[PATCH v1 2/3] async: Introduce async_schedule_dev_nocall()

Rafael J. Wysocki
2023-12-27T20:41:45Z

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

In preparation for subsequent changes, introduce a specialized variant
of async_schedule_dev() that will not invoke the argument function
synchronously when it cannot be scheduled for asynchronous execution.

The new function, async_schedule_dev_nocall(), will be used for fixing
possible deadlocks in the system-wide power management core code.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/base/power/main.c | 12 ++++++++----
include/linux/async.h | 2 ++
kernel/async.c | 29 +++++++++++++++++++++++++++++
3 files changed, 39 insertions(+), 4 deletions(-)

Index: linux-pm/kernel/async.c
===================================================================
--- linux-pm.orig/kernel/async.c
+++ linux-pm/kernel/async.c
@@ -244,6 +244,35 @@ async_cookie_t async_schedule_node(async
EXPORT_SYMBOL_GPL(async_schedule_node);

/**
+ * async_schedule_dev_nocall - A simplified variant of async_schedule_dev()
+ * @func: function to execute asynchronously
+ * @dev: device argument to be passed to function
+ *
+ * @dev is used as both the argument for the function and to provide NUMA
+ * context for where to run the function.
+ *
+ * If the asynchronous execution of @func is scheduled successfully, return
+ * true. Otherwise, do nothing and return false, unlike async_schedule_dev()
+ * that will run the function synchronously then.
+ */
+bool async_schedule_dev_nocall(async_func_t func, struct device *dev)
+{
+ struct async_entry *entry;
+
+ entry = kzalloc(sizeof(struct async_entry), GFP_KERNEL);
+
+ /* Give up if there is no memory or too much work. */
+ if (!entry || atomic_read(&entry_count) > MAX_WORK) {
+ kfree(entry);
+ return false;
+ }
+
+ __async_schedule_node_domain(func, dev, dev_to_node(dev),
+ &async_dfl_domain, entry);
+ return true;
+}
+
+/**
* async_synchronize_full - synchronize all asynchronous function calls
*
* This function waits until all asynchronous function calls have been done.
Index: linux-pm/include/linux/async.h
===================================================================
--- linux-pm.orig/include/linux/async.h
+++ linux-pm/include/linux/async.h
@@ -90,6 +90,8 @@ async_schedule_dev(async_func_t func, st
return async_schedule_node(func, dev, dev_to_node(dev));
}

+bool async_schedule_dev_nocall(async_func_t func, struct device *dev);
+
/**
* async_schedule_dev_domain - A device specific version of async_schedule_domain
* @func: function to execute asynchronously