linux-kernel - [PATCH v3] devcoredump: Send uevent once devcd is ready

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Date:   Fri, 17 Nov 2023 20:19:32 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     <johannes@...solutions.net>, <gregkh@...uxfoundation.org>,
        <rafael@...nel.org>
CC:     <linux-kernel@...r.kernel.org>,
        Mukesh Ojha <quic_mojha@...cinc.com>, <stable@...r.kernel.org>
Subject: [PATCH v3] devcoredump: Send uevent once devcd is ready

dev_coredumpm() creates a devcoredump device and adds it
to the core kernel framework which eventually end up
sending uevent to the user space and later creates a
symbolic link to the failed device. An application
running in userspace may be interested in this symbolic
link to get the name of the failed device.

In a issue scenario, once uevent sent to the user space
it start reading '/sys/class/devcoredump/devcdX/failing_device'
to get the actual name of the device which might not been
created and it is in its path of creation.

To fix this, suppress sending uevent till the failing device
symbolic link gets created and send uevent once symbolic
link is created successfully.

Fixes: 833c95456a70 ("device coredump: add new device coredump class")
Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
Cc: stable@...r.kernel.org
---
Change in v3:
 - Cced stable.

Change in v2:
 - Added Fixes tag as per suggestion from [Johannes]

 drivers/base/devcoredump.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/base/devcoredump.c b/drivers/base/devcoredump.c
index 91536ee05f14..7e2d1f0d903a 100644
--- a/drivers/base/devcoredump.c
+++ b/drivers/base/devcoredump.c
@@ -362,6 +362,7 @@ void dev_coredumpm(struct device *dev, struct module *owner,
 	devcd->devcd_dev.class = &devcd_class;

 	mutex_lock(&devcd->mutex);
+	dev_set_uevent_suppress(&devcd->devcd_dev, true);
 	if (device_add(&devcd->devcd_dev))
 		goto put_device;

@@ -376,6 +377,8 @@ void dev_coredumpm(struct device *dev, struct module *owner,
 		              "devcoredump"))
 		dev_warn(dev, "devcoredump create_link failed\n");

+	dev_set_uevent_suppress(&devcd->devcd_dev, false);
+	kobject_uevent(&devcd->devcd_dev.kobj, KOBJ_ADD);
 	INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
 	schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);
 	mutex_unlock(&devcd->mutex);
-- 
2.7.4