From: "Li, Aubrey" <aubrey.li@linux.intel.com>
To: paulmck@kernel.org, "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc: linux-kernel@vger.kernel.org, vpillai <vpillai@digitalocean.com>,
Aaron Lu <aaron.lwe@gmail.com>,
Aubrey Li <aubrey.intel@gmail.com>,
peterz@infradead.org, Ben Segall <bsegall@google.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>, Mel Gorman <mgorman@suse.de>,
Steven Rostedt <rostedt@goodmis.org>,
Vincent Guittot <vincent.guittot@linaro.org>
Subject: Re: [PATCH] sched: Use RCU-sched in core-scheduling balancing logic
Date: Mon, 23 Mar 2020 14:58:18 +0800 [thread overview]
Message-ID: <f77b9432-933c-a9fe-5541-437cf0094a65@linux.intel.com> (raw)
In-Reply-To: <20200314003004.GI3199@paulmck-ThinkPad-P72>
On 2020/3/14 8:30, Paul E. McKenney wrote:
> On Fri, Mar 13, 2020 at 07:29:18PM -0400, Joel Fernandes (Google) wrote:
>> rcu_read_unlock() can incur an infrequent deadlock in
>> sched_core_balance(). Fix this by using the RCU-sched flavor instead.
>>
>> This fixes the following spinlock recursion observed when testing the
>> core scheduling patches on PREEMPT=y kernel on ChromeOS:
>>
>> [ 14.998590] watchdog: BUG: soft lockup - CPU#0 stuck for 11s! [kworker/0:10:965]
>>
>
> The original could indeed deadlock, and this would avoid that deadlock.
> (The commit to solve this deadlock is sadly not yet in mainline.)
>
> Acked-by: Paul E. McKenney <paulmck@kernel.org>
I saw this in dmesg with this patch, is it expected?
Thanks,
-Aubrey
[ 117.000905] =============================
[ 117.000907] WARNING: suspicious RCU usage
[ 117.000911] 5.5.7+ #160 Not tainted
[ 117.000913] -----------------------------
[ 117.000916] kernel/sched/core.c:4747 suspicious rcu_dereference_check() usage!
[ 117.000918]
other info that might help us debug this:
[ 117.000921]
rcu_scheduler_active = 2, debug_locks = 1
[ 117.000923] 1 lock held by swapper/52/0:
[ 117.000925] #0: ffffffff82670960 (rcu_read_lock_sched){....}, at: sched_core_balance+0x5/0x700
[ 117.000937]
stack backtrace:
[ 117.000940] CPU: 52 PID: 0 Comm: swapper/52 Kdump: loaded Not tainted 5.5.7+ #160
[ 117.000943] Hardware name: Intel Corporation S2600WFD/S2600WFD, BIOS SE5C620.86B.01.00.0412.020920172159 02/09/2017
[ 117.000945] Call Trace:
[ 117.000955] dump_stack+0x86/0xcb
[ 117.000962] sched_core_balance+0x634/0x700
[ 117.000982] __balance_callback+0x49/0xa0
[ 117.000990] __schedule+0x1416/0x1620
[ 117.001000] ? lockdep_hardirqs_off+0xa0/0xe0
[ 117.001005] ? _raw_spin_unlock_irqrestore+0x41/0x70
[ 117.001024] schedule_idle+0x28/0x40
[ 117.001030] do_idle+0x17e/0x2a0
[ 117.001041] cpu_startup_entry+0x19/0x20
[ 117.001048] start_secondary+0x16c/0x1c0
[ 117.001055] secondary_startup_64+0xa4/0xb0
>
>> ---
>> kernel/sched/core.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 3045bd50e249..037e8f2e2686 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -4735,7 +4735,7 @@ static void sched_core_balance(struct rq *rq)
>> struct sched_domain *sd;
>> int cpu = cpu_of(rq);
>>
>> - rcu_read_lock();
>> + rcu_read_lock_sched();
>> raw_spin_unlock_irq(rq_lockp(rq));
>> for_each_domain(cpu, sd) {
>> if (!(sd->flags & SD_LOAD_BALANCE))
>> @@ -4748,7 +4748,7 @@ static void sched_core_balance(struct rq *rq)
>> break;
>> }
>> raw_spin_lock_irq(rq_lockp(rq));
>> - rcu_read_unlock();
>> + rcu_read_unlock_sched();
>> }
>>
>> static DEFINE_PER_CPU(struct callback_head, core_balance_head);
>> --
>> 2.25.1.481.gfbce0eb801-goog
>>
next prev parent reply other threads:[~2020-03-23 6:58 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-13 23:29 [PATCH] sched: Use RCU-sched in core-scheduling balancing logic Joel Fernandes (Google)
2020-03-14 0:30 ` Paul E. McKenney
2020-03-23 6:58 ` Li, Aubrey [this message]
2020-03-23 15:21 ` Joel Fernandes
2020-03-24 3:01 ` Li, Aubrey
2020-03-24 13:30 ` Paul E. McKenney
2020-03-24 15:12 ` Paul E. McKenney
2020-03-24 18:49 ` Joel Fernandes
2020-03-25 0:40 ` Li, Aubrey
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