From: Christoph Hellwig <hch@lst.de>
To: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org
Subject: Re: boot stall regression due to blk-mq: use percpu_ref for mq usage count
Date: Tue, 23 Sep 2014 08:09:06 +0200 [thread overview]
Message-ID: <20140923060906.GA10547@lst.de> (raw)
In-Reply-To: <20140923060141.GF11740@mtj.dyndns.org>
On Tue, Sep 23, 2014 at 02:01:41AM -0400, Tejun Heo wrote:
> On Tue, Sep 23, 2014 at 07:59:24AM +0200, Christoph Hellwig wrote:
> > "[PATCHSET percpu/for-3.18] percpu_ref: implement switch_to_atomic/percpu()"
> >
> > looks way to big for 3.17, and the regression was introduced in the 3.17
> > merge window. I'm not sure what was broken before, but it defintively
> > survived a lot of testing.
>
> Do we even care about fixing it for 3.17? scsi-mq isn't enabled by
> default even for 3.18. The open-coded percpu ref thing was subtly
> broken there. It'd be difficult to trigger but I'm fairly sure it'd
> crap out in the wild once in a blue moon.
It's compiled in by default, and people are extremly eager to test it.
next prev parent reply other threads:[~2014-09-23 6:09 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-19 11:38 boot stall regression due to blk-mq: use percpu_ref for mq usage count Christoph Hellwig
2014-09-19 19:13 ` Jens Axboe
2014-09-23 5:55 ` Christoph Hellwig
2014-09-23 5:56 ` Tejun Heo
2014-09-23 5:57 ` Tejun Heo
2014-09-23 5:59 ` Christoph Hellwig
2014-09-23 6:01 ` Tejun Heo
2014-09-23 6:03 ` Tejun Heo
2014-09-23 6:09 ` Christoph Hellwig [this message]
2014-09-23 6:11 ` Tejun Heo
2014-09-23 14:57 ` Elliott, Robert (Server Storage)
2014-09-23 15:49 ` Jens Axboe
2014-09-23 19:24 ` [PATCH block/for-3.17-fixes/core] blk-mq, percpu_ref: implement a kludge for SCSI blk-mq stall during probe Tejun Heo
2014-09-23 19:29 ` Jens Axboe
2014-09-23 19:48 ` Tejun Heo
2014-09-24 8:23 ` Christoph Hellwig
2014-09-24 14:30 ` Jens Axboe
2014-09-24 14:33 ` Tejun Heo
2014-09-24 14:33 ` Jens Axboe
2014-09-24 17:20 ` [PATCH percpu/for-3.18] Revert "blk-mq, percpu_ref: implement a kludge for SCSI blk-mq stall during probe" Tejun Heo
2014-09-23 6:08 ` [PATCH block/for-3.18/core] blk-mq: start q->mq_usage_counter in atomic mode Tejun Heo
2014-09-24 17:33 ` Tejun Heo
2014-09-24 17:43 ` [PATCH percpu/for-3.18] blk-mq, percpu_ref: " Tejun Heo
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