Lock a registry key programmatically to avoid concurrency issues

Question

I'm writing an app that needs to write registry values inside of a key in a particular order, and other applications could be writing to the same key, at the same time.

Is there a way to temporarily lock a registry key for writes, to avoid multiple processes writing to this registry key at the same time, and the values getting messed up / out of order?

e.g. I need to write to HKCU\Software\Company\Product\ which already contains the values below:

• Start1 = "abc"
• Start2 = "def"
• Start3 = "ghi"

Because the last one is Start3, I need to create Start4.

The problem is if another process is running at the same time, detects that Start3 is the last one, and overrides my Start4 that I just created (because it didn't see it due to concurrency).

What would be a good way to prevent that from happening?

I don't have control over which (or how many) applications are writing to this key, and as such I can't tell them to pause or anything like that...

I'm looking for something like the pseudo-code below:

Registry.Lock("HKCU\Software\Company\Product\");
Registry.Write("Start4", "jkl");
Registry.Unlock("HKCU\Software\Company\Product\");

Answer 1

It looks like I'm going to answer my own question unfortunately.

Writing and Deleting Registry Data

It is not possible to lock a registry key during a write operation to synchronize access to the data. However, you can control access to a registry key using security attributes. For more information, see Registry Key Security and Access Rights.

More than one registry operation can be performed within a single transaction. To associate a registry key with a transaction, an application can use the RegCreateKeyTransacted or RegOpenKeyTransacted function. For more information about transactions, see Kernel Transaction Manager.

From: https://learn.microsoft.com/en-us/windows/win32/sysinfo/writing-and-deleting-registry-data

Answer 2

You have to use proper synchronization using the Mutex functions. Registry API, as most Windows API, is not threadsafe.