From: Steve Best <sbest@redhat.com>
Date: Fri, 30 Jul 2010 18:57:36 -0400
Subject: [scsi] ips driver sleeps while holding spin_lock
Message-id: <20100730184630.1139.8578.sendpatchset@squad5-lp1.lab.bos.redhat.com>
Patchwork-id: 27264
O-Subject: [PATCH RHEL5.6 BZ616961] ips driver sleeps while holding spin_lock
Bugzilla: 616961

RHBZ#:
======
https://bugzilla.redhat.com/show_bug.cgi?id=619961

Description:
============
Don't sleep when we could be holding a spin_lock

The attached patch reverts the msleep() calls to MDELAY() calls.  MDELAY is a
macro which calls mdelay() and also touches the soft lockup timer to keep the
soft lockup watchdog working during these delays.

The functions which call msleep() will be called with spin_locks held during
reset. This can result in deadlocks when an interrupt or other thread attempts
to acquire the spin_lock.

Also, a secondary change was made to convert the spin_lock IPS_(UN)LOCK*
locking macros to use the _irqsave/_irqrestore variants.  The spin_lock is
acquired in the interrupt handler so users of the spin_lock need to disable
interrupts to prevent a possible deadlock with the interrupt handler as well.

The initialization/reset code for the driver gets called under a spin_lock when
the scsi layer issues a reset request because commands aren't completing.  This
can cause a deadlock when msleep() is called by the hardware reset logic since
the scsi error handling thread then sleeps while holding a spin_lock and
interrupts from the hardware are still enabled.

Changes are from the mainline kernel which also reverted the msleep calls.

RHEL Version Found:
===================
RHEL 5.4

kABI Status:
============
No symbols were harmed.

Brew:
=====
http://brewweb.devel.redhat.com/brew/taskinfo?taskID=2641534

Upstream:
=========
Most of the patch was from upstream. commit id
bf4713418b9d8543e7b64bf6c742f1959828033e, which is a reversion
of what was done in 15084a4a63bc300c18b28a8a9afac870c552abce because
of this problem.

Test Status:
============

David Jeffery gave the customer a kernel with this patch and
changes were tested by the customer who had been experiencing the bug.
Using a kernel with the patch built into it, the customer reported they were no
longer experiencing the deadlock.  For some reason, their serveraid adapter
regularly stops responding and needs a reset for the system to keep running.

===============================================================
Steve Best
IBM on-site partner

Signed-off-by: Jarod Wilson <jarod@redhat.com>

diff --git a/drivers/scsi/ips.c b/drivers/scsi/ips.c
index 3c63928..700cb3f 100644
--- a/drivers/scsi/ips.c
+++ b/drivers/scsi/ips.c
@@ -226,8 +226,8 @@ module_param(ips, charp, 0);
 #define __devexit_p(x) x
 #endif
 #else
-#define IPS_LOCK_SAVE(lock,flags) do{spin_lock(lock);(void)flags;}while(0)
-#define IPS_UNLOCK_RESTORE(lock,flags) do{spin_unlock(lock);(void)flags;}while(0)
+#define IPS_LOCK_SAVE(lock,flags) do{spin_lock_irqsave(lock, flags);}while(0)
+#define IPS_UNLOCK_RESTORE(lock,flags) do{spin_unlock_irqrestore(lock, flags);}while(0)
 #endif
 
 #define IPS_DMA_DIR(scb) ((!scb->scsi_cmd || ips_is_passthru(scb->scsi_cmd) || \
@@ -5014,7 +5014,7 @@ ips_init_copperhead(ips_ha_t * ha)
 				break;
 
 			/* Delay for 1 Second */
-			msleep(IPS_ONE_SEC);
+			MDELAY(IPS_ONE_SEC);
 		}
 
 		if (j >= 45)
@@ -5040,7 +5040,7 @@ ips_init_copperhead(ips_ha_t * ha)
 				break;
 
 			/* Delay for 1 Second */
-			msleep(IPS_ONE_SEC);
+			MDELAY(IPS_ONE_SEC);
 		}
 
 		if (j >= 240)
@@ -5058,7 +5058,7 @@ ips_init_copperhead(ips_ha_t * ha)
 			break;
 
 		/* Delay for 1 Second */
-		msleep(IPS_ONE_SEC);
+		MDELAY(IPS_ONE_SEC);
 	}
 
 	if (i >= 240)
@@ -5108,7 +5108,7 @@ ips_init_copperhead_memio(ips_ha_t * ha)
 				break;
 
