
> rcu_preempt_deferred_qs() override the preemption disabling. Similar logic
> overrides disabled interrupts in rcu_preempt_check_callbacks() because in
> this case the quiescent state happened just before the corresponding
> scheduling-clock interrupt.
>
> In theory, this change lifts a long-standing restriction that required that if
> interrupts were disabled across a call to rcu_read_unlock() that the matching
> rcu_read_lock() also be contained within that interrupts-disabled region of
> code. Because the reporting of the corresponding RCU-preempt quiescent
> state is now deferred until after interrupts have been enabled, it is no longer
> possible for this situation to result in deadlocks involving the scheduler's
> runqueue and priority-inheritance locks. This may allow some code
> simplification that might reduce interrupt latency a bit. Unfortunately, in
> practice this would also defer deboosting a low-priority task that had been
> subjected to RCU priority boosting, so real-time-response considerations
> might well force this restriction to remain in place.
>
> Because RCU-preempt grace periods are now blocked not only by RCU read-
> side critical sections, but also by disabling of interrupts, preemption, and
> softirqs, it will be possible to eliminate RCU-bh and RCU-sched in favor of
> RCU-preempt in CONFIG_PREEMPT=y kernels. This may require some
> additional plumbing to provide the network denial-of-service guarantees
> that have been traditionally provided by RCU-bh. Once these are in place,
> CONFIG_PREEMPT=n kernels will be able to fold RCU-bh into RCU-sched.
> This would mean that all kernels would have but one flavor of RCU, which
> would open the door to significant code cleanup.
>
> Moving to a single flavor of RCU would also have the beneficial effect of
> reducing the NOCB kthreads by at least a factor of two.
>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck:
> Apply rcu_read_unlock_special() preempt_count() feedback
> from Joel Fernandes. ]
> [ paulmck: Adjust rcu_eqs_enter() call to rcu_preempt_deferred_qs() in
> response to bug reports from kbuild test robot. ] [ paulmck: Fix bug located
> by kbuild test robot involving recursion
> via rcu_preempt_deferred_qs(). ]
> ---
> .../RCU/Design/Requirements/Requirements.html | 50 +++---
> include/linux/rcutiny.h | 5 +
> kernel/rcu/tree.c | 9 ++
> kernel/rcu/tree.h | 3 +
> kernel/rcu/tree_exp.h | 71 +++++++--
> kernel/rcu/tree_plugin.h | 144 +++++++++++++-----
> 6 files changed, 205 insertions(+), 77 deletions(-)
>
We started seeing the trace below in our regression system, after I bisected I found this is the offending commit.
This appears immediately on boot.
Please let me know if you need any additional details.
Thanks,
Ran
[2018-10-27 05:53:07] ================================================================================
[2018-10-27 05:53:07] UBSAN: Undefined behaviour in kernel/rcu/tree_plugin.h:620:28
[2018-10-27 05:53:07] signed integer overflow:
[2018-10-27 05:53:07] 0 - -2147483648 cannot be represented in type 'int'
[2018-10-27 05:53:07] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.0-for-upstream-dbg-2018-10-25_03-10-39-82 #1
[2018-10-27 05:53:07] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
[2018-10-27 05:53:07] Call Trace:
[2018-10-27 05:53:07] dump_stack+0x9a/0xeb
[2018-10-27 05:53:07] ubsan_epilogue+0x9/0x7c
