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[02/21] x86: intel_epb: Don't rely on link order

Message ID E1r5R2m-00Csyb-2S@rmk-PC.armlinux.org.uk (mailing list archive)
State New, archived
Headers show
Series Initial cleanups for vCPU hotplug | expand

Commit Message

Russell King (Oracle) Nov. 21, 2023, 1:44 p.m. UTC
From: James Morse <james.morse@arm.com>

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@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
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(-)

Comments

Rafael J. Wysocki Nov. 22, 2023, 8:12 p.m. UTC | #1
On Tue, Nov 21, 2023 at 2:44 PM Russell King <rmk+kernel@armlinux.org.uk> wrote:
>
> From: James Morse <james.morse@arm.com>
>
> 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@arm.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

and I'd suggest sending this separately to the x86 list.

> ---
> 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);
> --
> 2.30.2
>
>
diff mbox series

Patch

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);