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Date: Thu, 06 Sep 2012 10:10:44 +0800 From: Lai Jiangshan <laijs@...fujitsu.com> To: Tejun Heo <tj@...nel.org> CC: linux-kernel@...r.kernel.org Subject: Re: [PATCH 03/11 V5] workqueue: new day don't need WORKER_REBIND for busy rebinding On 09/06/2012 02:31 AM, Tejun Heo wrote: > On Wed, Sep 05, 2012 at 06:37:40PM +0800, Lai Jiangshan wrote: >> because old busy_worker_rebind_fn() have to wait until all idle worker finish. >> so we have to use two flags WORKER_UNBOUND and WORKER_REBIND to avoid >> prematurely clear all NOT_RUNNING bit when highly frequent offline/online. >> >> but current code don't need to wait idle workers. so we don't need to >> use two flags, just one is enough. remove WORKER_REBIND from busy rebinding. > > ROGUE / REBIND thing existed for busy workers from the beginning when > there was no idle worker rebinding, so this definitely wasn't about > whether idle rebind is synchronous or not. In very old day, this definitely wasn't about whether idle rebind is synchronous or not. but after you reimplement rebind_worker(), it is the only reason for WORKER_REBIND in busy rebinding. if I miss something, this 03/11 will be wrong. the old code did not comment all why WORKER_REBIND is needed. so we have to think more about the correctness of this 03/11. > Trying to remember > what... ah, okay, setting of DISASSOCIATED and setting of WORKER_ROGUE > didn't use to happen together with gcwq->lock held. CPU_DOWN would > first set ROGUE and then later on set DISASSOCIATED, so if the > rebind_fn kicks in inbetween that, it would break CPU_DOWN. > > I think now that both CPU_DOWN and UP are done under single holding of > gcwq->lock, this should be safe. It would be nice to note what > changed in the patch description and the atomicity requirement as a > comment tho. > Oh, I forgot to add changelog about single holding of gcwq->lock. Thanks Lai -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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