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Message-ID: <20240207184100.18066-2-djeffery@redhat.com>
Date: Wed, 7 Feb 2024 13:40:55 -0500
From: David Jeffery <djeffery@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-nvme@...ts.infradead.org,
linux-scsi@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J . Wysocki" <rafael@...nel.org>,
David Jeffery <djeffery@...hat.com>,
Laurence Oberman <loberman@...hat.com>
Subject: [RFC PATCH 1/6] minimal async shutdown infrastructure
Adds the async_shutdown_start and async_shutdown_end calls to perform async
shutdown. Implements a very minimalist method of async shutdown support
within device_shutdown(). The device at the head of the shutdown list is
checked against a list of devices under async shutdown. If the head is a
parent of a device on the async list, all active async shutdown operations
are completed before the parent's shutdown call is performed.
The number of async operations also has a max limit to prevent the list being
checked for a child from getting overly large.
Signed-off-by: David Jeffery <djeffery@...hat.com>
Tested-by: Laurence Oberman <loberman@...hat.com>
---
drivers/base/core.c | 116 +++++++++++++++++++++++++++++++++-
include/linux/device/bus.h | 8 ++-
include/linux/device/driver.h | 7 ++
3 files changed, 127 insertions(+), 4 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 14d46af40f9a..5bc2282c00cd 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -4719,12 +4719,92 @@ int device_change_owner(struct device *dev, kuid_t kuid, kgid_t kgid)
}
EXPORT_SYMBOL_GPL(device_change_owner);
+
+#define MAX_ASYNC_SHUTDOWNS 32
+static int async_shutdown_count;
+static LIST_HEAD(async_shutdown_list);
+
+/**
+ * If a device has a child busy with an async shutdown or there are too many
+ * async shutdowns active, the device may not be shut down at this time.
+ */
+static bool may_shutdown_device(struct device *dev)
+{
+ struct device *tmp;
+
+ if (async_shutdown_count >= MAX_ASYNC_SHUTDOWNS)
+ return false;
+
+ list_for_each_entry(tmp, &async_shutdown_list, kobj.entry) {
+ if (tmp->parent == dev)
+ return false;
+ }
+ return true;
+}
+
+/**
+ * Call and track each async shutdown call
+ */
+static void async_shutdown_start(struct device *dev, void (*callback) (struct device *))
+{
+ if (initcall_debug)
+ dev_info(dev, "async_shutdown_start\n");
+
+ (*callback)(dev);
+ list_add_tail(&dev->kobj.entry, &async_shutdown_list);
+ async_shutdown_count++;
+}
+
+/**
+ * Wait for all async shutdown operations currently active to complete
+ */
+static void wait_for_active_async_shutdown(void)
+{
+ struct device *dev, *parent;
+
+ while (!list_empty(&async_shutdown_list)) {
+ dev = list_entry(async_shutdown_list.next, struct device,
+ kobj.entry);
+
+ parent = dev->parent;
+
+ /*
+ * Make sure the device is off the list
+ */
+ list_del_init(&dev->kobj.entry);
+ if (parent)
+ device_lock(parent);
+ device_lock(dev);
+ if (dev->bus && dev->bus->async_shutdown_end) {
+ if (initcall_debug)
+ dev_info(dev,
+ "async_shutdown_end called\n");
+ dev->bus->async_shutdown_end(dev);
+ } else if (dev->driver && dev->driver->async_shutdown_end) {
+ if (initcall_debug)
+ dev_info(dev,
+ "async_shutdown_end called\n");
+ dev->driver->async_shutdown_end(dev);
+ }
+ device_unlock(dev);
+ if (parent)
+ device_unlock(parent);
+
+ put_device(dev);
+ put_device(parent);
+ }
+ if (initcall_debug)
+ printk(KERN_INFO "device shutdown: waited for %d async shutdown callbacks\n", async_shutdown_count);
+ async_shutdown_count = 0;
+}
+
/**
* device_shutdown - call ->shutdown() on each device to shutdown.
*/
void device_shutdown(void)
{
struct device *dev, *parent;
+ bool async_busy;
wait_for_device_probe();
device_block_probing();
@@ -4741,6 +4821,8 @@ void device_shutdown(void)
dev = list_entry(devices_kset->list.prev, struct device,
kobj.entry);
+ async_busy = false;
+
/*
* hold reference count of device's parent to
* prevent it from being freed because parent's
@@ -4748,6 +4830,17 @@ void device_shutdown(void)
*/
parent = get_device(dev->parent);
get_device(dev);
+
+ if (!may_shutdown_device(dev)) {
+ put_device(dev);
+ put_device(parent);
+
+ spin_unlock(&devices_kset->list_lock);
+ wait_for_active_async_shutdown();
+ spin_lock(&devices_kset->list_lock);
+ continue;
+ }
+
/*
* Make sure the device is off the kset list, in the
* event that dev->*->shutdown() doesn't remove it.
