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From: "David Somayajulu" <david.somayajulu@qlogic.com>
To: "Ed Lin" <ed.lin@promise.com>, "Michael Reed" <mdr@sgi.com>
Cc: "linux-scsi" <linux-scsi@vger.kernel.org>,
	"linux-kernel" <linux-kernel@vger.kernel.org>,
	"james.Bottomley" <james.Bottomley@SteelEye.com>,
	"jeff" <jeff@garzik.org>,
	"Promise_Linux" <Promise_Linux@promise.com>,
	"Jens Axboe" <axboe@kernel.dk>
Subject: RE: [patch] scsi: use lock per host instead of per device for shared queue tag host
Date: Wed, 24 Jan 2007 17:02:33 -0800	[thread overview]
Message-ID: <0BB3E5E7462EEA4295BC02D49691DC078289A8@AVEXCH1.qlogic.org> (raw)
In-Reply-To: <B70A50D07063384EB9BCE3330D18414F02F5AF83@nonameb.ptu.promise.com>

> It seems another driver(qla4xxx) is also using shared queue tag.
> It is natural to imagine there might be same symptom in that
> driver. But I don't know the driver and have no hardware so I
> can not say anything certain about it.

qla4xxx implements slightly differently, in the sense we don't have the
equivalent of         
struct st_ccb ccb[MU_MAX_REQUEST]; 
which is in struct st_hba. In other words we don't have a local array
which like stex to keep track of the outstanding commands to the hba.

We had a discussion on this one while implementing block-layer tagging
in qla4xxx and Jens Axboe added the test_and_set_bit() in the following
code in blk_queue_start_tag() to take care of it.
	do {
		tag = find_first_zero_bit(bqt->tag_map, bqt->max_depth);
		if (tag >= bqt->max_depth)
			return 1;
	} while (test_and_set_bit(tag, bqt->tag_map));
Please see the following link for the discussion
http://marc.theaimsgroup.com/?l=linux-scsi&m=115886351206726&w=2

Cheers
David Somayajulu
QLogic Corporation

  reply	other threads:[~2007-01-25  1:02 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-24 23:33 Ed Lin
2007-01-25  1:02 ` David Somayajulu [this message]
  -- strict thread matches above, loose matches on Subject: below --
2007-01-26  1:15 Ed Lin
2007-01-26  1:21 ` Jeff Garzik
2007-01-25  3:14 Ed Lin
2007-01-25 15:34 ` Jens Axboe
2007-01-25 15:47   ` Jens Axboe
2007-01-24  0:53 Ed Lin
2007-01-24 15:59 ` Michael Reed
2007-01-24 16:59 ` James Bottomley

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