[SCSI] aacraid: Relax the tight timeout loop on fib commands

The loop that waited for syncronous fib commands was causing a CPU stall
when a timeout actually occured.

1) Switch to using a more accurate timeout mechanism.
2) Do not pace the loop with udelay(). Use cpu_relax() to allow for
   scheduling to occur.

Signed-off-by: Ben Collins <bcollins@ubuntu.com>
Acked-by: Achim Leubner <Achim_Leubner@pmc-sierra.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/scsi/aacraid/commsup.c b/drivers/scsi/aacraid/commsup.c
index 4b32ca442433..906a5013edae 100644
--- a/drivers/scsi/aacraid/commsup.c
+++ b/drivers/scsi/aacraid/commsup.c
@@ -564,10 +564,10 @@ int aac_fib_send(u16 command, struct fib *fibptr, unsigned long size,
                          * functioning because an interrupt routing or other
                          * hardware failure has occurred.
                          */
-                        unsigned long count = 36000000L; /* 3 minutes */
+                        unsigned long timeout = jiffies + (180 * HZ); /* 3 minutes */
                         while (down_trylock(&fibptr->event_wait)) {
                                 int blink;
-                                if (--count == 0) {
+                                if (time_is_before_eq_jiffies(timeout)) {
                                         struct aac_queue * q = &dev->queues->queue[AdapNormCmdQueue];
                                         spin_lock_irqsave(q->lock, qflags);
                                         q->numpending--;
@@ -588,7 +588,10 @@ int aac_fib_send(u16 command, struct fib *fibptr, unsigned long size,
                                         }
                                         return -EFAULT;
                                 }
-                                udelay(5);
+                                /* We used to udelay() here but that absorbed
+                                 * a CPU when a timeout occured. Not very
+                                 * useful. */
+                                cpu_relax();
                         }
                 } else if (down_interruptible(&fibptr->event_wait)) {
                         /* Do nothing ... satisfy