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staging: unisys: visorbus: use kernel timer instead of workqueue 

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@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Acked-By: Neil Horman <nhorman@tuxdriver.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
hifive-unleashed-5.1
Tim Sell 2016-06-10 21:48:08 -04:00 committed by Greg Kroah-Hartman
parent 83011b6cbe
commit 9ebab64952
2 changed files with 21 additions and 43 deletions
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10
drivers/staging/unisys/include/visorbus.h
View File

@ -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;

54
drivers/staging/unisys/visorbus/visorbus_main.c
View File

@ -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
@ -1268,13 +1255,6 @@ 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.
*/
@ -1297,10 +1277,6 @@ 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,