On Tue, 07 Nov 2023 10:29:28 +0000 Russell King <rmk+kernel@xxxxxxxxxxxxxxx> wrote: > From: James Morse <james.morse@xxxxxxx> > > 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 <james.morse@xxxxxxx> > Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx> Seems reasonable. FWIW Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > --- > 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(-) > > diff --git a/arch/x86/kernel/cpu/intel_epb.c b/arch/x86/kernel/cpu/intel_epb.c > index e4c3ba91321c..f18d35fe27a9 100644 > --- a/arch/x86/kernel/cpu/intel_epb.c > +++ b/arch/x86/kernel/cpu/intel_epb.c > @@ -237,4 +237,4 @@ static __init int intel_epb_init(void) > cpuhp_remove_state(CPUHP_AP_X86_INTEL_EPB_ONLINE); > return ret; > } > -subsys_initcall(intel_epb_init); > +late_initcall(intel_epb_init);
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