From b1124cd3ec97406c767b90bf7e93ecd2d2915592 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 19 Dec 2011 16:42:34 -0800 Subject: [SCSI] libsas: introduce sas_drain_work() When an lldd invokes ->notify_port_event() it can trigger a chain of libsas events to: 1/ form the port and find the direct attached device 2/ if the attached device is an expander perform domain discovery A call to flush_workqueue() will only flush the initial port formation work. Currently libsas users need to call scsi_flush_work() up to the max depth of chain (which will grow from 2 to 3 when ata discovery is moved to its own discovery event). Instead of open coding multiple calls switch to use drain_workqueue() to flush sas work. drain_workqueue() does not handle new work submitted during the drain so libsas needs a bit of infrastructure to hold off unchained work submissions while a drain is in flight. A lldd ->notify() event is considered 'unchained' while a sas_discover_event() is 'chained'. As Tejun notes: "For now, I think it would be best to add private wrapper in libsas to support deferring unchained work items while draining." Signed-off-by: Dan Williams Signed-off-by: James Bottomley --- drivers/scsi/libsas/sas_event.c | 55 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) (limited to 'drivers/scsi/libsas/sas_event.c') diff --git a/drivers/scsi/libsas/sas_event.c b/drivers/scsi/libsas/sas_event.c index 9c084bc09bbd..e5035aa4c2a6 100644 --- a/drivers/scsi/libsas/sas_event.c +++ b/drivers/scsi/libsas/sas_event.c @@ -22,10 +22,65 @@ * */ +#include #include #include "sas_internal.h" #include "sas_dump.h" +static void sas_queue_work(struct sas_ha_struct *ha, struct work_struct *work) +{ + if (!test_bit(SAS_HA_REGISTERED, &ha->state)) + return; + + if (test_bit(SAS_HA_DRAINING, &ha->state)) + list_add(&work->entry, &ha->defer_q); + else + scsi_queue_work(ha->core.shost, work); +} + +static void sas_queue_event(int event, unsigned long *pending, + struct work_struct *work, + struct sas_ha_struct *ha) +{ + if (!test_and_set_bit(event, pending)) { + unsigned long flags; + + spin_lock_irqsave(&ha->state_lock, flags); + sas_queue_work(ha, work); + spin_unlock_irqrestore(&ha->state_lock, flags); + } +} + +int sas_drain_work(struct sas_ha_struct *ha) +{ + struct workqueue_struct *wq = ha->core.shost->work_q; + struct work_struct *w, *_w; + int err; + + err = mutex_lock_interruptible(&ha->drain_mutex); + if (err) + return err; + + set_bit(SAS_HA_DRAINING, &ha->state); + /* flush submitters */ + spin_lock_irq(&ha->state_lock); + spin_unlock_irq(&ha->state_lock); + + drain_workqueue(wq); + + spin_lock_irq(&ha->state_lock); + clear_bit(SAS_HA_DRAINING, &ha->state); + list_for_each_entry_safe(w, _w, &ha->defer_q, entry) { + list_del_init(&w->entry); + sas_queue_work(ha, w); + } + spin_unlock_irq(&ha->state_lock); + mutex_unlock(&ha->drain_mutex); + + return 0; +} +EXPORT_SYMBOL_GPL(sas_drain_work); + static void notify_ha_event(struct sas_ha_struct *sas_ha, enum ha_event event) { BUG_ON(event >= HA_NUM_EVENTS); -- cgit v1.2.3