diff options
| -rw-r--r-- | drivers/scsi/scsi.c | 189 | ||||
| -rw-r--r-- | include/linux/interrupt.h | 1 |
2 files changed, 80 insertions, 110 deletions
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c index 0215c45cbd37..cdcf1e3c871a 100644 --- a/drivers/scsi/scsi.c +++ b/drivers/scsi/scsi.c @@ -130,8 +130,13 @@ const unsigned char scsi_command_size[8] = 16, 12, 10, 10 }; static unsigned long serial_number; -static Scsi_Cmnd *scsi_bh_queue_head; -static Scsi_Cmnd *scsi_bh_queue_tail; + +struct softscsi_data { + Scsi_Cmnd *head; + Scsi_Cmnd *tail; +}; + +static struct softscsi_data softscsi_data[NR_CPUS] __cacheline_aligned; /* * Note - the initial logging level can be set here to log events at boot time. @@ -271,12 +276,6 @@ static void scsi_wait_done(Scsi_Cmnd * SCpnt) static spinlock_t device_request_lock = SPIN_LOCK_UNLOCKED; /* - * Used to protect insertion into and removal from the queue of - * commands to be processed by the bottom half handler. - */ -static spinlock_t scsi_bhqueue_lock = SPIN_LOCK_UNLOCKED; - -/* * Function: scsi_allocate_request * * Purpose: Allocate a request descriptor. @@ -1089,37 +1088,29 @@ void scsi_do_cmd(Scsi_Cmnd * SCpnt, const void *cmnd, SCSI_LOG_MLQUEUE(3, printk("Leaving scsi_do_cmd()\n")); } -void scsi_tasklet_func(unsigned long); -static DECLARE_TASKLET(scsi_tasklet, scsi_tasklet_func, 0); - -/* +/** + * scsi_done - Mark this command as done + * @SCpnt: The SCSI Command which we think we've completed. + * * This function is the mid-level interrupt routine, which decides how - * to handle error conditions. Each invocation of this function must - * do one and *only* one of the following: + * to handle error conditions. Each invocation of this function must + * do one and *only* one of the following: * * 1) Insert command in BH queue. * 2) Activate error handler for host. * - * FIXME(eric) - I am concerned about stack overflow (still). An - * interrupt could come while we are processing the bottom queue, - * which would cause another command to be stuffed onto the bottom - * queue, and it would in turn be processed as that interrupt handler - * is returning. Given a sufficiently steady rate of returning - * commands, this could cause the stack to overflow. I am not sure - * what is the most appropriate solution here - we should probably - * keep a depth count, and not process any commands while we still - * have a bottom handler active higher in the stack. - * - * There is currently code in the bottom half handler to monitor - * recursion in the bottom handler and report if it ever happens. If - * this becomes a problem, it won't be hard to engineer something to - * deal with it so that only the outer layer ever does any real - * processing. + * There is no longer a problem with stack overflow. Interrupts queue + * Scsi_Cmnd on a per-CPU queue and the softirq handler removes them + * from the queue one at a time. + * + * This function is sometimes called from interrupt context, but sometimes + * from task context. */ void scsi_done(Scsi_Cmnd * SCpnt) { unsigned long flags; - int tstatus; + int cpu, tstatus; + struct softscsi_data *queue; /* * We don't have to worry about this one timing out any more. @@ -1155,7 +1146,6 @@ void scsi_done(Scsi_Cmnd * SCpnt) SCSI_LOG_MLCOMPLETE(1, printk("Ignoring completion of %p due to timeout status", SCpnt)); return; } - spin_lock_irqsave(&scsi_bhqueue_lock, flags); SCpnt->serial_number_at_timeout = 0; SCpnt->state = SCSI_STATE_BHQUEUE; @@ -1163,75 +1153,49 @@ void scsi_done(Scsi_Cmnd * SCpnt) SCpnt->bh_next = NULL; /* - * Next, put this command in the BH queue. - * - * We need a spinlock here, or compare and exchange if we can reorder incoming - * Scsi_Cmnds, as it happens pretty often scsi_done is called multiple times - * before bh is serviced. -jj + * Next, put this command in the softirq queue. * - * We already have the io_request_lock here, since we are called from the - * interrupt handler or the error handler. (DB) - * - * This may be true at the moment, but I would like to wean all of the low - * level drivers away from using io_request_lock. Technically they should - * all use their own locking. I am adding a small spinlock to protect - * this datastructure to make it safe for that day. (ERY) + * This is a per-CPU queue, so we just disable local interrupts + * and need no spinlock. */ - if (!scsi_bh_queue_head) { - scsi_bh_queue_head = SCpnt; - scsi_bh_queue_tail = SCpnt; + + local_irq_save(flags); + + cpu = smp_processor_id(); + queue = &softscsi_data[cpu]; + + if (!queue->head) { + queue->head = SCpnt; + queue->tail = SCpnt; } else { - scsi_bh_queue_tail->bh_next = SCpnt; - scsi_bh_queue_tail = SCpnt; + queue->tail->bh_next = SCpnt; + queue->tail = SCpnt; } - spin_unlock_irqrestore(&scsi_bhqueue_lock, flags); - /* - * Mark the bottom half handler to be run. - */ - tasklet_hi_schedule(&scsi_tasklet); + cpu_raise_softirq(cpu, SCSI_SOFTIRQ); + + local_irq_restore(flags); } -/* - * Procedure: scsi_bottom_half_handler - * - * Purpose: Called after we have finished processing interrupts, it - * performs post-interrupt handling for commands that may - * have completed. - * - * Notes: This is called with all interrupts enabled. This should