[SCSI] pm8001: simplify workqueue usage

pm8001 manages its own list of pending works and cancel them on device
free.  It is unnecessarily complex and has a race condition - the
works are canceled but not synced, so the work could still be running
during and after the data structures are freed.

This patch simplifies workqueue usage.

* A driver specific workqueue pm8001_wq is created to serve these
  work items.

* To avoid confusion, the "queue" suffixes are dropped from work items
  and functions.

* Delayed queueing was never used.  pm8001_work now uses work_struct
  instead.

* The driver no longer keeps track of pending works.  All pm8001_works
  are queued to pm8001_wq and the workqueue is flushed as necessary.

flush_scheduled_work() usage is removed during conversion.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jack Wang <jack_wang@usish.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

3 files changed, 41 insertions, 33 deletions

diff --git a/drivers/scsi/pm8001/pm8001_hwi.c b/drivers/scsi/pm8001/pm8001_hwi.c
index d8db0137c0c7..18b6c55cd08c 100644
--- a/drivers/scsi/pm8001/pm8001_hwi.c
+++ b/drivers/scsi/pm8001/pm8001_hwi.c
@@ -1382,53 +1382,50 @@ static u32 mpi_msg_consume(struct pm8001_hba_info *pm8001_ha,
         return MPI_IO_STATUS_BUSY;
 }
 
-static void pm8001_work_queue(struct work_struct *work)
+static void pm8001_work_fn(struct work_struct *work)
 {
-        struct delayed_work *dw = container_of(work, struct delayed_work, work);
-        struct pm8001_wq *wq = container_of(dw, struct pm8001_wq, work_q);
+        struct pm8001_work *pw = container_of(work, struct pm8001_work, work);
         struct pm8001_device *pm8001_dev;
-        struct domain_device    *dev;
+        struct domain_device *dev;
 
-        switch (wq->handler) {
+        switch (pw->handler) {
         case IO_OPEN_CNX_ERROR_IT_NEXUS_LOSS:
-                pm8001_dev = wq->data;
+                pm8001_dev = pw->data;
                 dev = pm8001_dev->sas_device;
                 pm8001_I_T_nexus_reset(dev);
                 break;
         case IO_OPEN_CNX_ERROR_STP_RESOURCES_BUSY:
-                pm8001_dev = wq->data;
+                pm8001_dev = pw->data;
                 dev = pm8001_dev->sas_device;
                 pm8001_I_T_nexus_reset(dev);
                 break;
         case IO_DS_IN_ERROR:
-                pm8001_dev = wq->data;
+                pm8001_dev = pw->data;
                 dev = pm8001_dev->sas_device;
                 pm8001_I_T_nexus_reset(dev);
                 break;
         case IO_DS_NON_OPERATIONAL:
-                pm8001_dev = wq->data;
+                pm8001_dev = pw->data;
                 dev = pm8001_dev->sas_device;
                 pm8001_I_T_nexus_reset(dev);
                 break;
         }
-        list_del(&wq->entry);
-        kfree(wq);
+        kfree(pw);
 }
 
 static int pm8001_handle_event(struct pm8001_hba_info *pm8001_ha, void *data,
                                int handler)
 {
-        struct pm8001_wq *wq;
+        struct pm8001_work *pw;
         int ret = 0;
 
-        wq = kmalloc(sizeof(struct pm8001_wq), GFP_ATOMIC);
-        if (wq) {
-                wq->pm8001_ha = pm8001_ha;
-                wq->data = data;
-                wq->handler = handler;
-                INIT_DELAYED_WORK(&wq->work_q, pm8001_work_queue);
-                list_add_tail(&wq->entry, &pm8001_ha->wq_list);
-                schedule_delayed_work(&wq->work_q, 0);
+        pw = kmalloc(sizeof(struct pm8001_work), GFP_ATOMIC);
+        if (pw) {
+                pw->pm8001_ha = pm8001_ha;
+                pw->data = data;
+                pw->handler = handler;
+                INIT_WORK(&pw->work, pm8001_work_fn);
+                queue_work(pm8001_wq, &pw->work);
         } else
                 ret = -ENOMEM;
 
diff --git a/drivers/scsi/pm8001/pm8001_init.c b/drivers/scsi/pm8001/pm8001_init.c
index b95285f3383f..002360da01e3 100644
--- a/drivers/scsi/pm8001/pm8001_init.c
+++ b/drivers/scsi/pm8001/pm8001_init.c
@@ -51,6 +51,8 @@ static int pm8001_id;
 
 LIST_HEAD(hba_list);
 
