[PATCH 09/13] hpsa: use atomics for commands_outstanding

Don Brace
2014-11-14T23:25:34Z

From: Stephen M. Cameron <stephenmcameron@gmail.com>

Use atomics for commands_outstanding instead of protecting with spin locks.

Signed-off-by: Don Brace <don.brace@pmcs.com>
Signed-off-by: Stephen M. Cameron <stephenmcameron@gmail.com>
Reviewed-by: Joe Handzik <joseph.t.handzik@hp.com>
---
drivers/scsi/hpsa.c | 26 +++++++++-----------------
drivers/scsi/hpsa.h | 27 +++++++--------------------
2 files changed, 16 insertions(+), 37 deletions(-)

diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index 95c34a5..c9554e6 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -394,7 +394,8 @@ static ssize_t host_show_commands_outstanding(struct device *dev,
struct Scsi_Host *shost = class_to_shost(dev);
struct ctlr_info *h = shost_to_hba(shost);

- return snprintf(buf, 20, "%d\n", h->commands_outstanding);
+ return snprintf(buf, 20, "%d\n",
+ atomic_read(&h->commands_outstanding));
}

static ssize_t host_show_transport_mode(struct device *dev,
@@ -700,7 +701,6 @@ static inline u32 next_command(struct ctlr_info *h, u8 q)
{
u32 a;
struct reply_queue_buffer *rq = &h->reply_queue[q];
- unsigned long flags;

if (h->transMethod & CFGTBL_Trans_io_accel1)
return h->access.command_completed(h, q);
@@ -711,9 +711,7 @@ static inline u32 next_command(struct ctlr_info *h, u8 q)
if ((rq->head[rq->current_entry] & 1) == rq->wraparound) {
a = rq->head[rq->current_entry];
rq->current_entry++;
- spin_lock_irqsave(&h->lock, flags);
- h->commands_outstanding--;
- spin_unlock_irqrestore(&h->lock, flags);
+ atomic_dec(&h->commands_outstanding);
} else {
a = FIFO_EMPTY;
}
@@ -5445,15 +5443,9 @@ static void start_io(struct ctlr_info *h, unsigned long *flags)

/* Put job onto the completed Q */
addQ(&h->cmpQ, c);
-
- /* Must increment commands_outstanding before unlocking
- * and submitting to avoid race checking for fifo full
- * condition.
- */
- h->commands_outstanding++;
-
- /* Tell the controller execute command */
+ atomic_inc(&h->commands_outstanding);
spin_unlock_irqrestore(&h->lock, *flags);
+ /* Tell the controller execute command */
h->access.submit_command(h, c);
spin_lock_irqsave(&h->lock, *flags);
}
@@ -5499,6 +5491,7 @@ static inline void finish_cmd(struct CommandList *c)
unsigned long flags;
int io_may_be_stalled = 0;
struct ctlr_info *h = c->h;
+ int count;

spin_lock_irqsave(&h->lock, flags);
removeQ(c);
@@ -5519,11 +5512,10 @@ static inline void finish_cmd(struct CommandList *c)
* want to get in a cycle where we call start_io every time
* through here.
*/
- if (unlikely(h->fifo_recently_full) &&
- h->commands_outstanding < 5)
- io_may_be_stalled = 1;
-
+ count = atomic_read(&h->commands_outstanding);
spin_unlock_irqrestore(&h->lock, flags);
+ if (unlikely(h->fifo_recently_full) && count < 5)
+ io_may_be_stalled = 1;

dial_up_lockup_detection_on_fw_flash_complete(c->h, c);
if (likely(c->cmd_type == CMD_IOACCEL1 || c->cmd_type == CMD_SCSI
diff --git a/drivers/scsi/hpsa.h b/drivers/scsi/hpsa.h
index 80fa9a9..8e06d9e 100644
--- a/drivers/scsi/hpsa.h
+++ b/drivers/scsi/hpsa.h
@@ -118,7 +118,7 @@ struct ctlr_info {
struct CfgTable __iomem *cfgtable;
int interrupts_enabled;
int max_commands;
- int commands_outstanding;
+ atomic_t commands_outstanding;
# define PERF_MODE_INT 0
# define DOORBELL_INT 1
# define SIMPLE_MODE_INT 2
@@ -395,7 +395,7 @@ static void SA5_performant_intr_mask(struct ctlr_info *h, unsigned long val)
static unsigned long SA5_performant_completed(struct ctlr_info *h, u8 q)
{
struct reply_queue_buffer *rq = &h->reply_queue[q];
- unsigned long flags, register_value = FIFO_EMPTY;
+ unsigned long register_value = FIFO_EMPTY;

/* msi auto clears the interrupt pending bit. */
if (!(h->msi_vector || h->msix_vector)) {
@@ -413,9 +413,7 @@ static unsigned long SA5_performant_completed(struct ctlr_info *h, u8 q)
if ((rq->head[rq->current_entry] & 1) == rq->wraparound) {
register_value = rq->head[rq->current_entry];
rq->current_entry++;
- spin_lock_irqsave(&h->lock, flags);
- h->commands_outstanding--;
- spin_unlock_irqrestore(&h->lock, flags);
+ atomic_dec(&h->commands_outstanding);
} else {
register_value = FIFO_EMPTY;
}
@@ -433,11 +431,7 @@ static unsigned long SA5_performant_completed(struct ctlr_info *h, u8 q)
*/
static unsigned long SA5_fifo_full(struct ctlr_info *h)
{
- if (h->commands_outstanding >= h->max_commands)
- return 1;
- else
- return 0;
-
+ return atomic_read(&h->commands_outstanding) >= h->max_commands;
}
/*
* returns value read from hardware.
@@ -448,13 +442,9 @@ static unsigned long SA5_completed(struct ctlr_info *h,
{
unsigned long register_value
= readl(h->vaddr + SA5_REPLY_PORT_OFFSET);
- unsigned long flags;

- if (register_value != FIFO_EMPTY) {
- spin_lock_irqsave(&h->lock, flags);
- h->commands_outstanding--;
- spin_unlock_irqrestore(&h->lock, flags);
- }
+ if (register_value != FIFO_EMPTY)
+ atomic_dec(&h->commands_outstanding);

#ifdef HPSA_DEBUG
if (register_value != FIFO_EMPTY)
@@ -510,7 +500,6 @@ static unsigned long SA5_ioaccel_mode1_completed(struct ctlr_info *h, u8 q)
{
u64 register_value;
struct reply_queue_buffer *rq = &h->reply_queue[q];
- unsigned long flags;

BUG_ON(q >= h->nreply_queues);

@@ -528,9 +517,7 @@ static unsigned long SA5_ioaccel_mode1_completed(struct ctlr_info *h, u8 q)
wmb();
writel((q << 24) | rq->current_entry, h->vaddr +
IOACCEL_MODE1_CONSUMER_INDEX);
- spin_lock_irqsave(&h->lock, flags);
- h->commands_outstanding--;
- spin_unlock_irqrestore(&h->lock, flags);
+ atomic_dec(&h->commands_outstanding);
}
return (unsigned long) register_value;
}