From: Tejun Heo <htejun@gmail.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
Jens Axboe <jens.axboe@oracle.com>,
linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: Prevent busy looping
Date: Wed, 11 Jun 2008 17:03:32 +0900 [thread overview]
Message-ID: <484F86D4.8050907@gmail.com> (raw)
In-Reply-To: <20080611080502.4aa43980@core>
Alan Cox wrote:
>> Elias's synthetic test case triggered infinite loop because it wasn't
>> a proper ->qc_defer(). ->qc_defer() should never defer commands when
>> the target is idle.
>
> Target or host ? We *do* defer commands in the case of an idle channel
> when dealing with certain simplex controllers that can only issue one
> command per host not one per cable (and in fact in the general case we
> can defer commands due to activity on the other drive on the cable).
The term was confusing. I used target to mean both device
(ATA_DEFER_LINK) and host (ATA_DEFER_PORT). Hmmm... in simplex case,
yeah, blocked counters need to be > 1. We'll need to increase blocked
counts after all. I'll test blocked counts of 2 w/ PMP and make sure it
doesn't incur unnecessary delays and post the patch.
Thanks.
--
tejun
next prev parent reply other threads:[~2008-06-11 8:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20080416151305.8788.63912.stgit@denkblock.local>
[not found] ` <20080416163152.GK12774@kernel.dk>
[not found] ` <87r6d5l9pb.fsf@denkblock.local>
[not found] ` <20080417071335.GR12774@kernel.dk>
2008-04-17 8:50 ` Prevent busy looping Elias Oltmanns
2008-06-11 7:11 ` Tejun Heo
2008-06-11 7:05 ` Alan Cox
2008-06-11 8:03 ` Tejun Heo [this message]
2008-06-12 3:06 ` Tejun Heo
2008-06-12 11:32 ` Elias Oltmanns
2008-06-12 13:43 ` Tejun Heo
2008-06-12 14:18 ` James Bottomley
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