[patch 29/52] [PATCH] cio: introduce subchannel todos

Martin Schwidefsky
2009-11-13T15:12:19Z

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From: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>

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>
---

drivers/s390/cio/cio.h | 8 ++++++-
drivers/s390/cio/css.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++
drivers/s390/cio/css.h | 3 ++
drivers/s390/cio/device.c | 23 ++++------------------
4 files changed, 63 insertions(+), 19 deletions(-)

Index: quilt-2.6/drivers/s390/cio/cio.h
===================================================================
--- quilt-2.6.orig/drivers/s390/cio/cio.h 2009-11-13 15:48:33.000000000 +0100
+++ quilt-2.6/drivers/s390/cio/cio.h 2009-11-13 16:08:18.000000000 +0100
@@ -68,6 +68,11 @@
__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 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)));

Index: quilt-2.6/drivers/s390/cio/css.c
===================================================================
--- quilt-2.6.orig/drivers/s390/cio/css.c 2009-11-13 16:08:18.000000000 +0100
+++ quilt-2.6/drivers/s390/cio/css.c 2009-11-13 16:08:18.000000000 +0100
@@ -133,6 +133,8 @@
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 @@
kfree(sch);
return ERR_PTR(ret);
}
+ INIT_WORK(&sch->todo_work, css_sch_todo);
return sch;
}

@@ -190,6 +193,51 @@
}
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;
Index: quilt-2.6/drivers/s390/cio/css.h
===================================================================
--- quilt-2.6.orig/drivers/s390/cio/css.h 2009-11-13 15:48:33.000000000 +0100
+++ quilt-2.6/drivers/s390/cio/css.h 2009-11-13 16:08:18.000000000 +0100
@@ -11,6 +11,8 @@
#include <asm/chpid.h>
#include <asm/schid.h>

+#include "cio.h"
+
/*
* path grouping stuff
*/
@@ -151,4 +153,5 @@

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
Index: quilt-2.6/drivers/s390/cio/device.c
===================================================================
--- quilt-2.6.orig/drivers/s390/cio/device.c 2009-11-13 16:08:18.000000000 +0100
+++ quilt-2.6/drivers/s390/cio/device.c 2009-11-13 16:08:18.000000000 +0100
@@ -1051,23 +1051,6 @@
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 @@
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 @@
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,