Commit cec72f3e authored Jul 01, 2020 by Saravana Kannan Committed by Greg Kroah-Hartman Jul 10, 2020

driver core: Don't do deferred probe in parallel with kernel_init thread

The current deferred probe implementation can mess up suspend/resume
ordering if deferred probe thread is kicked off in parallel with the
main initcall thread (kernel_init thread) [1].

For example:

Say device-B is a consumer of device-A.

Initcall thread					Deferred probe thread
===============					=====================
1. device-A is added.
2. device-B is added.
3. dpm_list is now [device-A, device-B].
4. driver-A defers probe of device-A.
						5. device-A is moved to
						   end of dpm_list
						6. dpm_list is now
						   [device-B, device-A]
7. driver-B is registereed and probes device-B.
8. dpm_list stays as [device-B, device-A].

The reverse order of dpm_list is used for suspend. So in this case
device-A would incorrectly get suspended before device-B.

Commit 716a7a25 ("driver core: fw_devlink: Add support for batching
fwnode parsing") kicked off the deferred probe thread early during boot
to run in parallel with the initcall thread and caused suspend/resume
regressions.  This patch removes the parallel run of the deferred probe
thread to avoid the suspend/resume regressions.

[1] - https://lore.kernel.org/lkml/CAGETcx8W96KAw-d_siTX4qHB_-7ddk0miYRDQeHE6E0_8qx-6Q@mail.gmail.com/



Fixes: 716a7a25 ("driver core: fw_devlink: Add support for batching fwnode parsing")
Signed-off-by: Saravana Kannan <saravanak@google.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200701194259.3337652-2-saravanak@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 9ebcfadb

drivers/base/base.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -153,7 +153,6 @@ extern char make_class_name(const char name, struct kobject *kobj);
		extern int devres_release_all(struct device *dev);
		extern void device_block_probing(void);
		extern void device_unblock_probing(void);
		extern void driver_deferred_probe_force_trigger(void);

		/* /sys/devices directory */
		extern struct kset *devices_kset;

drivers/base/core.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -1323,7 +1323,6 @@ void fw_devlink_resume(void)
		goto out;

		device_link_add_missing_supplier_links();
		driver_deferred_probe_force_trigger();
		out:
		mutex_unlock(&defer_fw_devlink_lock);
		}

drivers/base/dd.c

+0 −5

Original line number	Diff line number	Diff line
		@@ -164,11 +164,6 @@ static void driver_deferred_probe_trigger(void)
		if (!driver_deferred_probe_enable)
		return;

		driver_deferred_probe_force_trigger();
		}

		void driver_deferred_probe_force_trigger(void)
		{
		/*
		* A successful probe means that all the devices in the pending list
		* should be triggered to be reprobed. Move all the deferred devices

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