[SCSI] hpsa: refine interrupt handler locking for greater concurrency

Use spinlocks with finer granularity in the submission and
completion paths to allow concurrent execution for multiple
reply queues.  In particular, do not hold a spin lock while
submitting a request to the device, nor during most of the
interrupt handler.
Signed-off-by: Matt Gates <matthew.gates@hp.com>
Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/hpsa.c

@@ -533,6 +533,7 @@ static inline u32 next_command(struct ctlr_info *h, u8 q)
 {
 	u32 a;
 	struct reply_pool *rq = &h->reply_queue[q];
+	unsigned long flags;
 
 	if (unlikely(!(h->transMethod & CFGTBL_Trans_Performant)))
 		return h->access.command_completed(h, q);
@@ -540,7 +541,9 @@ 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);
 	} else {
 		a = FIFO_EMPTY;
 	}
@@ -575,8 +578,8 @@ static void enqueue_cmd_and_start_io(struct ctlr_info *h,
 	spin_lock_irqsave(&h->lock, flags);
 	addQ(&h->reqQ, c);
 	h->Qdepth++;
-	start_io(h);
 	spin_unlock_irqrestore(&h->lock, flags);
+	start_io(h);
 }
 
 static inline void removeQ(struct CommandList *c)
@@ -2091,9 +2094,8 @@ static int hpsa_scsi_queue_command_lck(struct scsi_cmnd *cmd,
 		done(cmd);
 		return 0;
 	}
-	/* Need a lock as this is being allocated from the pool */
-	c = cmd_alloc(h);
 	spin_unlock_irqrestore(&h->lock, flags);
+	c = cmd_alloc(h);
 	if (c == NULL) {			/* trouble... */
 		dev_err(&h->pdev->dev, "cmd_alloc returned NULL!\n");
 		return SCSI_MLQUEUE_HOST_BUSY;
@@ -2627,14 +2629,21 @@ static struct CommandList *cmd_alloc(struct ctlr_info *h)
 	int i;
 	union u64bit temp64;
 	dma_addr_t cmd_dma_handle, err_dma_handle;
+	unsigned long flags;
 
+	spin_lock_irqsave(&h->lock, flags);
 	do {
 		i = find_first_zero_bit(h->cmd_pool_bits, h->nr_cmds);
-		if (i == h->nr_cmds)
+		if (i == h->nr_cmds) {
+			spin_unlock_irqrestore(&h->lock, flags);
 			return NULL;
+		}
 	} while (test_and_set_bit
 		 (i & (BITS_PER_LONG - 1),
 		  h->cmd_pool_bits + (i / BITS_PER_LONG)) != 0);
+	h->nr_allocs++;
+	spin_unlock_irqrestore(&h->lock, flags);
+
 	c = h->cmd_pool + i;
 	memset(c, 0, sizeof(*c));
 	cmd_dma_handle = h->cmd_pool_dhandle
@@ -2643,7 +2652,6 @@ static struct CommandList *cmd_alloc(struct ctlr_info *h)
 	memset(c->err_info, 0, sizeof(*c->err_info));
 	err_dma_handle = h->errinfo_pool_dhandle
 	    + i * sizeof(*c->err_info);
-	h->nr_allocs++;
 
 	c->cmdindex = i;
 
@@ -2699,11 +2707,14 @@ static struct CommandList *cmd_special_alloc(struct ctlr_info *h)
 static void cmd_free(struct ctlr_info *h, struct CommandList *c)
 {
 	int i;
+	unsigned long flags;
 
 	i = c - h->cmd_pool;
+	spin_lock_irqsave(&h->lock, flags);
 	clear_bit(i & (BITS_PER_LONG - 1),
 		  h->cmd_pool_bits + (i / BITS_PER_LONG));
 	h->nr_frees++;
+	spin_unlock_irqrestore(&h->lock, flags);
 }
 
 static void cmd_special_free(struct ctlr_info *h, struct CommandList *c)
@@ -3307,7 +3318,9 @@ static void __iomem *remap_pci_mem(ulong base, ulong size)
 static void start_io(struct ctlr_info *h)
 {
 	struct CommandList *c;
+	unsigned long flags;
 
+	spin_lock_irqsave(&h->lock, flags);
 	while (!list_empty(&h->reqQ)) {
 		c = list_entry(h->reqQ.next, struct CommandList, list);
 		/* can't do anything if fifo is full */
@@ -3320,12 +3333,23 @@ static void start_io(struct ctlr_info *h)
 		removeQ(c);
 		h->Qdepth--;
 
-		/* Tell the controller execute command */
-		h->access.submit_command(h, c);
-
 		/* 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++;
+		if (h->commands_outstanding > h->max_outstanding)
+			h->max_outstanding = h->commands_outstanding;
+
+		/* Tell the controller execute command */
+		spin_unlock_irqrestore(&h->lock, flags);
+		h->access.submit_command(h, c);
+		spin_lock_irqsave(&h->lock, flags);
 	}
+	spin_unlock_irqrestore(&h->lock, flags);
 }
 
 static inline unsigned long get_next_completion(struct ctlr_info *h, u8 q)
@@ -3356,7 +3380,11 @@ static inline int bad_tag(struct ctlr_info *h, u32 tag_index,
 
 static inline void finish_cmd(struct CommandList *c)
 {
+	unsigned long flags;
+
+	spin_lock_irqsave(&c->h->lock, flags);
 	removeQ(c);
+	spin_unlock_irqrestore(&c->h->lock, flags);
 	if (likely(c->cmd_type == CMD_SCSI))
 		complete_scsi_command(c);
 	else if (c->cmd_type == CMD_IOCTL_PEND)
@@ -3403,14 +3431,18 @@ static inline void process_nonindexed_cmd(struct ctlr_info *h,
 {
 	u32 tag;
 	struct CommandList *c = NULL;
+	unsigned long flags;
 
 	tag = hpsa_tag_discard_error_bits(h, raw_tag);
+	spin_lock_irqsave(&h->lock, flags);
 	list_for_each_entry(c, &h->cmpQ, list) {
 		if ((c->busaddr & 0xFFFFFFE0) == (tag & 0xFFFFFFE0)) {
+			spin_unlock_irqrestore(&h->lock, flags);
 			finish_cmd(c);
 			return;
 		}
 	}
+	spin_unlock_irqrestore(&h->lock, flags);
 	bad_tag(h, h->nr_cmds + 1, raw_tag);
 }
 
