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>
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83011b6cbe
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9ebab64952
2 changed files with 21 additions and 43 deletions
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@ -34,8 +34,9 @@
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#include <linux/poll.h>
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#include <linux/kernel.h>
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#include <linux/uuid.h>
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#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include "periodic_work.h"
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#include "channel.h"
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struct visor_driver;
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@ -126,8 +127,8 @@ struct visor_driver {
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* device: Device struct meant for use by the bus driver
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* only.
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* list_all: Used by the bus driver to enumerate devices.
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* periodic_work: Device work queue. Private use by bus driver
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* only.
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* timer: Timer fired periodically to do interrupt-type
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* activity.
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* being_removed: Indicates that the device is being removed from
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* the bus. Private bus driver use only.
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* visordriver_callback_lock: Used by the bus driver to lock when handling
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@ -157,7 +158,8 @@ struct visor_device {
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/* These fields are for private use by the bus driver only. */
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struct device device;
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struct list_head list_all;
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struct periodic_work *periodic_work;
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struct timer_list timer;
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bool timer_active;
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bool being_removed;
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struct semaphore visordriver_callback_lock;
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bool pausing;
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@ -19,7 +19,6 @@
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#include "visorbus.h"
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#include "visorbus_private.h"
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#include "version.h"
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#include "periodic_work.h"
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#include "vbuschannel.h"
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#include "guestlinuxdebug.h"
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#include "vmcallinterface.h"
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@ -116,7 +115,6 @@ struct bus_type visorbus_type = {
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.bus_groups = visorbus_bus_groups,
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};
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static struct workqueue_struct *periodic_dev_workqueue;
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static long long bus_count; /** number of bus instances */
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/** ever-increasing */
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@ -222,10 +220,6 @@ visorbus_release_device(struct device *xdev)
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{
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struct visor_device *dev = to_visor_device(xdev);
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if (dev->periodic_work) {
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visor_periodic_work_destroy(dev->periodic_work);
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dev->periodic_work = NULL;
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}
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if (dev->visorchannel) {
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visorchannel_destroy(dev->visorchannel);
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dev->visorchannel = NULL;
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@ -530,35 +524,36 @@ unregister_driver_attributes(struct visor_driver *drv)
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}
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static void
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dev_periodic_work(void *xdev)
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dev_periodic_work(unsigned long __opaque)
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{
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struct visor_device *dev = xdev;
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struct visor_device *dev = (struct visor_device *)__opaque;
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struct visor_driver *drv = to_visor_driver(dev->device.driver);
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down(&dev->visordriver_callback_lock);
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if (drv->channel_interrupt)
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drv->channel_interrupt(dev);
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up(&dev->visordriver_callback_lock);
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if (!visor_periodic_work_nextperiod(dev->periodic_work))
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put_device(&dev->device);
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mod_timer(&dev->timer, jiffies + POLLJIFFIES_NORMALCHANNEL);
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}
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static void
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dev_start_periodic_work(struct visor_device *dev)
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{
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if (dev->being_removed)
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if (dev->being_removed || dev->timer_active)
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return;
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/* now up by at least 2 */
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get_device(&dev->device);
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if (!visor_periodic_work_start(dev->periodic_work))
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put_device(&dev->device);
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dev->timer.expires = jiffies + POLLJIFFIES_NORMALCHANNEL;
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add_timer(&dev->timer);
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dev->timer_active = true;
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}
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static void
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dev_stop_periodic_work(struct visor_device *dev)
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{
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if (visor_periodic_work_stop(dev->periodic_work))
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put_device(&dev->device);
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if (!dev->timer_active)
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return;
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del_timer_sync(&dev->timer);
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dev->timer_active = false;
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put_device(&dev->device);
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}
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/** This is called automatically upon adding a visor_device (device_add), or
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@ -776,17 +771,9 @@ create_visor_device(struct visor_device *dev)
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dev->device.release = visorbus_release_device;
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/* keep a reference just for us (now 2) */
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get_device(&dev->device);
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dev->periodic_work =
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visor_periodic_work_create(POLLJIFFIES_NORMALCHANNEL,
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periodic_dev_workqueue,
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dev_periodic_work,
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dev, dev_name(&dev->device));
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if (!dev->periodic_work) {
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POSTCODE_LINUX_3(DEVICE_CREATE_FAILURE_PC, chipset_dev_no,
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DIAG_SEVERITY_ERR);
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err = -EINVAL;
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goto err_put;
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}
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init_timer(&dev->timer);
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dev->timer.data = (unsigned long)(dev);
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dev->timer.function = dev_periodic_work;
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/* bus_id must be a unique name with respect to this bus TYPE
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* (NOT bus instance). That's why we need to include the bus
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@ -1268,13 +1255,6 @@ visorbus_init(void)
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goto error;
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}
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periodic_dev_workqueue = create_singlethread_workqueue("visorbus_dev");
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if (!periodic_dev_workqueue) {
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POSTCODE_LINUX_2(CREATE_WORKQUEUE_PC, DIAG_SEVERITY_ERR);
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err = -ENOMEM;
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goto error;
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}
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/* This enables us to receive notifications when devices appear for
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* which this service partition is to be a server for.
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*/
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@ -1297,10 +1277,6 @@ visorbus_exit(void)
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visorchipset_register_busdev(NULL, NULL, NULL);
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remove_all_visor_devices();
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flush_workqueue(periodic_dev_workqueue); /* better not be any work! */
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destroy_workqueue(periodic_dev_workqueue);
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periodic_dev_workqueue = NULL;
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list_for_each_safe(listentry, listtmp, &list_all_bus_instances) {
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struct visor_device *dev = list_entry(listentry,
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struct visor_device,
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