notifier: Return an error when callback is already registered
The notifier registration routine doesn't return a proper error value
when a callback has already been registered, leading people to track
whether that registration has happened at the call site:
https://lore.kernel.org/amd-gfx/20210512013058.6827-1-mukul.joshi@amd.com/
Which is unnecessary.
Return -EEXIST to signal that case so that callers can act accordingly.
Enforce callers to check the return value, leading to loud screaming
during build:
arch/x86/kernel/cpu/mce/core.c: In function ‘mce_register_decode_chain’:
arch/x86/kernel/cpu/mce/core.c:167:2: error: ignoring return value of \
‘blocking_notifier_chain_register’, declared with attribute warn_unused_result [-Werror=unused-result]
blocking_notifier_chain_register(&x86_mce_decoder_chain, nb);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Drop the WARN too, while at it.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
2 files changed