reduce - * interrupt latency, stack depth, and reentrancy of the low-level - * drivers. - * - * The io_request_lock is required in all the routine. There was a subtle - * race condition when scsi_done is called after a command has already - * timed out but before the time out is processed by the error handler. - * (DB) - * - * I believe I have corrected this. We simply monitor the return status of - * del_timer() - if this comes back as 0, it means that the timer has fired - * and that a timeout is in progress. I have modified scsi_done() such - * that in this instance the command is never inserted in the bottom - * half queue. Thus the only time we hold the lock here is when - * we wish to atomically remove the contents of the queue. +/** + * scsi_softirq - Perform post-interrupt handling for completed commands + * + * This is called with all interrupts enabled. This should reduce + * interrupt latency, stack depth, and reentrancy of the low-level + * drivers. */ -void scsi_tasklet_func(unsigned long ignore) +static void scsi_softirq(struct softirq_action *h) { - Scsi_Cmnd *SCpnt; - Scsi_Cmnd *SCnext; - unsigned long flags; - + int cpu = smp_processor_id(); + struct softscsi_data *queue = &softscsi_data[cpu]; - while (1 == 1) { - spin_lock_irqsave(&scsi_bhqueue_lock, flags); - SCpnt = scsi_bh_queue_head; - scsi_bh_queue_head = NULL; - spin_unlock_irqrestore(&scsi_bhqueue_lock, flags); + while (queue->head) { + Scsi_Cmnd *SCpnt, *SCnext; - if (SCpnt == NULL) { - return; - } - SCnext = SCpnt->bh_next; + local_irq_disable(); + SCpnt = queue->head; + queue->head = NULL; + local_irq_enable(); for (; SCpnt; SCpnt = SCnext) { SCnext = SCpnt->bh_next; @@ -1249,10 +1213,11 @@ void scsi_tasklet_func(unsigned long ignore) break; case NEEDS_RETRY: /* - * We only come in here if we want to retry a command. The - * test to see whether the command should be retried should be - * keeping track of the number of tries, so we don't end up looping, - * of course. + * We only come in here if we want to retry a + * command. The test to see whether the + * command should be retried should be keeping + * track of the number of tries, so we don't + * end up looping, of course. */ SCSI_LOG_MLCOMPLETE(3, printk("Command needs retry %d %d 0x%x\n", SCpnt->host->host_busy, SCpnt->host->host_failed, SCpnt->result)); @@ -1261,12 +1226,14 @@ void scsi_tasklet_func(unsigned long ignore) break; case ADD_TO_MLQUEUE: /* - * This typically happens for a QUEUE_FULL message - - * typically only when the queue depth is only - * approximate for a given device. Adding a command - * to the queue for the device will prevent further commands - * from being sent to the device, so we shouldn't end up - * with tons of things being sent down that shouldn't be. + * This typically happens for a QUEUE_FULL + * message - typically only when the queue + * depth is only approximate for a given + * device. Adding a command to the queue for + * the device will prevent further commands + * from being sent to the device, so we + * shouldn't end up with tons of things being + * sent down that shouldn't be. */ SCSI_LOG_MLCOMPLETE(3, printk("Command rejected as device queue full, put on ml queue %p\n", SCpnt)); @@ -1274,8 +1241,8 @@ void scsi_tasklet_func(unsigned long ignore) break; default: /* - * Here we have a fatal error of some sort. Turn it over to - * the error handler. + * Here we have a fatal error of some sort. + * Turn it over to the error handler. */ SCSI_LOG_MLCOMPLETE(3, printk("Command failed %p %x active=%d busy=%d failed=%d\n", SCpnt, SCpnt->result, @@ -1295,8 +1262,10 @@ void scsi_tasklet_func(unsigned long ignore) SCpnt->state = SCSI_STATE_FAILED; SCpnt->host->in_recovery = 1; /* - * If the host is having troubles, then look to see if this was the last - * command that might have failed. If so, wake up the error handler. + * If the host is having troubles, then + * look to see if this was the last + * command that might have failed. If + * so, wake up the error handler. */ if (SCpnt->host->host_busy == SCpnt->host->host_failed) { SCSI_LOG_ERROR_RECOVERY(5, printk("Waking error handler thread (%d)\n", @@ -1305,15 +1274,14 @@ void scsi_tasklet_func(unsigned long ignore) } } else { /* - * We only get here if the error recovery thread has died. + * We only get here if the error + * recovery thread has died. */ scsi_finish_command(SCpnt); } - } + } /* switch */ } /* for(; SCpnt...) */ - - } /* while(1==1) */ - + } /* while(queue->head) */ } /* @@ -2548,6 +2516,9 @@ static int __init init_scsi(void) printk(KERN_INFO "scsi: host order: %s\n", scsihosts); scsi_host_no_init (scsihosts); + /* Where we handle work queued by scsi_done */ + open_softirq(SCSI_SOFTIRQ, scsi_softirq, NULL); + return 0; } @@ -2556,8 +2527,6 @@ static void __exit exit_scsi(void) Scsi_Host_Name *shn, *shn2 = NULL; int i; - tasklet_kill(&scsi_tasklet); - devfs_unregister (scsi_devfs_handle); for (shn = scsi_host_no_list;shn;shn = shn->next) { if (shn->name) diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index fbc10eab16f4..3870d26066e9 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -57,6 +57,7 @@ enum HI_SOFTIRQ=0, NET_TX_SOFTIRQ, NET_RX_SOFTIRQ, + SCSI_SOFTIRQ, TASKLET_SOFTIRQ }; |