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

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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>
This commit is contained in:
Ben Collins 2012-06-11 14:44:44 -04:00 • committed by James Bottomley
parent 361ee9c3f3
commit 30002f1c02
1 changed files with 6 additions and 3 deletions
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9
drivers/scsi/aacraid/commsup.c
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@ -564,10 +564,10 @@ int aac_fib_send(u16 command, struct fib *fibptr, unsigned long size,
* functioning because an interrupt routing or other * functioning because an interrupt routing or other
* hardware failure has occurred. * hardware failure has occurred.
*/ */
unsigned long count = 36000000L; /* 3 minutes */ unsigned long timeout = jiffies + (180 * HZ); /* 3 minutes */
while (down_trylock(&fibptr->event_wait)) { while (down_trylock(&fibptr->event_wait)) {
int blink; int blink;
if (--count == 0) { if (time_is_before_eq_jiffies(timeout)) {
struct aac_queue * q = &dev->queues->queue[AdapNormCmdQueue]; struct aac_queue * q = &dev->queues->queue[AdapNormCmdQueue];
spin_lock_irqsave(q->lock, qflags); spin_lock_irqsave(q->lock, qflags);
q->numpending--; q->numpending--;
@ -588,7 +588,10 @@ int aac_fib_send(u16 command, struct fib *fibptr, unsigned long size,
} }
return -EFAULT; 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)) { } else if (down_interruptible(&fibptr->event_wait)) {
/* Do nothing ... satisfy /* Do nothing ... satisfy