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[SCSI] libsas: introduce sas_work to fix sas_drain_work vs sas_queue_work

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When requeuing work to a draining workqueue the last work instance may
not be idle, so sas_queue_work() must not touch work->entry.  Introduce
sas_work with a drain_node list_head to have a private list for
collecting work deferred due to drain collision.

Fixes reports like:
  BUG: unable to handle kernel NULL pointer dereference at           (null)
  IP: [<ffffffff810410d4>] process_one_work+0x2e/0x338

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
Dan Williams 2012-03-09 11:00:06 -08:00 • committed by James Bottomley
parent f8fc75dc57
commit 22b9153faa
7 changed files with 83 additions and 62 deletions
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24
drivers/scsi/libsas/sas_event.c
View file

@ -27,19 +27,21 @@
#include "sas_internal.h"
#include "sas_dump.h"
void sas_queue_work(struct sas_ha_struct *ha, struct work_struct *work)
void sas_queue_work(struct sas_ha_struct *ha, struct sas_work *sw)
{
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);
if (test_bit(SAS_HA_DRAINING, &ha->state)) {
/* add it to the defer list, if not already pending */
if (list_empty(&sw->drain_node))
list_add(&sw->drain_node, &ha->defer_q);
} else
scsi_queue_work(ha->core.shost, &sw->work);
}
static void sas_queue_event(int event, unsigned long *pending,
struct work_struct *work,
struct sas_work *work,
struct sas_ha_struct *ha)
{
if (!test_and_set_bit(event, pending)) {
@ -55,7 +57,7 @@ static void sas_queue_event(int event, unsigned long *pending,
void __sas_drain_work(struct sas_ha_struct *ha)
{
struct workqueue_struct *wq = ha->core.shost->work_q;
struct work_struct *w, *_w;
struct sas_work *sw, *_sw;
set_bit(SAS_HA_DRAINING, &ha->state);
/* flush submitters */
@ -66,9 +68,9 @@ void __sas_drain_work(struct sas_ha_struct *ha)
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);
list_for_each_entry_safe(sw, _sw, &ha->defer_q, drain_node) {
list_del_init(&sw->drain_node);
sas_queue_work(ha, sw);
}
spin_unlock_irq(&ha->state_lock);
}
@ -151,7 +153,7 @@ int sas_init_events(struct sas_ha_struct *sas_ha)
int i;
for (i = 0; i < HA_NUM_EVENTS; i++) {
INIT_WORK(&sas_ha->ha_events[i].work, sas_ha_event_fns[i]);
INIT_SAS_WORK(&sas_ha->ha_events[i].work, sas_ha_event_fns[i]);
sas_ha->ha_events[i].ha = sas_ha;
}