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Message-ID: <20110412025145.GJ9673@mtj.dyndns.org> Date: Tue, 12 Apr 2011 11:51:45 +0900 From: Tejun Heo <tj@...nel.org> To: James Bottomley <James.Bottomley@...senPartnership.com> Cc: Steven Whitehouse <swhiteho@...hat.com>, linux-kernel@...r.kernel.org, Jens Axboe <jaxboe@...ionio.com> Subject: Re: Strange block/scsi/workqueue issue Hello, James. On Mon, Apr 11, 2011 at 07:47:56PM -0500, James Bottomley wrote: > Actually, I don't think it's anything to do with the user process stuff. > The problem seems to be that the block delay function ends up being the > last user of the SCSI device, so it does the final put of the sdev when > it's finished processing. This will trigger queue destruction > (blk_cleanup_queue) and so on with your analysis. Hmm... this I can understand. > The problem seems to be that with the new workqueue changes, the queue > itself may no longer be the last holder of a reference on the sdev > because the queue destruction is in the sdev release function and a > queue cannot now be destroyed from its own delayed work. This is a bit > contrary to the principles SCSI was using, which was that we drive queue > lifetime from the sdev, not vice versa. But confused here. Why does it make any difference whether the release operation is in the request_fn context or not? What makes SCSI refcounting different from others? Thanks. -- tejun -- 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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