[S390] cio: introduce subchannel todos

Ensure that current and future users of sch->work do not overwrite
each other by introducing a single mechanism for delayed subchannel
work.

Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

4 files changed, 63 insertions, 19 deletions

diff --git a/drivers/s390/cio/cio.h b/drivers/s390/cio/cio.h
index 2e43558c704b..bf7f80f5a330 100644
--- a/drivers/s390/cio/cio.h
+++ b/drivers/s390/cio/cio.h
@@ -68,6 +68,11 @@ struct schib {
         __u8 mda[4];             /* model dependent area */
 } __attribute__ ((packed,aligned(4)));
 
+enum sch_todo {
+        SCH_TODO_NOTHING,
+        SCH_TODO_UNREG,
+};
+
 /* subchannel data structure used by I/O subroutines */
 struct subchannel {
         struct subchannel_id schid;
@@ -95,7 +100,8 @@ struct subchannel {
         struct device dev;      /* entry in device tree */
         struct css_driver *driver;
         void *private; /* private per subchannel type data */
-        struct work_struct work;
+        enum sch_todo todo;
+        struct work_struct todo_work;
         struct schib_config config;
 } __attribute__ ((aligned(8)));
 
diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index b4df5a56cfe2..92ff88ac1107 100644
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -133,6 +133,8 @@ out:
         return rc;
 }
 
+static void css_sch_todo(struct work_struct *work);
+
 static struct subchannel *
 css_alloc_subchannel(struct subchannel_id schid)
 {
@@ -147,6 +149,7 @@ css_alloc_subchannel(struct subchannel_id schid)
                 kfree(sch);
                 return ERR_PTR(ret);
         }
+        INIT_WORK(&sch->todo_work, css_sch_todo);
         return sch;
 }
 
@@ -190,6 +193,51 @@ void css_sch_device_unregister(struct subchannel *sch)
 }
 EXPORT_SYMBOL_GPL(css_sch_device_unregister);
 
+static void css_sch_todo(struct work_struct *work)
+{
+        struct subchannel *sch;
+        enum sch_todo todo;
+
+        sch = container_of(work, struct subchannel, todo_work);
+        /* Find out todo. */
+        spin_lock_irq(sch->lock);
+        todo = sch->todo;
+        CIO_MSG_EVENT(4, "sch_todo: sch=0.%x.%04x, todo=%d\n", sch->schid.ssid,
+                      sch->schid.sch_no, todo);
+        sch->todo = SCH_TODO_NOTHING;
+        spin_unlock_irq(sch->lock);
+        /* Perform todo. */
+        if (todo == SCH_TODO_UNREG)
+                css_sch_device_unregister(sch);
+        /* Release workqueue ref. */
+        put_device(&sch->dev);
+}
+
+/**
+ * css_sched_sch_todo - schedule a subchannel operation
+ * @sch: subchannel
+ * @todo: todo
+ *
+ * Schedule the operation identified by @todo to be performed on the slow path
+ * workqueue. Do nothing if another operation with higher priority is already
+ * scheduled. Needs to be called with subchannel lock held.
+ */
+void css_sched_sch_todo(struct subchannel *sch, enum sch_todo todo)
+{
+        CIO_MSG_EVENT(4, "sch_todo: sched sch=0.%x.%04x todo=%d\n",
+                      sch->schid.ssid, sch->schid.sch_no, todo);
+        if (sch->todo >= todo)
+                return;
+        /* Get workqueue ref. */
+        if (!get_device(&sch->dev))
+                return;
+        sch->todo = todo;
+        if (!queue_work(slow_path_wq, &sch->todo_work)) {
+                /* Already queued, release workqueue ref. */
+                put_device(&sch->dev);
+        }
+}
+
 static void ssd_from_pmcw(struct chsc_ssd_info *ssd, struct pmcw *pmcw)
 {
         int i;
diff --git a/drivers/s390/cio/css.h b/drivers/s390/cio/css.h
index 68d6b0bf151c..fe84b92cde60 100644
--- a/drivers/s390/cio/css.h
+++ b/drivers/s390/cio/css.h
@@ -11,6 +11,8 @@
 #include <asm/chpid.h>
 #include <asm/schid.h>
 
+#include "cio.h"
+
 /*
  * path grouping stuff
  */
@@ -151,4 +153,5 @@ int css_sch_is_valid(struct schib *);
 
 extern struct workqueue_struct *slow_path_wq;
 void css_wait_for_slow_path(void);
+void css_sched_sch_todo(struct subchannel *sch, enum sch_todo todo);
 #endif
diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index 6097763f1035..0dcfc0ee3d81 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -1051,23 +1051,6 @@ static void io_subchannel_init_fields(struct subchannel *sch)
         io_subchannel_init_config(sch);
 }
 
-static void io_subchannel_do_unreg(struct work_struct *work)
-{
-        struct subchannel *sch;
-
-        sch = container_of(work, struct subchannel, work);
-        css_sch_device_unregister(sch);
-        put_device(&sch->dev);
-}
-
-/* Schedule unregister if we have no cdev. */
-static void io_subchannel_schedule_removal(struct subchannel *sch)
-{
-        get_device(&sch->dev);
-        INIT_WORK(&sch->work, io_subchannel_do_unreg);
-        queue_work(slow_path_wq, &sch->work);
-}
-
 /*
  * Note: We always return 0 so that we bind to the device even on error.
  * This is needed so that our remove function is called on unregister.
@@ -1124,7 +1107,9 @@ static int io_subchannel_probe(struct subchannel *sch)
         return 0;
 
 out_schedule:
-        io_subchannel_schedule_removal(sch);
+        spin_lock_irq(sch->lock);
+        css_sched_sch_todo(sch, SCH_TODO_UNREG);
+        spin_unlock_irq(sch->lock);
         return 0;
 }
 
@@ -1469,6 +1454,8 @@ static int io_subchannel_sch_event(struct subchannel *sch, int process)
         spin_lock_irqsave(sch->lock, flags);
         if (!device_is_registered(&sch->dev))
                 goto out_unlock;
+        if (work_pending(&sch->todo_work))
+                goto out_unlock;
         action = sch_get_action(sch);
         CIO_MSG_EVENT(2, "event: sch 0.%x.%04x, process=%d, action=%d\n",
                       sch->schid.ssid, sch->schid.sch_no, process,