linux-kernel - Re: [PATCH 0/6] workqueue: simpler&better workers management synchronization

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Date:	Mon, 21 Apr 2014 09:33:40 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Lai Jiangshan <laijs@...fujitsu.com>
CC:	Tejun Heo <tj@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/6] workqueue: simpler&better workers management synchronization

On 04/12/2014 06:50 PM, Lai Jiangshan wrote:
> Sorry,
> the cover letter was forgotten to send to LKML.

Hi, Tejun

Any comments about the patchset.
(general comments, high level comments)

Thanks.
Lai

> 
> On 04/12/2014 06:45 PM, Lai Jiangshan wrote:
>> Each patches remove codes!
>>
>> Patch1&2 are the basic patches. They add a *united* mechanism for managing
>> percpu pools' workers' & unbound pools' workers' & rescuers' CPUMASK.
>>
>> Patch1&4 make workers-concurrency-enabling atomically when cpu_online()
>> and create_worker(). after this, workers-concurrency-enabling-disabling
>> are all atomically.
>>
>> Old manager_mutex protects:
>> 1) workers creation&destruction
>> 2) workers cpumask managing when cpu_online()/workers-creation
>> 3) workers concurrency enabling&disabling.
>>
>> Now, the above three things' synchronization are separated.
>> 1) We don't need manager_mutex protects workers creation&destruction
>>    1.1) creation is only happened when the cpu is first online, the unbound pool
>> 	is just created, and manage_workers(). they have their one synchronization.
>>    1.2) destruction only happens on idle-timeout handler, protected by pool->lock.
>>    1.3) put_unbound_pool() uses manager_arb&workers_leave(new) to synchronize
>> 	with workers creation&destruction.
>>
>> 2) bind_mutex and bind_list handle all the workers'(percpu,unbound,
>>    normal,rescuer) cpumask when cpu_online()/workers-creation/worker-destrution.
>>    we don't need manager_mutex.
>>
>> 3) pool->lock and worker_idr handle workers concurrency enabling&disabling.
>>
>> Note, bind_list is always a super set of worker_idr, and when cpu-online or
>> workers-creation, cpumask is set at first and then concurrency-enabling.
>> concurrency-management depends on local-wakeup which depends on cpumask
>> is properly set for all the workers.
>>
>> This patchset depends on previous patch:
>> "workqueue: fix possible race condition when rescuer VS pwq-release"
>>
>> Thanks,
>> Lai
>>
>>
>> Lai Jiangshan (6):
>>   workqueue: generic routine to restore percpu/unbound pools' workers'
>>     cpumask
>>   workqueue: generic framework to manage normal&rescuer workers'
>>     cpumask
>>   workqueue: make destroy_worker() atomically
>>   workqueue: commit worker to pool's concurrency setting atomically.
>>   workqueue: remove manager_mutex
>>   workqueue: destroy worker directly in idle timeout handler
>>
>>  kernel/workqueue.c          |  366 ++++++++++++------------------------------
>>  kernel/workqueue_internal.h |    1 +
>>  2 files changed, 106 insertions(+), 261 deletions(-)
>>
> 
> .
> 

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