Re: [PATCH RFC 02/22] x86: intel_epb: Don't rely on link order

Gavin Shan <[email protected]> Mon, 13 Nov 2023 10:03:17 +1000

Newsgroups	gmane.linux.acpi.devel,gmane.linux.power-management.general,gmane.linux.kernel.cross-arch,gmane.linux.kernel,gmane.linux.ports.arm.kernel,gmane.linux.ports.riscv,gmane.linux.documentation,gmane.linux.ports.ia64,gmane.linux.ports.parisc
Message-ID	<[email protected]>

On 11/7/23 20:29, Russell King (Oracle) wrote:
> From: James Morse <[email protected]>
> 
> intel_epb_init() is called as a subsys_initcall() to register cpuhp
> callbacks. The callbacks make use of get_cpu_device() which will return
> NULL unless register_cpu() has been called. register_cpu() is called
> from topology_init(), which is also a subsys_initcall().
> 
> This is fragile. Moving the register_cpu() to a different
> subsys_initcall()  leads to a NULL dereference during boot.
> 
> Make intel_epb_init() a late_initcall(), user-space can't provide a
> policy before this point anyway.
> 
> Signed-off-by: James Morse <[email protected]>
> Signed-off-by: Russell King (Oracle) <[email protected]>
> ---
> subsys_initcall_sync() would be an option, but moving the register_cpu()
> calls into ACPI also means adding a safety net for CPUs that are online
> but not described properly by firmware. This lives in subsys_initcall_sync().
> ---
>   arch/x86/kernel/cpu/intel_epb.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 

Reviewed-by: Gavin Shan <[email protected]>