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Message-ID: <1464147962-26650-9-git-send-email-david.kershner@unisys.com>
Date: Tue, 24 May 2016 23:45:46 -0400
From: David Kershner <david.kershner@...sys.com>
To: <corbet@....net>, <tglx@...utronix.de>, <mingo@...hat.com>,
<hpa@...or.com>, <david.kershner@...sys.com>,
<gregkh@...uxfoundation.org>, <erik.arfvidson@...sys.com>,
<timothy.sell@...sys.com>, <hofrat@...dl.org>,
<dzickus@...hat.com>, <jes.sorensen@...hat.com>,
<alexander.curtin@...sys.com>, <janani.rvchndrn@...il.com>,
<sudipm.mukherjee@...il.com>, <prarit@...hat.com>,
<david.binder@...sys.com>, <nhorman@...hat.com>,
<dan.j.williams@...el.com>, <linux-kernel@...r.kernel.org>,
<linux-doc@...r.kernel.org>,
<driverdev-devel@...uxdriverproject.org>,
<sparmaintainer@...sys.com>
CC: Tim Sell <Timothy.Sell@...sys.com>
Subject: [PATCH 08/24] staging: unisys: visorbus: use kernel timer instead of workqueue
From: Tim Sell <Timothy.Sell@...sys.com>
A kernel timer is now used as the vehicle to periodically call the
channel_interrupt function of registered visor drivers, instead of a
workqueue.
This simplifies a lot of things by making periodic_work.c and
periodic_work.h no longer necessary. This change also means that the
channel_interrupt() callbacks registered by visor drivers (via
visorbus_register_visor_driver()) will now be called in atomic context
(i.e., canNOT sleep) rather than kernel thread context (CAN sleep).
Fortunately this did NOT necessitate any change to the existing
channel_interrupt() callbacks, because none of them ever perform any
operations that would be invalid in atomic context.
Signed-off-by: Tim Sell <Timothy.Sell@...sys.com>
Signed-off-by: David Kershner <david.kershner@...sys.com>
---
drivers/staging/unisys/include/visorbus.h | 10 +++--
drivers/staging/unisys/visorbus/visorbus_main.c | 54 +++++++------------------
2 files changed, 21 insertions(+), 43 deletions(-)
diff --git a/drivers/staging/unisys/include/visorbus.h b/drivers/staging/unisys/include/visorbus.h
index 9baf1ec..9bb88bb 100644
--- a/drivers/staging/unisys/include/visorbus.h
+++ b/drivers/staging/unisys/include/visorbus.h
@@ -34,8 +34,9 @@
#include <linux/poll.h>
#include <linux/kernel.h>
#include <linux/uuid.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
-#include "periodic_work.h"
#include "channel.h"
struct visor_driver;
@@ -126,8 +127,8 @@ struct visor_driver {
* device: Device struct meant for use by the bus driver
* only.
* list_all: Used by the bus driver to enumerate devices.
- * periodic_work: Device work queue. Private use by bus driver
- * only.
+ * timer: Timer fired periodically to do interrupt-type
+ * activity.
* being_removed: Indicates that the device is being removed from
* the bus. Private bus driver use only.
