linux-kernel - [PATCH v2 02/11] scsi: Drop struct Scsi_Host->host_lock usage in scsi_dispatch

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Date:	Fri, 17 Sep 2010 11:21:59 -0700
From:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:	linux-scsi <linux-scsi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Vasu Dev <vasu.dev@...ux.intel.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	James Bottomley <James.Bottomley@...e.de>,
	Mike Christie <michaelc@...wisc.edu>
Cc:	James Smart <james.smart@...lex.com>,
	Andrew Vasquez <andrew.vasquez@...gic.com>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	Hannes Reinecke <hare@...e.de>,
	Joe Eykholt <jeykholt@...co.com>,
	Christoph Hellwig <hch@....de>,
	Nicholas Bellinger <nab@...ux-iscsi.org>
Subject: [PATCH v2 02/11] scsi: Drop struct Scsi_Host->host_lock usage in scsi_dispatch_cmd()

From: Nicholas Bellinger <nab@...ux-iscsi.org>

This patch converts scsi_dispatch_cmd() to no longer lock() + unlock()
struct Scsi_Host->host_lock while calling scsi_cmd_get_serial() and
SHT->queuecommand() dispatcher.  This patch follows commit 5900e428420d
which means we can now safely call scsi_cmd_get_serial() without the
host_lock held.

Signed-off-by: Nicholas A. Bellinger <nab@...ux-iscsi.org>
---
 drivers/scsi/scsi.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 4724ce7..d1aa209 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -658,7 +658,6 @@ static inline void scsi_cmd_get_serial(struct Scsi_Host *host, struct scsi_cmnd
 int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 {
 	struct Scsi_Host *host = cmd->device->host;
-	unsigned long flags = 0;
 	unsigned long timeout;
 	int rtn = 0;
 
@@ -744,7 +743,6 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 		goto out;
 	}
 
-	spin_lock_irqsave(host->host_lock, flags);
 	/*
 	 * AK: unlikely race here: for some reason the timer could
 	 * expire before the serial number is set up below.
@@ -760,7 +758,7 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 		trace_scsi_dispatch_cmd_start(cmd);
 		rtn = host->hostt->queuecommand(cmd, scsi_done);
 	}
-	spin_unlock_irqrestore(host->host_lock, flags);
+
 	if (rtn) {
 		trace_scsi_dispatch_cmd_error(cmd, rtn);
 		if (rtn != SCSI_MLQUEUE_DEVICE_BUSY &&
-- 
1.7.2.3

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