[2018-10-27 05:53:07] handle_overflow+0x235/0x278
[2018-10-27 05:53:07] ? __ubsan_handle_negate_overflow+0x1bd/0x1bd
[2018-10-27 05:53:07] ? sched_clock_local+0xd4/0x140
[2018-10-27 05:53:07] ? kvm_clock_read+0x14/0x30
[2018-10-27 05:53:07] rcu_preempt_deferred_qs+0x12a/0x150
[2018-10-27 05:53:07] rcu_note_context_switch+0x1b9/0x1ac0
[2018-10-27 05:53:07] __schedule+0x22d/0x1fd0
[2018-10-27 05:53:07] ? pci_mmcfg_check_reserved+0x130/0x130
[2018-10-27 05:53:07] ? sched_set_stop_task+0x330/0x330
[2018-10-27 05:53:07] ? lockdep_hardirqs_on+0x360/0x620
[2018-10-27 05:53:07] schedule_idle+0x45/0x80
[2018-10-27 05:53:07] do_idle+0x23e/0x3e0
[2018-10-27 05:53:07] ? check_flags.part.26+0x440/0x440
[2018-10-27 05:53:07] ? arch_cpu_idle_exit+0x40/0x40
[2018-10-27 05:53:07] ? __wake_up_common+0x156/0x5c0
[2018-10-27 05:53:07] ? _raw_spin_unlock_irqrestore+0x59/0x70
[2018-10-27 05:53:07] cpu_startup_entry+0x19/0x20
[2018-10-27 05:53:07] start_secondary+0x420/0x570
[2018-10-27 05:53:07] ? set_cpu_sibling_map+0x2f90/0x2f90
[2018-10-27 05:53:07] secondary_startup_64+0xa4/0xb0
[2018-10-27 05:53:07] ================================================================================
[2018-10-27 05:53:07] ================================================================================
[2018-10-27 05:53:07] UBSAN: Undefined behaviour in kernel/rcu/tree_plugin.h:624:28
[2018-10-27 05:53:07] signed integer overflow:
[2018-10-27 05:53:07] -2147483648 + -2147483648 cannot be represented in type 'int'
[2018-10-27 05:53:07] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.0-for-upstream-dbg-2018-10-25_03-10-39-82 #1
[2018-10-27 05:53:07] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
[2018-10-27 05:53:07] Call Trace:
[2018-10-27 05:53:07] dump_stack+0x9a/0xeb
[2018-10-27 05:53:07] ubsan_epilogue+0x9/0x7c
[2018-10-27 05:53:07] handle_overflow+0x235/0x278
[2018-10-27 05:53:07] ? __ubsan_handle_negate_overflow+0x1bd/0x1bd
[2018-10-27 05:53:07] ? check_flags.part.26+0x440/0x440
[2018-10-27 05:53:07] ? _raw_spin_unlock_irqrestore+0x3c/0x70
[2018-10-27 05:53:07] ? _raw_spin_unlock_irqrestore+0x3c/0x70
[2018-10-27 05:53:07] ? lockdep_hardirqs_off+0x1fd/0x2c0
[2018-10-27 05:53:07] ? kvm_clock_read+0x14/0x30
[2018-10-27 05:53:07] rcu_preempt_deferred_qs+0x145/0x150
[2018-10-27 05:53:07] rcu_note_context_switch+0x1b9/0x1ac0
[2018-10-27 05:53:07] __schedule+0x22d/0x1fd0
[2018-10-27 05:53:07] ? pci_mmcfg_check_reserved+0x130/0x130
[2018-10-27 05:53:07] ? sched_set_stop_task+0x330/0x330
[2018-10-27 05:53:07] ? lockdep_hardirqs_on+0x360/0x620
[2018-10-27 05:53:07] schedule_idle+0x45/0x80
[2018-10-27 05:53:07] do_idle+0x23e/0x3e0
[2018-10-27 05:53:07] ? check_flags.part.26+0x440/0x440
[2018-10-27 05:53:07] ? arch_cpu_idle_exit+0x40/0x40
[2018-10-27 05:53:07] ? __wake_up_common+0x156/0x5c0
[2018-10-27 05:53:07] ? _raw_spin_unlock_irqrestore+0x59/0x70
[2018-10-27 05:53:07] cpu_startup_entry+0x19/0x20
[2018-10-27 05:53:07] start_secondary+0x420/0x570
[2018-10-27 05:53:07] ? set_cpu_sibling_map+0x2f90/0x2f90
[2018-10-27 05:53:07] secondary_startup_64+0xa4/0xb0
[2018-10-27 05:53:07] ================================================================================
next prev parent reply other threads:[~2018-10-29 11:24 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-29 22:20 [PATCH tip/core/rcu 0/19] RCU flavor-consolidation changes for v4.20/v5.0 Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 01/19] rcu: Refactor rcu_{nmi,irq}_{enter,exit}() Paul E. McKenney