@@ -4769,26 +4862,43 @@ void device_shutdown(void)
dev_info(dev, "shutdown_pre\n");
dev->class->shutdown_pre(dev);
}
- if (dev->bus && dev->bus->shutdown) {
+ if (dev->bus && dev->bus->async_shutdown_start) {
+ async_shutdown_start(dev, dev->bus->async_shutdown_start);
+ async_busy = true;
+ } else if (dev->bus && dev->bus->shutdown) {
if (initcall_debug)
dev_info(dev, "shutdown\n");
dev->bus->shutdown(dev);
+ } else if (dev->driver && dev->driver->async_shutdown_start) {
+ async_shutdown_start(dev, dev->driver->async_shutdown_start);
+ async_busy = true;
} else if (dev->driver && dev->driver->shutdown) {
if (initcall_debug)
dev_info(dev, "shutdown\n");
dev->driver->shutdown(dev);
+ } else {
+ if (initcall_debug)
+ dev_info(dev, "no shutdown callback\n");
}
device_unlock(dev);
if (parent)
device_unlock(parent);
- put_device(dev);
- put_device(parent);
+ /* if device has an async shutdown, drop the ref when done */
+ if (!async_busy) {
+ put_device(dev);
+ put_device(parent);
+ }
spin_lock(&devices_kset->list_lock);
}
spin_unlock(&devices_kset->list_lock);
+ /*
+ * Wait for any async shutdown still running.
+ */
+ if (!list_empty(&async_shutdown_list))
+ wait_for_active_async_shutdown();
}
/*
diff --git a/include/linux/device/bus.h b/include/linux/device/bus.h
index 5ef4ec1c36c3..7a4a2ff0bc23 100644
--- a/include/linux/device/bus.h
+++ b/include/linux/device/bus.h
@@ -48,7 +48,11 @@ struct fwnode_handle;
* will never get called until they do.
* @remove: Called when a device removed from this bus.
* @shutdown: Called at shut-down time to quiesce the device.
- *
+ * @async_shutdown_start: Optional call to support and begin the shutdown
+ * process on the device in an asynchronous manner.
+ * @async_shutdown_end: Optional call to complete an asynchronous
+ * shutdown of the device. Must be provided if a
+ * sync_shutdown_start call is provided.
* @online: Called to put the device back online (after offlining it).
* @offline: Called to put the device offline for hot-removal. May fail.
*
@@ -87,6 +91,8 @@ struct bus_type {
void (*sync_state)(struct device *dev);
void (*remove)(struct device *dev);
void (*shutdown)(struct device *dev);
+ void (*async_shutdown_start)(struct device *dev);
+ void (*async_shutdown_end)(struct device *dev);
int (*online)(struct device *dev);
int (*offline)(struct device *dev);
diff --git a/include/linux/device/driver.h b/include/linux/device/driver.h
index 7738f458995f..af0ad2d3687a 100644
--- a/include/linux/device/driver.h
+++ b/include/linux/device/driver.h
@@ -71,6 +71,11 @@ enum probe_type {
* @remove: Called when the device is removed from the system to
* unbind a device from this driver.
* @shutdown: Called at shut-down time to quiesce the device.
+ * @async_shutdown_start: Optional call to support and begin the shutdown
+ * process on the device in an asynchronous manner.
+ * @async_shutdown_end: Optional call to complete an asynchronous
+ * shutdown of the device. Must be provided if a
+ * sync_shutdown_start call is provided.
* @suspend: Called to put the device to sleep mode. Usually to a
* low power state.
* @resume: Called to bring a device from sleep mode.
@@ -110,6 +115,8 @@ struct device_driver {
void (*sync_state)(struct device *dev);
int (*remove) (struct device *dev);
void (*shutdown) (struct device *dev);
+ void (*async_shutdown_start) (struct device *dev);
+ void (*async_shutdown_end) (struct device *dev);
int (*suspend) (struct device *dev, pm_message_t state);
int (*resume) (struct device *dev);
const struct attribute_group **groups;
--
2.43.0
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