[SCSI] megaraid_sas: switch fw_outstanding to an atomic_t

This patch( originally submitted by Christoph Hellwig) removes
instance_lock and changes fw_outstanding variable data type to
atomic_t.

Signed-off-by: Sumant Patro <Sumant.Patro@lsil.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

3 files changed, 24 insertions, 18 deletions

diff --git a/Documentation/scsi/ChangeLog.megaraid_sas b/Documentation/scsi/ChangeLog.megaraid_sas
index 2dafa63bd370..0a85a7e8120e 100644
--- a/Documentation/scsi/ChangeLog.megaraid_sas
+++ b/Documentation/scsi/ChangeLog.megaraid_sas
@@ -1,3 +1,16 @@
+
+1 Release Date    : Wed Feb 03 14:31:44 PST 2006 - Sumant Patro <Sumant.Patro@lsil.com>
+2 Current Version : 00.00.02.04
+3 Older Version   : 00.00.02.04 
+
+i.      Remove superflous instance_lock
+
+        gets rid of the otherwise superflous instance_lock and avoids an unsave 
+        unsynchronized access in the error handler.
+
+                - Christoph Hellwig <hch@lst.de>
+
+
 1 Release Date    : Wed Feb 03 14:31:44 PST 2006 - Sumant Patro <Sumant.Patro@lsil.com>
 2 Current Version : 00.00.02.04
 3 Older Version   : 00.00.02.04 
diff --git a/drivers/scsi/megaraid/megaraid_sas.c b/drivers/scsi/megaraid/megaraid_sas.c
index 39729460b00e..0c9516ff636f 100644
--- a/drivers/scsi/megaraid/megaraid_sas.c
+++ b/drivers/scsi/megaraid/megaraid_sas.c
@@ -741,7 +741,6 @@ static int
 megasas_queue_command(struct scsi_cmnd *scmd, void (*done) (struct scsi_cmnd *))
 {
         u32 frame_count;
-        unsigned long flags;
         struct megasas_cmd *cmd;
         struct megasas_instance *instance;
 
@@ -776,9 +775,7 @@ megasas_queue_command(struct scsi_cmnd *scmd, void (*done) (struct scsi_cmnd *))
         /*
          * Issue the command to the FW
          */
-        spin_lock_irqsave(&instance->instance_lock, flags);
-        instance->fw_outstanding++;
-        spin_unlock_irqrestore(&instance->instance_lock, flags);
+        atomic_inc(&instance->fw_outstanding);
 
         instance->instancet->fire_cmd(cmd->frame_phys_addr ,cmd->frame_count-1,instance->reg_set);
 
@@ -826,19 +823,20 @@ static int megasas_wait_for_outstanding(struct megasas_instance *instance)
 
         for (i = 0; i < wait_time; i++) {
 
-                if (!instance->fw_outstanding)
+                int outstanding = atomic_read(&instance->fw_outstanding);
+
+                if (!outstanding)
                         break;
 
                 if (!(i % MEGASAS_RESET_NOTICE_INTERVAL)) {
                         printk(KERN_NOTICE "megasas: [%2d]waiting for %d "
-                               "commands to complete\n", i,
-                               instance->fw_outstanding);
+                               "commands to complete\n",i,outstanding);
                 }
 
                 msleep(1000);
         }
 
-        if (instance->fw_outstanding) {
+        if (atomic_read(&instance->fw_outstanding)) {
                 instance->hw_crit_error = 1;
                 return FAILED;
         }
@@ -1050,7 +1048,6 @@ megasas_complete_cmd(struct megasas_instance *instance, struct megasas_cmd *cmd,
 {
         int exception = 0;
         struct megasas_header *hdr = &cmd->frame->hdr;
-        unsigned long flags;
 
         if (cmd->scmd) {
                 cmd->scmd->SCp.ptr = (char *)0;
@@ -1082,9 +1079,7 @@ megasas_complete_cmd(struct megasas_instance *instance, struct megasas_cmd *cmd,
 
                 if (exception) {
 
-                        spin_lock_irqsave(&instance->instance_lock, flags);
-                        instance->fw_outstanding--;
-                        spin_unlock_irqrestore(&instance->instance_lock, flags);
+                        atomic_dec(&instance->fw_outstanding);
 
                         megasas_unmap_sgbuf(instance, cmd);
                         cmd->scmd->scsi_done(cmd->scmd);
@@ -1132,9 +1127,7 @@ megasas_complete_cmd(struct megasas_instance *instance, struct megasas_cmd *cmd,
                         break;
                 }
 
-                spin_lock_irqsave(&instance->instance_lock, flags);
-                instance->fw_outstanding--;
-                spin_unlock_irqrestore(&instance->instance_lock, flags);
+                atomic_dec(&instance->fw_outstanding);
 
                 megasas_unmap_sgbuf(instance, cmd);
                 cmd->scmd->scsi_done(cmd->scmd);
@@ -2171,11 +2164,12 @@ megasas_probe_one(struct pci_dev *pdev, const struct pci_device_id *id)
          */
         INIT_LIST_HEAD(&instance->cmd_pool);
 
+        atomic_set(&instance->fw_outstanding,0);
+
         init_waitqueue_head(&instance->int_cmd_wait_q);
         init_waitqueue_head(&instance->abort_cmd_wait_q);
 
         spin_lock_init(&instance->cmd_pool_lock);
-        spin_lock_init(&instance->instance_lock);
 
         sema_init(&instance->aen_mutex, 1);
         sema_init(&instance->ioctl_sem, MEGASAS_INT_CMDS);
diff --git a/drivers/scsi/megaraid/megaraid_sas.h b/drivers/scsi/megaraid/megaraid_sas.h
index 89639f0c38ef..927d6ffef05f 100644
--- a/drivers/scsi/megaraid/megaraid_sas.h
+++ b/drivers/scsi/megaraid/megaraid_sas.h
@@ -1077,9 +1077,8 @@ struct megasas_instance {
         struct pci_dev *pdev;
         u32 unique_id;
 
-        u32 fw_outstanding;
+        atomic_t fw_outstanding;
         u32 hw_crit_error;
-        spinlock_t instance_lock;
 
         struct megasas_instance_template *instancet;
 };