+struct workqueue_struct *pm8001_wq;
+
 /**
  * The main structure which LLDD must register for scsi core.
  */
@@ -134,7 +136,6 @@ static void __devinit pm8001_phy_init(struct pm8001_hba_info *pm8001_ha,
 static void pm8001_free(struct pm8001_hba_info *pm8001_ha)
 {
         int i;
-        struct pm8001_wq *wq;
 
         if (!pm8001_ha)
                 return;
@@ -150,8 +151,7 @@ static void pm8001_free(struct pm8001_hba_info *pm8001_ha)
         PM8001_CHIP_DISP->chip_iounmap(pm8001_ha);
         if (pm8001_ha->shost)
                 scsi_host_put(pm8001_ha->shost);
-        list_for_each_entry(wq, &pm8001_ha->wq_list, entry)
-                cancel_delayed_work(&wq->work_q);
+        flush_workqueue(pm8001_wq);
         kfree(pm8001_ha->tags);
         kfree(pm8001_ha);
 }
@@ -381,7 +381,6 @@ pm8001_pci_alloc(struct pci_dev *pdev, u32 chip_id, struct Scsi_Host *shost)
         pm8001_ha->sas = sha;
         pm8001_ha->shost = shost;
         pm8001_ha->id = pm8001_id++;
-        INIT_LIST_HEAD(&pm8001_ha->wq_list);
         pm8001_ha->logging_level = 0x01;
         sprintf(pm8001_ha->name, "%s%d", DRV_NAME, pm8001_ha->id);
 #ifdef PM8001_USE_TASKLET
@@ -758,7 +757,7 @@ static int pm8001_pci_suspend(struct pci_dev *pdev, pm_message_t state)
         int i , pos;
         u32 device_state;
         pm8001_ha = sha->lldd_ha;
-        flush_scheduled_work();
+        flush_workqueue(pm8001_wq);
         scsi_block_requests(pm8001_ha->shost);
         pos = pci_find_capability(pdev, PCI_CAP_ID_PM);
         if (pos == 0) {
@@ -870,17 +869,26 @@ static struct pci_driver pm8001_pci_driver = {
  */
 static int __init pm8001_init(void)
 {
-        int rc;
+        int rc = -ENOMEM;
+
+        pm8001_wq = alloc_workqueue("pm8001", 0, 0);
+        if (!pm8001_wq)
+                goto err;
+
         pm8001_id = 0;
         pm8001_stt = sas_domain_attach_transport(&pm8001_transport_ops);
         if (!pm8001_stt)
-                return -ENOMEM;
+                goto err_wq;
         rc = pci_register_driver(&pm8001_pci_driver);
         if (rc)
-                goto err_out;
+                goto err_tp;
         return 0;
-err_out:
+
+err_tp:
         sas_release_transport(pm8001_stt);
+err_wq:
+        destroy_workqueue(pm8001_wq);
+err:
         return rc;
 }
 
@@ -888,6 +896,7 @@ static void __exit pm8001_exit(void)
 {
         pci_unregister_driver(&pm8001_pci_driver);
         sas_release_transport(pm8001_stt);
+        destroy_workqueue(pm8001_wq);
 }
 
 module_init(pm8001_init);
diff --git a/drivers/scsi/pm8001/pm8001_sas.h b/drivers/scsi/pm8001/pm8001_sas.h
index 7f064f9ca828..bdb6b27dedd6 100644
--- a/drivers/scsi/pm8001/pm8001_sas.h
+++ b/drivers/scsi/pm8001/pm8001_sas.h
@@ -50,6 +50,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/pci.h>
 #include <linux/interrupt.h>
+#include <linux/workqueue.h>
 #include <scsi/libsas.h>
 #include <scsi/scsi_tcq.h>
 #include <scsi/sas_ata.h>
@@ -379,18 +380,16 @@ struct pm8001_hba_info {
 #ifdef PM8001_USE_TASKLET
         struct tasklet_struct   tasklet;
 #endif
-        struct list_head        wq_list;
         u32                     logging_level;
         u32                     fw_status;
         const struct firmware   *fw_image;
 };
 
-struct pm8001_wq {
-        struct delayed_work work_q;
+struct pm8001_work {
+        struct work_struct work;
         struct pm8001_hba_info *pm8001_ha;
         void *data;
         int handler;
-        struct list_head entry;
 };
 
 struct pm8001_fw_image_header {
@@ -460,6 +459,9 @@ struct fw_control_ex {
         void                    *param3;
 };
 
+/* pm8001 workqueue */
+extern struct workqueue_struct *pm8001_wq;
+
 /******************** function prototype *********************/
 int pm8001_tag_alloc(struct pm8001_hba_info *pm8001_ha, u32 *tag_out);
 void pm8001_tag_init(struct pm8001_hba_info *pm8001_ha);