linux-kernel - [PATCH 02/12] scsi: Add IRQ_DISABLE_SCSI

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Date:	Sun, 19 Dec 2010 13:21:57 -0800
From:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:	linux-scsi <linux-scsi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	James Bottomley <James.Bottomley@...e.de>,
	Jeff Garzik <jeff@...zik.org>, Christoph Hellwig <hch@....de>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	Hannes Reinecke <hare@...e.de>,
	Mike Christie <michaelc@...wisc.edu>
Cc:	Mike Anderson <andmike@...ux.vnet.ibm.com>,
	Tejun Heo <tj@...nel.org>, Vasu Dev <vasu.dev@...ux.intel.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Ravi Anand <ravi.anand@...gic.com>,
	Andrew Vasquez <andrew.vasquez@...gic.com>,
	Joe Eykholt <jeykholt@...co.com>,
	James Smart <james.smart@...lex.com>,
	Douglas Gilbert <dgilbert@...erlog.com>,
	adam radford <aradford@...il.com>,
	Kashyap Desai <Kashyap.Desai@....com>,
	MPTFusionLinux <DL-MPTFusionLinux@....com>,
	Nicholas Bellinger <nab@...ux-iscsi.org>
Subject: [PATCH 02/12] scsi: Add IRQ_DISABLE_SCSI_QCMD wrapper

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

This patch adds a IRQ_DISABLE_SCSI_QCMD() wrapper macro used by LLDs
that can now run in host_lock less mode, but still need interrupts disabled
using local_irq_save() before calling their lld_queuecommand() dispatcher.

jgarzik says this method is in fact slower than doing a spin_lock_irqsave() on
internal lib_lld_queuecommand() callers (as is done in libiscsi and libata)
but is still needed by the majority of lock_less LLDs.

Signed-off-by: Nicholas A. Bellinger <nab@...ux-iscsi.org>
---
 include/scsi/scsi_host.h |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index e7e3858..321b114 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -521,6 +521,20 @@ struct scsi_host_template {
 		return rc;						\
 	}
 
+/*
+ * Used for LLDs running in lock-less mode, but that still require having
+ * interrupts disable during their lld_queuecommand() dispatch.
+ */
+#define IRQ_DISABLE_SCSI_QCMD(func_name)				\
+	int func_name(struct Scsi_Host *shost, struct scsi_cmnd *cmd)	\
+	{								\
+		unsigned long irq_flags;				\
+		int rc;							\
+		local_irq_save(irq_flags);				\
+		rc = func_name##_irq_disable(cmd, cmd->scsi_done);	\
+		local_irq_restore(irq_flags);				\
+		return rc;						\
+	}
 
 /*
  * shost state: If you alter this, you also need to alter scsi_sysfs.c
-- 
1.7.3.4

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