On Mon, Nov 08, 2021 at 11:19:24AM +0100, Borislav Petkov wrote:
From: Borislav Petkov bp@suse.de
Hi all,
this is a huge patchset for something which is really trivial - it changes the notifier registration routines to return an error value if a notifier callback is already present on the respective list of callbacks. For more details scroll to the last patch.
Everything before it is converting the callers to check the return value of the registration routines and issue a warning, instead of the WARN() notifier_chain_register() does now.
What reason is there for moving the check into the callers? It seems like pointless churn. Why not add the error return code, change the WARN to pr_warn, and leave the callers as they are? Wouldn't that end up having exactly the same effect?
For that matter, what sort of remedial action can a caller take if the return code is -EEXIST? Is there any point in forcing callers to check the return code if they can't do anything about it?
Before the last patch has been applied, though, that checking is a NOP which would make the application of those patches trivial - every maintainer can pick a patch at her/his discretion - only the last one enables the build warnings and that one will be queued only after the preceding patches have all been merged so that there are no build warnings.
Why should there be _any_ build warnings? The real problem occurs when a notifier callback is added twice, not when a caller fails to check the return code. Double-registration is not the sort of thing that can be detected at build time.
Alan Stern
Due to the sheer volume of the patches, I have addressed the respective patch and the last one, which enables the warning, with addressees for each maintained area so as not to spam people unnecessarily.
If people prefer I carry some through tip, instead, I'll gladly do so - your call.
And, if you think the warning messages need to be more precise, feel free to adjust them before committing.
Thanks!