2018-08-30 18:10 ` Steven Rostedt
2018-08-30 23:02 ` Paul E. McKenney
2018-08-31 2:25 ` Byungchul Park
2018-08-29 22:20 ` [PATCH tip/core/rcu 02/19] rcu: Defer reporting RCU-preempt quiescent states when disabled Paul E. McKenney
2018-10-29 11:24 ` Ran Rozenstein [this message]
2018-10-29 14:27 ` Paul E. McKenney
2018-10-30 3:44 ` Joel Fernandes
2018-10-30 12:58 ` Paul E. McKenney
2018-10-30 22:21 ` Joel Fernandes
2018-10-31 18:22 ` Paul E. McKenney
2018-11-02 19:43 ` Paul E. McKenney
2018-11-26 13:55 ` Ran Rozenstein
2018-11-26 19:00 ` Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 03/19] rcutorture: Test extended "rcu" read-side critical sections Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 04/19] rcu: Allow processing deferred QSes for exiting RCU-preempt readers Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 05/19] rcu: Remove now-unused ->b.exp_need_qs field from the rcu_special union Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 06/19] rcu: Add warning to detect half-interrupts Paul E. McKenney
2019-03-11 13:39 ` Joel Fernandes
2019-03-11 22:29 ` Paul E. McKenney
2019-03-12 15:05 ` Joel Fernandes
2019-03-12 15:20 ` Paul E. McKenney
2019-03-13 15:09 ` Joel Fernandes
2019-03-13 15:27 ` Steven Rostedt
2019-03-13 15:51 ` Paul E. McKenney
2019-03-13 16:51 ` Steven Rostedt
2019-03-13 18:07 ` Paul E. McKenney
2019-03-14 12:31 ` Joel Fernandes
2019-03-14 13:36 ` Steven Rostedt
2019-03-14 13:37 ` Steven Rostedt
2019-03-14 21:27 ` Joel Fernandes
2019-03-15 7:31 ` Byungchul Park
2019-03-15 7:44 ` Byungchul Park
2019-03-15 13:46 ` Joel Fernandes
2018-08-29 22:20 ` [PATCH tip/core/rcu 07/19] rcu: Apply RCU-bh QSes to RCU-sched and RCU-preempt when safe Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 08/19] rcu: Report expedited grace periods at context-switch time Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 09/19] rcu: Define RCU-bh update API in terms of RCU Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 10/19] rcu: Update comments and help text for no more RCU-bh updaters Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 11/19] rcu: Drop "wake" parameter from rcu_report_exp_rdp() Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 12/19] rcu: Fix typo in rcu_get_gp_kthreads_prio() header comment Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 13/19] rcu: Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 14/19] rcu: Express Tiny RCU updates in terms of RCU rather than RCU-sched Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 15/19] rcu: Remove RCU_STATE_INITIALIZER() Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 16/19] rcu: Eliminate rcu_state structure's ->call field Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 17/19] rcu: Remove rcu_state structure's ->rda field Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 18/19] rcu: Remove rcu_state_p pointer to default rcu_state structure Paul E. McKenney
2018-08-29 22:20 ` [PATCH tip/core/rcu 19/19] rcu: Remove rcu_data_p pointer to default rcu_data structure Paul E. McKenney
2018-08-29 22:22 ` [PATCH tip/core/rcu 0/19] RCU flavor-consolidation changes for v4.20/v5.0 Paul E. McKenney
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