From 28e408cd4c0742c098c2484e7e12514347a5003c Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@google.com>
Date: Thu, 3 Jun 2021 13:36:10 +0200
Subject: [PATCH] Revert "drivers: base: Fix device link removal"

This reverts commit d007150b4e15bfcb8d36cfd88a5645d42e44d383 which is
commit 80dd33cf72d1ab4f0af303f1fa242c6d6c8d328f upstream.

It breaks the abi and will be brought back at the proper time that we
can.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I5b49602baf86e11e10eecb1c300ea8634826dbd2
---
 drivers/base/core.c    | 37 ++++++++++++++-----------------------
 include/linux/device.h |  6 ++++--
 2 files changed, 18 insertions(+), 25 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 588d6d4f6a49..313a7ef22716 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -191,11 +191,6 @@ int device_links_read_lock_held(void)
 {
 	return srcu_read_lock_held(&device_links_srcu);
 }
-
-static void device_link_synchronize_removal(void)
-{
-	synchronize_srcu(&device_links_srcu);
-}
 #else /* !CONFIG_SRCU */
 static DECLARE_RWSEM(device_links_lock);
 
@@ -226,10 +221,6 @@ int device_links_read_lock_held(void)
 	return lockdep_is_held(&device_links_lock);
 }
 #endif
-
-static inline void device_link_synchronize_removal(void)
-{
-}
 #endif /* !CONFIG_SRCU */
 
 static bool device_is_ancestor(struct device *dev, struct device *target)
@@ -451,13 +442,8 @@ static struct attribute *devlink_attrs[] = {
 };
 ATTRIBUTE_GROUPS(devlink);
 
-static void device_link_release_fn(struct work_struct *work)
+static void device_link_free(struct device_link *link)
 {
-	struct device_link *link = container_of(work, struct device_link, rm_work);
-
-	/* Ensure that all references to the link object have been dropped. */
-	device_link_synchronize_removal();
-
 	while (refcount_dec_not_one(&link->rpm_active))
 		pm_runtime_put(link->supplier);
 
@@ -466,19 +452,24 @@ static void device_link_release_fn(struct work_struct *work)
 	kfree(link);
 }
 
+#ifdef CONFIG_SRCU
+static void __device_link_free_srcu(struct rcu_head *rhead)
+{
+	device_link_free(container_of(rhead, struct device_link, rcu_head));
+}
+
 static void devlink_dev_release(struct device *dev)
 {
 	struct device_link *link = to_devlink(dev);
 
-	INIT_WORK(&link->rm_work, device_link_release_fn);
-	/*
-	 * It may take a while to complete this work because of the SRCU
-	 * synchronization in device_link_release_fn() and if the consumer or
-	 * supplier devices get deleted when it runs, so put it into the "long"
-	 * workqueue.
-	 */
-	queue_work(system_long_wq, &link->rm_work);
+	call_srcu(&device_links_srcu, &link->rcu_head, __device_link_free_srcu);
 }
+#else
+static void devlink_dev_release(struct device *dev)
+{
+	device_link_free(to_devlink(dev));
+}
+#endif
 
 static struct class devlink_class = {
 	.name = "devlink",
diff --git a/include/linux/device.h b/include/linux/device.h
index 5ec9be377a76..3c71b779668e 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -566,7 +566,7 @@ struct device {
  * @flags: Link flags.
  * @rpm_active: Whether or not the consumer device is runtime-PM-active.
  * @kref: Count repeated addition of the same link.
- * @rm_work: Work structure used for removing the link.
+ * @rcu_head: An RCU head to use for deferred execution of SRCU callbacks.
  * @supplier_preactivated: Supplier has been made active before consumer probe.
  */
 struct device_link {
@@ -579,7 +579,9 @@ struct device_link {
 	u32 flags;
 	refcount_t rpm_active;
 	struct kref kref;
-	struct work_struct rm_work;
+#ifdef CONFIG_SRCU
+	struct rcu_head rcu_head;
+#endif
 	bool supplier_preactivated; /* Owned by consumer probe. */
 	ANDROID_KABI_RESERVE(1);
 	ANDROID_KABI_RESERVE(2);