isci: cleanup "starting" state handling

The lldd actively disallows requests in the "starting" state.  Retrying
or holding off commands in this state is sub-optimal:
1/ it adds another state check to the fast path
2/ retrying can cause libsas to give up

However, isci's ->lldd_dev_found() routine already waits for controller
start to complete before allowing further progress.  Checking the
"starting" state in isci_task_execute_task and the isr is redundant and
misleading.  Clean this up and introduce a controller-wide event queue
to start reeling in "completion" proliferation in the driver.

The "stopping" state cleanups are in a similar vein, rely on the the isr
and other paths being precluded from occurring rather than implementing
state checking logic.

Reported-by: Christoph Hellwig <hch@infradead.org>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Edmund Nadolski <edmund.nadolski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/drivers/scsi/isci/host.h b/drivers/scsi/isci/host.h
index 421d3debdaed..26768c5bbe01 100644
--- a/drivers/scsi/isci/host.h
+++ b/drivers/scsi/isci/host.h
@@ -109,13 +109,15 @@ struct isci_host {
         u8 sas_addr[SAS_ADDR_SIZE];
 
         enum isci_status status;
+        #define IHOST_START_PENDING 0
+        #define IHOST_STOP_PENDING 1
+        unsigned long flags;
+        wait_queue_head_t eventq;
         struct Scsi_Host *shost;
         struct tasklet_struct completion_tasklet;
         struct list_head mdl_struct_list;
         struct list_head requests_to_complete;
         struct list_head requests_to_abort;
-        struct completion stop_complete;
-        struct completion start_complete;
         spinlock_t scic_lock;
         struct isci_host *next;
 };
@@ -202,6 +204,17 @@ static inline void isci_host_can_dequeue(
         spin_unlock_irqrestore(&isci_host->queue_lock, flags);
 }
 
+static inline void wait_for_start(struct isci_host *ihost)
+{
+        wait_event(ihost->eventq, !test_bit(IHOST_START_PENDING, &ihost->flags));
+}
+
+static inline void wait_for_stop(struct isci_host *ihost)
+{
+        wait_event(ihost->eventq, !test_bit(IHOST_STOP_PENDING, &ihost->flags));
+}
+
+
 /**
  * isci_host_from_sas_ha() - This accessor retrieves the isci_host object
  *    reference from the Linux sas_ha_struct reference.