@@ -3447,7 +3479,6 @@ static irqreturn_t hpsa_intx_discard_completions(int irq, void *queue)
 {
 	struct ctlr_info *h = queue_to_hba(queue);
 	u8 q = *(u8 *) queue;
-	unsigned long flags;
 	u32 raw_tag;
 
 	if (ignore_bogus_interrupt(h))
@@ -3455,47 +3486,39 @@ static irqreturn_t hpsa_intx_discard_completions(int irq, void *queue)
 
 	if (interrupt_not_for_us(h))
 		return IRQ_NONE;
-	spin_lock_irqsave(&h->lock, flags);
 	h->last_intr_timestamp = get_jiffies_64();
 	while (interrupt_pending(h)) {
 		raw_tag = get_next_completion(h, q);
 		while (raw_tag != FIFO_EMPTY)
 			raw_tag = next_command(h, q);
 	}
-	spin_unlock_irqrestore(&h->lock, flags);
 	return IRQ_HANDLED;
 }
 
 static irqreturn_t hpsa_msix_discard_completions(int irq, void *queue)
 {
 	struct ctlr_info *h = queue_to_hba(queue);
-	unsigned long flags;
 	u32 raw_tag;
 	u8 q = *(u8 *) queue;
 
 	if (ignore_bogus_interrupt(h))
 		return IRQ_NONE;
 
-	spin_lock_irqsave(&h->lock, flags);
-
 	h->last_intr_timestamp = get_jiffies_64();
 	raw_tag = get_next_completion(h, q);
 	while (raw_tag != FIFO_EMPTY)
 		raw_tag = next_command(h, q);
-	spin_unlock_irqrestore(&h->lock, flags);
 	return IRQ_HANDLED;
 }
 
 static irqreturn_t do_hpsa_intr_intx(int irq, void *queue)
 {
 	struct ctlr_info *h = queue_to_hba((u8 *) queue);
-	unsigned long flags;
 	u32 raw_tag;
 	u8 q = *(u8 *) queue;
 
 	if (interrupt_not_for_us(h))
 		return IRQ_NONE;
-	spin_lock_irqsave(&h->lock, flags);
 	h->last_intr_timestamp = get_jiffies_64();
 	while (interrupt_pending(h)) {
 		raw_tag = get_next_completion(h, q);
@@ -3507,18 +3530,15 @@ static irqreturn_t do_hpsa_intr_intx(int irq, void *queue)
 			raw_tag = next_command(h, q);
 		}
 	}
-	spin_unlock_irqrestore(&h->lock, flags);
 	return IRQ_HANDLED;
 }
 
 static irqreturn_t do_hpsa_intr_msi(int irq, void *queue)
 {
 	struct ctlr_info *h = queue_to_hba(queue);
-	unsigned long flags;
 	u32 raw_tag;
 	u8 q = *(u8 *) queue;
 
-	spin_lock_irqsave(&h->lock, flags);
 	h->last_intr_timestamp = get_jiffies_64();
 	raw_tag = get_next_completion(h, q);
 	while (raw_tag != FIFO_EMPTY) {
@@ -3528,7 +3548,6 @@ static irqreturn_t do_hpsa_intr_msi(int irq, void *queue)
 			process_nonindexed_cmd(h, raw_tag);
 		raw_tag = next_command(h, q);
 	}
-	spin_unlock_irqrestore(&h->lock, flags);
 	return IRQ_HANDLED;
 }
 

drivers/scsi/hpsa.h

@@ -246,9 +246,6 @@ static void SA5_submit_command(struct ctlr_info *h,
 		c->Header.Tag.lower);
 	writel(c->busaddr, h->vaddr + SA5_REQUEST_PORT_OFFSET);
 	(void) readl(h->vaddr + SA5_SCRATCHPAD_OFFSET);
-	h->commands_outstanding++;
-	if (h->commands_outstanding > h->max_outstanding)
-		h->max_outstanding = h->commands_outstanding;
 }
 
 /*
@@ -287,7 +284,7 @@ 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_pool *rq = &h->reply_queue[q];
-	unsigned long register_value = FIFO_EMPTY;
+	unsigned long flags, register_value = FIFO_EMPTY;
 
 	/* msi auto clears the interrupt pending bit. */
 	if (!(h->msi_vector || h->msix_vector)) {
@@ -305,7 +302,9 @@ 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);
 	} else {
 		register_value = FIFO_EMPTY;
 	}
@@ -338,9 +337,13 @@ 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)
+	if (register_value != FIFO_EMPTY) {
+		spin_lock_irqsave(&h->lock, flags);
 		h->commands_outstanding--;
+		spin_unlock_irqrestore(&h->lock, flags);
+	}
 
 #ifdef HPSA_DEBUG
 	if (register_value != FIFO_EMPTY)