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Subject: Re: [PATCH] sched/deadline: Add missing update_rq_clock() in
 dl_task_timer()
To: Wanpeng Li <kernellwp@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        kvm <kvm@vger.kernel.org>
References: <1488865888-15894-1-git-send-email-wanpeng.li@hotmail.com>
 <CANRm+CwDky=co2sk2a-96fGzVs_LNawf=yh9JwtNb_oSjVBQDQ@mail.gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
        Wanpeng Li <wanpeng.li@hotmail.com>, Juri Lelli <juri.lelli@arm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Matt Fleming <matt@codeblueprint.co.uk>
From: Daniel Bristot de Oliveira <bristot@redhat.com>
Message-ID: <7b012738-bc10-6ba4-b576-a13175d09a4a@redhat.com>
Date: Wed, 15 Mar 2017 11:44:22 +0100
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On 03/15/2017 08:53 AM, Wanpeng Li wrote:
> Ping, :)
> 2017-03-07 13:51 GMT+08:00 Wanpeng Li <kernellwp@gmail.com>:
>> From: Wanpeng Li <wanpeng.li@hotmail.com>
>>
>> The following warning can be triggered by hot-unplugging the CPU
>> on which an active SCHED_DEADLINE task is running on:
>>
>>  ------------[ cut here ]------------
>>  WARNING: CPU: 7 PID: 0 at kernel/sched/sched.h:833 replenish_dl_entity+0x71e/0xc40
>>  rq->clock_update_flags < RQCF_ACT_SKIP
>>  CPU: 7 PID: 0 Comm: swapper/7 Tainted: G    B           4.11.0-rc1+ #24
>>  Hardware name: LENOVO ThinkCentre M8500t-N000/SHARKBAY, BIOS FBKTC1AUS 02/16/2016
>>  Call Trace:
>>   <IRQ>
>>   dump_stack+0x85/0xc4
>>   __warn+0x172/0x1b0
>>   warn_slowpath_fmt+0xb4/0xf0
>>   ? __warn+0x1b0/0x1b0
>>   ? debug_check_no_locks_freed+0x2c0/0x2c0
>>   ? cpudl_set+0x3d/0x2b0
>>   replenish_dl_entity+0x71e/0xc40
>>   enqueue_task_dl+0x2ea/0x12e0
>>   ? dl_task_timer+0x777/0x990
>>   ? __hrtimer_run_queues+0x270/0xa50
>>   dl_task_timer+0x316/0x990
>>   ? enqueue_task_dl+0x12e0/0x12e0
>>   ? enqueue_task_dl+0x12e0/0x12e0
>>   __hrtimer_run_queues+0x270/0xa50
>>   ? hrtimer_cancel+0x20/0x20
>>   ? hrtimer_interrupt+0x119/0x600
>>   hrtimer_interrupt+0x19c/0x600
>>   ? trace_hardirqs_off+0xd/0x10
>>   local_apic_timer_interrupt+0x74/0xe0
>>   smp_apic_timer_interrupt+0x76/0xa0
>>   apic_timer_interrupt+0x93/0xa0
>>
>> The DL task will be migrated to a suitable later deadline rq once the DL
>> timer fires and currnet rq is offline. The rq clock of the new rq should
>> be updated. This patch fixes it by updating the rq clock after holding
>> the new rq's rq lock.
>>
>> Cc: Juri Lelli <juri.lelli@arm.com>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Ingo Molnar <mingo@kernel.org>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Matt Fleming <matt@codeblueprint.co.uk>
>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>

Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>

-- Daniel