 			/* Delay for 1 Second */
-			msleep(IPS_ONE_SEC);
+			MDELAY(IPS_ONE_SEC);
 		}
 
 		if (j >= 45)
@@ -5134,7 +5134,7 @@ ips_init_copperhead_memio(ips_ha_t * ha)
 				break;
 
 			/* Delay for 1 Second */
-			msleep(IPS_ONE_SEC);
+			MDELAY(IPS_ONE_SEC);
 		}
 
 		if (j >= 240)
@@ -5152,7 +5152,7 @@ ips_init_copperhead_memio(ips_ha_t * ha)
 			break;
 
 		/* Delay for 1 Second */
-		msleep(IPS_ONE_SEC);
+		MDELAY(IPS_ONE_SEC);
 	}
 
 	if (i >= 240)
@@ -5204,7 +5204,7 @@ ips_init_morpheus(ips_ha_t * ha)
 			break;
 
 		/* Delay for 1 Second */
-		msleep(IPS_ONE_SEC);
+		MDELAY(IPS_ONE_SEC);
 	}
 
 	if (i >= 45) {
@@ -5230,7 +5230,7 @@ ips_init_morpheus(ips_ha_t * ha)
 			if (Post != 0x4F00)
 				break;
 			/* Delay for 1 Second */
-			msleep(IPS_ONE_SEC);
+			MDELAY(IPS_ONE_SEC);
 		}
 
 		if (i >= 120) {
@@ -5260,7 +5260,7 @@ ips_init_morpheus(ips_ha_t * ha)
 			break;
 
 		/* Delay for 1 Second */
-		msleep(IPS_ONE_SEC);
+		MDELAY(IPS_ONE_SEC);
 	}
 
 	if (i >= 240) {
@@ -5320,12 +5320,12 @@ ips_reset_copperhead(ips_ha_t * ha)
 		outb(IPS_BIT_RST, ha->io_addr + IPS_REG_SCPR);
 
 		/* Delay for 1 Second */
-		msleep(IPS_ONE_SEC);
+		MDELAY(IPS_ONE_SEC);
 
 		outb(0, ha->io_addr + IPS_REG_SCPR);
 
 		/* Delay for 1 Second */
-		msleep(IPS_ONE_SEC);
+		MDELAY(IPS_ONE_SEC);
 
 		if ((*ha->func.init) (ha))
 			break;
@@ -5365,12 +5365,12 @@ ips_reset_copperhead_memio(ips_ha_t * ha)
 		writeb(IPS_BIT_RST, ha->mem_ptr + IPS_REG_SCPR);
 
 		/* Delay for 1 Second */
-		msleep(IPS_ONE_SEC);
+		MDELAY(IPS_ONE_SEC);
 
 		writeb(0, ha->mem_ptr + IPS_REG_SCPR);
 
 		/* Delay for 1 Second */
-		msleep(IPS_ONE_SEC);
+		MDELAY(IPS_ONE_SEC);
 
 		if ((*ha->func.init) (ha))
 			break;
@@ -5411,7 +5411,7 @@ ips_reset_morpheus(ips_ha_t * ha)
 		writel(0x80000000, ha->mem_ptr + IPS_REG_I960_IDR);
 
 		/* Delay for 5 Seconds */
-		msleep(5 * IPS_ONE_SEC);
+		MDELAY(5 * IPS_ONE_SEC);
 
 		/* Do a PCI config read to wait for adapter */
 		pci_read_config_byte(ha->pcidev, 4, &junk);
diff --git a/drivers/scsi/ips.h b/drivers/scsi/ips.h
index f46c382..14b4449 100644
--- a/drivers/scsi/ips.h
+++ b/drivers/scsi/ips.h
@@ -50,7 +50,7 @@
 #ifndef _IPS_H_
    #define _IPS_H_
 
-#include <linux/version.h>
+#include <linux/nmi.h>
    #include <asm/uaccess.h>
    #include <asm/io.h>
 
@@ -116,9 +116,12 @@
             dev_printk(level , &((pcidev)->dev) , format , ## arg)
    #endif
 
-   #ifndef MDELAY
-      #define MDELAY mdelay
-   #endif
+   #define MDELAY(n) \
+	do {                            \
+		mdelay(n);              \
+		touch_nmi_watchdog();   \
+	} while (0)
+
 
    #ifndef min
       #define min(x,y) ((x) < (y) ? x : y)