Revert "drivers: core: synchronize really_probe() and dev_uevent()"

jira LE-3587
Rebuild_History Non-Buildable kernel-4.18.0-553.62.1.el8_10
commit-author Dmitry Torokhov <[email protected]>
commit dc1771f
Empty-Commit: Cherry-Pick Conflicts during history rebuild.
Will be included in final tarball splat. Ref for failed cherry-pick at:
ciq/ciq_backports/kernel-4.18.0-553.62.1.el8_10/dc1771f7.failed

This reverts commit c0a4009.

Probing a device can take arbitrary long time. In the field we observed
that, for example, probing a bad micro-SD cards in an external USB card
reader (or maybe cards were good but cables were flaky) sometimes takes
longer than 2 minutes due to multiple retries at various levels of the
stack. We can not block uevent_show() method for that long because udev
is reading that attribute very often and that blocks udev and interferes
with booting of the system.

The change that introduced locking was concerned with dev_uevent()
racing with unbinding the driver. However we can handle it without
locking (which will be done in subsequent patch).

There was also claim that synchronization with probe() is needed to
properly load USB drivers, however this is a red herring: the change
adding the lock was introduced in May of last year and USB loading and
probing worked properly for many years before that.

Revert the harmful locking.

	Cc: [email protected]
	Signed-off-by: Dmitry Torokhov <[email protected]>
	Reviewed-by: Masami Hiramatsu (Google) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
	Signed-off-by: Greg Kroah-Hartman <[email protected]>
(cherry picked from commit dc1771f)
	Signed-off-by: Jonathan Maple <[email protected]>

# Conflicts:
#	drivers/base/core.c

Author: PlaidCat

ciq/ciq_backports/kernel-4.18.0-553.62.1.el8_10/dc1771f7.failed

@@ -0,0 +1,62 @@
+Revert "drivers: core: synchronize really_probe() and dev_uevent()"
+
+jira LE-3587
+Rebuild_History Non-Buildable kernel-4.18.0-553.62.1.el8_10
+commit-author Dmitry Torokhov <[email protected]>
+commit dc1771f718548f7d4b93991b174c6e7b5e1ba410
+Empty-Commit: Cherry-Pick Conflicts during history rebuild.
+Will be included in final tarball splat. Ref for failed cherry-pick at:
+ciq/ciq_backports/kernel-4.18.0-553.62.1.el8_10/dc1771f7.failed
+
+This reverts commit c0a40097f0bc81deafc15f9195d1fb54595cd6d0.
+
+Probing a device can take arbitrary long time. In the field we observed
+that, for example, probing a bad micro-SD cards in an external USB card
+reader (or maybe cards were good but cables were flaky) sometimes takes
+longer than 2 minutes due to multiple retries at various levels of the
+stack. We can not block uevent_show() method for that long because udev
+is reading that attribute very often and that blocks udev and interferes
+with booting of the system.
+
+The change that introduced locking was concerned with dev_uevent()
+racing with unbinding the driver. However we can handle it without
+locking (which will be done in subsequent patch).
+
+There was also claim that synchronization with probe() is needed to
+properly load USB drivers, however this is a red herring: the change
+adding the lock was introduced in May of last year and USB loading and
+probing worked properly for many years before that.
+
+Revert the harmful locking.
+
+	Cc: [email protected]
+	Signed-off-by: Dmitry Torokhov <[email protected]>
+	Reviewed-by: Masami Hiramatsu (Google) <[email protected]>
+Link: https://lore.kernel.org/r/[email protected]
+	Signed-off-by: Greg Kroah-Hartman <[email protected]>
+(cherry picked from commit dc1771f718548f7d4b93991b174c6e7b5e1ba410)
+	Signed-off-by: Jonathan Maple <[email protected]>
+
+# Conflicts:
+#	drivers/base/core.c
+diff --cc drivers/base/core.c
+index 85168dc6be18,f9c1c623bca5..000000000000
+--- a/drivers/base/core.c
++++ b/drivers/base/core.c
+@@@ -2572,11 -2726,8 +2572,13 @@@ static ssize_t uevent_show(struct devic
+  	if (!env)
+  		return -ENOMEM;
+  
+- 	/* Synchronize with really_probe() */
+- 	device_lock(dev);
+  	/* let the kset specific function add its keys */
+++<<<<<<< HEAD
+ +	retval = kset->uevent_ops->uevent(kset, &dev->kobj, env);
+ +	device_unlock(dev);
+++=======
++ 	retval = kset->uevent_ops->uevent(&dev->kobj, env);
+++>>>>>>> dc1771f71854 (Revert "drivers: core: synchronize really_probe() and dev_uevent()")
+  	if (retval)
+  		goto out;
+  
+* Unmerged path drivers/base/core.c