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Commit 396883e2 authored by Stephen M. Cameron's avatar Stephen M. Cameron Committed by James Bottomley
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[SCSI] hpsa: prevent stalled i/o 



If a fifo full condition is encountered, i/o requests will stack
up in the h->reqQ queue.  The only thing which empties this queue
is start_io, which only gets called when new i/o requests come in.
If none are forthcoming, i/o in h->reqQ will be stalled.

To fix this, whenever fifo full condition is encountered, this
is recorded, and the interrupt handler examines this to see
if a fifo full condition was recently encountered when a
command completes and will call start_io to prevent i/o's in
h->reqQ from getting stuck.

I've only ever seen this problem occur when running specialized
test programs that pound on the the CCISS_PASSTHRU ioctl.

Signed-off-by: default avatarStephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent 0390f0c0

drivers/scsi/hpsa.c

+30 −2
Original line number Original line Diff line number Diff line
@@ -3483,9 +3483,11 @@ static void start_io(struct ctlr_info *h) 
		c = list_entry(h->reqQ.next, struct CommandList, list);

		c = list_entry(h->reqQ.next, struct CommandList, list);

		/* can't do anything if fifo is full */

		/* can't do anything if fifo is full */

		if ((h->access.fifo_full(h))) {

		if ((h->access.fifo_full(h))) {

			h->fifo_recently_full = 1;

			dev_warn(&h->pdev->dev, "fifo full\n");

			dev_warn(&h->pdev->dev, "fifo full\n");

			break;

			break;

		}

		}

		h->fifo_recently_full = 0;





		/* Get the first entry from the Request Q */

		/* Get the first entry from the Request Q */

		removeQ(c);

		removeQ(c);
@@ -3539,15 +3541,41 @@ static inline int bad_tag(struct ctlr_info *h, u32 tag_index, 
static inline void finish_cmd(struct CommandList *c)

static inline void finish_cmd(struct CommandList *c)

{

{

	unsigned long flags;

	unsigned long flags;

	int io_may_be_stalled = 0;

	struct ctlr_info *h = c->h;





	spin_lock_irqsave(&c->h->lock, flags);

	spin_lock_irqsave(&h->lock, flags);

	removeQ(c);

	removeQ(c);

	spin_unlock_irqrestore(&c->h->lock, flags);



	/*

	 * Check for possibly stalled i/o.

	 *

	 * If a fifo_full condition is encountered, requests will back up

	 * in h->reqQ.  This queue is only emptied out by start_io which is

	 * only called when a new i/o request comes in.  If no i/o's are

	 * forthcoming, the i/o's in h->reqQ can get stuck.  So we call

	 * start_io from here if we detect such a danger.

	 *

	 * Normally, we shouldn't hit this case, but pounding on the

	 * CCISS_PASSTHRU ioctl can provoke it.  Only call start_io if

	 * commands_outstanding is low.  We want to avoid calling

	 * start_io from in here as much as possible, and esp. don't

	 * 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;



	spin_unlock_irqrestore(&h->lock, flags);



	dial_up_lockup_detection_on_fw_flash_complete(c->h, c);

	dial_up_lockup_detection_on_fw_flash_complete(c->h, c);

	if (likely(c->cmd_type == CMD_SCSI))

	if (likely(c->cmd_type == CMD_SCSI))

		complete_scsi_command(c);

		complete_scsi_command(c);

	else if (c->cmd_type == CMD_IOCTL_PEND)

	else if (c->cmd_type == CMD_IOCTL_PEND)

		complete(c->waiting);

		complete(c->waiting);

	if (unlikely(io_may_be_stalled))

		start_io(h);

}

}





static inline u32 hpsa_tag_contains_index(u32 tag)

static inline u32 hpsa_tag_contains_index(u32 tag)

drivers/scsi/hpsa.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -136,6 +136,7 @@ struct ctlr_info { 
	atomic_t firmware_flash_in_progress;

	atomic_t firmware_flash_in_progress;

	u32 lockup_detected;

	u32 lockup_detected;

	struct list_head lockup_list;

	struct list_head lockup_list;

	u32 fifo_recently_full;

	/* Address of h->q[x] is passed to intr handler to know which queue */

	/* Address of h->q[x] is passed to intr handler to know which queue */

	u8 q[MAX_REPLY_QUEUES];

	u8 q[MAX_REPLY_QUEUES];

	u32 TMFSupportFlags; /* cache what task mgmt funcs are supported. */

	u32 TMFSupportFlags; /* cache what task mgmt funcs are supported. */