From: Stephen M. Cameron <scameron@xxxxxxxxxxxxxxxxxx>
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: Stephen M. Cameron <scameron@xxxxxxxxxxxxxxxxxx>
---
drivers/scsi/hpsa.c | 32 ++++++++++++++++++++++++++++++--
drivers/scsi/hpsa.h | 1 +
2 files changed, 31 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index 1f6809b..682f431 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -3651,9 +3651,11 @@ static void start_io(struct ctlr_info *h)
c = list_entry(h->reqQ.next, struct CommandList, list);
/* can't do anything if fifo is full */
if ((h->access.fifo_full(h))) {
+ h->fifo_recently_full = 1;
dev_warn(&h->pdev->dev, "fifo full\n");
break;
}
+ h->fifo_recently_full = 0;
/* Get the first entry from the Request Q */
removeQ(c);
@@ -3707,15 +3709,41 @@ static inline int bad_tag(struct ctlr_info *h, u32 tag_index,
static inline void finish_cmd(struct CommandList *c)
{
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);
- 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);
if (likely(c->cmd_type == CMD_SCSI))
complete_scsi_command(c);
else if (c->cmd_type == CMD_IOCTL_PEND)
complete(c->waiting);
+ if (unlikely(io_may_be_stalled))
+ start_io(h);
}
static inline u32 hpsa_tag_contains_index(u32 tag)
diff --git a/drivers/scsi/hpsa.h b/drivers/scsi/hpsa.h
index 839c533..bea2365 100644
--- a/drivers/scsi/hpsa.h
+++ b/drivers/scsi/hpsa.h
@@ -137,6 +137,7 @@ struct ctlr_info {
atomic_t firmware_flash_in_progress;
u32 lockup_detected;
struct list_head lockup_list;
+ u32 fifo_recently_full;
/* Address of h->q[x] is passed to intr handler to know which queue */
u8 q[MAX_REPLY_QUEUES];
u32 TMFSupportFlags; /* cache what task mgmt funcs are supported. */
--
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