* visordriver_callback_lock: Used by the bus driver to lock when handling
@@ -157,7 +158,8 @@ struct visor_device {
/* These fields are for private use by the bus driver only. */
struct device device;
struct list_head list_all;
- struct periodic_work *periodic_work;
+ struct timer_list timer;
+ bool timer_active;
bool being_removed;
struct semaphore visordriver_callback_lock;
bool pausing;
diff --git a/drivers/staging/unisys/visorbus/visorbus_main.c b/drivers/staging/unisys/visorbus/visorbus_main.c
index 608ca1a..24b27ff 100644
--- a/drivers/staging/unisys/visorbus/visorbus_main.c
+++ b/drivers/staging/unisys/visorbus/visorbus_main.c
@@ -19,7 +19,6 @@
#include "visorbus.h"
#include "visorbus_private.h"
#include "version.h"
-#include "periodic_work.h"
#include "vbuschannel.h"
#include "guestlinuxdebug.h"
#include "vmcallinterface.h"
@@ -116,7 +115,6 @@ struct bus_type visorbus_type = {
.bus_groups = visorbus_bus_groups,
};
-static struct workqueue_struct *periodic_dev_workqueue;
static long long bus_count; /** number of bus instances */
/** ever-increasing */
@@ -222,10 +220,6 @@ visorbus_release_device(struct device *xdev)
{
struct visor_device *dev = to_visor_device(xdev);
- if (dev->periodic_work) {
- visor_periodic_work_destroy(dev->periodic_work);
- dev->periodic_work = NULL;
- }
if (dev->visorchannel) {
visorchannel_destroy(dev->visorchannel);
dev->visorchannel = NULL;
@@ -530,35 +524,36 @@ unregister_driver_attributes(struct visor_driver *drv)
}
static void
-dev_periodic_work(void *xdev)
+dev_periodic_work(unsigned long __opaque)
{
- struct visor_device *dev = xdev;
+ struct visor_device *dev = (struct visor_device *)__opaque;
struct visor_driver *drv = to_visor_driver(dev->device.driver);
- down(&dev->visordriver_callback_lock);
if (drv->channel_interrupt)
drv->channel_interrupt(dev);
- up(&dev->visordriver_callback_lock);
- if (!visor_periodic_work_nextperiod(dev->periodic_work))
- put_device(&dev->device);
+ mod_timer(&dev->timer, jiffies + POLLJIFFIES_NORMALCHANNEL);
}
static void
dev_start_periodic_work(struct visor_device *dev)
{
- if (dev->being_removed)
+ if (dev->being_removed || dev->timer_active)
return;
/* now up by at least 2 */
get_device(&dev->device);
- if (!visor_periodic_work_start(dev->periodic_work))
- put_device(&dev->device);
+ dev->timer.expires = jiffies + POLLJIFFIES_NORMALCHANNEL;
+ add_timer(&dev->timer);
+ dev->timer_active = true;
}
static void
dev_stop_periodic_work(struct visor_device *dev)
{
- if (visor_periodic_work_stop(dev->periodic_work))
- put_device(&dev->device);
+ if (!dev->timer_active)
+ return;
+ del_timer_sync(&dev->timer);
+ dev->timer_active = false;
+ put_device(&dev->device);
}
/** This is called automatically upon adding a visor_device (device_add), or
@@ -776,17 +771,9 @@ create_visor_device(struct visor_device *dev)
dev->device.release = visorbus_release_device;
/* keep a reference just for us (now 2) */
get_device(&dev->device);
- dev->periodic_work =
- visor_periodic_work_create(POLLJIFFIES_NORMALCHANNEL,
- periodic_dev_workqueue,
- dev_periodic_work,
- dev, dev_name(&dev->device));
- if (!dev->periodic_work) {
- POSTCODE_LINUX_3(DEVICE_CREATE_FAILURE_PC, chipset_dev_no,
- DIAG_SEVERITY_ERR);
- err = -EINVAL;
- goto err_put;
- }
+ init_timer(&dev->timer);
+ dev->timer.data = (unsigned long)(dev);
+ dev->timer.function = dev_periodic_work;
/* bus_id must be a unique name with respect to this bus TYPE
* (NOT bus instance). That's why we need to include the bus
@@ -1265,13 +1252,6 @@ visorbus_init(void)
goto error;
}
- periodic_dev_workqueue = create_singlethread_workqueue("visorbus_dev");
- if (!periodic_dev_workqueue) {
- POSTCODE_LINUX_2(CREATE_WORKQUEUE_PC, DIAG_SEVERITY_ERR);
- err = -ENOMEM;
- goto error;
- }
-
/* This enables us to receive notifications when devices appear for
* which this service partition is to be a server for.
*/
@@ -1294,10 +1274,6 @@ visorbus_exit(void)
visorchipset_register_busdev(NULL, NULL, NULL);
remove_all_visor_devices();
- flush_workqueue(periodic_dev_workqueue); /* better not be any work! */
- destroy_workqueue(periodic_dev_workqueue);
- periodic_dev_workqueue = NULL;
-
list_for_each_safe(listentry, listtmp, &list_all_bus_instances) {
struct visor_device *dev = list_entry(listentry,
struct visor_device,
--
1.9.1
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